Hydrogen peroxide as an inducer of seed germination: its effects on antioxidative metabolism and plant hormone contents in pea seedlings.

摘要

Hydrogen peroxide (H₂O₂) pre-treatment increased germination percentage as well as the growth of pea seedlings in a concentration-dependent manner. The effects of H₂O₂ on germination were more prominent when seeds were incubated in darkness than under light conditions. H₂O₂ pre-treatment induced an accumulation of oxidised ascorbate (DHA: dehydroascorbate) as well as a decrease in reduced glutathione (GSH). As a consequence of DHA accumulation, the redox state of ascorbate was decreased. Ascorbate peroxidase (APX) and modehydroascorbate reductase (MDHAR) activities were higher when seeds were subjected to a 12-h photoperiod than in darkness. Catalase (CAT), peroxidase (POX), ascorbate oxidase (AAO), glutathione reductase (GR) and glutathione-S-transferase (GST) activities were, in general, higher when seeds were grown in darkness. H₂O₂ pre-treatment increased APX and MDHAR activities under both incubation conditions and POX and AAO activities in darkness. The increase in the ascorbate oxidising enzymes (APX, AAO and POX) correlated with the increase in the growth of the pea seedlings and with the decrease in the redox state of ascorbate. A cross-talk between ROS and plant hormones was examined. The results showed a strong correlation between the effect of H₂O₂ on seedling growth during post-germination period and a decrease in ABA, zeatin riboside (ZR) content and, to a lesser extent, in SA and JA content. H₂O₂ possibly affects the metabolism of ABA, ZR, SA and JA either by reducing their synthesis or by increasing their catabolism. The results suggest interplay between the cellular redox state and plant hormones, which is orchestrated by H₂O₂, in the regulation of early seedling growth in pea.