灌浆结实期高温对水稻剑叶生理特性和稻米品质的影响

以水稻耐热品系996和热敏感品系4628为材料,在灌浆结实期利用人工气候室进行高温处理（9：00-17：00,37℃,17：00-翌日9：00,30℃）和适温处理（CK,9：00-17：00,30℃,17：00-翌日9：00,25℃）22d,研究高温胁迫对水稻剑叶光合特性、膜透性、抗氧化酶活性及稻米品质的影响,并进行对比分析.结果表明：（1）灌浆结实期高温胁迫下水稻剑叶叶绿素含量、叶绿素a/b和净光合速率均降低,超氧化物歧化酶（SOD）、过氧化物酶（POD）活性表现出胁迫初期升高,高温处理5d后,随胁迫时间延长呈降低趋势,热敏感品系4628剑叶中叶绿素含量、净光合速率和抗氧化酶活性下降幅度大于耐热品系996；（2）高温下剑叶丙二醛（MDA）含量上升,相对电导率增加,热敏感品系4628增加幅度大于耐热品系996；（3）高温胁迫下垩白粒率和垩白度显著增加,精米率和整精米率显著降低,直链淀粉含量降低,蛋白质含量增加.灌浆结实期高温胁迫下,水稻功能叶抗氧化酶活性降低,膜透性增加,光合能力及光合产物的运输与卸载能力下降,可能是稻米品质降低的重要原因.

Effects of High Temperature Stress During Grain-filling Period on Physiological Characteristics in Flag Leaves and Grain Quality of Rice

Taking two rice lines including heat-tolerant line 996 and heat-sensitive line 4628 as materials, the experiment was conducted in growth chamber to investigate the effects of high temperature （9：00-17：00,37℃; 17：00- 9：00, 30℃ ） and optimal temperature （9：00 -17： 00, 30℃; 17：00 -9： 00, 25℃ ） on photosynthesis characteristics, membrane permeability, antioxidant enzymes activities in flag leaves during grain-filling period and grain quality. The results showed that chlorophyll content, chlorophyll a/b, net photosynthetic rate of flag leaves in rice decreased, the activities of superoxide （SOD） and peroxidase （ POD ） in flag leaves increased at early stage with high temperature stress, then decreased during grain-filling period. The decreasing range of chlorophyll content, net photosynthetic rate, SOD and POD activity in flag leaves of heat-sensitive line 4628 was greater than those of heat- tolerant line 996. MDA content and relative conductivity in flag leaves increased with high temperature stress, the increasing range of MDA content and relative conductivity in flag leaves of heat-sensitive line 4628 was greater than those of heat-tolerant line 996. With high temperature stress, milled rice rate, head rice rate, amylose content of both lines decreased at grain filling stages, while chalkness rate, chalkness, protein content increased. The main reason of grain quality degeneration under high temperature stress included antioxidant enzymes activities decreasing, membrane permeability increasing, photosynthesis capacity and transport and unloading capacity of photosynthetic products in function leaves decreasing.