Rhizosphere wettability decreases with root age: a problem or a strategy to increase water uptake of young roots?
Rhizosphere wettability decreases with root age: a problem or a strategy to increase water uptake of young roots?
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DOI：
10.3389/fpls.2013.00298
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发表时间：
2013
影响因子：
5.6
通讯作者：
Carminati A
中科院分区：
文献类型：
--
作者：
Carminati A
由于植物根系吸收水分，土壤干燥，预计在根系附近（所谓的根际）会发生水分耗竭。然而，最近的实验表明，羽扇豆的根际比干期的非根际土壤湿润。令人惊讶的是，根际保持暂时干燥灌溉后。这种根际水分动态可以用根系分泌粘液的干湿动态来解释。粘液在负水势下保持大量水分的能力可能有利于根系吸水。然而，干燥后的粘液疏水性可能会暂时限制灌溉后的局部吸水。这种根际动力学的影响还不清楚。特别是，它是不知道根际动态如何变化沿着根和土壤含水量的函数。我的假设是，根际的再湿润率主要是根龄的函数。利用中子照相技术研究了不同干湿周期下羽扇豆根系沿着根际水分动态的变化。射线照片显示，快速和几乎立即再润湿的根际的远端根段，在近端段的根际的缓慢再润湿相反。根际土壤再湿速率与灌水前含水量无关，而是时间的函数。得出的结论是，根际疏水性沿着根系并不均匀，但它仅覆盖较老的根段和近端的根段，而年轻的根段与土壤水力连接良好。我把这些根际动态包括在根吸水的微观模型中。在模型中，根际土壤含水量与水势的关系不是唯一的，而是随时间变化的，根际土壤的再润湿速率随时间而减小。rhisosphere的变化似乎是一个最佳的适应策略，以增加年轻的根段，这可能达到新的可用水的吸水，并部分断开旧的根段已经耗尽的土壤。
As plant roots take up water and the soil dries, water depletion is expected to occur in the vicinity of roots, the so called rhizosphere. However, recent experiments showed that the rhizosphere of lupines was wetter than the bulk soil during the drying period. Surprisingly, the rhizosphere remained temporarily dry after irrigation. Such water dynamics in the rhizosphere can be explained by the drying/wetting dynamics of mucilage exuded by roots. The capacity of mucilage to hold large volumes of water at negative water potential may favor root water uptake. However, mucilage hydrophobicity after drying may temporarily limit the local water uptake after irrigation. The effects of such rhizosphere dynamics are not yet understood. In particular, it is not known how the rhizosphere dynamics vary along roots and as a function of soil water content. My hypothesis was that the rewetting rate of the rhizosphere is primarily function of root age. Neutron radiography was used to monitor how the rhizosphere water dynamics vary along the root systems of lupines during drying/wetting cycles of different duration. The radiographs showed a fast and almost immediate rewetting of the rhizosphere of the distal root segments, in contrast to a slow rewetting of the rhizosphere of the proximal segments. The rewetting rate of the rhizosphere was not function of the water content before irrigation, but it was function of time. It is concluded that rhizosphere hydrophobicity is not uniform along roots, but it covers only the older and proximal root segments, while the young root segments are hydraulically well-connected to the soil. I included these rhizosphere dynamics in a microscopic model of root water uptake. In the model, the relation between water content and water potential in the rhizosphere is not unique and it varies over time, and the rewetting rate of the rhizosphere decreases with time. The rhisosphere variability seems an optimal adaptation strategy to increase the water uptake of young root segments, which possibly reached new available water, and partly disconnect the old root segments from the already depleted soil.
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影响因子：
4.2
作者：
Iijima, M;Higuchi, T;Barlow, PW
通讯作者：
Barlow, PW
影响因子：
4.9
作者：
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影响因子：
6.3
作者：
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作者：
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