Koch Axelle, Cai Gaochao, Ahmed Mutez Ali, Meunier Félicien, Carminati Andrea, Vanderborght Jan, Javaux Mathieu
Earth and Life Institute, Environmental Sciences, UCLouvain, Croix du Sud 2 L7.05.02, BE-1348 Louvain-la-Neuve, Belgium.
School of Agriculture and Biotechnology, Shenzhen Campus of Sun Yat-Sen University, 518107 Shenzhen, China.
Ann Bot. 2025 Dec 8;136(5-6):1047-1064. doi: 10.1093/aob/mcaf082.
Root water uptake (RWU) is influenced by rhizosphere conductance and soil-root contact, which vary with soil texture and root structure, including root hairs. Current simplified models often fail to capture the spatial complexity of these interactions in drying soils. The aim of this study was to examine how rhizosphere conductance, soil-root contact and root hairs affect RWU.
We used an explicit three-dimensional functional-structural model to investigate how root and rhizosphere hydraulics influence the transpiration rate-leaf water potential relationship of two maize (Zea mays) genotypes (with and without root hairs) grown in two contrasting soil textures (loam and sand) during soil drying. The model incorporated rhizosphere resistance in series with radial root resistance, with the latter being influenced by maturation (development of apoplastic barriers with age). It considered two critical processes: (1) the decrease in soil water potential between bulk soil and the soil-root interface; and (2) the extent of soil-root contact.
The simulations revealed that RWU was highly soil texture specific. In loam, the non-linearity in the transpiration rate-leaf water potential relationship was attributable primarily to localized uptake fluxes and high rhizosphere resistance as soil dried. In sand, however, where soil-root contact was less effective, rhizosphere conductance became a significant limiting factor for RWU, even at relatively higher soil water potential in comparison to loam. Root hairs did not make a significant contribution to rhizosphere conductance, probably owing to the dominant effect of soil-root interaction. Additionally, variations in root hydraulic conductance and its change with root tissue age impacted the accuracy of the model.
The explicit three-dimensional model provides a more precise representation of RWU dynamics by pinpointing exact uptake locations and primary limiting factors and by quantifying the proportion of root surface actively engaged in RWU. This approach offers notable improvements over conventional models for understanding the spatial dynamics of water uptake in different soil environments.
根系水分吸收（RWU）受根际导度和土壤-根系接触的影响，而这两者会随土壤质地和根系结构（包括根毛）的变化而变化。当前的简化模型往往无法捕捉干燥土壤中这些相互作用的空间复杂性。本研究的目的是探究根际导度、土壤-根系接触和根毛如何影响根系水分吸收。
我们使用一个明确的三维功能-结构模型，来研究根系和根际水力学如何影响两种玉米（Zea mays）基因型（有根毛和无根毛）在土壤干燥过程中生长于两种不同土壤质地（壤土和砂土）时的蒸腾速率-叶片水势关系。该模型将根际阻力与径向根系阻力串联起来，后者受成熟度（随着年龄增长质外体屏障的发育）影响。它考虑了两个关键过程：（1）土体与土壤-根系界面之间土壤水势的降低；（2）土壤-根系接触的程度。
模拟结果表明，根系水分吸收具有高度的土壤质地特异性。在壤土中，蒸腾速率-叶片水势关系的非线性主要归因于随着土壤干燥局部吸收通量和高根际阻力。然而，在砂土中，土壤-根系接触效果较差，根际导度成为根系水分吸收的一个重要限制因素，即使与壤土相比土壤水势相对较高时也是如此。根毛对根际导度没有显著贡献，可能是由于土壤-根系相互作用的主导效应。此外，根系水力导度的变化及其随根组织年龄的变化影响了模型的准确性。
明确的三维模型通过精确确定吸收位置和主要限制因素，并量化积极参与根系水分吸收活动的根表面积比例，更精确地呈现了根系水分吸收动态。这种方法相对于传统模型在理解不同土壤环境中水分吸收的空间动态方面有显著改进。
