EFFECT OF THE FORM OF THE AVAILABLE NITROGEN ON THE CALCIUM DEFICIENCY SYMPTOMS IN THE BEAN PLANT.

Calcium has been found to be one of the most important mineral elements needed for normal plant growth. In its absence plants exhibit very severe deficiency symptoms usually very early and if calcium is withheld further, death always results. Nightingale et. al. (7) made a detailed study of the responses of the tomato plant to calcium deficiency. The reason that calcium deficiency has a more severe effect on a plant than the deficiency of almost any other single element is probably in part because calcium has been found to have many functions in growth and development. These various r?les of calcium will not be discussed here, with the exception of one : the effect of calcium on nitrogen metabolism, as it is directly concerned with this report. After Eckerson (2) devised a method for measuring reductase activity, the plant's capacity to reduce nitrates to nitrites, which is the first phase of protein synthesis, she later studied the conditions which affect nitrate reduction and found calcium among other things to be essential (3). Other workers have also found that calcium malnutrition impairs normal nitrogen metabolism. Burrell (1) found soybeans grown without calcium to accumulate nitrates in the leaves, and to have a much smaller amount of insoluble and amino acid nitrogen than plants grown with calcium ; he believes this condition is brought about by reduced nitrate reduction. Ginsburg and Shive (5) on the other hand, also working with the soybean believe that calcium has no effect on the protein content. Hibbard and Grigsby (6) found calcium-deficient peas to contain smaller amounts of protein than the control plants but believe this is caused by the general disturbance of the plants rather than by the lack of any particular element. Presenting calcium and nitrogen analyses of a large number of plants Parker and Truog (8) found a very close correlation between the calcium and nitrogen content.