Abstract The lack of a continuous network of water-filled pores necessary for the flow of water in the soil has been related to the wilting of plants as well as to the limitations of soil sample equilibrium in pressure plates. The objectives of this study were: (i) to quantify deviations of the soil water content measured in pressure plates and dew point measurements at a matric potential of −15,000 hPa (commonly defined as the permanent wilting point), (ii) to determine the soil matric potential at which the physiological wilting of different plant species occurs in soil with contrasting texture, and (iii) to evaluate if the wilting of plants occurs at the hydraulic cut-off in soil. An experiment was conducted to determine the soil matric potential at which wilting of sunflower (Helianthus annuus L.), maize (Zea mays L.) and soybean (Glycine max L.) occurs in four soils with clay contents ranging from 7 to 57%. Soil water retention characteristics were determined by the pressure chamber and the dew point technique. Soil water retention data were fitted to empirical models for estimates of soil matric potential and water content at the hydraulic cut-off. The water contents at −15,000 hPa in samples equilibrated in pressure plates was similar to those obtained from the dew point method in our soils. Our results show that physiological wilting of plants is both plant species and soil dependent. In soils with low clay contents, different plant species wilted at similar water contents. However, in the clayey soils, the different crops showed different abilities in the uptake of water from the soil, where soybean wilted at significantly lower water contents than the other two species. The values of matric potential at the permanent wilting point found in our study were considerably lower than −15,000 hPa, suggesting that the commonly used definition of permanent wilting point as water content at −15,000 hPa is incorrect.

中文翻译：

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土壤类型和作物种类对植物永久枯萎的影响

摘要 水在土壤中流动所必需的连续充水孔隙网络的缺乏与植物枯萎以及压力板中土壤样品平衡的局限性有关。本研究的目的是：(i) 量化在 -15,000 hPa（通常定义为永久枯萎点）的基质势下压力板和露点测量中测量的土壤含水量的偏差，(ii) 确定在不同质地的土壤中发生不同植物生理萎蔫的土壤基质势，以及 (iii) 评估植物的萎蔫是否发生在土壤中的水力截断处。进行了一项试验以确定向日葵 (Helianthus annuus L.)、玉米 (Zea mays L.) 枯萎时的土壤基质势。) 和大豆 (Glycine max L.) 出现在粘土含量范围为 7% 至 57% 的四种土壤中。土壤保水特性由压力室和露点技术确定。土壤保水数据被拟合到经验模型中，用于估计水力截止时土壤基质势和含水量。在压力板中平衡的样品中 -15,000 hPa 的水含量与我们土壤中通过露点法获得的水含量相似。我们的研究结果表明，植物的生理萎蔫既取决于植物种类，也取决于土壤。在粘土含量低的土壤中，不同的植物物种在相似的含水量下枯萎。然而，在黏性土壤中，不同作物从土壤中吸收水分的能力不同，大豆在含水量明显低于其他两个品种的情况下枯萎。在我们的研究中发现的永久萎蔫点的基质势值远低于-15,000 hPa，表明通常使用的永久萎蔫点定义为-15,000 hPa的水含量是不正确的。