Functions of Ca :- Visual symptoms :- Predisposing factors:- Corrective measures :- Calcium is a relatively large divalent cation, which functions outside the cytoplasm, in the apoplasm and bound to cell walls and plasma membrane in exchangeable form. Calcium is a non-toxic mineral nutrient even at very high concentrations as its movement is restricted into cytoplasm and generally detoxifies higher content of other mineral nutrients in plants. Calcium deficient tissue contains higher polygalacturonase activity and this leads to the disintegration of cell walls and collapse of the affected tissues such as petioles and upper parts of the stems. In calcium deficient plants, buds are twisted with downward curling of leaf margins and downward hooking of leaf tips. As leaf expansion continues, these symptoms become more pronounced, with separations of margin tissue, which give the leaf a scalloped appearance. Tip and margin tissues become chlorotic and tips cease growing, giving the leaf a stubby appearance. Ca deficient leaves are thicker and sometimes greener than normal leaves. Symptoms become progressively less pronounced on older leaves and seldom occur at the lower stalk positions. Calcium deficiency occurs when soil calcium level is low or conditions for calcium uptake are not favourable. The unfavourable conditions include high salinity, high magnesium, ammonium, and/or potassium concentration, low soil moisture, low soluble soil calcium, high temperature etc. Calcium deficiency can be prevented by application of calcium containing fertilizers like calcium ammonium nitrate, single super phosphate, dolomite etc. and providing adequate irrigation during active plant growth stage.

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