Activity of Proteolytic Enzymes in Rye Seeds of Different Ages

Abstract

Summary Aminopeptidase, carboxypeptidase and endopeptidase activities were investigated in differently aged seeds of rye ( Secale cereale cv. Dankowskie Zlote ). Germinating intact seeds and imbibed embryo-less halves were investigated. The highest level of proteases was found to present in the youngest seeds having the highest viability, whereas the lowest level was found in the oldest seeds. However, this decrease was not proportional to the reduction in viability of the seeds. Aminopeptidase activity remained at a constant level in the endosperm, slightly increased in the embryos of germinating intact seeds and regularly decreased in embryo-less halves during imbibition. In the contrast, carboxypeptidase activity decreased in the endosperm of germinating seeds and imbibing embryo-less halves and did not show any variation in the embryos of old seeds, whereas it increased about 30% in the embryos of viable seeds. Endopeptidase activity tended to increase in the endosperm and embryos of viable germinating seeds and remained constant in imbibing halves. Gibberellic acid (GA 3 ), with or without cyclic AMP, did not increase the proteolytic activity in seed halves, and even brought about a decrease in the exopeptidase activities of the youngest viable seeds. Abscisic acid had no influence on the levels of the amino- and endopeptidase activities and consulted in a decrease in the carboxypeptidase activity of imbibing seed halves.