Effect Of High Temperature Heat Injury On Rice Growth And Establishment Of Early Warning System

With global warming and the increase of extreme weather,the persistent high temperature weather occurred frequently in the critical growth period of rice.The high temperature heat injury in the middle and lower reaches of the Yangtze River has become one of the major agrometeorological disasters that limit the potential of rice yield.In order to explore the effect of high temperature heat injury on rice growth,development and yield,and to establish a high temperature early warning system for rice.Suliangyou 295 and Nanjing 9108,the main varieties of Jiangsu Province,were selected as experimental materials and planted in pot.Respectively,at the late jointing.stage,meiosis stage,flowering stage and filling stage,the temperature was controlled by artificial climate box,different temperature(32?,35?,38?,41?)and duration(3d,5d,7d)were set,and rice growing in natural environment was used as control(CK),The changes of photosynthetic production,dry matter distribution and its dynamics in above-ground organs,nitrogen concentration,yield and yield components of rice under different treatments were analyzed in this paper.And a high temperature heat injury warning system for rice was established based on the developmental model and high temperature abortion model.The results of this experiment will provide morescientific planting and management methods for rice producers and managers in the future climate change process,so as to avoid or reduce the disaster losses caused by high temperature.The main results of this paper are as follows:(1)Under high temperature stress in different growth stages,the SPAD values of the two varieties decreased to a certain extent,and the higher the temperature and the longer the duration,the more obvious the decrease of chlorophyll content,and the difference existed between the two varieties.The decrease of chlorophyll content in leaves at late jointing stage and meiosis stage was affected by the high temperature,which was larger than that at flowering stage and filling stage.The actual photochemical efficiency(?PSII)and the maximum photochemical efficiency(Fv/Fm)of the two varieties showed a downward trend with the increase of temperature after 5 days of treatment at different temperatures,and when the temperature reached 41?,?PSII and Fv/Fm in the four growth stages were significantly lower than those of CK;in addition,?PSII and Fv/Fm showed that Suliangyou 295 was lower than Nanjing 9108 on the whole.(2)Under the same continuation at the meiosis stage of the two varieties,there was a strong negative correlation between temperature and panicle length at maturity.When the high temperature lasted for 5 days and 7 days,the panicle length of the two varieties and temperaturereached a very significant negative correlation.Under the same high temperature duration,the higher the temperature,the smaller the relative panicle length,and the longer the high temperature duration,the greater the effect on the panicle length.The relative panicle length of Suliangyou295 was less affected by temperature than that of Nanjing 9108.(3)The effects of high temperature at different growth stages on dry matter distribution in the above-ground organs of rice were as follows:under the same high temperature duration,with the increase of temperature,the distribution index of stem increased,the distribution index of panicle decreased,and the change of distribution index of leaf was not obvious at the time of mature harvest.The high temperature at meiosis stage had the greatest effect on the distribution proportion,followed by the late jointing stage and the flowering stage,and had the least effect on the filling stage.After high temperature treatment,a new branch appeared in the higher node position in the late growth stage of some treated rice.In the post-disaster recovery process,the distribution index of stem decreased gradually in a certain temperature range after high temperature treatment at late jointing stage,meiosis stage and flowering stage,but the stem distribution index after 41? treatment will gradually increase with the progress of the growth process,and the stem distribution index change after 38? treatment is relatively stable.After high temperature stress in the filling stage,the distribution index gravitydecreased quickly first and then maintained a relatively stable level.While spike distribution index increased faster and then maintained a relatively stable level,the higher the temperature and the longer the duration,the smaller the increase in the distribution index of the spike.(4)After the meiosis stage and flowering stage of Suliangyou295 were subjected to high temperature stress respectively,the nitrogen concentration of dry matter in stems,leaves and panicle increased in different degrees,and when the temperature reached 38?,the nitrogen concentration was significantly higher than that of CK.(5)The effects of high temperature on rice yield and yield components showed that high temperature at meiosis stage had the most serious effect on rice yield,followed by high temperature at flowering stage,less affected at late jointing stage,and least affected at filling stage.The moderate high temperature during the filling period was beneficial to the formation of the yield.In this experiment,the effect of high temperature on the yield at the late jointing stage and meiosis stage was mainly due to the decrease of the total grain number per panicle and the seed setting rate,while the high temperature at flowering stage and filling stage had no significant effect on the total grain number per panicle,but had a certain effect on the seed setting rate,and the effect of high temperature at flowering stage on seed setting rate was significantly greater than that at filling stage.(6)The sowing date experiment was carried out to establish the parameters of two rice varieties,and the difference of temperature and humidity between rice canopy and meteorological station was analyzed.The influence parameters of relative grain number per panicle and relative seed setting rate at meiosis stage and flowering stage were obtained by quadratic curve fitting.Based on these parameters,a model-based early-warning system for high-temperature heat damage of rice was established.