灌浆前期高温干旱复合胁迫对优质食味粳稻产量与穗后物质生产特征的影响

Effects of combined stress of high temperature and drought at early filling stage on characteristics of yield and after-heading dry matter production of high-quality japonica rice

【目的】研究灌浆前期高温干旱复合胁迫对优质食味粳稻产量与穗后物质生产特征的影响,为优质稻丰产抗逆栽培技术集成创新提供理论参考。【方法】以优质食味软米南粳9108和丰粳1606为试验材料,在抽穗后1~20 d设高温干旱(HD)、高温常规水分管理(HC)、常温干旱(CD)、常温常规水分(CK)4个处理,研究灌浆前期高温干旱复合胁迫对水稻产量、穗部性状及穗后干物重积累、转运特征的影响。【结果】着粒密度、千粒重、结实率、产量及收获指数在各处理间均表现为HD<HC<CD<CK,结实率、产量在各处理间差异极显著(P<0.01,下同),其余指标在HD与HC间差异不显著(P>0.05,下同),但均与CD、CK差异显著(P<0.05,下同)或极显著,除结实率和千粒重外,CD与CK差异不显著。一次或二次枝梗上的实粒数、实粒重、千粒重与结实率在不同处理间均表现为HD<HC<CD<CK,一次枝梗实粒数占比及实粒重占比表现相反趋势且均高于二次枝梗,其中一次、二次枝梗结实率在不同胁迫处理间差异极显著,HD、HC处理的实粒数、实粒重与CD、CK差异显著或极显著,CD与CK大多差异不显著。穗后不同时期各处理间地上部干物质积累量均表现为HD<HC<CD<CK,南粳9108 HD、HC和CD处理下穗后50 d的地上部干物质积累量较CK分别降低12.9%、10.7%和2.4%,2个品种穗后10~20 d干物质积累量增速最快,穗后30~50 d增幅平缓。各处理下单穗干重增速随抽穗后时间段推延而降低,且不同处理间均以HD、HC显著低于CD、CK。穗后干物质转运量、转运率及贡献率在不同处理间均表现为HD<HC<CD<CK,HD、HC间差异不显著,均与CD、CK差异极显著,CD与CK差异极显著。随穗后生育期推移,水稻剑叶SPAD值、净光合速率下降,净光合速率在不同处理间表现为HD<HC<CD<CK,SPAD值变化趋势与之相反。通径分析结果表明,一次枝梗各指标对水稻产量的直接系数和间接系数均大于二次枝梗,其中以一次枝梗实粒重对产量的直接和间接作用最大,其次为结实率。【结论】穗后20 d内高温干旱复合胁迫及单一高温、干旱胁迫主要通过降低结实率造成水稻减产,以一次枝梗实粒重对产量的直接和间接作用最大。相比南粳9108,丰粳1606对高温、干旱较钝感。干旱胁迫主要通过缩短灌浆时间减少穗部充实,高温及高温干旱复合胁迫通过降低灌浆速率与缩短灌浆时间双重影响穗部充实,故高温干复合胁迫、单一高温胁迫对水稻物质生产特性及产量的影响大于单一干旱胁迫。

【Objective】To study effects of combined stress of high temperature and drought at early filling stage on characteristics of yield and after-heading dry matter production of high-quality japonica rice,to provide theoretical refere nce for integrated innovation of cultivation technology of high-quality,high-yielding and stress-resistant rice.【Method】High-quality japonica rice Nanjing 9108 and Fengjing 1606 were chosen as materials,four treatments including high tem-perature and drought(HD),high temperature with conventional water management(HC),conventional temperature with drought(CD)and conventional temperature with conventional water management(CK)were set during 1-20 d after hea ding to study the effects of combined stress of high temperature and drought on rice yield and panicle traits,and after-hea ding dry matter accumulation and transport at early filling stage.【Result】Grains density,1000-grain weight,seed setting rate,actual yield and harvest index among different treatments was in the order of HD<HC<CD<CK,showing extremely significant difference(P<0.01,the same below)in seed setting rate and yield among the treatments.Compared with CD and CK,other indexes were not significantly different(P>0.05,the same below)under HD and HC,which were all sig-nificantly different(P<0.05,the same below)or extremely significantly from CD and CK.Except seed setting rate and 1000-grain weight,the difference between CD and CK was not significant.The number of filled grains,filled grains weight,1000-grain weight and seed setting rate on primary and secondary branches were in the order of HD<HC<CD<CK among different treatments,and the proportion of filled grain number and filled grain weight on primary branches showed the opposite trend and were higher than those on secondary branches.The seed setting rate on primary and secondary branches was extremely significantly different among stress treatments.Compared with CD and CK,differences in the number and weight of filled grains under HD and HC were significant or extremely significant,while the differences be-tween CD and CK were not significant.The dry matter accumulation of all stress treatments during different periods after heading appeared as HD<HC<CD<CK,and the dry matter accumulation at 50 d after heading of Nanjing 9108 under HD,HC and CD was 12.9%,10.7%and 2.4%lower than those of CK,respectively.The growth rate of dry matter accumulation increased rapidly at 10-20 d after heading,and turned stable at 30-50 d after heading.Under treatments,dry matter in-crease rate per panicle decreased as time went on and HD and HC were significantly lower than those in CD and CK.The dry matter transport,transport rate and contribution rate after heading were in the order of HD<HC<CD<CK,with no sig-nificant difference between HD and HC,significant difference between CD and CK and extremely significant difference between CD and CK.During growth period after heading,SPAD value and net photosynthetic rate of rice flag leaf de-creased,the net photosynthetic rate showed HD<HC<CD<CK among different treatments,while the SPAD value showed the opposite trend.According to path analysis,direct and indirect coefficients of rice yield on primary branches were higher than those on secondary branches and the direct and indirect effects of filled grain weight on primary branches on yield were the largest following by seed setting rate.【Conclusion】In general,combined stress of high temperature and drought,single high temperature stress and single drought stress at 20 d after heading reduce rice yield to different degrees through lowering seed setting rate and the filled grain weight on primary branches has the highest direct and indirect influences on yield.Compared with Nanjing 9108,Fengjing 1606 is insensitive to high temperature and drought.Drought stress mainly reduces panicle filling by shortening grain filling time.High temperature and combined stress of high temperature and drought affect panicle filling by reducing grain filling rate and shortening grain filling time.Therefore,the effects of com-bined stress of high temperature and drought and single high temperature stress on rice material production characteristics and yield are greater than those of single drought stress.