The ascorbate system in two bryophytes: Brachythecium velutinum and Marchantia polymorpha

Abstract

The ascorbate system, one of the major antioxidant systems, has been studied in two bryophytes: a moss, Brachythecium velutinum (Hedw.) B., S. & G., and a liverwort, Marchantia polymorpha L. The moss and liverwort gametophytes contain ascorbate both in the reduced and oxidized form; utilize ascorbate in removing hydrogen peroxide by means of ascorbate peroxidase and reconvert to ascorbate its oxidation products by means of dehydroascorbate reductase and monodehydroascorbate reductase. Ascorbate oxidase activity was measured in the cytosolic fraction suggesting a localization of the enzyme different from more evolved organisms. The ascorbate content was maintained in the moss after drought stress while it declines in the liverwort, which seems more sensitive to water stress. Since ascorbate recycling is more efficient in the moss than in the liverwort, this seems to suggest a correlation between efficiency of ascorbate recycling and water stress tolerance.