花后高温和干旱对冬小麦光合、抗氧化特性及粒重的影响

Effect of High Temperature and Drought after Anthesis on Photosynthesis,Antioxidant Properties and Grain Weight in Winter Wheat

为了解花后高温和干旱双重胁迫对小麦的效应,以石麦15为材料,于花后15d到21d进行高温（34~36℃）和干旱（土壤含水量为田间持水量的40%~45%）处理,研究了高温和干旱胁迫对小麦旗叶光合性能、旗叶丙二醛（MDA）含量和抗氧化酶活性、籽粒淀粉含量和千粒重的影响。结果表明,胁迫第7d（花后21d）时,干旱和高温-干旱双重胁迫显著降低了小麦旗叶净光合速率（Pn）和叶绿素相对含量（SPAD值）,胁迫解除后Pn降幅缩小,高温胁迫下Pn和SPAD值与对照的差异不显著。高温-干旱双重胁迫显著降低了旗叶Fv/Fm值,且胁迫解除后恢复程度较小。胁迫期间,旗叶MDA含量和过氧化物酶（POD）活性持续升高,超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性均呈先升后降趋势,SOD和CAT活性对干旱、高温-干旱双重胁迫更敏感,胁迫第7天时高温-干旱双重胁迫下降幅度最大。旗叶Pn和SPAD的变化趋势与籽粒淀粉积累量和千粒重变化趋势基本一致,说明灌浆期高温、干旱胁迫下小麦籽粒淀粉积累量和粒重的降低与质膜过氧化、叶绿素的降解和旗叶早衰导致的光合性能下降密切相关,在双重胁迫下光合性能受抑加剧。

High temperature and drought occur simultaneously during grain filling,which significantly reduce grain starch content and grain yield of wheat.This research was conducted to determine the effects of high temperature,dought and their combination on flag leaf photosynthetic potential,MDA content and activities of antioxidant enzymes in flag leaf and grain starch content and grain weight.Results showed that on the 7th day（DAA21）of stress,high temperature and drought and their combination significantly reduced flag leaf photosynthetic rate and SPAD value,the decline was significantly reduced when the stress was removed.High temperature stress reduced photosynthetic rate and SPAD value,but differences were not significant.The Fv/Fmof flag leaf was not sensitive to single high temperature or drought,but was sensitive to combined stress significantly.Fv/Fmvalues of flag leaf decreased because of the combination of high temperature and drought and represented a smaller degree of recovery after the stress was removed.The MDA content and POD activity of flag leaf continuouslyincreased from DAA14 to DAA21,yet SOD and CAT enzyme activity increased and then decreased with the increase of stress days.From the 7th day（DAA21）,combination stress significantly declined the activity of SOD and CAT enzymes.The MDA content and POD activity of wheat flag leaf were still significantly higher than control under the combination stress.The change tendency of Pn,SPAD,starch content and grain weight were basically similar,which indicated that the decrease of starch content and grain weight associated with membrane lipid peroxidation,chlorophyll degradation and early senescence of flag leaf under high temperature and drought.The damage of photosynthetic performance has been intensified by the high temperature and drought.