Changes in the ascorbate-glutathione system during storage of recalcitrant seeds of Acer saccharinum L.

Abstract

Two seed lots of Acer saccharinum (recalcitrant), with an initial moisture content of 50% and 55%, were stored at +3^oC for 6 months. After this time, their viability (measured as germinability) reached 100% and 30%, respectively. In embryo axes and cotyledons extracted from seeds, two major low molecular antioxidants were assayed: ascorbate (ASA and DHA) and glutathione (GSH and GSSG); and activities of enzymes of the ascorbate-glutathione cycle were measured: ascorbate peroxidase (APO) (E.C. 1.11.1.11), monodehydroascorbate reductase (MR) (E.C. 1.6.5.4), dehydroascorbate reductase (DHAR) (E.C. 1.8.5.1), and glutathione reductase (GR) (E.C. 1.6.4.2.). GSH and GSSG contents of embryo axes of stored seeds decreased, as compared to the control (fresh, non-stored seeds), but a larger decrease was observed in seeds with 30% viability. In cotyledons, a particularly high increase in the GSH content in relation to the control was observed in seeds with 100% viability, while the GSSG content was significantly lower in both stored seed lots than in the control. The ASA level was twice as high in seeds with 30% viability as in the control, both in embryo axes and in cotyledons. The activity of enzymes of the ascorbate-glutathione cycle was higher in embryo axes than in cotyledons. In embryo axes of seeds with 100% viability, enzyme activities were slightly lower than in the control, while in those of seeds with 30% viability, their activities were higher than in the control. The observed changes in activities of enzymes of the ascorbate-glutathione cycle and in ascorbate and glutathione levels suggest that the stored seeds of A. saccharinum have an active antioxidant system, which plays an important role in maintaining their viability during storage.