Effects Of High Temperature On The Development And Yield Component Of Rice

Rice is one of the most important food crops in China and even in Asia.As a thermophilic crop,rice has good heat resistance,but excessive temperature will lead to rice heat injury.The 5th Assessment report of IPCC pointed that the global temperature may be increased more than 1.5 C by the end of the 21st century.In addition,it is almost certainly that the frequency and strength of high temperature events would be increased with the global warming.So,it is crucial to study the effect of high temperature on the growth of rice.In order to explore the effect of high temperature on growth process and yield components and analyze the quantitative relationship between high temperature and grain number per panicle and seed setting rate,a control experiment with different high temperature levers and durations was conducted at booting and flowering stages with 2 varieties,Liangyouepeijiu and Nanjing45 in 2014-2015.In addition,for the sake of analyzing the response of yield components and flowering habits types of rice to heat stress,another control experiment was conducted from meiosis stage to flowering stages with different temperature levels(36 C,40?)and one day high temperature treatments with two rice cultivars,Nanjing45 and Guangliangyouxiang66.The results were as following:1.High temperature resulted in the decrease of photosynthetic rate in rice leaves,and decrease degree was related to the high temperature level and duration.At the booting stage with 41? and 7d high temperature treatment,the decrease percentages of photosynthetic rate for Liangyoupeijiu and Nanjing 45 were 44.6%,28.8%respectively.Under the same high temperature treatment,the decrement of leaf photosynthetic rate during flowering stage is greater than that at the booting stage.After high temperature treatment,the SPAD value also decreased and difference of SPAD between high temperature treatment and CK would be reduced gradually.However,the photosynthetic rate and SPAD value at 6-day later after high temperature treatment were still lower than that of the CK,which may be related to irreversible damage of leaf function caused by high temperature.2.High temperature resulted in the decrease of rice biomass in certain temperature range,and the decrease degree was related to the duration.However,under the 41 ? treatment,rice biomass lightly increases with the prolong of high temperature duration.The possible reason was the appearance of new tillers from tillering nodes of elongated internode,which led to the increase of photosynthetic products.High temperature also affected rice dry material distribution.The partition index of panicle would be deduced and that of stem would be increased although the the partition of leaf is less affected.3.High temperature also led to the decrease of rice yield,and decrease degree was related to the high temperature level and duration,the higher temperature and longer duration,the lower the yield of rice.Under the same high temperature stress,the flowering stage is more sensitive than booting stage.High temperature had no effect on panicle number of rice at booting and flowering stages,but spike grain number and seed setting rate would decline caused by high temperature at booting stage and seed setting rate would decrease at flowering stage.4.There were obvious differences in response of flowering pattern,seed setting rate for daily open florets to high temperature at different floret developmental stages and different flowering stages.The most sensitive stage of response of rice yield and seed setting rate to high temperature was the late stage of floret development,and the most insensitive stage was the early stage.The most sensitive stage of response of grain number per panicle to high temperature was medium stage during floret development.The effect of high temperature on inferior spikelets was greater than that on spuerior spikelets.High temperature led to a decrease in the maximum flowering percentage,but had no effect on flowering time.5.The experiment showed the grain number per panicle and seed setting rate decreased with the increase of temperature and prolong of high temperature duration.A quantitative relationship between the grain number per panicle and high temperature level and duration at booting stage was analyzed with experiment data in 2014,and validated with experiment data in 2015.The result showed that the grain number per panicle changed with temperature in a quadratic equation.A similar relationship was also presented in terms of seed setting rate.The result of validation showed that the grain number per panicle with rRMSE of Liangyoupeijiu and nanjing45 were 10.5%and 16.2%,respectively,and the seed setting rate with rRMSE of those were 10.0%and 20.0%,which suggested that the high temperature effect of grain number per panicle and seed setting rate at booting stage could be better simulated by the model.