Abstract Elevated CO2 and temperature are expected to result in drought stress with increased intensity and frequency, yet our understanding of subsequent plant response is generally limited. The objective of this study was to investigate the impacts of elevated CO2 and temperature on physiological traits affecting drought tolerance of cotton plants (Gossypium hirsutum). We grew cotton plants in the glasshouse under two CO2 treatments (Ca: 420 ppm; Ce: 640 ppm) and two temperature treatments (Ta: 32/24 °C; day/night; Te: 36/28 °C; day/night) with adequate irrigation and fertilization. Plant allometry, leaf gas exchange and a suite of hydraulic characteristics (xylem resistance to drought-induced embolism in the leaf and stem, leaf tolerance to dehydration-induced loss of rehydration capacity, and water transport capacity of stem) were examined. Xylem anatomical traits of the leaf and stem were also examined to elucidate the structural basis for potential physiological adjustments. Ce increased canopy leaf area and decreased leaf level water loss at Ta, and decreased stomatal conductance and transpiration at both temperatures. Moreover, Ce significantly increased stem conductivity at Ta, but xylem tissue was less resistant to drought induced embolism. Te altered the pattern of xylem conductivity and embolism resistance response to CO2, with the stem less hydraulically conductive while the xylem was more tolerant to embolism under Ce. The variation of stem conductivity and embolism resistance of the stem across CO2 and temperature treatments was likely to be partially explained by xylem anatomy. Overall, CO2 and temperature had interactive effects on traits associated with water relations of cotton, such that elevated CO2 compromised drought tolerance under ambient temperature, but these negative impacts were partially mitigated by elevated temperature.

中文翻译：

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温度改变棉花植物（Gossypium hirsutum）中水力结构对二氧化碳的响应

摘要 预计 CO2 和温度升高会导致干旱胁迫的强度和频率增加，但我们对后续植物响应的理解通常有限。本研究的目的是调查二氧化碳和温度升高对影响棉花植物（Gossypium hirsutum）耐旱性的生理性状的影响。我们在温室中种植棉花，采用两种 CO2 处理（Ca：420 ppm；Ce：640 ppm）和两种温度处理（Ta：32/24 °C；白天/黑夜；Te：36/28 °C；白天/黑夜） ) 有足够的灌溉和施肥。检查了植物异速生长、叶气体交换和一系列水力特性（木质部对叶和茎中干旱引起的栓塞的抗性、叶片对脱水引起的再水化能力丧失的耐受性以及茎的水分输送能力）。还检查了叶和茎的木质部解剖特征，以阐明潜在生理调整的结构基础。在 Ta 下，Ce 增加了冠层叶面积并减少了叶面水分流失，并降低了两个温度下的气孔导度和蒸腾作用。此外，Ce 显着增加了 Ta 处的茎电导率，但木质部组织对干旱诱导的栓塞的抵抗力较差。Te 改变了木质部传导性的模式和对 CO2 的栓塞抵抗反应，茎的水力传导性较低，而木质部在 Ce 下更能耐受栓塞。木质部解剖结构可能部分解释了茎在 CO2 和温度处理下的茎电导率和栓塞阻力的变化。全面的，