Which one of the following elements is not remobilisedin leaf?
(a) Nitrogen (b|) Phosphorus (c) Potassium (d) Calcium

The correct answer is calcium.

Calcium is not mobile in the plant. it is an important constituent of cell wall and can only be supplied in the xylem sap. Thus if the plant runs out of a supply of calcium it can not remobilise calcium from the older tissue.