The greenhouse effect caused by global warming was becoming more and more obvious, resulting in increased frequency of high temperature and high humidity, which significantly affected maize productivity. However, it was poorly understood how the interactions of high temperature and high humidity affected leaf senescence, photosynthetic performance and yield of summer maize. Three stress treatments including (a) high temperature stress (T), (b) waterlogging stress (W) and (c) complex stress (T‐W) were set at the third leaf stage (V3), the sixth leaf stage (V6) and the tasselling stage (VT) in 2019–2020 to explore the influence mechanism of complex stress. Each stress treatment period lasted 6 days. Non‐stressed plants served as control. Yield, antioxidant enzyme activity, photosynthetic characteristics, and dry matter accumulation were determined. Our study found that the activity of antioxidant enzymes was significantly decreased, while malonyldialdehyde (MDA) accumulation was increased under each stress treatment. As a result, the photosynthetic characteristics were impaired, manifested in a significant decrease in net photosynthetic rate (Pn), enzyme activities of phosphoenolpyruvate carboxylase (PEPCase) and ribulose diphosphate carboxylase (RUBPCase). The decrease in photosynthetic intensity affected by each stress treatment led to a significant decrease in total dry matter accumulation and grain yield. The most significant effects of waterlogging and combined stresses on yield occurred at the V3 stage, followed by the V6 and VT stages. However, the most significant effects of high temperature occurred at the VT stage, followed by the V6 and V3 stages. Moreover, the compound stress exacerbated damage to leaf senescence and photosynthetic properties of summer maize compared to the single stress of high temperature or waterlogging.

中文翻译：

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涝渍和高温复合胁迫加速玉米叶片衰老，不同生育期光合性能下降

全球变暖造成的温室效应日益明显，导致高温高湿频率增加，严重影响玉米产量。然而，人们对高温高湿相互作用如何影响夏玉米叶片衰老、光合性能和产量知之甚少。在第三叶期(V3)、第六叶期(V6)设置3个胁迫处理，包括(a)高温胁迫(T)、(b)涝害胁迫(W)和(c)复合胁迫(T-W) ）和2019-2020年抽雄阶段（VT），探讨复杂胁迫的影响机制。每个应激治疗期持续6天。非胁迫植物作为对照。测定了产量、抗氧化酶活性、光合特性和干物质积累。我们的研究发现，在每次应激处理下，抗氧化酶的活性显着降低，而丙二醛（MDA）的积累增加。结果，光合特性受损，表现为净光合速率显着下降（磷n)，磷酸烯醇丙酮酸羧化酶(PEPCase)和二磷酸核酮糖羧化酶(RUBPCase)的酶活性。受各胁迫处理影响的光合强度降低导致总干物质积累和籽粒产量显着降低。涝害和综合胁迫对产量的影响最显着发生在V3阶段，其次是V6阶段和VT阶段。然而，高温影响最显着发生在VT阶段，其次是V6和V3阶段。而且，与高温或涝渍单一胁迫相比，复合胁迫加剧了夏玉米叶片衰老和光合特性的损害。