Effects Of Warming Treatments On The Growth And Development,Yield And Quality Of Rice

The effect of global climate change combined with asymmetric warming on the yield and grain quality of crop plants such as rice(Oryza sativa L.)had already attracted plently of attention,but there are very limited studies focusing on effects of different warming patterns including daytime warming,nightime warming or all-day warming on the growth and develpment,yield and quality of rice under field conditions.To this end,a two-year experiment was conducted in 2016 and 2017 in Wuhan,Hubei province,to simulate the characteristic of future atmospheric temperature in the middle and lower reaches of the Yangtze River by an open-top hot-blast system.Four replicates of four widely planted indica rice cultivars(Huanghuazhan: HHZ;Shanyou63: SY63;Yangliangyou6: YLY6;Liangyoupeijiu: LYPJ)were subjected to four warming treatments(control: ambient temperature;NW: night-time warming;DW: daytime warming;AW: all-day warming)during the whole growth duration of these tested rice varieties.It was expected to reveal the underlying mechanism of the response of the growth and development,yield and grain quality of rice to warming by comparing impacts of NW and DW on them and the response differences between varieties,which would provide a theoretical foundation for the breeding of heat-resistant rice and decision-support for heat-resistant cultivation.The main results showd that:1.The 1?-2? rise on the basis of the air temperature in 2016 and 2017 significantly caused the rediction in rice yield.However,There were obviously different influences between different warming treatments on yield in terms of reduction revels.Of all the elevated-temperature treatments,AW was the most devastating treatment for all rice cultivars,negatively cutting down by 61.93%(2016)and 42.58%(2017).In 2016,NW and DW shared an identical reduction level at 31.06% and 30.76%,respectively.By contrast,NW had a much more severe impact on rice yield with 29.63% reduction than DW treatment with 21.66% reduction.2.The paths of NW and DW treatments leading to yield reductions of rice varieties were slightly different.There were no significant differences between the effects of NW and DW on grain filling percentage and 1000-grain weight,while NW caused more reduction than DW in spkilelets per panicle.Further comparison of intrinsic mechanisms of the reductions in grain filling percentage caused by NW and DW had shown that both NW and DW caused the degradation of pollen viability,the depletion in numbers of pollen adhering to the stigma and the weak pollen germination on the stigma and thereby decreased grain filling percentage.Interestingly,the anther dehiscence was higher sensitive to NW treatment than to DW treatment,while DW led to more dramatic reduction in pollen viability and adhesion of pollen to stigma.3.Plant heights of rice varieties were significantly reduced under warming treatments,but warming treatments did not significantly affect the specific leaf weight(SLW).The LAI of all the test varieties had no obvious variation under warming treatments,except for the significant increase of SY63,which was a widely welcomed heat-resistance genotype.Actually,variations of rice plant morphology under warming treatments cannot affect dry matter accumulation in different periods of rice,which has no limits on formation of yield.4.Warming treatments influenced some indicators related to the processing and apperance quality of rice.Each of AW,NW and DW had significantly reduced the head rice rate and increased chalkiness and chalky grain rate,but there were no impacts on other items of processing quality and apperance quality.Furthermore,the contents of amylose and consistency,which are two crucial factors to the taste quality,were significantly reduced by warming treatments.