植物生态学报

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干旱胁迫下木本植物水力系统的响应机制

罗丹丹1,王传宽2,金鹰3   

  1. 1. 东北林业大学生态研究中心
    2. 东北林业大学生态研究中心, 哈尔滨 150040
    3. 东北林业大学
  • 收稿日期:2021-03-25 修回日期:2021-08-17 发布日期:2021-08-26
  • 通讯作者: 王传宽
  • 基金资助:
    中央高校基本科研业务费专项资金项目;国家“十三五”重点研发计划项目;教育部长江学者和创新团队发展计划

Response mechanism of hydraulic system of woody plants to drought stress

Dan-dan Luo1,Chuan-Kuan WANG 3   

  • Received:2021-03-25 Revised:2021-08-17 Published:2021-08-26
  • Contact: Chuan-Kuan WANG
  • Supported by:
    Fundamental Research Funds for the Central Universities;National Science and Technology Support Program of China;Program for Changjiang Scholars and Innovative Research Team in University

摘要: 干旱导致树木死亡对生态系统功能和碳平衡有重大影响。植物水分运输系统失调是引发树木死亡的主要机制之一。然而,树木对干旱胁迫的响应是多维且复杂的,使得我们对植物水分运输系统和极端干旱条件下植物死亡机理的还认识不清。本文首先阐述了木本植物应对干旱胁迫的一般响应过程。其次,评述了衡量植物抗旱性的指标,着重介绍了可以综合评价植物干旱抗性特征的新参数,气孔安全阈值(SSM)。SSM值越高,表明植物气孔和水力之间的协调能力更强,木质部栓塞的可能性越低,水力策略更保守。之后,分别综述了植物不同器官(叶、茎和根)应对干旱胁迫的响应机制。植物达到死亡临界阈值的概率和时间取决于相关生理和形态学特征的相互作用。最后,介绍了木本植物水力恢复机制,并提出3个亟待开展的研究问题:(1)改进叶片水分运输(木质部和木质部外水力导度)的测量方法,量化四种不同途径的叶肉水分运输情况;(2)量化叶片表皮通透性变化,以便更好地理解植物水分利用策略;(3)将水碳耦合机制纳入植被动态预测模型,联系个体结构和生理特征与群落/景观格局和过程,以便更好地评估和监测干旱诱导树木死亡的风险。

关键词: 抗旱性, 木质部栓塞, 气孔调节, 树木死亡, 水力性状

Abstract: Drought-related tree mortality profoundly impacts ecosystem functions and the carbon budget, in which the principal mechanism involved has been suggested to be the catastrophic failure of the hydraulic systems. However, our understanding of tree hydraulic systems and the mechanisms of tree death during extreme drought conditions are limited because the responses of trees to drought stress are multi-dimensional and complex. In this review, we first integrated the general response process of woody plants to drought stress. Second, we expounded the indexes of measuring plant drought resistance, focusing on stomatal safety margin (SSM) that can be used to comprehensively evaluate the drought tolerance of plant. The large positive values of SSM indicate a stronger coordination ability between stomata and hydraulic traits, a lower possibility of xylem embolization, and a more conservative hydraulic strategy. After that, we introduced the response mechanisms of different plant organs (leaf, stem and root) to drought stress. The probability of reaching the critical threshold and duration of tree death was determined by the interaction of physiological and morphological traits. Finally, we discussed the hydraulic recovery mechanisms of woody plants, and put forward three research priorities in future: (1) to improve the methodology for measuring leaf hydraulic conductance (xylem and outside the xylem hydraulic conductance), and quantify the relative contributions of the four water transport pathways in mesophyll tissues; (2) to quantify the variation in epidermal permeability for better understanding plant water-use strategies; and (3) to improve vegetation dynamics models by considering the water-carbon coupling mechanisms, and link the structural and physiological traits of individual species up to the patterns and processes of communities and landscapes, so as to better assessing and monitoring the risk of drought-induced tree mortality.

Key words: drought resistance, xylem embolism, stomatal adjustment, tree mortality, hydraulic trait