Biology Question Paper

Topics: Pollination and Fertilisation

---

Section A: Multiple Choice Questions (100 Questions - 1 Mark Each)

Instructions: Choose the correct option for each question.

1. Pollination is the transfer of pollen from: a) Stigma to anther b) Anther to stigma c) Ovary to anther d) Stigma to ovary

2. Self-pollination occurs when pollen is transferred: a) Between different species b) From anther to stigma of the same flower or plant c) From one plant to another plant d) Through water only

3. Cross-pollination involves transfer of pollen: a) Within the same flower b) Between flowers of different species c) Between flowers of the same plant d) Between flowers of different plants of the same species

4. Which is an advantage of self-pollination? a) Produces new varieties b) More vigorous offspring c) Sure method of pollination d) Depends on external agents

5. Which is a disadvantage of self-pollination? a) Preserves parental characters b) Does not produce new varieties c) Sure method of pollination d) Independent of external agents

6. Cross-pollination produces: a) Weaker offspring b) Similar varieties c) New varieties d) Fewer seeds

7. Flowers pollinated by insects are usually: a) Small and inconspicuous b) Large and brightly colored c) Without scent d) Green in color

8. Wind-pollinated flowers are typically: a) Large and colorful b) Sweet-scented c) Small and inconspicuous d) Bright red

9. Water-pollinated flowers are usually: a) Large and colorful b) Sweet-scented c) Small and inconspicuous d) Very fragrant

10. Unisexuality refers to: a) Presence of both male and female organs b) Presence of either male or female organs c) Absence of reproductive organs d) Multiple reproductive organs

11. Dichogamy is: a) Spatial separation of anther and stigma b) Maturation of male and female parts at different times c) Inability to self-fertilize d) Presence of unisexual flowers

12. Self-sterility means: a) Plant cannot produce seeds b) Flower cannot be fertilized by its own pollen c) Plant has no reproductive organs d) Flower has only male parts

13. Herkogamy involves: a) Temporal separation b) Spatial separation of anther and stigma c) Chemical incompatibility d) Genetic sterility

14. Fertilisation is the: a) Transfer of pollen b) Fusion of gametes c) Formation of fruits d) Germination of seeds

15. After pollination, the pollen grain: a) Dies immediately b) Germinates on the stigma c) Moves to the ovary d) Forms a seed

16. The pollen tube grows: a) Upward from stigma b) Downward to the ovule c) Sideways from anther d) Around the flower

17. Double fertilisation occurs in: a) Gymnosperms b) Angiosperms c) Ferns d) Mosses

18. In double fertilisation, how many male gametes are involved? a) One b) Two c) Three d) Four

19. Triple fusion involves: a) Three male gametes b) Second male gamete with two polar nuclei c) Three female nuclei d) All gametes together

20. The result of triple fusion is: a) Zygote formation b) Embryo formation c) Endosperm formation d) Seed coat formation

21. A fruit is a mature: a) Seed b) Ovule c) Ovary d) Anther

22. A seed contains: a) Only embryo b) Only food reserves c) Embryo and food reserves d) Only protective coat

23. The primary function of fruit is to: a) Attract insects b) Protect seeds and aid dispersal c) Store water d) Produce more flowers

24. Seeds are important for: a) Pollination b) Fertilisation c) Reproduction d) Photosynthesis

25. Insect-pollinated flowers have: a) No nectar b) Sweet scent c) Dull colors d) Rough texture

26. Which agent is most reliable for cross-pollination? a) Wind b) Water c) Insects d) Gravity

27. Self-pollination is also called: a) Allogamy b) Autogamy c) Xenogamy d) Geitonogamy

28. Cross-pollination between flowers of the same plant is: a) Autogamy b) Geitonogamy c) Xenogamy d) Allogamy

29. The male reproductive part of a flower is: a) Pistil b) Carpel c) Stamen d) Ovary

30. The female reproductive part of a flower is: a) Anther b) Filament c) Stamen d) Pistil

31. Pollen grains are produced in: a) Ovary b) Stigma c) Anther d) Style

32. The sticky top of pistil is: a) Style b) Stigma c) Ovary d) Ovule

33. Ovules are present in: a) Anther b) Stigma c) Style d) Ovary

34. After fertilisation, ovule becomes: a) Fruit b) Seed c) Flower d) Leaf

35. After fertilisation, ovary becomes: a) Seed b) Fruit c) Leaf d) Root

36. The embryo sac is also called: a) Microgametophyte b) Megagametophyte c) Sporophyte d) Zygote

37. In angiosperms, the endosperm is: a) Haploid b) Diploid c) Triploid d) Tetraploid

38. The zygote is: a) Haploid b) Diploid c) Triploid d) Tetraploid

39. Pollination by birds is called: a) Entomophily b) Anemophily c) Ornithophily d) Hydrophily

40. Pollination by wind is called: a) Entomophily b) Anemophily c) Ornithophily d) Hydrophily

41. Pollination by insects is called: a) Entomophily b) Anemophily c) Ornithophily d) Hydrophily

42. Pollination by water is called: a) Entomophily b) Anemophily c) Ornithophily d) Hydrophily

43. Which type of pollination ensures genetic diversity? a) Self-pollination b) Cross-pollination c) Both equally d) Neither

44. Cleistogamous flowers show: a) Only cross-pollination b) Only self-pollination c) Both types d) No pollination

45. The stigma receives: a) Ovules b) Seeds c) Pollen grains d) Fruits

46. Pollen tube carries: a) Female gametes b) Male gametes c) Nutrients only d) Water only

47. Double fertilisation was discovered by: a) Darwin b) Mendel c) Nawaschin d) Morgan

48. The primary endosperm nucleus is: a) Haploid b) Diploid c) Triploid d) Tetraploid

49. Seed dispersal is aided by: a) Fruits only b) Wind only c) Animals only d) Fruits, wind, and animals

50. Parthenocarpy is: a) Fruit formation without fertilisation b) Seed formation without pollination c) Flower formation without leaves d) Root formation without soil

51. Which structure protects the developing embryo? a) Anther b) Stigma c) Seed coat d) Pollen grain

52. The food storage tissue in seeds is: a) Embryo b) Seed coat c) Endosperm d) Integument

53. Micropyle is: a) Small pore in ovule b) Small anther c) Small stigma d) Small petal

54. Chalaza is located at: a) Top of ovule b) Bottom of ovule c) Side of ovule d) Center of ovule

55. Nucellus is: a) Outer covering of ovule b) Inner tissue of ovule c) Stalk of ovule d) Opening of ovule

56. Integuments form: a) Embryo b) Endosperm c) Seed coat d) Fruit wall

57. Hilum is: a) Scar on seed b) Opening in seed c) Food in seed d) Embryo in seed

58. Cotyledons are: a) Seed leaves b) True leaves c) Flower parts d) Root parts

59. Monocots have how many cotyledons? a) One b) Two c) Three d) Four

60. Dicots have how many cotyledons? a) One b) Two c) Three d) Four

61. Plumule develops into: a) Root system b) Shoot system c) Seed coat d) Fruit

62. Radicle develops into: a) Shoot system b) Root system c) Leaves d) Flowers

63. Hypocotyl is located: a) Above cotyledons b) Below cotyledons c) Within cotyledons d) Outside seed

64. Epicotyl is located: a) Below cotyledons b) Above cotyledons c) Within cotyledons d) Outside seed

65. Germination is: a) Formation of seeds b) Growth of seedling from seed c) Formation of fruits d) Pollination process

66. Epigeal germination involves: a) Cotyledons remaining underground b) Cotyledons coming above ground c) No cotyledons d) Multiple cotyledons

67. Hypogeal germination involves: a) Cotyledons coming above ground b) Cotyledons remaining underground c) No germination d) Rapid germination

68. Which is essential for seed germination? a) Light only b) Water only c) Air only d) Water, air, and suitable temperature

69. Dormancy in seeds is: a) Death of embryo b) Temporary suspension of growth c) Rapid germination d) Continuous growth

70. Viability of seeds refers to: a) Size of seeds b) Color of seeds c) Ability to germinate d) Weight of seeds

71. Artificial pollination is done to: a) Prevent fertilisation b) Control breeding c) Stop seed formation d) Reduce fruit production

72. Emasculation involves: a) Removing pistil b) Removing stamens c) Removing petals d) Removing sepals

73. Bagging is done to: a) Collect pollen b) Prevent unwanted pollination c) Speed up pollination d) Store seeds

74. Cross-pollination is prevented by: a) Large flowers b) Bright colors c) Self-compatibility d) Temporal isolation

75. Protandry is: a) Anthers maturing before stigma b) Stigma maturing before anthers c) Simultaneous maturation d) No maturation

76. Protogyny is: a) Anthers maturing before stigma b) Stigma maturing before anthers c) Simultaneous maturation d) No maturation

77. Heterostyly involves: a) Different flower colors b) Different style lengths c) Different petal numbers d) Different sepal sizes

78. Incompatibility prevents: a) Pollination b) Fertilisation c) Seed formation d) All of the above

79. Apomixis is: a) Sexual reproduction b) Asexual reproduction through seeds c) Vegetative reproduction d) No reproduction

80. Polyembryony is: a) One embryo per seed b) Multiple embryos per seed c) No embryo in seed d) Embryo outside seed

81. Endosperm provides: a) Protection to embryo b) Nutrition to embryo c) Shape to seed d) Color to seed

82. Non-endospermic seeds have: a) No food storage b) Food stored in cotyledons c) Food stored in seed coat d) External food source

