Protein reutilisation in corms of Colchicum autumnale

Abstract

Colchicum autumnale L. is a monocotyledonous geophyte with hysteranthous leaves, i.e. flowering and leaf growth occur in different time periods. Because after the starch, the second prominent storage compound of corm is represented by proteins, we were interested in nitrogen remobilisation during the annual life cycle of C. autumnale. In this context the content of soluble and insoluble proteins were measured in parallel with determination of some exo-and endopeptidase activities. Our results indicate that the continual proteolysis occurs in both mother and new daughter corms during the whole life-cycle of the plant. L-Ala-aminopeptidase and trypsin-like endopeptidase were the most active peptidases in both mother and daughter corms. As the protein level of mother corm did not change significantly during the development of the future above-ground part under the soil surface (the first, autumnal developmental stage), the developmental profile of nitrate reductase activity was estimated followed by evaluation of total nitrogen and amino acid contents. Significant activity of root nitrate reductase was detected in the roots only in the second, vernal stage. Our results showed that the stored proteins constituted a relevant nitrogen source partly required by the growth processes of the late autumnal stage, but mainly by the intensive growth of leaves and reproductive structures during the second, photosynthetically active stage of the life-cycle.