Aims

Growth reductions and yield losses from drought could be mitigated by developing rice genotypes with more efficient root systems. We examined spatiotemporal responses to drought in order to determine whether roots developing in upper vs. deeper soil layers respond differently to drought stress.

Methods

Root anatomical and architectural phenotypes of two rice genotypes, Azucena (drought tolerant) and IR64 (drought susceptible), were measured weekly in well-watered and vegetative-stage drought stress treatments in solid medium with stratified moisture availability. Basal and apical segments were collected from older, deeper nodal roots and apical segments from younger, shallow roots for assessment of anatomy and lateral rooting phenotypes. The relationship between root anatomy and root respiration rates was tested in solution culture and solid medium.

Results

Compared to IR64, Azucena had deeper root systems and larger diameter roots in both treatments but reduced its living tissue area in response to drought, while IR64 roots exhibited less plasticity in root diameter. Root respiration rates were positively correlated with root diameter and living tissue area, providing evidence that root anatomy affects the metabolic cost of tissues. In response to drought, Azucena showed reduced theoretical axial hydraulic conductance in shallow roots and at the base of deep roots but slightly greater conductance at the tip of deep roots, while IR64 displayed low plasticity in metaxylem phenotypes.

Conclusion

We propose that the plasticity of root phenotypes in Azucena contributes to its drought tolerance by reducing the metabolic cost of soil exploration and improving the efficiency of water transport.

中文翻译：

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水稻根系结构和解剖结构对干旱的时空响应

目标

通过开发具有更有效根系的水稻基因型，可以减轻干旱造成的生长减少和产量损失。我们检查了对干旱的时空响应，以确定在上层和深层土壤中发育的根是否对干旱胁迫有不同的反应。

方法

每周测量两种水稻基因型 Azucena（耐旱）和 IR64（耐旱）的根解剖和结构表型，在具有分层水分可用性的固体培养基中进行充分浇水和营养阶段干旱胁迫处理。从较老、较深的结节根和较年轻、浅根的顶端部分收集基底和顶端部分，以评估解剖结构和侧生根表型。在溶液培养和固体培养基中测试了牙根解剖结构和牙根呼吸率之间的关系。

结果

与 IR64 相比，Azucena 在两种处理中都具有更深的根系和更大的根直径，但由于干旱而减少了其活组织面积，而 IR64 根的根直径表现出较小的可塑性。根呼吸率与根直径和活组织面积呈正相关，提供了根解剖影响组织代谢成本的证据。为应对干旱，Azucena 在浅根和深根基部的理论轴向水力传导率降低，但在深根尖端的传导率略高，而 IR64 在后木质部表型中表现出低可塑性。

结论

我们提出，Azucena 根表型的可塑性通过降低土壤勘探的代谢成本和提高水运效率来提高其耐旱性。