Effects of acid stress on polyamine levels,ion efflux,protective enzymes and macromolecular synthesis in cereal leaves

Wheat or oat leaf segments were floated on acid solutions and the changes in several parameters measured. The putrescine content of wheat leaves was 12.8-fold greater at pH 3.5 than at pH 6 after 72 h. The increase in putrescine was accompanied by an increase in the amount of K⁺ efflux from the leaf tissue to the external solution. The activities of superoxide dismutase and catalase of wheat leaves at pH 3.5 decreased to 51% and 40%, respectively, of their levels at pH 6 by 24 h. [³H]Uridine and [³H]leucine incorporation into macromolecules in oat leaves (with the lower epidermis removed) decreased to 58% and 28% of the control in response to acid stress in 8 h, at the same time as a 5-fold increase in putrescine. When DL--difluoro-methyarginine was added to the pH 3.5 buffered solution, the effect of acid was slightly less, with the incorporation into macromolecules being 64% and 35% of the pH 6 control. The results indicated that the putrescine accumulation under acid stress was concomitant with ion efflux, and a decrease in both macromolecular synthesis and the activities of superoxide dismutase and catalase in cereal leaves.Abbreviations Put putrescine - Spd spermidine - Spm spermine - SOD superoxide dismutase - CAT catalase - ADC arginine decarboxylase - DFMA DL--difluoromethylarginineThis paper is dedicated to Dr. A.W. Galston in honor for his great achievements and in recognition of his continuing contributions to the study of plant science.