Abstract：
OBJECTIVE: Five species of cotton (Gossypium) were exposed to 38°C days during early vegetative development. Commercial cotton (Gossypium hirsutum) was contrasted with four wild cotton species (G. australe, G. bickii, G. robinsonii and G. sturtianum) that are endemic to central and northern Australia.
METHODS: Plants were grown at daytime maxima of 30°C or 38°C for 25 d, commencing at the four-leaf stage. Leaf areas and shoot biomass were used to calculate relative rates of growth and specific leaf areas. Leaf gas exchange measurements revealed assimilation and transpiration rates, as well as electron transport rates (ETR) and carboxylation efficiency (CE) in steady-state conditions. Finally, leaf morphological traits (mean leaf area and leaf shape were quantified), along with leaf surface decorations, imaged using scanning electron microscopy.
RESULTS: Shoot morphology was differentially affected by heat, with three of the four wild species growing faster at 38°C than at 30°C, whereas early growth in G. hirsutum was severely inhibited by heat. Areas of individual leaves and leaf numbers both contributed to these contrasting growth responses, with fewer, smaller leaves at 38°C in G. hirsutum. CO2 assimilation and transpiration rates of G. hirsutum were also dramatically reduced by heat. Cultivated cotton failed to achieve evaporative cooling, contrasting with the transpiration-driven cooling in the wild species. Heat substantially reduced ETR and CE in G. hirsutum, with much smaller effects in the wild species. We speculate that leaf shape, as assessed by invaginations of leaf margins, and leaf size contributed to heat dispersal differentially among the five species. Similarly, reflectance of light radiation was also highly distinctive for each species.
CONCLUSIONS: These four wild Australian relatives of cotton have adapted to hot days that are inhibitory to commercial cotton, deploying a range of physiological and structural adaptations to achieve accelerated growth at 38°C.
METHODS: Plants were grown at daytime maxima of 30°C or 38°C for 25 d, commencing at the four-leaf stage. Leaf areas and shoot biomass were used to calculate relative rates of growth and specific leaf areas. Leaf gas exchange measurements revealed assimilation and transpiration rates, as well as electron transport rates (ETR) and carboxylation efficiency (CE) in steady-state conditions. Finally, leaf morphological traits (mean leaf area and leaf shape were quantified), along with leaf surface decorations, imaged using scanning electron microscopy.
RESULTS: Shoot morphology was differentially affected by heat, with three of the four wild species growing faster at 38°C than at 30°C, whereas early growth in G. hirsutum was severely inhibited by heat. Areas of individual leaves and leaf numbers both contributed to these contrasting growth responses, with fewer, smaller leaves at 38°C in G. hirsutum. CO2 assimilation and transpiration rates of G. hirsutum were also dramatically reduced by heat. Cultivated cotton failed to achieve evaporative cooling, contrasting with the transpiration-driven cooling in the wild species. Heat substantially reduced ETR and CE in G. hirsutum, with much smaller effects in the wild species. We speculate that leaf shape, as assessed by invaginations of leaf margins, and leaf size contributed to heat dispersal differentially among the five species. Similarly, reflectance of light radiation was also highly distinctive for each species.
CONCLUSIONS: These four wild Australian relatives of cotton have adapted to hot days that are inhibitory to commercial cotton, deploying a range of physiological and structural adaptations to achieve accelerated growth at 38°C.
摘要：
目的：五种棉花（棉属）在营养发育早期暴露于38°C天。商品棉（陆地棉）与四种野生棉种（G。澳大利亚,G.Bickii,G.robinsonii和G.sturtianum）是澳大利亚中部和北部特有的。
方法：植物在30°C或38°C的白天最大值下生长25d，从四叶阶段开始。叶面积和芽生物量用于计算相对生长速率和比叶面积。叶片气体交换测量显示同化和蒸腾速率，以及稳态条件下的电子传输速率（ETR）和羧化效率（CE）。最后,叶片形态性状(量化平均叶面积和叶形)，随着叶子表面装饰，使用扫描电子显微镜成像。
结果：芽形态受到热的不同影响，四个野生物种中的三个在38°C时比在30°C时生长得更快，而热严重抑制了陆地棉的早期生长。单个叶片的面积和叶片数量都对这些相反的生长响应做出了贡献，少了,较小的叶子在38°C。热也大大降低了陆生G的CO2同化和蒸腾速率。栽培棉花未能实现蒸发冷却，与野生物种的蒸腾驱动的冷却形成鲜明对比。热量大大降低了陆生G中的ETR和CE，对野生物种的影响要小得多。我们推测叶子的形状，根据叶片边缘的内陷评估，叶片大小对五个物种之间的热量扩散有不同的贡献。同样，每个物种的光辐射反射率也非常独特。
结论：这四个野生澳大利亚棉花近缘种适应了对商品棉花具有抑制作用的炎热天气，部署一系列的生理和结构适应，以实现在38°C加速生长。
方法：植物在30°C或38°C的白天最大值下生长25d，从四叶阶段开始。叶面积和芽生物量用于计算相对生长速率和比叶面积。叶片气体交换测量显示同化和蒸腾速率，以及稳态条件下的电子传输速率（ETR）和羧化效率（CE）。最后,叶片形态性状(量化平均叶面积和叶形)，随着叶子表面装饰，使用扫描电子显微镜成像。
结果：芽形态受到热的不同影响，四个野生物种中的三个在38°C时比在30°C时生长得更快，而热严重抑制了陆地棉的早期生长。单个叶片的面积和叶片数量都对这些相反的生长响应做出了贡献，少了,较小的叶子在38°C。热也大大降低了陆生G的CO2同化和蒸腾速率。栽培棉花未能实现蒸发冷却，与野生物种的蒸腾驱动的冷却形成鲜明对比。热量大大降低了陆生G中的ETR和CE，对野生物种的影响要小得多。我们推测叶子的形状，根据叶片边缘的内陷评估，叶片大小对五个物种之间的热量扩散有不同的贡献。同样，每个物种的光辐射反射率也非常独特。
结论：这四个野生澳大利亚棉花近缘种适应了对商品棉花具有抑制作用的炎热天气，部署一系列的生理和结构适应，以实现在38°C加速生长。
