| Water deficit is one of the main environmental factors affecting plant growth and development, has become one of the major obstacles limiting crop production. Water stress significantly inhibites the completion of plant morphology, and affects fertility and yield formation processes. Melatonin is a signaling molecule in plants and animals, but also has a strong antioxidant effect of endogenous free radical scavenger, and can improve the antioxidant system activity within the cell. Environmental stress plants will accumulate more melatonin, exogenous melatonin can improve the ability of anti-stress plants. Reasearch of the effect of melatonin on winter wheat drought resistance mechanism could guid the wheat drought-resistant cultivation and have an important theoretical and practical significance. To clarify the growth of melatonin on wheat growth and physiology under the influence of the critical period of water stress, the study was conducted by plot and field experiments, by using wheat cultivar "Xinong 979" for the material, and measured different periods of drought stress on winter wheat photosynthetic feature, root morphology, protected activity, changes in osmotic adjustment substance and dry matter accumulation, finally discussed the effect of melatonin on different growing stages of winter wheat to drought resistance. The results were as follow:1. pot experiment results showed that treatments under water stress reduced seedling photosynthetic capacity, photosynthetic pigments content and leaf area in seed priming by melatonin significantly increased wheat leaf chlorophyll content and leaf area under water stress, melatonin treatments also could weak down the adverse effects of drought on seedling growth, reduce MDA content, enhance protection activity, increase the total root length, root volume, root diameter and the number of tips to reduce the extent of the drought damage for wheat.2. At jointing stage, photosynthetic pigments content, photosynthesis, stomatal conductance and transpiration rate were decreased under water stress. Fv / Fm(maximum photochemical rate), qP(photochemical quenching) and ETR(electron transport rate) was significantly reduced, and qN increased significantly. Treatments of melatonin caused Fv / Fm, qP and ETR declining significantly lower treatments under water stress, which effectively alleviate drought stress on photosynthetic efficiency of wheat. Under drought stress, with the increasing concentration of melatonin, the SOD activity, POD activity, CAT activity and soluble protein content were all increased first and decreased, the melatonin 300μmol / L concentration of initiator(T2) treatment effect was most obvious, and grain filling rate was higher than other treatments, and significantly increased the plant height, stem diameter, number of spikelets per panicle and grain weight under the drought of the jointing stage.3. The field test results showed that wheat flag leaf net photosynthetic rate, stomatal conductance and transpiration rate were decreasing under water stress at grain filling stage. Melatonin 100μmol / L concentration(T1) treatment and 300μmol / L concentration(T2) priming could mitigate the effects of water stress on the flag leaf photosynthetic rate, improve SPAD value and leaf area. With the extension of drought stress time, the protein content of leaf decreased. Melatonin treatment promoted the stress under the grain, stem and leaf biomass accumulation under water stress, increased the economic yield and biological yield, economic coefficient,in the filling stage of wheat under water stress, the best melatonin concentration was 100μmol / L. |
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