玉米花期高温响应的基因型差异及其生理机制

倒伏是制约旱种水稻大面积推广的主要因素之一。以籼型杂交稻汕优63和粳稻9516为材料，研究了旱种水稻倒伏的原因及其机理。结果表明，与水种相比，旱种水稻的倒伏率明显高，结实率和粒重明显降低，产量明显降低。自抽穗至成熟，旱种水稻基部节间强度(厚度、单位长度重量)、碳水化合物(尤其是淀粉)含量低于常规水种稻，α-淀粉酶活性明显高于水种稻。水稻基部节间淀粉含量与节间厚度和单位长度重量呈极显著正相关，与α-淀粉酶活性呈显著或极显著负相关。淀粉输出与α-淀粉酶活性呈显著或极显著正相关。施用硅、钾肥能降低旱种水稻基部节间α-淀粉酶活性，提高基部节间淀粉含量，增强基部节间强度，大幅度降低倒伏率，提高旱种水稻的结实率和粒重，从而提高产量。孕穗期去1/2叶，效果则相反。表明在旱种条件下，水稻基部节间α-淀粉酶活性高，促进了节间贮存淀粉的降解，降低了基部节间强度，造成旱种水稻的倒伏。

Genotypic Responses and Physiological Mechanisms of Maize(Zea mays L.)to High Temperature Stress during Flowering

High temperature is one of the key limiting factors leading to serious yield reduction in maize production.The effect of high temperature treatments during flowering(0-8 d before silking and 0-8 d after silking)on yield and physiological response was investigated using heat-tolerant maize genotype Xundan 20 and heat-sensitive maize genotype Zhuyu 309.The results showed that high temperature treatment significantly reduced pollen fertility rate in heat-sensitive genotype,but the effect was similar to that of control in heat-tolerant genotype.The heat-sensitive genotype had a significant reduction in grain yield with a longer reduction rate under the treatment after flowering than before flowering,which was less affected for heat-tolerant genotype.The heat-stress treatment significantly increased the activities of enzymes for the leaves for the heat-tolerant genotype,while decreased the activities of enzymes involved in antioxidant system in heat-sensitive genotype.High temperature reduced photosynthetic rate in ear leaves and ATPase activity in kernels for both the heat-sensitive and heat-tolerant genotypes,but the decrease was not significant for the heat-tolerant genotype.High temperature increased malondialdehyde content in ear leaves and reduced root activity for heat-sensitive genotype.However,root activity of heat-tolerant genotypes increased significantly under high temperature.These results suggested that higher root activity,higher ATPase activity in kernels,and higher photosynthetic rate and activities of antioxidant enzymes in leaves would be important physiological traits leading to a higher grain yield for a heat-tolerant maize genotype.