83. Endospermic seeds have: a) Food in cotyledons b) Food in endosperm c) No food storage d) Food in seed coat

84. Albuminous seeds are: a) Without endosperm b) With endosperm c) Without embryo d) With multiple embryos

85. Ex-albuminous seeds are: a) With endosperm b) Without endosperm c) With multiple endosperms d) Without embryo

86. Pericarp is: a) Seed coat b) Fruit wall c) Embryo covering d) Pollen coating

87. True fruits develop from: a) Ovary only b) Entire flower c) Receptacle only d) Sepals only

88. False fruits develop from: a) Ovary only b) Parts other than ovary c) Embryo only d) Endosperm only

89. Simple fruits develop from: a) Single flower with one ovary b) Single flower with multiple ovaries c) Multiple flowers d) No flowers

90. Aggregate fruits develop from: a) Single flower with one ovary b) Single flower with multiple ovaries c) Multiple flowers d) No ovary

91. Multiple fruits develop from: a) Single flower b) Single ovary c) Multiple flowers d) Multiple seeds

92. Dehiscent fruits: a) Do not open when ripe b) Open when ripe to release seeds c) Never ripen d) Have no seeds

93. Indehiscent fruits: a) Open when ripe b) Do not open when ripe c) Have multiple openings d) Open before ripening

94. Fleshy fruits have: a) Hard pericarp b) Soft and juicy pericarp c) No pericarp d) Multiple pericarps

95. Dry fruits have: a) Juicy pericarp b) Hard and dry pericarp c) No pericarp d) Soft pericarp

96. Wind dispersal is aided by: a) Heavy seeds b) Light seeds with wings c) Fleshy fruits d) Hard seed coats

97. Animal dispersal involves: a) Dry fruits b) Fleshy edible fruits c) Very small seeds d) Hard fruits

98. Water dispersal requires: a) Heavy seeds b) Light seeds that float c) Sticky seeds d) Buried seeds

99. Explosive dispersal occurs in: a) All fruits b) Some dehiscent fruits c) Fleshy fruits only d) Indehiscent fruits only

100. Seed germination percentage indicates: a) Seed size b) Seed viability c) Seed color d) Seed weight

---

Section B: Short Answer Questions (100 Questions - 1 Mark Each)

Instructions: Write brief answers in one or two sentences.

1. Define pollination.
2. What is self-pollination?
3. What is cross-pollination?
4. Name one advantage of self-pollination.
5. Name one disadvantage of self-pollination.
6. Name one advantage of cross-pollination.
7. Name one disadvantage of cross-pollination.
8. What type of flowers are pollinated by insects?
9. What type of flowers are pollinated by wind?
10. What is unisexuality?
11. Define dichogamy.
12. What is self-sterility?
13. Define herkogamy.
14. What is fertilisation?
15. What happens after pollination?
16. What is double fertilisation?
17. What is triple fusion?
18. Define fruit.
19. Define seed.
20. What is the function of fruits?
21. What is the significance of seeds?
22. What is autogamy?
23. What is allogamy?
24. What is geitonogamy?
25. What is xenogamy?
26. Name the male reproductive part of a flower.
27. Name the female reproductive part of a flower.
28. Where are pollen grains produced?
29. What is stigma?
30. Where are ovules located?
31. What does ovule become after fertilisation?
32. What does ovary become after fertilisation?
33. What is embryo sac?
34. What is the ploidy of endosperm?
35. What is the ploidy of zygote?
36. What is ornithophily?
37. What is anemophily?
38. What is entomophily?
39. What is hydrophily?
40. What are cleistogamous flowers?
41. What does pollen tube carry?
42. Who discovered double fertilisation?
43. What is parthenocarpy?
44. What is seed coat?
45. What is endosperm?
46. What is micropyle?
47. What is chalaza?
48. What is nucellus?
49. What do integuments form?
50. What is hilum?
51. What are cotyledons?
52. How many cotyledons do monocots have?
53. How many cotyledons do dicots have?
54. What does plumule develop into?
55. What does radicle develop into?
56. What is hypocotyl?
57. What is epicotyl?
58. What is germination?
59. What is epigeal germination?
60. What is hypogeal germination?
61. What is essential for seed germination?
62. What is seed dormancy?
63. What is seed viability?
64. What is artificial pollination?
65. What is emasculation?
66. What is bagging?
67. What is protandry?
68. What is protogyny?
69. What is heterostyly?
70. What prevents fertilisation in incompatible crosses?
71. What is apomixis?
72. What is polyembryony?
73. What is the function of endosperm?
74. What are non-endospermic seeds?
75. What are endospermic seeds?
76. What are albuminous seeds?
77. What are ex-albuminous seeds?
78. What is pericarp?
79. What are true fruits?
80. What are false fruits?
81. What are simple fruits?
82. What are aggregate fruits?
83. What are multiple fruits?
84. What are dehiscent fruits?
85. What are indehiscent fruits?
86. What are fleshy fruits?
87. What are dry fruits?
88. How are seeds dispersed by wind?
89. How are seeds dispersed by animals?
90. How are seeds dispersed by water?
91. What is explosive seed dispersal?
92. What indicates seed viability?
93. Name one wind-pollinated plant.
94. Name one insect-pollinated plant.
95. What is the primary endosperm nucleus?
96. What is the female gametophyte called?
97. What is the male gametophyte called?
98. What structure guides the pollen tube?
99. What is the outermost layer of seed?
100. What is the food storage tissue in seeds?

---

Section C: Short Questions (100 Questions - 2 Marks Each)

Instructions: Write detailed answers in 2-3 sentences.

1. Explain the process of pollination and its importance.
2. Compare self-pollination and cross-pollination.
3. Describe two advantages and disadvantages of self-pollination.
4. Describe two advantages and disadvantages of cross-pollination.
5. Explain the characteristics of insect-pollinated flowers.
6. Explain the characteristics of wind-pollinated flowers.
7. Describe unisexuality as an adaptation for cross-pollination.
8. Explain dichogamy and its significance.
9. Describe self-sterility mechanism in plants.
10. Explain herkogamy with an example.
11. Define fertilisation and explain its significance.
12. Describe the events that occur after pollination.
13. Explain the process of double fertilisation.
14. Describe triple fusion and its product.
15. Explain the development of fruit and seed after fertilisation.
16. Describe the significance of fruits in plant reproduction.
17. Explain the importance of seeds in plant life cycle.
18. Compare autogamy, geitonogamy, and xenogamy.
19. Describe the structure and function of stamen.
20. Describe the structure and function of pistil.
21. Explain the role of anther in reproduction.
22. Describe the function of stigma in pollination.
23. Explain the location and function of ovules.
24. Describe the transformation of ovule into seed.
25. Explain the transformation of ovary into fruit.
26. Describe the structure of embryo sac.
27. Explain the ploidy levels in angiosperm reproduction.
28. Compare different types of pollination by agents.
29. Describe cleistogamous flowers and their advantage.
30. Explain the journey of male gametes through pollen tube.
31. Describe the historical significance of double fertilisation discovery.
32. Explain parthenocarpy and give an example.
33. Describe the protective function of seed coat.
34. Explain the nutritive function of endosperm.
35. Describe the structure and function of micropyle.
36. Explain the significance of chalaza in ovule.
37. Describe the role of nucellus in ovule development.
38. Explain how integuments contribute to seed formation.
39. Describe the significance of hilum in seeds.
40. Explain the structure and function of cotyledons.
41. Compare monocot and dicot seeds based on cotyledons.
42. Describe the development of plumule and radicle.
43. Explain the difference between hypocotyl and epicotyl.
44. Describe the process and conditions for seed germination.
45. Compare epigeal and hypogeal germination.
46. Explain the factors essential for successful germination.
47. Describe seed dormancy and its ecological significance.
48. Explain seed viability and its testing methods.
49. Describe the technique of artificial pollination.
50. Explain emasculation and its purpose in plant breeding.
51. Describe bagging technique in controlled pollination.
52. Compare protandry and protogyny mechanisms.
53. Explain heterostyly as a mechanism preventing self-pollination.
54. Describe incompatibility mechanisms in plants.
55. Explain apomixis and its significance.
56. Describe polyembryony with examples.
57. Compare the nutritive strategies of endospermic and non-endospermic seeds.
58. Explain the difference between albuminous and ex-albuminous seeds.
59. Describe the structure and function of pericarp.
60. Compare true fruits and false fruits with examples.
61. Classify fruits based on their origin and give examples.
62. Compare dehiscent and indehiscent fruits.
63. Distinguish between fleshy and dry fruits.
64. Describe adaptations for wind dispersal of seeds.
65. Explain mechanisms of animal-mediated seed dispersal.
66. Describe adaptations for water dispersal of seeds.
67. Explain explosive seed dispersal mechanisms.
68. Describe methods to determine seed germination percentage.
69. Compare the efficiency of different pollination agents.
70. Explain the relationship between flower structure and pollination method.
71. Describe the evolutionary advantages of cross-pollination.
72. Explain the role of temporal isolation in preventing hybridization.
73. Describe spatial adaptations that promote cross-pollination.
74. Explain the significance of genetic diversity in plant populations.
75. Describe the process of pollen tube growth and guidance.
76. Explain the cellular events during fertilisation.
77. Describe the formation of endosperm and its types.
78. Explain the development of embryo after fertilisation.
79. Describe the maturation process of seeds.
80. Explain the environmental triggers for seed germination.
81. Describe the metabolic changes during germination.
82. Explain the role of plant hormones in germination.
83. Describe adaptations of desert plants for reproduction.
84. Explain reproductive strategies in aquatic plants.
85. Describe the coevolution of flowers and pollinators.
86. Explain the economic importance of controlled pollination.
87. Describe the conservation significance of seed banks.
88. Explain the role of fruits in ecosystem dynamics.
89. Describe agricultural applications of understanding pollination.
90. Explain the impact of environmental changes on pollination.
91. Describe the molecular basis of self-incompatibility.
92. Explain the genetic control of flower development.
93. Describe the physiological changes during fruit ripening.
94. Explain the dormancy mechanisms in different seed types.
95. Describe the factors affecting seed longevity.
96. Explain the role of seed dispersal in plant distribution.
97. Describe the relationship between seed size and dispersal method.
98. Explain the importance of pollination in biodiversity conservation.
99. Describe the challenges faced by plants in pollination.
100. Explain the future prospects of artificial reproductive technologies in plants.

