Damage Mechanism On Rice Panicle And Leaf And Nitrogen Effects Of High Temperature Stress Of Flowering Stage

This study using the Indica Restorer line heat type 996 and heat sensitive sense type R343 as experimental material,under artificial simulation condition of high temperature stress,investigated the influence of flowering high temperature stress on physiological characteristics of panicles and leaves,and discussed the regulation effect of nitrogen form rations on physiological characteristics of rice under high temperature stress.The results are as follows:1.Flowering high temperature stress had different degrees of impact on the pollen grain and spikelets form of R343 and 996.Compared with normal temperature treatment,high temperature treatment dampened pollen quantity and quality(activity),and resulted in anther deform,filaments wilt and fracture,and stigma withering,ultimately leading to significant reduction in the rate of seed(p<0.05).The pollen activity and anther shedding ability of 996 were less damaged than R343.There were more pollens on the stigma and It came earlier to the glume opening peak.Therefore,higher fertility rate of 996 was guaranteed.2.Under high temperature during flowering stage,the rice leaf net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),relative electron transport rate(ETR)and the actual photosynthetic efficiency(Y(?))were significantly decreased than normal temperature treatment(16.33~30.9%,16.37~33.7%,13.8~41.5%,16.7~21.5%).whereas non-photochemical quenching(NPQ)increased(19.7~22.12%),and maximum photosynthetic efficiency had no obvious difference among these stimulations.3.Analysing the effects of different form rations of nitrogen on the heat damage of rice at flowering stage,it was shown that under high temperature stress,the number of opening spikelet of all treatments decreased than normal temperature treatment.Compared with the N1 treatment,N3 treatment led a lower open peak of single day,and flowers more scattered.The temperature of ears and leaves in N1 and N2 was lower than N3.The activities of leaves' SOD,POD and CAT in N3 were significantly lower than N1(11.7%~14.7%?21.7%~8.3%?11.7%~28.2%),meanwhile the activities of spikelet' SOD,POD and CAT in N3 were also significantly lower than N1(22.1%~44.4%?19.5%~8.5%?20.9%~22.2%).Pn of 996 in N2 was highest,while Pn of R343 was maximum in N1.Treatment of nitrate nitrogen no less than 50%(N1,N2)brought the highest rice leaves Y(II)and ETR lowest NPQ,the rise of nitrate nitrogen application rate,and the reduction of the damage of high temperature in PS II reaction center.4.N1,N2 condition can ease the damage of fertility rate caused by high temperature stress.(The fertility rate of N1,N2 decreased by 18.6%~77.9% and 25.0%~75.1% respectively),while the treatment of N3 aggravated the harm to fertility rate(N3:46.5% ~ 87.5%).The rice packet neck rate of pure nitrate nitrogen treatment(N3,27.1%~3.27%)was significantly lower than that of pure ammonium nitrogen treatment(N1,35.98%~3.27%).The number of grain of N1 treatment was 4.6%~10.4% lower than that of N3 treatment.The rice under high temperature stress during flowering got higher fertilization rate via increasing the amount of ammonium nitrogen fertilizer,otherwise properly increasing nitrate nitrogen can help upregulate the number of grains and reduce the packet neck phenomenon due to high temperature.