THE EFFECT OF NITROGEN SUPPLY ON SOME INDICES OF PLANT‐WATER RELATIONS OF BEANS (PHASEOLUS VULGARIS L.)

Abstract

The effect of nitrogen supply on some indices of plant‐water relations was studied on potted bean plants. When soil moisture was relatively high, the leaves of N‐deficient plants transpired less than those of N‐supplied plants, the transpiration rate being closely associated with the chlorophyll content of the leaves of various ages. In detached leaves which were saturated by floating over distilled water, stomatal width was markedly wider in N‐supplied than in N‐deficient plants. Throughout the available moisture range, the water saturation deficit was higher in N‐supplied leaves. In the dry range of soil moisture, chlorotic leaves transpired more than normal green leaves; N‐deficient plants failed to exhibit a sharp rise in the content of soluble metabolites in the sap, when approaching the wilting range. The content of ‘cell wall materials’ was higher in N‐deficient plants. The relationships between these indices is discussed; it is tentatively concluded that nitrogen deficiency impairs the ability of the plants to adjust their water status to changes in soil moisture by regulation of stomatal transpiration and of sap‐solute concentration. Copyright © 1970, Wiley Blackwell. All rights reserved