Morphology of Flowering Plants - Exercises

Subject: Biology
Chapter: 5 - Morphology of Flowering Plants

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Exercises

1. How is a pinnately compound leaf different from a palmately compound leaf? Answer:

• Pinnately Compound Leaf: A number of leaflets are present on a common axis, the rachis, which represents the midrib of the leaf (e.g., Neem).
• Palmately Compound Leaf: The leaflets are attached at a common point, i.e., at the tip of the petiole (e.g., Silk cotton).

2. Explain with suitable examples the different types of phyllotaxy. Answer: Phyllotaxy is the pattern of arrangement of leaves on the stem or branch:

• Alternate: A single leaf arises at each node in an alternate manner (e.g., China rose, Mustard, Sunflower).
• Opposite: A pair of leaves arise at each node and lie opposite to each other (e.g., Calotropis, Guava).
• Whorled: More than two leaves arise at a node and form a whorl (e.g., Alstonia).

3. Define the following terms: (a) Aestivation: The mode of arrangement of sepals or petals in a floral bud with respect to other members of the same whorl. (b) Placentation: The arrangement of ovules within the ovary. (c) Actinomorphic: A flower that can be divided into two equal radial halves in any radial plane passing through the centre (radial symmetry, e.g., Mustard). (d) Zygomorphic: A flower that can be divided into two similar halves only in one particular vertical plane (bilateral symmetry, e.g., Pea). (e) Superior Ovary: In a hypogynous flower, the gynoecium occupies the highest position while other parts are situated below it. (f) Perigynous Flower: A flower where the gynoecium is situated in the centre and other parts are located on the rim of the thalamus at the same level. (g) Epipetalous Stamen: When stamens are attached to the petals (e.g., Brinjal).

4. Differentiate between: (a) Racemose and Cymose Inflorescence:

• Racemose: The main axis continues to grow, and the flowers are borne laterally in an acropetal succession.
• Cymose: The main axis terminates in a flower, hence growth is limited. Flowers are borne in a basipetal order. (b) Apocarpous and Syncarpous Ovary:
• Apocarpous: When more than one carpel is present and they are free from each other (e.g., Lotus, Rose).
• Syncarpous: When more than one carpel is present and they are fused together (e.g., Mustard, Tomato).

5. Draw the labelled diagram of the following: (Note: Visual diagrams are typically included in textbooks. Below are the key parts to be labelled) (i) Gram Seed: Seed coat, hilum, micropyle, two cotyledons, plumule, radicle. (ii) V.S. of Maize Seed: Seed coat fused with fruit wall, endosperm, aleurone layer, scutellum (cotyledon), coleoptile, plumule, radicle, coleorhiza.

6. Take one flower of the family Solanaceae and write its semi-technical description. Also draw their floral diagram. Answer (e.g., Solanum nigrum):

• Habit: Herb.
• Vegetative: Stem herbaceous, aerial, erect, branched. Leaves alternate, simple, exstipulate, reticulate venation.
• Floral: Inflorescence solitary/axillary or cymose. Flower bisexual, actinomorphic. Calyx 5 united sepals, persistent, valvate. Corolla 5 united petals, valvate. Androecium 5 stamens, epipetalous. Gynoecium bicarpellary, syncarpous, ovary superior, placenta swollen with many ovules, axile. Fruit berry/capsule.
• Floral Formula: ⊕ ⚥ K₍₅₎ C₍₅₎ A₅ G̠₍₂₎

7. Describe the various types of placentations found in flowering plants. Answer:

• Marginal: Placenta forms a ridge along the ventral suture; ovules in two rows (e.g., Pea).
• Axile: Placenta is axial and ovules are attached to it in a multilocular ovary (e.g., Tomato, Lemon).
• Parietal: Ovules develop on the inner wall of the ovary or peripheral part (e.g., Mustard).
• Free Central: Ovules are borne on a central axis and septa are absent (e.g., Dianthus).
• Basal: Placenta develops at the base of the ovary; a single ovule is attached to it (e.g., Sunflower).

8. What is a flower? Describe the parts of a typical angiosperm flower. Answer: A flower is the reproductive unit in angiosperms, a modified shoot meant for sexual reproduction. A typical flower has four whorls:

1. Calyx: Outermost whorl of sepals (protects bud).
2. Corolla: Whorl of petals (attracts pollinators).
3. Androecium: Male part consisting of stamens (anther and filament).
4. Gynoecium: Female part consisting of carpels (stigma, style, and ovary).

9. Define the term inflorescence. Explain the basis for the different types inflorescence in flowering plants. Answer: Inflorescence is the arrangement of flowers on the floral axis. The basis for differentiation is whether the apex develops into a flower (terminating growth) or continues to grow:

• Racemose: Apex continues to grow; flowers are in acropetal succession.
• Cymose: Apex terminates in a flower; flowers are in basipetal order.

10. Describe the arrangement of floral members in relation to their insertion on thalamus. Answer:

• Hypogynous: Gynoecium is at the top; other parts below it. Ovary is superior (e.g., China rose).
• Perigynous: Gynoecium in the centre; other parts on the rim of thalamus at the same level. Ovary is half-inferior (e.g., Rose).
• Epigynous: Thalamus encloses the ovary completely; other parts arise above it. Ovary is inferior (e.g., Guava).