| Drought is one of the most important abiotic stresses affecting rice growth and development.In the middle-lower reaches of the Yangtze river and southern China,seasonal drought stress occurs frequently,which seriously hinders the development of rice production.The response to drought stress in rice was significantly different at different growth stages,however the mechanism was not entirely clear.Therefore,field experiments were carried out at the experimental base of Huazhong Agricultural University,in 2013-2014,2018.Field experiments were conducted with two different genotype rice(Yangliangyou 6-YLY6 and Hanyou 113-HY113)under four water treatments(traditional flooding-F;drought stress at booting stage-BS;drought stress at heading and flowering stage-HS;drought stress at milking stage-MS)and water treatment was main plot,the cultivar was sub-plots.The effects of drought stress and rehydration after drought on rice physiological characteristics,yield and quality and water use efficiency were revealed at rice booting stage,heading and flowering stage and milking stage.The main results are as follows:1.Drought stress at booting stage,heading and flowering stage and milking stage significantly reduced the leaf water potential(LWP)and air leaf temperature gap(ALTG)by 27.83-67.59%,32.04%-44.11%,respectively.LWP and ALTG could return to control level after 2 days rehydration.Because of drought straining at booting stage and heading and flowering stage,LWP,ALTG and SPAD values were significantly lower than control after 15-30 days rehygration.Whereas,no significant difference were observed after drought straining at milking stage.2.Drought stress at booting stage,heading and flowering stage and milking stage significantly reduced the stomatal conductance(Gs),net photosynthetic rate(Pn),transpiration rate(Tr)by 29.76%-52.95%,20.67%-47.06%,7.72%-79.21%,respectively.Which led the significantly decreased in leaves photosynthetic capacity.Pn could return to control level after 2 days rehydration,and the compensation effect was more significant after the drought training at booting stage and heading and flowering stage.Whereas the time come to 15-30 days rehygration,no significant difference were observed after drought straining at milking stage.3.Compared with traditional flooding,drought stress at booting stage and heading and flowering stage significantly increased the instantaneous water use efficiency(IWUE)by 167% and 133%,and IWUE at milking stage was decreased significantly by 12.99%.IWUE could return to control level after 2 days rehydration after drought training,while IWUE significantly increased by 54.38% at milking stage.Which indicated that the compensation effect of rehydration on Pn is greater than Tr at the late stage of reproductive stages.Drought stress at booting stage and milking stage significantly increased the carbon isotope resolution(?13C)in leaf and reduced ?13C in grain,The indication of ?13C for WUE is different in organ and growth period.4.Drought stress at booting stage and heading and flowering stage significantly reduced grain yield by 23.81%-28.84% and 17.52%-20.32%,respectively.While no significant changes were observed at milking stgae under drought stress.The reduction of effective panicles,the number of grains per panicle and the filled grains can explain the yield loss at booting stgae under drought;the reduction of the number of grains per panicle and the filled grains can explain the yield loss at heading and flowering stage under drought;the increase in filled grains compensates for the yield loss caused by the reduction in 1000-grain weight at milking stage under drought.5.Drought stress at booting stage significantly reduced chalky kernel and chalkiness degree by 52.41%-62.28% and 55.28%-57.06%,respectively.Whereas,drought stress at heading and flowering and milking stage significantly increased chalky kernel and chalkiness degree by 26.86%-64.03% and 25.51%-34.50%,respectively.Drought stress significantly increased the protein content of rice by 13.10%-20.69%,but no significant effects on processing quality were observed.6.Drought stress significantly increased abscisic acid(ABA)by 30.04%-65.83%,proline(Pro)46.96%-181%,Peroxidase(POD)28.41-61.69%,and catalase(CAT)16.53-77.23%,respectively.Which indicating that cell osmotic potential and reactive oxygen species increased significantly.Cytokinin(CTK)and auxin(IAA)were significantly lower than control after 15-30 days rehygration.Whereas,no significant difference were observed after drought straining at milking stage.Drought stress in the early reproductive growth stage would cause leaf senescence.In summary,drought stress at the reproductive growth stage significantly reduced the physiological functions of leaves,especially the lack of photosynthetic capacity.Although the compensation effects were observed after rehydration,drought stress induced premature senescencess.which led to insufficient dry matter accumulation at later period,accelerate the filling rate and shorten the filling time,cause a decline in yield and quality... |
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