Comparison of the effects of cytokinins on enzyme development in different cell compartments of the shoot organs of rye seedlings

Abstract

Variation in cytokinin supply has different effects on protein formation and enzyme development in primary leaves and coleoptiles of rye seedlings. The accumulation of enzyme activities, localized in different cell compartments of the leaves, responds with different sensivities.

• In developing primary leaves of dark-grown rye seedlings total protein content and the activities of several enzymes are decreased by lowering the cytokinin supply by excision of the roots. Higher activities are again restored by application of kinetin to plants previously deprived of their roots. However, the activities of the photosynthetic enzymes so far investigated, and of the microbody enzymes, glycolate oxidase and hydroxypyruvate reductase, show a much more marked response to changes in the cytokinin level than either the total protein content or the activities of glucose-6-phosphate dehydrogenase or of the mitochondrial enzymes fumarase and cytochrome c oxidase.

• In the coleoptiles of rye seedlings, light drastically enhances the breakdown of total protein and the decrease of all enzyme activities measured. By contrast to the behavior of primary leaves, total protein formation and the accumulation of all enzyme activities measured are strikingly prolonged after root excision which was expected to result in a lowered cytokinin supply. Subsequent addition of kinetin enhances the decay of protein and most of the enzyme activities determined and thus, in a similar way to the effect of light, seems to promote the senescence of the coleoptiles.