Effect Of Temperature Free-Air Controlled Enhancement After Flowering On Rice Yield And Quality

High temperature, heat and the drought caused by climate warming was the largest meteorological disasters influence on human, also had potential impact on rice production. Under the background of global warming, it had important sense on the agricultural technology research and development to study of high temperature on yield, quality of rice and its physiological mechanism for croping.The current warming system of the international climate change research were abundant, but many of them use the closed artificial climate chamber and air conditioning heating greenhouse warming, and mainly plants by potted, the created warming environment was very different of natural conditions of paddy temperature increase. Our laboratory introduced the open-warming (T-FACE, Temperature Free-air Controlled Enhancement) system from the United States in2009, in order to achieve a treatment to simulate global warming under field conditions. The experiment with the platform of T-FACE, to study the response of senescence related enzymes, the characteristics of grain-filling,yield and quality of different heat resistance varieties to T-FACE, to provide the necessary conditions to accurately resolve rice yield, grain quality trends and mechanisms under the global warming,experiments of Two indica hybrid rice cultivars (heat-sensitive varieties’Teyou559’and heat-resistant varieties ’Shanyou63’) with four warming treatment:normal temperature control (CK), high day temperature (HDT), high night temperature (HNT) and high day and night temperature (HDNT) were conducted in Danyang experimental station from2009to2011, where1.5℃increased in the daytime and3℃in nighttime were set based on the prediction of global climate change. The main results are as follows:(1) Effect of T-FACE on increasing temperatureT-FACE system monitor the temperature through infrared temperature sensor, feedback it to the control module, and according to the value of the measured temperature and the set temperature to adjust the output power, finish the field temperature control. T-FACE set temperature scale for1.5℃at daytime,3℃at nighttime and1.36℃at daytime, 2.62℃at nighttime were the measured temperature.T-FACE system allowed7m2range of rice canopy temperature to increase uniform and it also made different magnitude in free air condition (daytime1.5℃and nighttime3℃) to simulate the asymmetrical characteristics of global climate change. The biggest magnitude could be up to2.62℃. But due to the airflow restrictions, warming a rate of less than the set value, the study also show that at different stages of grain filling the wheat canopy temperature is also relatively uniform, which proved the system is stable warming equipment.(2) Effect of T-FACE on senescence related enzymes after floweringThe rice flag leaf net photosynthetic rate and stomatal conductance decreased while night-time respiration rate increased after T-FACE treatment. The day temperature is the main cause of the decline of net photosynthetic rate, the night temperature is the main cause of night respiration rate increased.The leaf chlorophyll and SOD content decreased while MDA content increased after T-FACE treatment, where heat-sensitive varieties changed greater than heat-resistant varieties. The effect of T-FACE on HDNT was significantly higher than that of HDT and HNT, but there was nearly no difference between the HDT and HNT due to the same stress duration and its intermittent repair. Warming reduced the change of these indices mentioned above when the plants suffered low temperature.(3) Effect of T-FACE on yield and its formation processThe main effects of T-FACE on yield were1000-grain weight and seed setting rate, and panicle number and grain nvimber were not significant.The shortened activity filling stage of inferior grain and low filling rate were two main reasons inducing decrease of grain weight, which decreased seed setting rate and1000-grain weight, eventually, resulted in low yield. The decrease amplitude for heat-resistant varieties was lower than that of heat-sensitive varieties. HDNT showed the most influential response to T-FACE among four treatments. Compared with CK, the effect of HNT was superior to HDT.(4) Effect of T-FACE on quality and endosperm structureIn contrast with the increase of chalky rice rate and chalkiness degree, the brown rice rate, milled rice rate and head rice rate decreased response to T-FACE, while the grain shape remained constant. Albumin, globulin and glutelin content increased while prolamin content decreased. The amylose content under HNT and HDNT decreased which was opposite to HDT. The research of RVA showed high peak viscosity, hot viscosity, breakdown and initial gelatinization temperature but low final viscosity and setback. The crystalline properties of starch changed including the increased relative crystallinity, peak intensity distribution. The grain abdomen amyloplas which was less affected under HDT suffered poor development under HNT and HDNT.In summary, the HDNT treatment had maximum effect on rice leaves SPAD, net photosynthetic rate and respiratory enzymes of antioxidant. At the same time T-FACE treatment reduced the yield of rice and its index, the effects of HDNT treatment were maximum amplitude, wherein the heat sensitive varieties yield had more decline than the heat resistant varieties. After the influence of T-FACE on rice quality quota were not identical, it drop the quality indexes of milling and appearance, improved the indicators of nutrition quality, each index of the cooking and eating quality and starch structure took variation, in which HNT and HDNT treatment had a large impact.