The Effect of Acid Feeding on Amine Formation in Barley

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Abstract
It is probable that one of the functions of potassium in the plant is to maintain the ionic balance of the cell, and it has been suggested that in potassium deficiency, the production of organic bases such as putrescine serves to balance an excess of organic acids which might occur under these conditions. The mechanism for the increase in activity of the enzymes in the pathway leading to the formation of putrescine in potassium-deficient barley leaves was studied, therefore, by investigating the effect of artificially increasing the acidity by feeding inorganic acids to the roots of barley seedlings. Feeding hydrochloric acid caused significant increases in L-arginine carboxy-lase (arginine decarboxylase) and N-carbamylputrescine amidohydrolase activity in the leaves when expressed on the basis of fresh weight, dry weight, total nitrogen, or protein nitrogen, and a similar increase was induced on feeding sulphuric acid. Acid feeding did not cause a significant change in potassium content on a dry-weight basis. The arginine, agmatine, and putrescine contents were increased in the acid-fed leaves. The possibility that the increased arginine content in the acid-fed leaves led to an increase in arginine decarboxylase by enzyme induction was investigated by feeding arginine through the roots to barley seedlings. No increase in decarboxylase activity could be detected.