Grafting increases the salt tolerance of tomato by improvement of photosynthesis and enhancement of antioxidant enzymes activity

Plant growth, K and Na concentration, gas exchange. chlorophyl I fluorescence parameters and antioxidant enzymes activities were investigated in non-grafted, self-grafted and rootstock grafted plants, exposed to 0, 50, 100 and 150 mM NaCl concentration, over a 2-week period. 100 and 150 mM NaCl significantly decreased the net CO2 assimilation rate W and stomatal conductance (G,). as well as photochemical quenching coefficient (q(p)), efficiency of the excitation energy capture by open PSII reaction centers (F-v'/F-m') and actual quantum yield of photosynthesis (Phi(PSU)). However, only slight reversible photoinhibition occurred at 150 mM NaCl in non-grafted and self-grafted plants. However. the inhibition induced by salinity was significantly alleviated in rootstock-grafted plants. Lipid peroxidation was largely increased by 100 and 150 mM NaCl treatment in non-grafted and self-grafted tomato plants, and was less influenced in rootstock-grafted plants. This alleviation of oxidative damage was due to the increase in activities of catalase (CAT) and enzymes involved in ascorbate-glutathione cycle such as ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR). The alleviation of growth inhibition of rootstock-grafted plants by salt stress may be related to improvement of photosynthesis and enhancement of antioxidant enzymes activity. (c) 2009 Elsevier B.V. All rights reserved.