Plant Ecophysiology and Evolution Group, State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi University, Nanning, Guangxi 530004, China.
Guangxi Key Laboratory of Forest Ecology and Conservation, College of Forestry, Guangxi University, Nanning 530004, China.
Plant Physiol. 2022 Nov 28;190(4):2246-2259. doi: 10.1093/plphys/kiac403.
Fine roots and leaves, the direct interfaces of plants with their external environment along the soil-plant-atmosphere continuum, are at the front line to ensure plant adaptation to their growing habitat. This study aimed to compare the vulnerability to water deficit of fine roots and leaves of woody species from karst and mangrove forests-two water-stressed habitats-against that of timber and ornamental woody species grown in a well-watered common garden. Thus, pressure-volume curves in both organs of 37 species (about 12 species from each habitat) were constructed. Fine roots wilted at a less negative water potential than leaves in 32 species and before branch xylem lost 50% of its hydraulic conductivity in the 17 species with available data on branch xylem embolism resistance. Thus, turgor loss in fine roots can act as a hydraulic fuse mechanism against water stress. Mangroves had higher leaf resistance against wilting and lower leaf-specific area than the karst and common garden plants. Their fine roots had high specific root lengths (SRL) and high capacitance to buffer water stress. Karst species had high leaf bulk modulus, low leaf capacitance, and delayed fine root wilting. This study showed the general contribution of fine roots to the protection of the whole plant against underground water stress. Our findings highlight the importance of water storage in the leaves and fine roots of mangrove species and high tolerance to water deficit in the leaves of mangrove species and the fine roots of some karst species.
细根和叶片是植物与其外部环境沿着土壤-植物-大气连续体直接接触的部位，处于确保植物适应生长环境的最前线。本研究旨在比较喀斯特和红树林两种水分胁迫生境中木本植物的细根和叶片对水分亏缺的脆弱性，以及与在水分充足的普通花园中生长的木材和观赏木本植物的脆弱性。因此，构建了 37 个物种（每个生境约 12 个物种）的细根和叶片的压力-容积曲线。在 32 个物种中，细根的萎蔫发生在比叶片更负的水势下，在有关于枝木质部栓塞阻力的可用数据的 17 个物种中，细根的木质部导水率丧失了 50%。因此，细根中的膨压损失可以作为一种抵抗水分胁迫的水力熔断机制。与喀斯特和普通花园植物相比，红树林具有更高的叶片抗萎蔫能力和更低的叶片比叶面积。它们的细根具有较高的比根长（SRL）和较高的缓冲水分胁迫的能力。喀斯特物种具有较高的叶片体积模量、较低的叶片电容和延迟的细根萎蔫。本研究表明了细根对保护整个植物免受地下水分胁迫的普遍贡献。我们的研究结果强调了在叶片和红树林物种细根中储存水分的重要性，以及在一些喀斯特物种的叶片和细根中对水分亏缺的高耐受性。
