Koehler Tina, Kim Yunhee, Tung Shu-Yin, Heymans Adrien, Tyborski Nicolas, Steiner Franziska, Wild Andreas J, Pausch Johanna, Ahmed Mutez A, Schneider Hannah M
Root-Soil Interaction, TUM School of Life Sciences, Technical University of Munich, Munich, Germany.
Institute for Agroecology and Organic Farming, Bavarian State Research Center for Agriculture (LfL), Freising, Germany.
Ann Bot. 2025 Dec 8;136(5-6):1031-1046. doi: 10.1093/aob/mcaf075.
Root anatomy, determining the composition and organization of root tissues, has implications for water uptake and transport, and potential for enhancing crop resilience amid changing environmental conditions and erratic water supply. While our understanding of the functional relationship between root anatomical traits and soil resource acquisition continues to improve, anatomical traits are commonly investigated on adventitious roots emerging from a single node or averaged across nodes. We test the hypothesis that drought adaptations of anatomical and hydraulic phenes are specific to the nodal origin of the root.
We grew four maize (Zea mays L.) genotypes in the field under control and drought conditions, imposed by rainout shelters. Subsequently, we investigated the effect of soil drought on crown root anatomical phenes between consecutive shoot nodes. Based on these phenotypes, we inferred root cross-sectional hydraulic properties by integrating simulations of root anatomical networks via the GRANAR model and translating the outputs into hydraulic properties using the MECHA model.L.
At the individual node level, drought-induced changes in root anatomical and hydraulic phenes were neither consistently significant nor unidirectional across nodes or genotypes. Notably, only second node crown roots consistently exhibited significant changes in response to drought. However, we observed distinct treatment differences in the development of phenes between consecutive shoot nodes. Most root anatomical and hydraulic phenes showed a (hyper)allometric relationship with increasing root cross-sectional area from older to younger roots. However, under drought, those allometric trajectories shifted. Specifically, root cross-sectional area and the areas of stele, cortex, metaxylem and aerenchyma, as well as cortical cell size and the axial hydraulic conductance increased more strongly from older to younger roots under drought. In contrast, metaxylem number increased more strongly under controlled conditions.
Our findings suggest that examining the drought response of root anatomical phenes at a single node may not provide a comprehensive understanding of root system responses to the environment.
根系解剖结构决定了根组织的组成和组织方式，对水分吸收和运输具有重要意义，并且在环境条件变化和供水不稳定的情况下，具有增强作物适应能力的潜力。虽然我们对根系解剖特征与土壤资源获取之间的功能关系的理解不断加深，但解剖特征通常是在从单个节点长出的不定根上进行研究，或者是对多个节点的情况进行平均研究。我们检验了这样一个假设，即解剖和水力表型的干旱适应性因根的节点起源而异。
我们在田间利用防雨棚营造对照和干旱条件，种植了四种玉米（Zea mays L.）基因型。随后，我们研究了土壤干旱对连续茎节间冠根解剖表型的影响。基于这些表型，我们通过GRANAR模型对根系解剖网络进行模拟，并使用MECHA模型将输出结果转化为水力特性，从而推断出根横截面的水力特性。
在单个节点水平上，干旱引起的根解剖和水力表型变化在不同节点或基因型之间既不一致显著，也不是单向的。值得注意的是，只有第二节的冠根对干旱始终表现出显著变化。然而，我们观察到连续茎节间表型发育存在明显的处理差异。大多数根解剖和水力表型与根横截面积从老根到幼根的增加呈现（超）异速生长关系。然而，在干旱条件下，这些异速生长轨迹发生了变化。具体而言，在干旱条件下，根横截面积、中柱、皮层、后生木质部和通气组织的面积，以及皮层细胞大小和轴向水力传导率从老根到幼根增加得更为强烈。相比之下，后生木质部数量在对照条件下增加得更为强烈。
我们的研究结果表明，在单个节点上研究根解剖表型的干旱响应可能无法全面了解根系对环境的响应。
