INFLUENCE OF PHOSPHORUS SUPPLY AND THE FORM OF AVAILABLE NITROGEN ON THE NITROGEN METABOLISM OF THE TOMATO PLANT

Abstract

Further study was made on some of the interrelationships that exist between the metabolism of P and N in the tomato plant. Tomato plants receiving urea as a source of N did not develop deficiency symptoms due to lack of P as soon as did plants receiving nitrate N. This delay was due to the high P reserve of the plants receiving urea. Plants receiving nitrate as a source of N and moderately, but definitely, suffering from P deficiency, showed an accumulation of nitrates in all parts of the plant. This was due to accumulation following rapid absorption rather than as a result of the plant''s inability to reduce the nitrates. Plants utilizing urea as a source of N made no better relative growth on different levels of P than did plants receiving nitrate N. The importance of P in regulating the N metabolism of the plant may have been overemphasized.