Abstract This study quantified maize (Zea mays L.) water use efficiency for grain yield (WUEg) in response to plant density under contrasting water regimes; and focused on relevant eco-physiologial processes underlying the responses of maize WUEg to plant density (i.e., the proportion of transpiration in the total water used, T/ET; and the crop growth rate during the critical period for kernel set, CGRcp). Maize crops were grown at Balcarce, Argentina during two seasons. Treatments included two water regimes (i.e., rainfed and irrigated) and three plant densities (4, 8 and 12 plants m−2). Measurements comprised (i) soil water content and iPAR during the whole growing season, (ii) shoot biomass around silking and (iii) grain yield and shoot biomass at physiological maturity. Crop ET was calculated by means of water balance and soil evaporation was measured with micro-lysimeters. The response of WUEg to increasing plant density from 4 to 8 or from 4 to 12 plants m−2 was influenced by seasonal water supply. Both seasonal ET and T/ET consistently increased with plant densities across contrasting water regimes. Although increments in T/ET partition were in accordance with increasing iPAR, they did not promote higher WUEg at low water supply. Grain yield increased with plant density, except in the driest environment where no response of either grain yield nor WUEg to plant density was detected. Our results showed that the response of CGRcp to plant density increments (i) depended on the water supply, and (ii) contributed to explain WUEg response to plant density under contrasting water supplies.

中文翻译：

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不同水分条件下玉米水分利用效率对植物密度响应的生态生理过程

摘要 本研究量化了玉米 (Zea mays L.) 水分利用效率对谷物产量 (WUEg) 的响应，以响应不同水分条件下的植物密度；并关注玉米 WUEg 对植物密度响应的相关生态生理过程（即，蒸腾作用在总用水量中的比例，T/ET；以及籽粒关键期作物生长速率，CGRcp）。玉米作物在阿根廷的巴尔卡塞种植了两个季节。处理包括两种水情（即雨养和灌溉）和三种植物密度（4、8 和 12 株植物 m-2）。测量包括 (i) 整个生长季节的土壤含水量和 iPAR，(ii) 抽丝周围的地上部生物量和 (iii) 生理成熟时的谷物产量和地上部生物量。作物 ET 是通过水平衡计算的，土壤蒸发是用微蒸渗仪测量的。WUEg 对植物密度从 4 增加到 8 或从 4 增加到 12 株 m-2 的响应受季节性供水的影响。季节性 ET 和 T/ET 都随着不同水体的植物密度而持续增加。尽管 T/ET 分配的增加与 iPAR 的增加一致，但它们并没有在低供水情况下促进更高的 WUEg。谷物产量随植物密度而增加，除了在最干燥的环境中，没有检测到谷物产量和 WUEg 对植物密度的响应。我们的结果表明，CGRcp 对植物密度增量的响应 (i) 取决于供水，并且 (ii) 有助于解释在对比供水下 WUEg 对植物密度的响应。