Calcium, an important element in plant mineral nutrition, is necessary for the structure, stability and formation of membranes. It plays an important role in cell wall structure. Calcium is also of importance in some enzyme systems and at the nuclei, where a lack of calcium would result in improper cell division. Early symptoms of calcium deficiency in general is evident in the younger growing tips of the plants (i.e., growing points of stems and roots and younger leaves).
Source: • Minnesota Commercial Flower Growers Bulletin Vol. 41 No. 4