Changes in Nitrogen Fractions and Proteolytic Enzymes of Soybean Plants Treated with 2,4-Dichlorophenoxyacetic Acid.

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Abstract
Plants treated with 5 ppm 2,4-D in nutrient solution for one day were analyzed for several nitrogen constituents and for proteolytic enzyme activity. Control and treated plants were grown in minus-N solution during and following exposure to 2,4-D in order to determine effects of treatment on nitrogen already absorbed and largely assimilated prior to 2,4-D treatment. Nitrate assimilation was equally rapid in treated and control plants, contributing a small fraction to the total organic N pool. By the third day after treatment the amount of protein N in leaves of treated plants was considerably lower than that in the controls, but the opposite was true for stems and roots. As much as 30% of the leaf proteins of treated plants were hydrolyzed and products were translocated to stems and roots where more protein was formed. Marked increase in soluble organic N fractions in stems and roots also resulted from 2,4-D treatment. Decreased proteinase and peptidase activity in leaves and increased proteinase and peptidase activity in stems and roots followed treatment with 2,4-D. Apparently in vitro measurements of proteolytic activity were not a suitable index of the equilibrium between hydrolytic and synthetic reactions affecting protein levels within a given organ.