Plant roots often encounter heterogeneity in soil water content and respond by compensating water uptake from wet zones to cope with the transpiration demand. Simultaneously, plants may also exhibit root-mediated hydraulic redistribution from wet to dry zones. Experiments were conducted to simultaneously monitor compensated root water uptake and hydraulic redistribution in the vadose zone. Vertical and horizontal split-root lysimeters were used to hydraulically isolate maize roots under altering soil water conditions. Compensated root water uptake and root-mediated hydraulic redistribution were monitored by continuous measurement of water content in the lysimeter compartments. Soil water heterogeneity and limited soil water availability were found to accelerate the root water uptake from moist region to compensate the reduced water availability in dry zone. However, no measurable root mediated hydraulic redistribution was observed in short term basis, despite high water potential gradient in the root zone of both lysimeters. The night-time transpiration and xylem refilling processes seem to override the hydraulic redistribution on a diurnal basis in our experiment. Our study shows that compensated root water uptakeplays a major role in meeting the transpiration demand. In contrast, the role of root mediated hydraulic redistribution is found to benegligible in maize plant.

中文翻译：

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异质土壤水分条件下的根系吸水：解开补偿性根系吸水和水力再分配的实验研究

植物根系经常遇到土壤含水量的异质性，并通过补偿湿区的水分吸收来应对蒸腾需求。同时，植物也可能​​表现出从湿区到干区的根介导的水力再分配。进行了实验以同时监测包气带中补偿的根吸水和水力再分配。垂直和水平分裂根蒸渗仪用于在改变土壤水分条件下水力分离玉米根。通过连续测量蒸渗器隔室中的水含量来监测补偿的根吸水和根介导的水力再分配。发现土壤水分的异质性和有限的土壤水分可用性加速了潮湿地区根系水分的吸收，以补偿干旱地区水分可用性的减少。然而，在短期内没有观察到可测量的根系介导的水力再分配，尽管两个蒸渗仪根区的水势梯度很高。在我们的实验中，夜间蒸腾和木质部再填充过程似乎超越了昼夜水力再分配。我们的研究表明，补偿的根系水分吸收在满足蒸腾需求方面发挥着重要作用。相比之下，发现根介导的水力再分配在玉米植物中的作用可以忽略不计。尽管两种蒸渗仪的根区都有高水势梯度。在我们的实验中，夜间蒸腾和木质部再填充过程似乎超越了昼夜水力再分配。我们的研究表明，补偿的根系水分吸收在满足蒸腾需求方面发挥着重要作用。相比之下，发现根介导的水力再分配在玉米植物中的作用可以忽略不计。尽管两种蒸渗仪的根区都有高水势梯度。在我们的实验中，夜间蒸腾和木质部再填充过程似乎超越了昼夜水力再分配。我们的研究表明，补偿的根系水分吸收在满足蒸腾需求方面发挥着重要作用。相比之下，发现根介导的水力再分配在玉米植物中的作用可以忽略不计。