Do pigeon pea and sesbania supply groundwater to intercropped maize through hydraulic lift?—Hydrogen stable isotope investigation of xylem waters
Do pigeon pea and sesbania supply groundwater to intercropped maize through hydraulic lift?—Hydrogen stable isotope investigation of xylem waters
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DOI：
10.1016/j.fcr.2003.08.007
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发表时间：
2004-03
影响因子：
5.8
通讯作者：
Nobuhito Sekiya;K. Yano
中科院分区：
文献类型：
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作者：
Nobuhito Sekiya;K. Yano
水力提升是指水分通过植物根系在水势不同的土层之间的运动。我们预期，将深根植物引入间作系统可以为相关作物提供通过水力提升利用土壤深层水分的机会。在赞比亚国家灌溉研究站进行的一项实地实验中，使用了一种稳定的氢同位素（氘）来研究这种可能性。将玉米（Zea mays）植株种植在深根豆科植物木豆（Cajanus cajan）和田菁（Sesbania sesban）附近，这些植物的根进入地下水，其氘/氢同位素比值（δD）不同于降雨。我们假设，当水力抬升发生时，浅根玉米木质部沃茨的δD值会更接近地下水的δD值，这会受到玉米和豆科植物之间距离的影响。靠近木豆的玉米δD值与地下水的δD值接近，而远离木豆的玉米δD值与地下水的δ D值不接近。然而，我们不能检测到这样的距离依赖性在玉米植株附近的田菁。在田间试验的基础上，对鸽豆-玉米组合进行了温室试验。植物生长在两个土壤层之间具有空气间隙的分根容器中。使木豆根在注入D2 O的底层土壤中发育，而玉米根被限制在表层土壤中。注射后立即在每株玉米植株的木质部沃茨中检测到高于天然存在水平的较高D浓度，证实木豆从底部提升水并将其转移到玉米。此外，通过对木豆进行遮光处理，木豆对玉米的供水量增加，这意味着调节水力提升功能的可能性。它的结论是，至少木豆可以提供水从更深的土壤层相关联的玉米植物通过水力升降机，这样一个喷头一样的功能（抽水和水转移到周围的植物）可以调节抑制蒸腾速率的农业实践。
Hydraulic lift is a movement of water between soil layers contrasting in water potential through plant root systems. We expected that an introduction of deep-rooted plants into intercropping systems could provide an opportunity for the associated crops to utilize water from deep in the soil layers through hydraulic lift. A stable hydrogen isotope (deuterium) was used to investigate this possibility in a field experiment conducted at the Zambia National Irrigation Research Station. Maize (Zea mays) plants were grown adjacent to the deep rooting legumes, pigeon pea (Cajanus cajan) and sesbania (Sesbania sesban), whose roots accessed groundwater having the deuterium/hydrogen isotope ratios (δD) different from those of rainfall. We hypothesized that the δD values of xylem waters from shallow-rooted maize would become closer to those of groundwater when hydraulic lift occurred, and this would be affected by the distance between the maize and the legumes. The maize near pigeon pea showed δD values closer to those of groundwater while the maize at a distance did not. However, we could not detect such a distance-dependence in maize plants grown adjacent to sesbania. Based on the field trial, a glasshouse experiment was implemented for the pigeon pea–maize association. The plants were grown in a split-root container with an air gap between the two soil layers. The pigeon pea roots were allowed to develop in the bottom soil injected with D2O while the maize roots were confined in the top soil. Immediately after the injection, a higher D concentration above the level of natural occurrence was detected in xylem waters from each of the maize plants, confirming that pigeon pea lifted water from the bottom and transferred it to the maize. Moreover, the water supply from the pigeon pea to the maize was enhanced by the shading treatment on the pigeon pea, implying the possibility of regulating the function of the hydraulic lift. It is concluded that at least pigeon pea can supply water from deeper soil layers to the associating maize plants through hydraulic lift, and that such a sprinkler-like function (pumping up and transferring water to surrounding plants) may be regulated by agricultural practices that suppress transpiration rate.