Class 11
Created by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
Created by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
A comprehensive guide to essential mineral elements, their roles, deficiency symptoms, and the mechanism of absorption in plants.
Plants, like all living organisms, require various inorganic and organic substances for their growth and development. Mineral nutrition focuses on the inorganic elements that plants absorb from the soil.
A total of about 105 elements have been discovered so far, and more than 60 are found in different plants. However, only a few are considered essential.
Essential elements are divided into two broad categories based on their quantitative requirements:
Elements required in large amounts (excess of 10 mmole of dry matter).
Mnemonic: C. HOPKNS CaMg A classic way to remember the macronutrients: C H****O PKN****S Ca Mg (read as "C. Hopkins Cafe, Mighty Good").
Elements needed in very small amounts (less than 10 mmole of dry matter).
| Element | Key Functions | Deficiency Symptoms |
|---|---|---|
| Nitrogen (N) | Constituent of proteins, nucleic acids, vitamins, and hormones. | Chlorosis (yellowing of leaves), stunted growth. |
| Phosphorus (P) | Component of ATP, cell membranes, and certain proteins. | Purple spots on leaves, poor root growth. |
| Magnesium (Mg) | Core of the chlorophyll molecule; activates enzymes for respiration. | Interveinal chlorosis. |
| Iron (Fe) | Essential for chlorophyll synthesis; part of cytochromes. | Chlorosis in young leaves. |
When the supply of an essential element becomes limited, plant growth is retarded. The concentration of an essential element below which plant growth is retarded is termed as critical concentration.
Key Symptoms
The process of absorption can be demarcated into two main phases:
An initial rapid uptake of ions into the 'free space' or 'outer space' of cells. It is a passive process (occurs through ion channels).
Ions are taken in slowly into the 'inner space' or 'cytoplasm' of the cells. It is an active process, requiring expenditure of metabolic energy (ATP).
Nitrogen is the most prevalent element in living organisms. Plants compete with microbes for the limited nitrogen available in the soil.
The process of conversion of atmospheric nitrogen () to ammonia ().
The Nitrogenase Enzyme
Nitrogenase is highly sensitive to molecular oxygen. Root nodules contain leghaemoglobin (an oxygen scavenger) to protect the enzyme and maintain anaerobic conditions.
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