Effect of Glucose on the Growth and Photosynthetic Characteristics of Hawthorn (Crataegus pinnatifida Bge.) under Salt Stress

For investigation on the alleviating effects of exogenous glucose on the leaves of hawthorn under salt stress,the effects of exogenous glucose on the photosynthesis and chlorophyll fluorescence characteristics as well as the activity of related cytoprotection enzymes of hawthorn under salt stress were studied.The results indicated that glucose could alleviate the damage of leaf photosynthetic structure caused by salt stress,increase the net photosynthetic rate(Pn) and stomatal conductance(Gs),decrease the intercellular CO2 concentration(Ci),and increase the maximum photochemical efficiency of PS Ⅱ(Fv/Fm),the potential quantum yield of PSII(Fv/Fo),the probability that an absorbed photon would move an electron into the electron transport chain beyond QA-(ΦEo) as well as the performance index on absorption basis(PIABS).The value of Pn,Fv/Fm and PIABS in exogenous glucose treatments increased by 3.4%-59.8%,5.4%-18.2% and 5.6%-78.4% compared to the salt stress treatment,respectively,which indicated that exogenous glucose could increase light energy utilization efficiency and the photosynthetic efficiency of PS Ⅱ of hawthorn seedlings.Meanwhile,exogenous glucose could also significantly increase the activities of SOD and POD in the leaves,reduce MDA content.The SOD and POD activities in 5.0 mmol.L-1 glucose treatment were about 21.1% and 15.3% higher than those under salt stress treatment,and the MDA content was about 30.1% lower.