[Effects of exogenous GSH on photosynthetic characteristics and expression of key enzyme genes of CO2 assimilation in leaves of tomato seedlings under NaCl stress].

By spraying tomato leaves with reduced glutathione (GSH), oxidized glutathione (GSSG) and glutathione synthesis inhibitor (BSO), respectively, the effects of glutathion-mediated redox state on leaf photosynthesis in tomato under NaCl stress were investigated. The results showed that the application of exogenous GSH significantly induced an increase in reducing power level, in- creased the net photosynthetic rate (Pn), stomatal conductance (g(s)), transpiration rate (Tr), as well as the maximum quantum yield of PS II (Fv/Fm), actual photochemical efficiency of PS II (ΦPS II), photochemical quenching coefficient (q(P)) and non-photochemical quenching coefficient (NPQ), and enhanced the Rubisco activity and expression levels of RbcL, RbcS and RCA genes in leaves of tomato seedlings under NaCl stress. These results suggested that GSH alleviated salt-induced oxidative stress by protecting PS II from damage caused by excess energy, and improving the photochemical efficiency of PS II and dark reaction activity of photosynthesis. Although spraying GSSG decreased the level of reducing power and further aggravated the damage and photoinhibition of the leaf photosynthetic apparatus, Pn was not affected in combined stressed (NaCl and GSSG) plants, which might be due to the up-regulation of expression levels of RbcL and RbcS genes. The application of BSO had no significant effects on redox state, CO2 conductivity capacity and PS II photochemical efficiency in tomato leaves under NaCl stress. However, compared to salt singly stressed plants, BSO application increased Pn, likely due to the up-regulation of Rubisco initial activity and RCA and RbcS expression levels.