---

Section D: Long Answer Questions (50 Questions - 3 Marks Each)

Instructions: Write comprehensive answers with proper explanations, examples, and diagrams where necessary.

1. Describe the process of pollination in detail, including the different types and their mechanisms. Explain the significance of each type in plant reproduction.

2. Compare and contrast self-pollination and cross-pollination. Discuss their advantages, disadvantages, and evolutionary significance in plant reproduction.

3. Explain the various agents of pollination. Describe the floral adaptations associated with each type of pollination agent and provide relevant examples.

4. Describe the natural adaptations that promote cross-pollination in flowering plants. Explain how each adaptation prevents self-pollination and ensures genetic diversity.

5. Explain the process of fertilisation in angiosperms. Describe the events from pollen germination to zygote formation, including the unique features of angiosperm fertilisation.

6. Describe double fertilisation in detail. Explain the process, participants, and products of this unique reproductive mechanism in flowering plants.

7. Explain the development of fruit and seed after fertilisation. Describe the structural changes and physiological processes involved in their formation.

8. Discuss the significance of fruits and seeds in plant reproduction and survival. Explain their roles in protection, dispersal, and continuation of species.

9. Describe the structure of a typical angiosperm ovule. Explain the function of each part and trace the development from ovule to seed.

10. Explain the structure and development of embryo sac. Describe its role in fertilisation and the formation of endosperm and embryo.

11. Describe the different types of pollination based on the relationship between flowers. Explain autogamy, geitonogamy, and xenogamy with their biological significance.

12. Explain the morphological and physiological adaptations of flowers for insect pollination. Describe the coevolutionary relationship between flowers and their insect pollinators.

13. Describe the adaptations of flowers for wind pollination. Explain how these adaptations ensure efficient pollen transfer and reproductive success.

14. Explain the concept of dichogamy and its types. Describe how temporal separation of male and female phases promotes cross-pollination.

15. Describe the various mechanisms of self-incompatibility in plants. Explain how these mechanisms prevent inbreeding and maintain genetic diversity.

16. Explain the artificial techniques used in plant breeding for controlled pollination. Describe emasculation, bagging, and artificial pollination procedures.

17. Describe the structure and composition of seeds. Explain the role of different seed parts in germination and early seedling development.

18. Compare endospermic and non-endospermic seeds. Describe their structural differences and nutritional strategies for embryo development.

19. Explain the process of seed germination. Describe the physiological and biochemical changes that occur during germination and early growth.

20. Compare epigeal and hypogeal germination. Describe the mechanisms and advantages of each type with suitable examples.

21. Describe the environmental factors affecting seed germination. Explain how temperature, moisture, light, and oxygen influence the germination process.

22. Explain seed dormancy and its types. Describe the mechanisms of dormancy and their ecological significance in plant survival.

23. Describe the various methods of seed dispersal. Explain the adaptations of fruits and seeds for different dispersal mechanisms.

24. Explain the classification of fruits based on their development and structure. Describe simple, aggregate, and multiple fruits with examples.

25. Compare dehiscent and indehiscent fruits. Describe their structural features and the mechanisms of seed release.

26. Describe the economic and ecological importance of pollination. Explain the role of pollinators in agriculture and ecosystem maintenance.

27. Explain the concept of apomixis in plants. Describe its types, mechanisms, and significance in plant reproduction and breeding.

28. Describe polyembryony in plants. Explain its occurrence, types, and significance in plant propagation and breeding programs.

29. Explain the role of plant hormones in reproductive processes. Describe their involvement in flower development, pollination, and fruit formation.

30. Describe the molecular mechanisms of pollen-pistil interaction. Explain the recognition systems and signaling pathways involved in compatible pollination.

31. Explain the evolutionary significance of sexual reproduction in plants. Describe how it contributes to genetic diversity and adaptation.

32. Describe the reproductive strategies of plants in different environments. Explain adaptations for reproduction in aquatic, desert, and alpine conditions.

33. Explain the concept of heterostyly and its role in promoting cross-pollination. Describe the different types and their mechanisms.

34. Describe the development and maturation of pollen grains. Explain the structure of mature pollen and its role in fertilisation.

35. Explain the process of fruit ripening. Describe the physiological and biochemical changes that occur during fruit maturation.

36. Describe the conservation of plant genetic resources through seed banking. Explain the techniques and importance of preserving plant diversity.

37. Explain the impact of climate change on plant reproduction. Describe how changing environmental conditions affect pollination and seed production.

38. Describe the coevolution of flowers and their pollinators. Explain how mutual adaptations have shaped floral diversity and pollinator relationships.

39. Explain the techniques used in modern plant breeding for crop improvement. Describe how understanding of reproduction is applied in developing new varieties.

40. Describe the role of biotechnology in plant reproduction. Explain applications like tissue culture, genetic transformation, and molecular markers.

41. Explain the concept of breeding systems in plants. Describe how different mating patterns affect population genetics and evolution.

42. Describe the mechanisms of hybrid vigor (heterosis) in plants. Explain how cross-pollination contributes to improved traits in offspring.

43. Explain the process of microsporogenesis and microgametogenesis. Describe the development from microspore mother cell to mature pollen grain.

44. Describe the process of megasporogenesis and megagametogenesis. Explain the development from megaspore mother cell to mature embryo sac.

45. Explain the cellular and molecular events during pollen tube growth. Describe the guidance mechanisms that direct the pollen tube to the ovule.

46. Describe the formation and development of endosperm. Explain the different types of endosperm development and their significance.

47. Explain the process of embryogenesis in angiosperms. Describe the stages from zygote to mature embryo formation.

48. Describe the structural and functional adaptations of wind-dispersed seeds and fruits. Explain how these adaptations ensure successful dispersal.

49. Explain the mechanisms of self-incompatibility at the molecular level. Describe the sporophytic and gametophytic systems of incompatibility.

50. Describe the future challenges and opportunities in plant reproductive biology. Explain how modern techniques can address issues in agriculture and conservation.

---

Answer Key

Answer Script: Pollination and Fertilisation

---

Section A: Multiple Choice Questions

1. b) Anther to stigma
2. b) From anther to stigma of the same flower or plant
3. d) Between flowers of different plants of the same species
4. c) Sure method of pollination
5. b) Does not produce new varieties
6. c) New varieties
7. b) Large and brightly colored
8. c) Small and inconspicuous
9. c) Small and inconspicuous
10. b) Presence of either male or female organs
11. b) Maturation of male and female parts at different times
12. b) Flower cannot be fertilized by its own pollen
13. b) Spatial separation of anther and stigma
14. b) Fusion of gametes
15. b) Germinates on the stigma
16. b) Downward to the ovule
17. b) Angiosperms
18. b) Two
19. b) Second male gamete with two polar nuclei
20. c) Endosperm formation
21. c) Ovary
22. c) Embryo and food reserves
23. b) Protect seeds and aid dispersal
24. c) Reproduction
25. b) Sweet scent
26. c) Insects
27. b) Autogamy
28. b) Geitonogamy
29. c) Stamen
30. d) Pistil
31. c) Anther
32. b) Stigma
33. d) Ovary
34. b) Seed
35. b) Fruit
36. b) Megagametophyte
37. c) Triploid
38. b) Diploid
39. c) Ornithophily
40. b) Anemophily
41. a) Entomophily
42. d) Hydrophily
43. b) Cross-pollination
44. b) Only self-pollination
45. c) Pollen grains
46. b) Male gametes
47. c) Nawaschin
48. c) Triploid
49. d) Fruits, wind, and animals
50. a) Fruit formation without fertilisation
51. c) Seed coat
52. c) Endosperm
53. a) Small pore in ovule
54. b) Bottom of ovule
55. b) Inner tissue of ovule
56. c) Seed coat
57. a) Scar on seed
58. a) Seed leaves
59. a) One
60. b) Two
61. b) Shoot system
62. b) Root system
63. b) Below cotyledons
64. b) Above cotyledons
65. b) Growth of seedling from seed
66. b) Cotyledons coming above ground
67. b) Cotyledons remaining underground
68. d) Water, air, and suitable temperature
69. b) Temporary suspension of growth
70. c) Ability to germinate
71. b) Control breeding
72. b) Removing stamens
73. b) Prevent unwanted pollination
74. d) Temporal isolation
75. a) Anthers maturing before stigma
76. b) Stigma maturing before anthers
77. b) Different style lengths
78. b) Fertilisation
79. b) Asexual reproduction through seeds
80. b) Multiple embryos per seed
81. b) Nutrition to embryo
82. b) Food stored in cotyledons
83. b) Food in endosperm
84. b) With endosperm
85. b) Without endosperm
86. b) Fruit wall
87. a) Ovary only
88. b) Parts other than ovary
89. a) Single flower with one ovary
90. b) Single flower with multiple ovaries
91. c) Multiple flowers
92. b) Open when ripe to release seeds
93. b) Do not open when ripe
94. b) Soft and juicy pericarp
95. b) Hard and dry pericarp
96. b) Light seeds with wings
97. b) Fleshy edible fruits
98. b) Light seeds that float
99. b) Some dehiscent fruits
100. b) Seed viability

