Research Of Torlerance To High Temperature After Anthesis In Stay-Green Wheat

In order to to reveal heat tolerance to stay-green wheat and explore the influence of high temperature after anthesis to related enzymes of grain starch synthesis in stay-green wheat. The field experiment was carried out using the stay-green wheat Wm8 and Ym66 and the control varieties XY6 and XY22. After anthesis, the warming awning was built by using the plastic film to carry on the high-temperature treatment. The green leaf number and area, the content of chlorophyll and MDA, membrane permeability, the water content of plant, dry matter translocation of different type of wheat and canopy temperature, as well as the activities of the related enzymes of grain starch synthesis in different wheat types were measured after anthesis. The obtained main results as follows:1. The result indicated high temperature after anthesis promote the leaf senescence quickly. For four varieties, the green leaf number and area and the content of chlorophyll significantly decreased, but the content of MDA and membrane permeability increased markedly. But in the stay-green wheat Ym66 and Wm8, the green leaf number and the content of chlorophyll were higher and MDA content and the relative electric conductivity were lower than those in the control cultivars after high temperature treatment. It means the stay-green wheat has long leaf function period and good membrane stability, so it has heat-resistence.2. The water content of plant in different type of wheat present higher under normal condition. The leaf, stem and shell of stay-green wheat have a relatively high water content under different treatment, this is good for normal physiological metabolism of the whole plant. And the water content of plant was very significantly correlated with the stay-green characteristic. The dry matter transportation of leaves and stems of stay-green wheat was also higher than non stay-green wheat under different treatment. The three dry matter transportation characteristics of stems are greater than that of leaves.3. The stay-green wheat Ym66 and Wm8 displayed a lower canopy temperature than non stay-green wheat XY22 during grain-filling under control treatment and high temperature treatment. This indicates the stay-green wheat has better heat tolerance than other cultivars.4. The activities of related enzymes of grain starch synthesis (sucrose synthase (SS), adnosine diphosphate glucose pyrophosphorylase (AGPP), soluble starch synthase (SSS)) in all four varieties presented a single-peak curve trend and decreased after high-temperature treatment. But activities of these enzymes in the stay-green wheat were also higher than those in the non stay-green wheat, suggesting that it was benefit for the starch accumulation in grain of stay-green wheat under high temperature. Among three enzymes, a significant different existed in SSS activity between high temperature treatment and control, and activities of above three enzymes were positively and very significantly correlated with grain-filling rate (r=0.905**,0.419**,0.801**), so they play a key role in starch synthesis in the grain of wheat.5. The ear weight, grain weight, seed yield and total biomass of different types of wheat were all decreased under high temperature treatment, but it was not evident in stay-green wheat. Compare to non stay-green wheat, the stay-green wheat have better resistance to high temperature than other varieties, and they have strong photosynthesis capacity and higher grain weight. Hence, breeding the new cultivars with stay-green characteristic would be effective to cut down the influence of high temperature stress during grain filling on wheat production.