Function and Deficiency symptoms of Calcium in plants
Function of Calcium in plants
i. Calcium is a constituent of cell walls in the form of calcium pectate. The middle lamella of plant cell walls is composed primarily of calcium and magnesium pectates. Calcium regulates the permeability of cellular membrane.
ii. It is also found in the cell vacuoles as Ca-oxalate and Ca-carbonate where it neutralizes the organic acids formed within the plant body and eliminates their toxic effects.
iii. It is essential for cell division and elongation, therefore, enhances root growth and development.
iv. It makes the stems stiff and thereby reduces lodging in cereals.
v. Calcium accelerates nitrogen fixation in legumes and helps in boosting nitrogen uptake by plants. It enhances the nodule formation in legumes and thereby rhizobial activity is increased.
vi. Calcium in small amounts is necessary for normal mitosis. It is a structural part of the chromosomes in which it binds the DNA with protein. Close correlation between calcium deficiency and chromosome abnormalities has also been supported.
vii. It is required by a number of enzymes for their proper functioning viz. lipase, phosphatase and amylase.
viii. Calcium acts as a buffer in plant system, and ameliorates the toxic effects of other nutrients if they are at toxic level in the plant.
Deficiency symptom of calcium in plants
i. The easily observed symptoms of calcium deficiency are quite striking. Meristematic regions found at stem, leaf, and root tips are greatly affected and eventually die, thus terminating growth in these organs. Cell walls become rigid or brittle in calcium-deficient plants.
ii. The young leaves become chiorotic which is followed by distortion of growing points of the stem. These symptoms appear considerably early at the seedling stage even before emergence of first leaf. Deficiency symptoms generally appear first in the younger leaves and the growing apices, probably as a consequence of the immobility of calcium in the plant.
iii. Chlorosis generally occurs along the margins of younger leaves, these areas usually becoming necrotic. Malformation or distortion of the younger leaves is also characteristic of calcium-deficient plants, a hooking of the leaf tip being the most easily detected symptom.
iv. In mustard young leaves become white and leaves become cup-shaped. The stems bend downwards and collapse.
v. In some root crops and in tomato and coriander, the main shoot may die-back followed by development of other lateral buds.
vi. In gram, lentil, etc. young leaflets are restricted in size, become chlorotic and distorted resulting into die-back and severe defoliation.
vii. vii. Ca deficiency causes blossom-end rot in tomato and brown heart in peanut (Arachis hypogaea).
viii. In wheat and barley the upper parts of the young leaves do not open and remain thread like in structure. The number of mitochondria in wheat roots is reduced under calcium-deficiency conditions.
ix. Calcium deficiency in cotton plants results in increased levels of carbohydrates in the leaves and decreased levels in the stems and roots due to decrease in carbohydrate translocation, an effect similar to that found in boron-deficient plants.
x. It also causes premature flower and fruit dropping.
Excessive amounts of calcium can decrease the availability of many micronutrients.