---

Section B: Short Answer Questions

1. Pollination is the transfer of pollen from a plant's male part to its female part.
2. Self-pollination is the pollen transfer from anther to stigma on the same flower or plant.
3. Cross-pollination is the pollen transfer from an anther on one plant to a stigma on another plant of the same species.
4. Self-pollination is a sure method and preserves parental characters.
5. Self-pollination does not create new varieties.
6. Cross-pollination produces new, more vigorous varieties.
7. Cross-pollination is not a sure method as it depends on external agents.
8. Insect-pollinated flowers are typically large, colorful, and scented.
9. Wind-pollinated flowers are small, inconspicuous, and lack scent.
10. Unisexuality is the condition of a flower having either male or female reproductive organs, but not both.
11. Dichogamy is the maturation of a flower's male and female parts at different times.
12. Self-sterility is the inability of a flower to be fertilized by its own pollen.
13. Herkogamy is the spatial separation of the anther and stigma within a flower.
14. Fertilisation is the fusion of male and female gametes to form a zygote.
15. After pollination, the pollen grain germinates on the stigma and grows a pollen tube towards the ovule.
16. Double fertilisation is a process in angiosperms involving the fusion of the female gametophyte with two male gametes.
17. Triple fusion is the fusion of the second male gamete with two polar nuclei to form the endosperm.
18. A fruit is the mature ovary of a flowering plant that encloses the seed or seeds.
19. A seed is a plant's unit of reproduction, containing an embryo, capable of developing into a new plant.
20. The function of a fruit is to protect the seeds and aid in their dispersal.
21. Seeds contain the embryo and food reserves, ensuring the continuation and propagation of the species.
22. Autogamy is the transfer of pollen from the anther to the stigma of the same flower.
23. Allogamy is another term for cross-pollination.
24. Geitonogamy is the transfer of pollen between different flowers on the same plant.
25. Xenogamy is the transfer of pollen between flowers on different plants of the same species.
26. The stamen is the male reproductive part of a flower.
27. The pistil (or carpel) is the female reproductive part of a flower.
28. Pollen grains are produced in the anther.
29. The stigma is the receptive tip of the pistil, responsible for receiving pollen.
30. Ovules are located inside the ovary.
31. After fertilisation, the ovule becomes the seed.
32. After fertilisation, the ovary becomes the fruit.
33. The embryo sac is the female gametophyte in angiosperms.
34. The endosperm is triploid (3n).
35. The zygote is diploid (2n).
36. Ornithophily is pollination by birds.
37. Anemophily is pollination by wind.
38. Entomophily is pollination by insects.
39. Hydrophily is pollination by water.
40. Cleistogamous flowers are those that do not open and thus only undergo self-pollination.
41. The pollen tube carries the male gametes to the ovule.
42. Double fertilisation was discovered by Nawaschin.
43. Parthenocarpy is the development of fruit without prior fertilisation.
44. The seed coat is the protective outer layer of a seed.
45. The endosperm is the nutritive tissue within the seed that feeds the embryo.
46. The micropyle is a small opening in the surface of an ovule through which the pollen tube may enter.
47. The chalaza is the basal part of the nucellus in an ovule, where the integuments and nucellus are joined.
48. The nucellus is the central part of an ovule, containing the embryo sac.
49. The integuments of the ovule develop into the seed coat.
50. The hilum is the scar on a seed marking the point of attachment to its seed vessel.
51. Cotyledons are the embryonic leaves in seed-bearing plants.
52. Monocots have one cotyledon.
53. Dicots have two cotyledons.
54. The plumule develops into the shoot system of the plant.
55. The radicle develops into the root system of the plant.
56. The hypocotyl is the part of a plant embryo or seedling that lies below the cotyledons.
57. The epicotyl is the region of a seedling stem above the cotyledons.
58. Germination is the process by which a plant grows from a seed.
59. Epigeal germination is where the cotyledons are pushed above the ground.
60. Hypogeal germination is where the cotyledons remain below the ground.
61. Water, air (oxygen), and a suitable temperature are essential for seed germination.
62. Seed dormancy is a state in which seeds are prevented from germinating even under favorable conditions.
63. Seed viability is the ability of a seed's embryo to germinate.
64. Artificial pollination is the manual transfer of pollen from one flower to another by humans.
65. Emasculation is the removal of anthers from a flower to prevent self-pollination.
66. Bagging is the process of covering an emasculated flower to prevent unwanted cross-pollination.
67. Protandry is the condition where the anthers mature before the stigma.
68. Protogyny is the condition where the stigma matures before the anthers.
69. Heterostyly is the occurrence of different style lengths in flowers of the same species.
70. Genetic or chemical incompatibility between the pollen and the stigma prevents fertilisation.
71. Apomixis is the formation of seeds without fertilisation, a form of asexual reproduction.
72. Polyembryony is the phenomenon of two or more embryos developing from a single fertilized egg.
73. The endosperm provides nutrition to the developing embryo.
74. Non-endospermic seeds store food in the cotyledons rather than a persistent endosperm.
75. Endospermic seeds have a persistent endosperm that stores food.
76. Albuminous seeds are another term for endospermic seeds.
77. Ex-albuminous seeds are another term for non-endospermic seeds.
78. The pericarp is the wall of a fruit, which develops from the ovary wall.
79. True fruits develop solely from the ovary.
80. False fruits develop from the ovary along with other floral parts like the thalamus.
81. Simple fruits develop from a single flower with one ovary.
82. Aggregate fruits develop from a single flower with multiple, separate ovaries.
83. Multiple fruits develop from a cluster of flowers (an inflorescence).
84. Dehiscent fruits split open at maturity to release their seeds.
85. Indehiscent fruits do not split open at maturity.
86. Fleshy fruits have a soft, juicy pericarp.
87. Dry fruits have a hard, dry pericarp.
88. Wind-dispersed seeds are typically lightweight and may have wing-like structures.
89. Animal-dispersed seeds are often contained within fleshy, edible fruits or have hooks/barbs.
90. Water-dispersed seeds are buoyant and have waterproof coverings.
91. Explosive dispersal is a mechanism where the fruit bursts open, forcibly ejecting the seeds.
92. The germination percentage of a sample of seeds indicates their viability.
93. Maize (corn) is a wind-pollinated plant.
94. Roses are an example of an insect-pollinated plant.
95. The primary endosperm nucleus is the triploid nucleus formed by triple fusion.
96. The female gametophyte is called the megagametophyte or embryo sac.
97. The male gametophyte is the pollen grain.
98. The synergids within the embryo sac help guide the pollen tube.
99. The outermost layer of a seed is the seed coat or testa.
100. The endosperm or cotyledons are the food storage tissues in seeds.

