Background and aims

In grapevines and other deep-rooting plants, heterogeneous drying from the surface to deeper soil layers drives water extraction by roots. Modelling and measurements have shown that dry soils, especially with sandy texture, create abrupt water potential gradient in the rhizosphere. At the scale of the thin contact between the soil and roots, the hydraulic continuity could be lost at the soil-root interface in dry soil conditions. This study aimed to understand how the multiscale interactions between soil and roots affect grapevine root water uptake and water potential.

Methods

Using a physically-based model, implementing rhizosphere and root system hydraulic properties, and loss of soil-root hydraulic continuity in dry soil conditions, we quantified belowground hydraulic conductances and their impact on grapevine root water uptake and water potential in different soil types with vertical hydraulic properties heterogeneity.

Results

Soil-root hydraulic disconnection prevented the plant from feeling the dry shallowest soil horizons avoiding very negative trunk water potentials, and moved water uptake towards deeper wet soil horizons. The main belowground hydraulic bottleneck of soil-plant system during drought is soil-texture dependent, with the rhizosphere limiting root water uptake in the sandy subplot, and the root system in the loamy subplot.

Conclusion

By highlighting the key roles of rhizosphere hydraulics, root hydraulics and hydraulic disconnection on root water uptake and plant water status, in different edaphic conditions, this study enhanced our mechanistic understanding on soil-root water relations in soil water limited conditions.

中文翻译：

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植物和土壤水势监测和建模相结合，证明干旱期间土壤根系水力断开

 背景和目标

在葡萄藤和其他深根植物中，从表面到更深土壤层的异质干燥推动了根部的水分提取。建模和测量表明，干燥的土壤，尤其是沙质土壤，会在根际产生突然的水势梯度。在土壤和根之间的薄接触规模上，在干燥土壤条件下，土壤-根界面处可能会失去水力连续性。本研究旨在了解土壤和根之间的多尺度相互作用如何影响葡萄根的水分吸收和水势。

 方法

使用基于物理的模型，实现根际和根系水力特性，以及干燥土壤条件下土壤根系水力连续性的损失，我们量化了地下水力导率及其对垂直水力特性异质性的不同土壤类型中葡萄藤根系水分吸收和水势的影响。

 结果

土壤根系水力断开使植物无法感觉到干燥、最浅的土壤层，从而避免了非常负的树干水势，并将水分吸收转移到更深的潮湿土壤层。干旱期间土壤-植物系统的主要地下水力瓶颈依赖于土壤质地，根际限制了沙质小样地的根系水分吸收，而壤土小样地的根系则受到限制。

 结论

通过强调根际水力学、根系水力学和水力断开对根系水分吸收和植物水分状况的关键作用，在不同的教育条件下，本研究增强了我们对土壤水分有限条件下土壤-根系水分关系的机械理解。