| Salicylic acid(SA) is a kind of small molecule phenolics,which is widespread in plants,and regulates growth and development of plants. SA is producted from phenylalanine metabolic pathway, involves in plant floral induction, stomatal opening, ion absorption and other metabolic processes. Under normal circumstances, the metabolism of physiological and biochemical process is stable and harmonious. However,metabolism in plants will be disorder due to the influence of some abiotic factors which make the plants adverse reaction. According to previous studies,the proper dilute SA improved photosynthesis of plants under freezing stress condition. It is important for theory and application to research deeply on exogenous SA for different wheat in photosynthesis and physiological indicators and to reveal the mechanism and guide the production of wheat.The protocol of this experiment included two tests, one was low temperature stress mimicking in room,the other was freezing stress caused by nature out of door. Three kinds of wheat were used in the experiment: cold resistant variety Dongnongdongmai 1(tolerates low to-30℃),cold-sensitive variety of winter wheat Jimai 22(tolerates low to-10℃)and spring wheat cultivar Longfumai 16.The main results were as follows:(1)Wheat received low temperature stress mimicking test indoorPotted three leaves stage of three varieties of wheat seedling were sprayed with SA(concentration 10-4mol / L). Photosynthetic parameters were measured after performing different low temperature stress treatment. The results were showed as below: As the temperature decreases,Net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs) and intercellular carbon dioxide concentration(Ci),PSⅡphoton yield(Fv/Fm) and photochemical quenching coefficient(q P) show a down trend and excessive expression with the temperature decreases. Photosynthetic electron transport rate(ETR) increased firstly, and then decreased in Dongnongdongmai 1 and Jimai 22 by the low temperature. Non-photochemical quenching coefficient(NPQ) decreased in spring wheat cultivar Longfumai 16,the other two wheat increase by the low temperature. SA improved photosynthetic activity and photoprotection comparing with control according to this photosynthesis parameters mentioned,especially most effect got from SA for Dongnongdongmai 1 and then effect from Jimai 22 spring wheat cultivar Longfumai 16 was less.Soluble sugar,soluble protein and proline were augmented with temperature decreasing,and Malondialdehyde 1(MDA) and H2O2 increased firstly end then decreased in the three kinds of wheat. SA group was higher than control group in soluble sugar, soluble protein and proline and lower in MDA and H2O2 Exogenous SA enhances wheat osmotic adjustment ability through increasing soluble sugar, soluble protein, proline content,and reduces lipid peroxidation damage through decreacing MDA and H2O2 so that freezing tolerance is improved in wheat. Exogenous SA enhances Dongnongdongmai 1 more than Jimai 22 and spring wheat cultivar Longfumai 16.(2)Outdoor Field Application Test:The experiment was carried out in outdoor field. Three leaves stage of three varieties of wheat were sprayed with SA(10-3mol/L),survival rate among cultivars overwinter was measured next year. Survival rate among cultivars overwinter in Dongnongdongmai 1 was higher than Jimai 22,no survival in spring wheat cultivar Longfumai 16 in both control and SA group. SA group was higher than control group in survival rate among cultivars overwinter in both Dongnongdongmai 1 and Jimai 22. Freezing tolerance is improved by exogenous SA for Dongnongdongmai 1 and Jimai 22. Dongnongdongmai 1 was improved further than Jimai 22. This is similar with test indoor. |
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