---

Section C: Short Questions

1. Pollination is the transfer of pollen from anther to stigma. It is crucial as it is the prerequisite for fertilisation, leading to seed and fruit production.
2. Self-pollination occurs within the same flower or plant, ensuring reproduction but limiting genetic diversity. Cross-pollination occurs between different plants, promoting genetic diversity but being less reliable.
3. Two advantages of self-pollination are that it is a certain method and preserves desirable parental traits. Two disadvantages are the lack of new varieties and potentially less vigorous offspring over generations.
4. Two advantages of cross-pollination are the creation of new varieties and the production of more vigorous, adaptable offspring. Two disadvantages are its dependency on external agents and the uncertainty of pollen transfer.
5. Insect-pollinated flowers are typically large, brightly colored, and produce nectar and a sweet scent. These features attract insects to facilitate pollen transfer.
6. Wind-pollinated flowers are usually small, inconspicuous, and lack nectar or scent. They produce large quantities of light, dry pollen to be easily carried by the wind.
7. Unisexuality, where flowers are either male or female, is an adaptation for cross-pollination. This structure makes self-pollination impossible and necessitates the transfer of pollen between different plants.
8. Dichogamy is the maturation of anthers and stigmas at different times. This temporal separation prevents self-pollination by ensuring that when pollen is shed, the stigma is not yet receptive, or vice-versa.
9. Self-sterility is a genetic mechanism where a flower's own pollen is incapable of fertilizing its ovules. This chemical incompatibility prevents self-fertilisation and promotes outbreeding.
10. Herkogamy is the spatial separation of anthers and stigma within a flower, such as the stigma being positioned well above the anthers. This physical barrier makes it difficult for pollen to land on the stigma of the same flower.
11. Fertilisation is the fusion of the male gamete with the female gamete (egg) to form a diploid zygote. Its significance lies in combining genetic material from two parents, initiating the development of a new individual.
12. After successful pollination, the pollen grain on the stigma absorbs moisture and germinates. It then grows a pollen tube down through the style to deliver the male gametes to the ovule for fertilisation.
13. Double fertilisation is a process unique to angiosperms. One male gamete fuses with the egg cell to form the diploid zygote, while the second male gamete fuses with the two polar nuclei to form the triploid endosperm.
14. Triple fusion is the part of double fertilisation where one male gamete fuses with the two polar nuclei in the central cell of the embryo sac. The product of this fusion is the primary endosperm nucleus, which develops into the nutritive endosperm.
15. After fertilisation, the ovary develops into the fruit, and the ovules within the ovary develop into seeds. The zygote develops into the embryo, and the primary endosperm nucleus develops into the endosperm.
16. Fruits protect the enclosed seeds from damage and desiccation. They also play a crucial role in seed dispersal by attracting animals or by having structures that aid wind or water dispersal.
17. Seeds are vital as they contain the embryo, which is the next generation of the plant, along with a food supply. They enable the species to survive unfavorable conditions and to be dispersed to new locations.
18. Autogamy is self-pollination within one flower. Geitonogamy is pollination between different flowers on the same plant (genetically similar to self-pollination). Xenogamy is true cross-pollination between flowers on different plants.
19. The stamen is the male reproductive organ, consisting of a filament (stalk) and an anther. The anther's function is to produce and release pollen grains.
20. The pistil is the female reproductive organ, typically consisting of a stigma, style, and ovary. The stigma receives pollen, the style connects the stigma to the ovary, and the ovary contains the ovules.
21. The anther is part of the stamen that contains microsporangia. Its primary role is to produce and store pollen grains, which contain the male gametes, and release them when mature.
22. The stigma is the receptive tip of the pistil, often sticky or feathery. Its function is to trap pollen grains, providing a surface where they can germinate.
23. Ovules are located inside the ovary. Each ovule contains the female gamete (egg cell) and, after fertilisation, develops into a seed.
24. After fertilisation, the diploid zygote within the ovule develops into an embryo. The integuments of the ovule harden to form the seed coat, and the entire ovule matures into a seed.
25. Following fertilisation, the walls of the ovary thicken and develop into the pericarp, or fruit wall. The entire ovary matures and ripens to become the fruit, enclosing the seed(s).
26. The embryo sac (megagametophyte) is a structure within the ovule of a flowering plant. It typically contains the egg cell, two synergids, a central cell with two polar nuclei, and three antipodal cells.
27. In angiosperms, the main plant body (sporophyte) is diploid (2n). The gametophytes (pollen and embryo sac) are haploid (n). After fertilisation, the zygote is diploid (2n) and the endosperm is triploid (3n).
28. Pollination agents include insects (entomophily), wind (anemophily), water (hydrophily), and birds (ornithophily). Each type corresponds to specific floral adaptations, such as colorful petals for insects or light pollen for wind.
29. Cleistogamous flowers are small, closed flowers that never open. Their advantage is that they ensure self-pollination and seed production even in the absence of pollinators.
30. The pollen tube, carrying two male gametes, grows from the stigma, through the style, and enters the ovule, typically through the micropyle. It is guided by chemical signals from the synergids within the embryo sac.
31. The discovery of double fertilisation by Sergei Nawaschin in 1898 was significant because it revealed a complex reproductive process unique to flowering plants. It explained the formation of both the embryo and the nutritive endosperm.
32. Parthenocarpy is the natural or artificial production of fruit without fertilisation of ovules, which makes the fruit seedless. A common example is the banana.
33. The seed coat, which develops from the ovule's integuments, provides a protective barrier for the embryo and endosperm inside. It guards against physical damage, desiccation, and pathogens.
34. The endosperm is a nutritive tissue that provides essential food reserves, such as starch, oils, and proteins, for the developing embryo. This nourishment supports the embryo during germination until it can photosynthesize.
35. The micropyle is a small pore in the integuments of the ovule. Its primary function is to allow the pollen tube to enter the ovule for fertilisation, and it can also serve as a channel for water uptake during germination.
36. The chalaza is the base of the ovule, where the nucellus and integuments are attached to the stalk (funicle). It is a region through which nutrients pass from the plant into the ovule.
37. The nucellus is the tissue that makes up the main body of the ovule, surrounding the embryo sac. It provides nutrition to the developing embryo sac.
38. The integuments are the outer layers of the ovule. After fertilisation, they develop into the seed coat (testa and tegmen), which protects the seed.
39. The hilum is a scar on the seed coat that marks the point where the seed was attached to the fruit wall via the funicle. It is visible on seeds like beans.
40. Cotyledons are embryonic leaves within the seed. In some plants (non-endospermic), they absorb the food reserves from the endosperm and become the primary storage tissue, while in others they help transfer nutrients to the embryo during germination.
41. Monocot seeds have a single cotyledon, which is often small and called a scutellum. Dicot seeds have two cotyledons, which are typically large and fleshy as they store food.
42. During germination, the plumule is the part of the embryo that develops into the shoot, including the stem and leaves. The radicle is the embryonic root that develops into the primary root of the new plant.
43. The hypocotyl is the portion of the embryonic axis below the point of cotyledon attachment. The epicotyl is the portion of the embryonic axis above the cotyledon attachment.
44. Seed germination is the sprouting of a seedling from a seed. It requires specific conditions: adequate water for metabolic activation, oxygen for respiration, and a suitable temperature for enzymatic activity.
45. In epigeal germination, the hypocotyl elongates and pulls the cotyledons above the ground. In hypogeal germination, the epicotyl elongates while the cotyledons remain below the soil surface.
46. The three essential factors for successful germination are water, oxygen, and optimal temperature. Some seeds may also require light or a period of dormancy to be broken.
47. Seed dormancy is a state of suspended growth, which prevents germination even when conditions are favorable. It is ecologically significant as it allows seeds to wait for the most opportune season to grow, increasing survival chances.
48. Seed viability refers to the capacity of a seed to germinate and produce a normal seedling. It can be tested by direct germination tests or biochemical tests like the tetrazolium test, which stains living tissues red.
49. Artificial pollination is the process where humans deliberately transfer pollen from a selected male parent to the stigma of a selected female parent. This technique is fundamental in plant breeding to create new varieties with desired traits.
50. Emasculation is the surgical removal of stamens or anthers from a bisexual flower before they mature. Its purpose is to prevent self-pollination in flowers that are being used for controlled cross-breeding experiments.
51. The bagging technique involves enclosing an emasculated flower in a bag, usually made of paper or plastic. This prevents contamination from foreign, unwanted pollen, ensuring that the flower is only pollinated by the desired source.
52. Protandry is a condition where the male parts (anthers) of a flower mature and release pollen before the female parts (stigma) are receptive. Protogyny is the opposite, where the stigma matures before the anthers.
53. Heterostyly is a genetic polymorphism where a plant species has two or three different forms of flowers with different style and stamen lengths. This structural difference promotes cross-pollination between different forms and prevents self-pollination.
54. Incompatibility is a genetic mechanism that prevents self-fertilisation. It involves a biochemical recognition system that allows the pistil to reject its own pollen or pollen from closely related individuals.
55. Apomixis is a form of asexual reproduction where seeds are produced without fertilisation. This allows for the creation of clonal offspring that are genetically identical to the parent plant, preserving desirable traits.
56. Polyembryony is the condition where more than one embryo is present within a single seed. It can occur naturally in species like citrus fruits and mangoes, where nucellar cells develop into additional embryos.
57. Endospermic seeds retain the endosperm as the primary food source. In non-endospermic seeds, the developing embryo absorbs all the nutrients from the endosperm, which are then stored in the fleshy cotyledons.
58. Albuminous seeds are those that possess a persistent endosperm at maturity (e.g., castor bean, maize). Ex-albuminous seeds lack a persistent endosperm because it has been consumed and stored in the cotyledons (e.g., pea, bean).
59. The pericarp is the wall of the fruit, which develops from the ovary wall after fertilisation. It is typically divided into three layers: the outer exocarp, middle mesocarp, and inner endocarp, which vary in texture and thickness.
60. True fruits, like mangoes and peas, develop exclusively from the ovary of a flower. False fruits, like apples and strawberries, develop from the ovary plus other floral parts such as the receptacle or thalamus.
61. Fruits can be classified as simple (from one ovary in one flower, e.g., cherry), aggregate (from multiple ovaries in one flower, e.g., raspberry), or multiple (from an entire inflorescence, e.g., pineapple).
62. Dehiscent fruits (e.g., pea pod) are dry fruits that split open along predefined lines at maturity to release their seeds. Indehiscent fruits (e.g., sunflower seed) are dry fruits that do not split open; the seed is dispersed along with the fruit.
63. Fleshy fruits, like berries and drupes, have a pericarp that is soft and pulpy at maturity. Dry fruits, like nuts and legumes, have a pericarp that is dry and hard when mature.
64. Seeds adapted for wind dispersal are typically very small, light, and may possess structures like wings (e.g., maple) or plumes (e.g., dandelion). These features allow them to be carried long distances by air currents.
65. Animal-mediated dispersal often involves animals eating fleshy fruits and excreting the seeds elsewhere (endozoochory). Alternatively, seeds may have hooks or barbs (e.g., burdock) that attach to an animal's fur or feathers (epizoochory).
66. Seeds adapted for water dispersal, like those of the coconut palm, are buoyant and have a waterproof pericarp. This allows them to float on water currents for extended periods to reach new coastlines.
67. Explosive dispersal is a mechanical method where the drying fruit creates tension that causes it to burst open suddenly. This forceful rupture flings the seeds away from the parent plant, as seen in plants like jewelweed or gorse.
68. Seed germination percentage is determined by planting a known number of seeds (e.g., 100) under optimal conditions. After a set period, the number of seeds that have successfully germinated is counted and expressed as a percentage of the total.
69. Insects are generally the most efficient and targeted pollination agents for the plants they co-evolved with. Wind pollination is less efficient and random, requiring massive pollen production, while water pollination is rare and limited to aquatic plants.
70. Flower structure is closely linked to its pollination method. For example, brightly colored, scented flowers with nectar attract insects, while inconspicuous, unscented flowers with feathery stigmas are typical of wind-pollinated plants.
71. The primary evolutionary advantage of cross-pollination is the promotion of genetic diversity. The mixing of genes from different individuals can create new combinations of traits, allowing populations to adapt to changing environments.
72. Temporal isolation, or allochrony, is when two species reproduce at different times of the day, season, or year. This acts as a pre-zygotic barrier that prevents them from interbreeding, even if they live in the same area.
73. Spatial adaptations like herkogamy (physical separation of anther and stigma) and heterostyly (different style lengths) promote cross-pollination. These physical arrangements make it difficult or impossible for self-pollination to occur.
74. Genetic diversity is crucial for the long-term survival of plant populations. It provides the raw material for natural selection, enabling populations to adapt to new pests, diseases, and environmental challenges.
75. Pollen tube growth is a guided process involving chemical signals (chemoattractants) released by the synergid cells within the embryo sac. These signals create a gradient that the pollen tube follows through the style to reach the ovule.
76. During fertilisation, the pollen tube releases two male gametes into the embryo sac. One gamete fuses with the egg cell nucleus (syngamy) to form the zygote, and the other fuses with the two polar nuclei (triple fusion) to form the endosperm nucleus.
77. Endosperm formation begins with the division of the primary endosperm nucleus. It can be of three types: nuclear (free nuclear divisions), cellular (divisions are followed by wall formation), or helobial (intermediate between the two).
78. After fertilisation, the diploid zygote undergoes a series of mitotic divisions to develop into an embryo. This process, called embryogenesis, establishes the basic body plan of the plant, including the cotyledons, plumule, and radicle.
79. Seed maturation involves the accumulation of food reserves (starch, proteins, lipids), desiccation (loss of water), and the hardening of the seed coat. The embryo enters a state of metabolic dormancy.
80. Environmental triggers for germination include water imbibition, favorable temperatures, and oxygen availability. Some seeds also require specific triggers like light, cold stratification (a period of cold), or scarification (breakdown of the seed coat).
81. During germination, the seed rapidly absorbs water, which rehydrates tissues and activates enzymes. These enzymes break down stored food reserves (endosperm or cotyledons) to provide energy and building blocks for the growing embryo.
82. Plant hormones play key roles in germination. Gibberellins promote the breakdown of stored food and embryo growth, while abscisic acid (ABA) generally enforces dormancy. The balance between these hormones controls the onset of germination.
83. Desert plants often have seeds with thick, tough coats and long dormancy periods to survive harsh conditions. They may only germinate after significant rainfall, and the plants themselves often have rapid life cycles to reproduce quickly.
84. Aquatic plants show diverse reproductive strategies. Some have flowers that emerge above water for wind or insect pollination, while others, like Vallisneria, release pollen that floats on the water surface to reach female flowers.
85. The coevolution of flowers and pollinators is a classic example of mutualism. Flowers have evolved specific shapes, colors, and scents to attract particular pollinators, while those pollinators have evolved specialized mouthparts or behaviors to access the nectar and pollen.
86. Controlled pollination is economically important for producing hybrid seeds with superior qualities (e.g., higher yield, disease resistance) in crops like corn and rice. It is also essential for producing fruits and seeds in many horticultural species.
87. Seed banks are facilities that store seeds to preserve genetic diversity for the future. By keeping seeds in low-temperature, low-humidity conditions, their viability can be maintained for decades or centuries, safeguarding against extinction and providing resources for future breeding.
88. Fruits are a vital food source for many animals, forming a key part of ecosystem food webs. The dispersal of seeds by these animals (frugivores) is critical for forest regeneration and maintaining plant population structures.
89. Understanding pollination is vital in agriculture for managing crops that depend on pollinators like bees. Farmers may introduce hives, plant pollinator-friendly strips, or use artificial pollination to ensure adequate fruit and seed set, maximizing crop yield.
90. Environmental changes, such as climate change and habitat loss, threaten pollinators and disrupt the synchrony between plants and their pollinators. This can lead to pollination failure, reduced seed production, and long-term declines in plant populations.
91. Self-incompatibility is controlled by a genetic locus (S-locus). In gametophytic incompatibility, the S-allele of the pollen must differ from the S-alleles of the pistil. In sporophytic incompatibility, the pollen is rejected if it shares an S-allele with the diploid parent plant that produced it.
92. Flower development is controlled by a set of homeotic genes, as described by the ABC model. Different combinations of these genes determine the identity of the floral organs: sepals, petals, stamens, and carpels.
93. Fruit ripening is a complex process involving hormonal changes, primarily an increase in ethylene production. This triggers softening of the cell walls, conversion of starches to sugars, and the production of pigments and aromatic compounds.
94. Dormancy mechanisms are varied. Physical dormancy involves an impermeable seed coat that prevents water uptake. Physiological dormancy involves inhibitory chemicals within the embryo that must be leached out or broken down over time.
95. Factors affecting seed longevity include the species' genetics, initial seed quality, and storage conditions. Low temperature and low relative humidity are the most critical factors for extending the lifespan of stored seeds.
96. Seed dispersal is crucial for plant distribution as it allows species to colonize new habitats, escape competition with the parent plant, and avoid pests and pathogens that may be concentrated near the parent.
97. There is often a trade-off between seed size and dispersal method. Small, lightweight seeds are well-suited for wind dispersal, while large, nutrient-rich seeds are often dispersed by animals that are attracted to the reward of an associated fruit.
98. Pollination is a keystone process in most terrestrial ecosystems. Its conservation is vital for maintaining biodiversity, as the reproduction of a vast majority of flowering plants, which form the base of the food web, depends on it.
99. Plants face challenges such as pollinator decline due to habitat loss and pesticide use, competition for pollinators, and the effects of climate change disrupting the timing of flowering. These challenges can lead to reduced reproductive success.
100. Future prospects include using genetic engineering to create crops that are self-pollinating or have improved pollinator attraction. Cryopreservation of pollen and seeds, along with advanced in-vitro fertilization techniques, will also play a role in conservation and breeding.

