Heat Shock Protein 70 May Improve the Ability of Antioxidant Defense Induced by the Combination of Drought and Heat in Maize Leaves
In order to determine the mechanism of heat shock protein (HSP70) increasing crops endurance to the combination of drought and heat, we investigated the physiological characteristics of four maize varieties with different responses to drought and heat stresses. The results are as follows: (1) Under drought, heat, the combination of drought and heat, the increase of malondial-delehyde (MDA) content in leaf was the lowest in Zhuyu 309 without endurance to three stresses and the highest in Longyu 602 with endurance to three stresses; under drought, leaf MDA increase in Zhengdan 958 with drought-endurance was less than that in Xundan 20 leaves with heat-endurance; under heat, leaf MDA increase was more in Zhengdan 958 than in Xundan 20. (2) In Zhengdan 958, Xundan 20, Longyu 602 leaves, the increase of ascorbate peroxidese (APX), glutathione reductase (GR), supero-xide dismutase (SOD), catalase (CAT) activities was more than that in Zhuyu 309 leaves under drought, heat, the combination of drought and heat; under drought, APX, GR, SOD, CAT activities of Zhengdan 958 leaves increased significantly more than those of Xundan 20', but those were contrary under heat; under the combination of drought and heat, APX, GR, SOD activities of Longyu 602 leaves increased significantly more than those of Zhengdan 958 and Xundan 20. (3) The pretreatrnent with HSP70 inhibitor quercetin (Q) significandy inhibited the increase of antioxidant enzymes activities in leaves of four maize varieties ex-posed to the three stresses. These results suggested that HSP70 involved in the increase of antioxidant enzyme activity in leaves of four maize varieties exposed to drought, heat and their combination, and APX, GR, SOD activities could be used as chemical and biological indicators to evaluate the crop endurance to drought, heat, and the combination of drought and heat stresses.
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