Effects of cytokinin on photosynthetic gas exchange, chlorophyll fluorescence parameters and antioxidative system in seedlings of eggplant (Solanum melongena L.) under salinity stress.

摘要

The effects of 6-benzyladenine (6-BA) on plant growth, photosynthetic gas exchange, chlorophyll fluorescence and antioxidant systems of eggplant (Solanum melongena L.) under salt stress were investigated. Eggplant seedlings were exposed to 90 mM NaCl with four levels of 6-BA (5, 10, 20 and 50 micro M) for 10 days. 6-BA at lower concentrations increased chlorophyll concentration, the net photosynthetic rate (P_N), stomatal conductance (g_s), and transpiration rate (E), intercellular CO₂ concentration (C_i) and water use efficiency (WUE), as well as the quantum efficiency of PSII photochemistry ( Phi PSII), photochemical quenching (q_p), and decreased non-photochemical quenching (NPQ), while higher concentrations reduced the effects or even exacerbated the occurrence of photosynthetic capacity. The activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) increased significantly during salt treatments, and induced the increase of the activities of these enzymes at certain concentrations of 6-BA. 6-BA also reduced significantly malonaldehyde (MDA) contents and O₂.- production. It was concluded that 6-BA could alleviate the detrimental effects of salt stress on plant growth by increasing photosynthetic efficiency and enhancing antioxidant enzyme systems in leaves at a proper concentration and of the varying 6-BA concentrations used, the most effective concentration for promoting growth was 10 micro M under saline conditions.