---

Section D: Long Answer Questions

1. Pollination Process: Pollination is the fundamental process of transferring pollen grains from the male anther to the female stigma of a flower. There are two main types: self-pollination and cross-pollination. Self-pollination (autogamy) occurs when pollen fertilizes the same flower or another flower on the same plant, which ensures reproduction but limits genetic variation. Cross-pollination (allogamy) involves the transfer of pollen between different plants of the same species, facilitated by agents like insects, wind, water, or birds. This method is significant as it introduces genetic variation, leading to more resilient and adaptable offspring.

2. Self vs. Cross-Pollination: Self-pollination involves a single parent, preserving its genetic traits. Its advantages are reliability (no external agent needed) and preservation of well-adapted genotypes. The main disadvantages are a lack of genetic diversity, which can lead to an accumulation of harmful mutations and reduced vigor (inbreeding depression). Cross-pollination involves two parents, promoting genetic recombination. Its advantages include increased genetic diversity, hybrid vigor, and enhanced adaptability to changing environments. Its disadvantages are its reliance on external pollinators and the uncertainty of successful pollen transfer. Evolutionarily, while self-pollination is a safe bet, cross-pollination is the driver of adaptation and long-term species survival.

3. Pollination Agents and Adaptations: The primary agents of pollination are insects, wind, water, and animals.

   • Insect-pollinated (Entomophilous) flowers are adapted with large, colorful petals, sweet scents, and nectar to attract insects like bees and butterflies.
   • Wind-pollinated (Anemophilous) flowers (e.g., grasses, maize) are typically small, inconspicuous, unscented, and produce vast amounts of light, non-sticky pollen to be easily carried by air currents. Their stigmas are often large and feathery to effectively trap airborne pollen.
   • Water-pollinated (Hydrophilous) flowers, found in aquatic plants, have small, inconspicuous flowers where pollen is released into the water.
   • Animal-pollinated flowers, such as those visited by birds or bats, are often large, robust, and produce copious nectar, with colors (like red for birds) or scents (musky for bats) that attract these specific pollinators.

4. Adaptations for Cross-Pollination: Plants have evolved several mechanisms to promote cross-pollination and prevent self-pollination.

   • Unisexuality: Flowers are either male or female (dioecy), making self-pollination impossible.
   • Dichogamy: Anthers and stigmas mature at different times. In protandry, anthers mature first; in protogyny, the stigma matures first.
   • Herkogamy: There is a physical or spatial separation between the anthers and stigma within a flower, preventing self-pollination.
   • Self-sterility/Incompatibility: A genetic mechanism where the pistil rejects pollen from the same flower or plant, preventing fertilization. These adaptations are crucial for ensuring genetic outcrossing and maintaining the health and diversity of the plant population.

5. Fertilisation in Angiosperms: After a compatible pollen grain lands on the stigma, it germinates, forming a pollen tube. This tube grows down the style, guided by chemical signals, and enters the ovule through the micropyle. The pollen tube carries two male gametes. Upon reaching the embryo sac, the tube ruptures, releasing the gametes. One male gamete fuses with the egg cell to form the diploid (2n) zygote, which will develop into the embryo. This fusion of gametes is the core of fertilisation, leading to the development of a new individual.

6. Double Fertilisation: Double fertilisation is a complex process unique to angiosperms. It involves two separate fusion events within the embryo sac. After the pollen tube releases two male gametes, the first male gamete fuses with the egg cell to form the diploid zygote (syngamy). The second male gamete migrates to the central cell and fuses with the two polar nuclei (triple fusion). This second fusion event results in the formation of a triploid (3n) primary endosperm nucleus, which then develops into the endosperm, a nutritive tissue that nourishes the developing embryo.

7. Fruit and Seed Development: Following successful double fertilisation, the ovule develops into a seed and the ovary develops into a fruit. The zygote divides and grows into the embryo. The primary endosperm nucleus develops into the endosperm, which provides food. The integuments of the ovule harden to become the protective seed coat. Simultaneously, the ovary wall (pericarp) begins to grow and differentiate, accumulating sugars, water, and other substances to become the fruit, which encloses and protects the developing seed(s).

8. Significance of Fruits and Seeds: Fruits are significant as they provide protection to the developing seeds against environmental hazards and predators. More importantly, they are the primary means of seed dispersal, using adaptations to attract animals or to facilitate transport by wind or water, moving the next generation to new locations. Seeds are the units of reproduction and survival; they contain the dormant embryo and a stored food supply. This allows the plant to endure unfavorable conditions and ensures the nourishment of the young seedling upon germination, continuing the species' life cycle.

9. Structure of Angiosperm Ovule: A typical angiosperm ovule is attached to the ovary wall by a stalk called the funicle. The main body of the ovule consists of a mass of tissue called the nucellus, which is enclosed by one or two protective layers called integuments. The integuments leave a small opening called the micropyle. Within the nucellus lies the embryo sac (female gametophyte). The base of the ovule where the funicle and integuments attach is the chalaza. After fertilisation, the ovule matures into the seed, with the integuments forming the seed coat and the nucellus often being consumed by the developing embryo.

