Effects Of High Temperature After Anthesis On Grain Weight And Protein Formation In Wheat

Wheat growing in a pot of diameter 0.3 m, height 0.27 m, filled with 12 kg loamy soil was transferred to the artificial temperature-controlled and moisture-controlled phytotron in different days after anthesis.The experiment mainly studied the effects of high temperature after anthesis on grain weight , protein formation and carbon-nitrogen metabolism in Yangmai 12 and Yangmai 9. The mitigating effects of growth regulating substances on heat damage were also analysed.1. Effects of heat shock after anthesis on grain weight and grain yield per ear. The results showed that grain weight and grain yield per ear at the temperature higher than 25℃were lower than those at normal temperature from anthesis to maturity. Grain weight and grain yield per ear reduced with the increase of temperature, which were significantly different among temperature treatments during various periods. High temperature at different stages after anthesis had different effects on grain weight. Grain weight and grain yield per ear treated with 25 or 30℃from the 19th to 21st day after anthesis (DAA) were lowest, while treated with 35 or 40℃from the 6th to 8th DAA were lowest. The shortening of grain filling period had a greater responsibility for the decrease of grain weight than the declining of grain filling rate under high temperature. The higher the temperature at day under the same night temperature, or the higher the temperature at night under the same day temperature, the lower the grain weight. Grain weight was highest in the treatment of 70% relative air moisture under 65~75% of the largest soil water holding, while lowest in the treatment of waterlogging under heat shock.2. Effects of high temperature after anthesis on protein in grains. Grain protein content at the temperature above 30℃from anthesis to maturity was significantly higher than that at normal temperature, which significantly increased with the rise in temperature. High temperature at different filling stages had different effects on protein content in grains. When heat shock temperature was above 35℃at the early filling stage, the effect of heat shock from the 6th to 8th DAA was the greatest. Under the same temperature at the middle and late stages, the effect of heat shock from the 19th to 21st DAA was greater, while that from the 36th to 38th DAA was lower. The higher the temperature at day under the same night temperature, or the higher the temperature at night under the same day temperature, the higher the grain protein and protein component contents. The lower the difference of day/night temperature or the relative air moisture, the higher the protein content.3. Effects of high temperature after anthesis on carbon-nitrogen metabolism. Root N content lowered to the minimum in 2 days after treatment with 35℃from the 25th to 27th DAA, while leaf N content in 3 days. The order of N content in stem and leaf sheath at maturity among different temperature treatments were 40℃﹥35℃﹥30﹥25℃. After the treatment from the 25th to 27th DAA, soluble sugar content in root , stem and leaf sheath lowered to the minimum in 3 days, that in glumes and leaf blade in 2 days.4. . Mitigating measures to post-anthesis high temperature damage. Spraying KH2PO4, triadimefon or boron on the 3rd DAA could increase grain weight and decrease protein content in Yangmai 9 with weak-gluten and Yangmai 12 with medium-gluten, and spraying urea could raise protein content, so heat shock damage could be mitigated. Spraying on the 3rd DAA was better than spraying after heat shock in mitigating effect. KH2PO4 and triadimefon could play a better role in mitigating heat damage after anthesis for Yangmai 9 with weak-gluten to get high yield and good quality, so did urea for Yangmai 12 with medium-gluten.