| Salinity is one of the most deleterious environmental factors limiting crop growth andyield. At present, the secondary salinization of soil have being become one of the seriousquestions in facility agriculture industry.Tomato is widely planted in greenhouse and thedemand of marker for it is large, but tomato production is facing many problems such as thedecrease of yield and fruit quality caused by salt stress.Therefore, it is very important to studythe effect of salt stress on tomato and salt tolerance mechanisms of tomato. In this study,tomato cultivar ‘Baiguoqiangfeng’ was used as experiment material, and hydroponicexperiments were conducted to investigate the effects of exogenous glutathion by spraingreduced glutathione (GSH), oxidized glutathione (GSSG) and glutathione synthesis inhibitor(BSO) onto tomato leaves on plant growth, leaf photosynthetic and CO2assimilationcharacteristics, redox state and reactive oxygen species scavenging capacity in tomato（Solanum lycopersicum）seedling under salt stress. The aim of this study was to clarify theregulation effects and mechanisms of GSH/GSSH on tomato（Solanum lycopersicum cv.Baiguoqiangfeng) seedlings subject to salinity stress. The main results obtained werepresented as follows:1.NaCl stress inhibited the growth of tomato seedlings, whereas application ofexogenous GSH and GSSG reversed the negative effects of salt stress. The effect ofalleviating NaCl-induced growth inhibition in tomato seedling under NaCl+GSSG treatmentwas better than that of NaCl+GSSG treatment. Exogenous BSO application furthersuppressed the growth of NaCl-stressed tomato seedlings.2.NaCl stress significantly inhibited net photosynthetic rate (Pn), actual photochemicalefficiency of PSII (ΦPSII) and the maximum quantum yield of PSII (Fv/Fm), decreased theJmax,Vc,max value and the activity of Rubisco, as well as the expression levels of genesrelation CO2assimilation in leaves of tomato seedlings, whereas application of exogenousGSH and GSSG significantly increased the net photosynthetic rate(Pn) and alleviatedsalt-induced photoinhibition through protecting PSII from damage by excess energy,improving the photochemical efficiency of PSII and dark reaction activity of photosynthesis,and increasing the Jmax and Vc,max, Rubisco activity and expression levels of key genesrelated to CO2assimilation in leaves of tomato seedlings under NaCl stress. As comparedwith NaCl+GSSG treatment, the application of GSH exerted a more positive effect on Pn andalleviated salt-induced photoinhibition in leaves of NaCl-stressed tomato seedlings. Theapplication of BSO further decreased Pn and aggravated the photosynthetic apparatus damageand photoinhibition in leaves of NaCl-stressed tomato seedling by decreasing thephotochemical efficiency of PSII, dark reaction activity of photosynthesis, Jmax and Vc,maxvalue, and the Rubisco activity and expression levels of key genes related to CO2 assimilation in leaves of tomato seedlings under NaCl stress.3. NaCl stress caused ROS accumulation and membrane lipid peroxidation due to thedecrease of reducing power levels, antioxidant enzymes activity including SOD, POD, CAT,APX, DHAR, MDHAR and GR and related antioxidant enzymes gene expression levels inleaves of tomato seedlings.The application of exogenous GSH and GSSG increased reactiveoxygen species scavenging capacity and alleviated salt-induced oxidative stress by enhancingthe levels of reducing power and the activities of SOD, POD,CAT and enzymes related withascorbate-glutathione cycle including APX, DHAR, MDHAR and GR and the expressionlevels of antioxidant enzymes gene in leaves of salt-stressed tomato seedlings, and decreasedthe accumulation of H2O2and O2-., thereby protecting tomato plants from oxidative stress. Ascompared with NaCl+GSSG treatment, the application of GSH exerted a more better effect onalleviating salt-induced oxidative stress in leaves of NaCl-stressed tomato seedlings.Application of exogenous BSO significantly decreased reducing power levels, the activities ofSOD,POD,CAT,GR,APX,DHAR,GPX and MDHAR and related antioxidant enzymes geneexpression in leaves of salt-stressed tomato seedlings, this could be responsible for the lowerROS scavenging capacity, and resulted in aggravating the membrane lipid peroxidation inleaves of salt-stressed tomato seedlings. |
