Lanthanum improves the antioxidant capacity in chloroplast of tomato seedlings through ascorbate-glutathione cycle under salt stress

This paper investigated the effects of LaCl3 on the ascorbate-glutathione (AsA-GSH) cycle in chloroplast of tomato seedlings under salt stress. Our findings displayed that salt stress significantly enhanced the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), and the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2), but significantly decreased AsA/DHA and GSH/GSSG, the net photosynthetic rate (PN), the contents of Chl and Car, plant height, stem diameter and dry weight, in contrast with the control. In contrast with salt stress alone, salt stress plus LaCl3 significantly increased the activities of above enzymes, AsA/DHA, GSH/GSSG, PN, Chl content and Car content, La accumulation, plant height, stem diameter and dry weight, and markedly cut down MDA content and H2O2 content in chloroplast. Meanwhile, pre-treatment with LaCl3 alone also markedly improved above indicators except MDA content and H2O2 content in chloroplast, in contrast with the control. These findings indicated that LaCl3 absorbed by plants up-regulated the antioxidant capacity in the chloroplast through AsA-GSH cycle, which improved the salt tolerance of tomato seedlings.