It is formed as calcium carbonate by ocean diatoms and is a large pool on the present and poast ocean floor. The white cliffs of Dover are exposed cliffs of calcium carbonate deposits from the sea.
Calcium varies in amounts in different plant tissues.
A Lack of calcium reduces meristem activity or the activity of the cell wall. Calcium deficiency shows up in new growth and must be available throughout the life of a plant. Lack of calcium is seen as a downward buckling of leaves. Calcium deficiency shows up as a light green band on the margins of younger leaves. Leaves look wilted and the top of the leaves can remain unfolded.