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

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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.