10. Embryo Sac Structure and Development: The embryo sac, or megagametophyte, is the female gametophyte of an angiosperm. It develops within the nucellus of the ovule from a functional megaspore. A mature embryo sac is typically a seven-celled, eight-nucleate structure. It contains one egg cell and two synergid cells at the micropylar end, three antipodal cells at the chalazal end, and a large central cell containing two polar nuclei. The embryo sac's role is central to fertilisation: the egg cell is fertilized to become the zygote, and the central cell is fertilized to become the endosperm.

11. Pollination Types (Autogamy, Geitonogamy, Xenogamy): These terms classify pollination based on the source and destination of the pollen.

    • Autogamy: Self-pollination where pollen from an anther lands on the stigma of the same flower. It ensures seed set but offers no genetic variation.
    • Geitonogamy: Pollen is transferred between different flowers on the same plant. Genetically it is identical to autogamy but ecologically it is cross-pollination as it may involve a pollinator.
    • Xenogamy: True cross-pollination where pollen is transferred between flowers on different plants of the same species. This is biologically significant as it is the only type that brings about genetic recombination and variation.

12. Insect Pollination Adaptations & Coevolution: Flowers adapted for insect pollination (entomophily) have co-evolved with their pollinators. They possess features like large, conspicuous, brightly colored petals to be visually attractive; sweet scents to signal their presence; and nectar as a food reward. The relationship is mutualistic: the plant gets pollinated, and the insect gets food. This has led to specialization, where the shape of a flower (e.g., a long tube) matches the mouthparts of its specific pollinator (e.g., a moth with a long proboscis).

13. Wind Pollination Adaptations: Flowers adapted for wind pollination (anemophily) prioritize efficiency over attraction. They are typically small, inconspicuous (often green or brown), and lack petals, scent, and nectar. They produce enormous quantities of pollen that is lightweight, dry, and non-sticky to travel easily on wind currents. The stigmas are often large, feathery, and exposed to effectively trap the airborne pollen, maximizing the chances of successful, albeit random, pollination.

14. Dichogamy: Dichogamy is the temporal separation of maturation of the male (anther) and female (stigma) parts of a flower to prevent autogamy. There are two types:

    • Protandry: The anthers mature and release pollen before the stigma of the same flower becomes receptive. This is more common.
    • Protogyny: The stigma becomes receptive before the anthers mature and shed their pollen. By ensuring the reproductive parts are not active at the same time, dichogamy forces the flower to participate in cross-pollination.

15. Self-Incompatibility Mechanisms: Self-incompatibility (SI) is a widespread genetic mechanism in flowering plants that prevents self-fertilisation and promotes outcrossing. It is controlled by a single locus (the S-locus) with multiple alleles. It functions as a biochemical recognition system; if the pollen grain carries an S-allele that matches one of the alleles in the pistil, the pollen germination or pollen tube growth is arrested. This rejection of "self" pollen ensures that only genetically different pollen can achieve fertilisation, thus maintaining genetic diversity.

16. Artificial Pollination Techniques: In plant breeding, artificial pollination is used to control parentage and create hybrids with desired traits. The process involves:

    • Emasculation: The removal of anthers from a bisexual flower before they mature to prevent any chance of self-pollination.
    • Bagging: The emasculated flower is immediately covered with a bag (usually paper) to prevent contamination by foreign or unwanted pollen.
    • Artificial Pollination: When the stigma of the bagged flower becomes receptive, pollen from a desired male parent is manually dusted onto it, and the flower is re-bagged until fruit development begins.

17. Seed Structure and Composition: A mature seed consists of three main parts.

    • Embryo: The young, diploid (2n) plantlet that develops from the zygote. It has a radicle (embryonic root), a plumule (embryonic shoot), and one or two cotyledons (seed leaves).
    • Endosperm: A nutritive tissue (usually triploid, 3n) that provides food for the embryo. In some seeds it persists, while in others it is absorbed by the cotyledons.
    • Seed Coat: A tough, protective outer layer derived from the integuments of the ovule. It guards the embryo against desiccation and mechanical injury.

18. Endospermic vs. Non-endospermic Seeds: The classification is based on whether the endosperm persists in the mature seed.

    • Endospermic (Albuminous) Seeds: In these seeds (e.g., maize, castor bean, wheat), the endosperm is not fully consumed by the embryo during development and remains as the primary food storage tissue. The cotyledons are often thin and papery.
    • Non-endospermic (Ex-albuminous) Seeds: In these seeds (e.g., pea, bean, gram), the endosperm is completely absorbed by the developing embryo. The food reserves are then stored in the large, fleshy cotyledons.

19. Seed Germination Process: Germination is the resumption of metabolic activity and growth by a mature seed embryo. The process begins with imbibition, the absorption of water, which rehydrates the cells. This activates enzymes that break down stored food reserves (starches, proteins, lipids) in the endosperm or cotyledons into usable energy. The radicle (embryonic root) is typically the first part to emerge, anchoring the seedling and absorbing water, followed by the emergence of the plumule (embryonic shoot). This entire process is dependent on favorable external conditions.

20. Epigeal vs. Hypogeal Germination: This classification is based on the fate of the cotyledons during germination.

    • Epigeal Germination: The hypocotyl (region below the cotyledons) elongates rapidly, forming a hook that pushes the cotyledons and plumule up above the soil surface. The cotyledons often turn green and photosynthesize for a short time (e.g., bean, castor).
    • Hypogeal Germination: The epicotyl (region above the cotyledons) elongates, while the cotyledons remain below the ground. The plumule grows up through the soil. This is common in monocots and some dicots (e.g., pea, maize). The advantage is that the food store is protected underground.

21. Environmental Factors for Germination: Several external factors are critical for a seed to germinate.

    • Water (Moisture): Essential for imbibition, activating enzymes, and transporting dissolved food to the embryo.
    • Oxygen: Required for aerobic respiration, which provides the energy needed for cell division and growth.
    • Suitable Temperature: Each species has an optimal temperature range for the enzymes involved in germination to function effectively.
    • Light: Some seeds (photo-blastic) require light to germinate, while for others, light can be inhibitory.

22. Seed Dormancy: Seed dormancy is a state in which a viable seed is prevented from germinating, even when the environmental conditions are favorable. This can be caused by a hard, impermeable seed coat (physical dormancy) or by chemical inhibitors within the embryo (physiological dormancy). Ecologically, dormancy is a crucial survival strategy. It staggers germination over time and ensures that seeds only sprout when conditions are most likely to support seedling survival (e.g., after a winter cold period or after sufficient rainfall).

23. Seed Dispersal Methods: Seed dispersal is the movement of seeds away from the parent plant, which is vital for colonizing new areas and reducing competition. Adaptations correspond to the dispersal agent:

    • Wind (Anemochory): Seeds are small, light, or have wing/plume structures (e.g., dandelion, maple).
    • Water (Hydrochory): Seeds have buoyant, waterproof coverings (e.g., coconut).
    • Animals (Zoochory): Seeds are enclosed in fleshy, edible fruits to be eaten and excreted, or have hooks/barbs to attach to fur (e.g., berries, burrs).
    • Explosive (Autochory): The fruit dehisces violently, flinging seeds away (e.g., jewelweed).

24. Fruit Classification: Fruits are classified based on their developmental origin.

    • Simple Fruits: Develop from a single flower with a single, simple or compound ovary (e.g., cherry, pea pod). They can be fleshy or dry.
    • Aggregate Fruits: Develop from a single flower that has multiple separate carpels (ovaries). Each ovary forms a small "fruitlet," and they mature into a single unit on a common receptacle (e.g., raspberry, strawberry).
    • Multiple Fruits: Develop from the fused ovaries of an entire inflorescence (a cluster of flowers). As the fruits grow, they merge into a single, larger structure (e.g., pineapple, fig).

25. Dehiscent vs. Indehiscent Fruits: This classification applies to dry fruits and is based on whether they open to release their seeds.

    • Dehiscent Fruits: The pericarp (fruit wall) splits open along sutures at maturity to release the seeds. Examples include legumes (pea pods), capsules (poppy), and follicles (milkweed). This is a form of active seed dispersal.
    • Indehiscent Fruits: The pericarp does not split open at maturity. The seed is dispersed while still enclosed within the fruit. Examples include achenes (sunflower), nuts (acorn), and caryopses (wheat).

26. Importance of Pollination: Pollination is a keystone ecological process with immense economic importance.

    • Ecologically: It is essential for the reproduction of over 85% of the world's flowering plants. These plants form the base of most terrestrial ecosystems, providing food and habitat for countless other species. Pollination sustains biodiversity.
    • Economically: A vast number of agricultural crops—including fruits, vegetables, nuts, and seeds—are dependent on animal pollinators, especially bees. Pollination services are critical for global food security and contribute billions of dollars to the world economy annually.

27. Apomixis: Apomixis is a form of asexual reproduction that mimics sexual reproduction by producing seeds without fertilisation. The embryo develops from a diploid cell in the ovule (e.g., a nucellar cell or an unreduced diploid egg). The resulting seed is genetically identical to the parent plant. Its significance in agriculture is immense, as it allows for the fixation and propagation of desirable hybrid traits (like hybrid vigor) through generations without the genetic segregation that occurs in sexual reproduction.

28. Polyembryony: Polyembryony is the phenomenon of having more than one embryo in a single seed. It can arise from the fertilisation of multiple egg cells, the cleavage of a single zygote, or the development of embryos from other cells in the ovule (like synergids or nucellar cells). It occurs commonly in citrus and mango. Its significance is in horticulture for producing multiple seedlings from one seed and in creating nucellar seedlings that are true-to-type and virus-free.

29. Plant Hormones in Reproduction: Plant hormones (phytohormones) regulate nearly all aspects of reproduction.

    • Auxins are involved in flower initiation and fruit development.
    • Gibberellins promote flowering (bolting), pollen tube growth, and fruit set. They are also critical for breaking seed dormancy and promoting germination.
    • Cytokinins stimulate cell division and are involved in fruit and embryo development.
    • Ethylene is famously known for its role in inducing fruit ripening.
    • Abscisic Acid (ABA) generally acts as an inhibitor, promoting seed dormancy and responding to stress.

