Characterization of the Peroxidase System in Winter Rye Seedlings:Compartmentation and Dependence on Leaf Development and Hydrogen Donors Used

Abstract

Summary The peroxidases of winter rye ( Secale cereale L.) seedlings were characterized by means of pH optimum, compartmentation and changes in activity and isoperoxidase pattern during primary leaf development. Peroxidase activity was measured with 9 different hydrogen donors in order to find donor-associated peculiarities. There are a number of parameters that depend on hydrogen donors: i) pH optima; ii) time course; iii) distribution along the leaf; iv) cellular compartmentation and v) isoperoxidase pattern. Gradual changes were found for hydrogen donors according to the character of compartmentation and distribution of peroxidase activity during leaf development, in a sequence dianisidine — guaiacol — catechol — vanillin — ascorbate. In contrast to dianisidine peroxidase activity, which was at a high level in the extracellular fraction of young tissues and sharply increased in older ones, ascorbate peroxidase activity was localized only in protoplasts of juvenile meristematic cells at the basis of the growing leaf. Extraction of tissues with a low ionic strength buffer (0.1 M Na-phosphate, pH 7.8) liberated the main portion (86–91 %) of total peroxidase activity. Both anionic and cationic isoperoxidases were localized intracellularly and extracellularly. The increase in total soluble peroxidase activity during leaf development was associated with the increase in activity of all the presented isoforms, with the exception of A3 and A4, but not with an appearance of new ones.