CALCIUM (Ca) 40.08 Atomic weight
Calcium is absorbed by plants as the calcium ion (Ca++). It is an essential part of cell wall structure and must be present for the formation of new cells. Calcium is non-mobile in plants. Young tissue is affected first under conditions of deficiency.
Calcium is the most abundant metallic element in the human body, and the fifth most abundant element in the earth’s crust. Calcium does not occur naturally in the free state, but its compounds make up 3.64% of the earth’s crust.
A deficient level of calcium in the soil impairs plant absorption and retention of other ions such as magnesium. The mechanism responsible for plant discrimination between K+ and Na+ depends on the presence of Ca+.+. A small amount of Calcium in a foliar solution increases the plants uptake of potassium by as much as 150% by changing cell membrane permeability. Maintenance of the plant tissue cell wall structure depends on calcium cross-linkages.
The brown discoloration that occurs in most Calcium deficient tissue could be the result of increased leakage of phenolic compounds into the cytoplasm. Oxidation of some of the enzymes would then occur.
There are basically four biological roles of Calcium in the growth and development of plants:
1) Calcium’s effect on plant membranes.
2) Its effect on cell wall structure
3) Its role in enzyme activities
4) Its interaction with phytohormones