30. Pollen-Pistil Interaction: This is a critical dialogue between the pollen grain and the pistil that determines compatibility. After landing on the stigma, the pollen is hydrated, and recognition occurs through a series of chemical signals involving proteins and lipids on both surfaces. In a compatible interaction, the pollen germinates and the pollen tube grows through the style, nourished and guided by the pistil's tissues. In an incompatible interaction (as in self-incompatibility), this process is blocked, preventing fertilisation.

31. Evolutionary Significance of Sexual Reproduction: The primary evolutionary significance of sexual reproduction in plants is the generation of genetic diversity. The fusion of gametes from two different parents (cross-pollination) and the process of meiosis create new combinations of alleles in the offspring. This genetic variation is the raw material upon which natural selection acts. It allows plant populations to adapt to changing environmental conditions, new diseases, and pests, ensuring the long-term survival and evolution of the species.

32. Reproductive Strategies in Different Environments:

    • Aquatic Plants: May have flowers above water for insect/wind pollination or specialized mechanisms for water pollination. Seeds are often adapted to float.
    • Desert Plants (Xerophytes): Often have rapid life cycles (ephemerals) that are completed after rare rainfall. Seeds have long dormancy to survive extended droughts. Pollination is often by specialized insects or birds.
    • Alpine Plants: Must reproduce in a short growing season. They often have brightly colored flowers to attract pollinators in a harsh environment and may rely on self-pollination as a backup.

33. Heterostyly: Heterostyly is a unique genetic polymorphism that promotes cross-pollination. A species with heterostyly has two (distyly) or three (tristyly) forms of flowers, differing in the lengths of their styles and stamens. For example, in a distylous species, one form has a long style and short stamens ("pin" flower), and the other has a short style and long stamens ("thrum" flower). Effective pollination usually only occurs between different forms (e.g., pollen from a thrum flower's anthers is best suited for a pin flower's stigma), thus enforcing outcrossing.

34. Pollen Grain Development: A pollen grain (microgametophyte) develops within the anther from a diploid microspore mother cell. This cell undergoes meiosis to produce four haploid microspores. Each microspore then develops into a pollen grain through mitosis. A mature pollen grain typically has a two-layered wall (outer exine, inner intine) and contains two cells: a large vegetative cell (which forms the pollen tube) and a smaller generative cell (which divides to form the two male gametes).

35. Fruit Ripening Process: Fruit ripening is a genetically programmed process that transforms a mature but unripe fruit into an edible one. It involves a cascade of physiological and biochemical changes, often triggered by the hormone ethylene. These changes include the breakdown of chlorophyll and synthesis of pigments (color change), the enzymatic conversion of starches and acids into sugars (sweetening), and the softening of the fruit wall due to the degradation of pectin. These changes serve to attract animals for seed dispersal.

36. Seed Banking: Seed banking is a method of ex-situ conservation where seeds are stored under controlled, low-temperature and low-humidity conditions to preserve plant genetic diversity. By slowing down metabolic processes, seed viability can be maintained for hundreds or even thousands of years. Seed banks act as a crucial insurance policy against the extinction of plant species in the wild and provide a valuable genetic resource for future research, habitat restoration, and crop improvement.

37. Climate Change Impact on Reproduction: Climate change poses a significant threat to plant reproduction. Rising temperatures can cause a phenological mismatch, where plants flower earlier than their pollinators emerge, leading to pollination failure. Changes in rainfall patterns can affect flowering and seed germination. Increased stress from drought or heat can reduce plant vigor, leading to lower flower, fruit, and seed production, ultimately threatening both wild plant populations and agricultural yields.

38. Coevolution of Flowers and Pollinators: Coevolution is the process of reciprocal evolutionary change between interacting species. The relationship between flowers and their pollinators is a classic example. Flowers have evolved specific colors, shapes, and scents to attract particular pollinators, while the pollinators have evolved complementary mouthparts, sensory abilities, and behaviors to efficiently exploit the floral resources (nectar/pollen). This has led to incredible diversity and specialization, such as the long beaks of hummingbirds matching the long tubular flowers they pollinate.

39. Modern Plant Breeding Techniques: Understanding plant reproduction is fundamental to modern breeding. Techniques like hybridization (controlled cross-pollination between genetically different parents) are used to create new crop varieties with hybrid vigor (heterosis), leading to higher yields and better performance. Knowledge of self-incompatibility and male sterility is exploited to produce hybrid seeds efficiently. Mutation breeding and polyploidy breeding are other techniques that manipulate plant genetics to achieve desired agricultural traits.

40. Biotechnology in Plant Reproduction: Biotechnology offers powerful tools to manipulate plant reproduction. Tissue culture allows for the rapid clonal propagation of plants (micropropagation). Genetic transformation enables the introduction of specific genes for traits like pest resistance or herbicide tolerance. Molecular markers are used to accelerate breeding programs by allowing breeders to select for desired genes without having to wait for the plant to mature (marker-assisted selection).

41. Breeding Systems in Plants: A plant's breeding system describes its method of mating. This ranges on a spectrum from complete outcrossing (obligate cross-pollination) to complete selfing (obligate self-pollination). The specific system (e.g., dioecy, self-incompatibility, cleistogamy) has profound effects on the genetic structure of its populations. Outcrossing maintains high genetic diversity within a population, while selfing leads to highly homozygous individuals and genetically uniform populations.

42. Hybrid Vigor (Heterosis): Hybrid vigor is the phenomenon where hybrid offspring resulting from a cross between two genetically distinct parents exhibit superior qualities (such as increased size, growth rate, or yield) compared to either parent. This is a direct benefit of cross-pollination. The exact genetic cause is complex but is related to the masking of deleterious recessive alleles and the creation of favorable dominant allele combinations in the hybrid offspring.

43. Microsporogenesis and Microgametogenesis: This two-stage process describes the formation of male gametes.

    • Microsporogenesis: The formation of microspores. Inside the anther, diploid microspore mother cells undergo meiosis to produce four haploid microspores.
    • Microgametogenesis: The development of the microspore into the mature pollen grain (microgametophyte). The microspore nucleus divides mitotically to form a vegetative cell and a generative cell. The generative cell will later divide again to form the two male gametes.

44. Megasporogenesis and Megagametogenesis: This two-stage process describes the formation of the female gametophyte.

    • Megasporogenesis: The formation of the megaspore. Inside the ovule, a single diploid megaspore mother cell undergoes meiosis to produce four haploid megaspores, of which typically only one survives.
    • Megagametogenesis: The development of the functional megaspore into the mature embryo sac (megagametophyte). The megaspore nucleus undergoes three rounds of mitosis without cell division, resulting in an eight-nucleate cell that then cellularizes into the typical seven-celled embryo sac.

45. Pollen Tube Growth: The growth of the pollen tube is a remarkable example of polarized cell growth. It is guided from the stigma to the ovule by a gradient of chemical signals (chemoattractants), particularly calcium ions and small proteins, secreted by the synergid cells of the embryo sac. The tube extends rapidly, transporting the two male gametes through the style in a process that is crucial for delivering the sperm cells for double fertilisation.

46. Endosperm Formation and Types: The endosperm is the nutritive tissue formed from the primary endosperm nucleus after triple fusion. Its development can occur in three main ways:

    • Nuclear Type: The primary nucleus undergoes repeated free-nuclear divisions without wall formation, creating a liquid endosperm (e.g., coconut water). Walls form later. This is the most common type.
    • Cellular Type: Each nuclear division is immediately followed by cell wall formation (e.g., Petunia).
    • Helobial Type: An intermediate type where the first division is cellular, creating two chambers, after which development is free-nuclear in each chamber.

47. Embryogenesis in Angiosperms: Embryogenesis is the process of the development of the zygote into a mature embryo. Following fertilisation, the zygote undergoes a series of programmed mitotic divisions. It first divides into a terminal cell (which forms the embryo proper) and a basal cell (which forms the suspensor). The embryo proper then passes through distinct stages—globular, heart-shaped, and torpedo-shaped—as the cotyledons, shoot apex (plumule), and root apex (radicle) are established, forming the basic body plan of the plant.

48. Adaptations of Wind-Dispersed Seeds/Fruits: Fruits and seeds dispersed by wind show clear structural adaptations to maximize air time and distance traveled. Common adaptations include being very small and lightweight, like dust (e.g., orchids), or possessing specialized structures like wings (samaras of maple or ash) that create lift, or feathery plumes (pappus of dandelion or milkweed) that act like parachutes to catch the wind. These features ensure that offspring are scattered far from the parent plant.

49. Molecular Self-Incompatibility: Self-incompatibility (SI) is controlled at the molecular level by genes at the S-locus, which code for recognition proteins.

    • Gametophytic SI: The incompatibility is determined by the haploid genotype of the pollen itself. S-proteins (RNases) in the style recognize and degrade the ribosomal RNA of "self" pollen tubes, halting their growth.
    • Sporophytic SI: The incompatibility is determined by the diploid genotype of the parent plant that produced the pollen. Recognition occurs on the stigma surface, involving interactions between proteins in the pollen coat and receptors on the stigma, which triggers a signaling cascade that prevents "self" pollen from hydrating and germinating.

50. Future Challenges and Opportunities in Plant Reproductive Biology: The primary challenge is ensuring global food security in the face of climate change and a growing population. This involves overcoming threats to pollination and dealing with reproductive failure in crops due to environmental stress. Opportunities lie in using modern biotechnology and genetic tools. We can develop crops that are less dependent on pollinators (e.g., by engineering autonomous seed set), have greater resilience to heat and drought, and use techniques like gene editing (CRISPR) to accelerate the breeding of more productive and sustainable crop varieties.