Effects of selenium valence states and application concentrations on plant growth, ascorbate-glutathione cycle in Citrus junos cv. Ziyang Xiangcheng

Abstract

Potted Citrus. junos cv. Ziyang Xiangcheng seedlings were used to study the effects of selenium (Se) valence states (Se6+ and Se4+) on plant growth and antioxidants and antixodases in ascorbate(AsA)-glutathione (GSH) cycle. The results showed that Se6+ and Se4+ (from 1.0 mg·L-1 to 8.0 mg·L-1) stimulated the seedling growth by increasing plant height, leaf areas, and fresh or dry mass. Applying Se6+significantly increased plant Se levels mainly in leaf, and applying Se4+ slightly increased Se content mainly in root. Certain valence states and concentrations of Se increased leaf chlorophyll and hydrogen peroxide (H2O2) content. Se6+≤2.0 mg·L-1 treatments enhanced the activates of glutathione reductase (GR) and glutathione peroxidase (GPX), and the contents of GSH and oxidized glutathione (GSSG), while Se6+≥4.0 mg·L-1 treatments reduced the antioxidant contents and antixodase activities of GSH cycle. Moreover, Se4+≤ 2.0 mg·L-1 treatments increased the activities of dehydroascorbate reductase (DHAR) and ascorbate peroxidase (APX), and resulted in higher AsA/[AsA+dehydroascorbic acid (DHA)] ratio. When Se4+≥4.0 mg·L -1, the antioxidant contents and antixodase activities of GSH cycle were increased. Together, this study showed that different valence states and application concentrations of Se showed different influences on AsA-GSH cycle in citrus, and 2.0 mg·L-1 Se6+ and 4.0 mg·L-1 Se4+ were the best concentrations for plant growth.