刺槐苗木干旱胁迫过程中水力学失败和碳饥饿的交互作用

doi:10.11707/j.1001-7488.20160601

摘要/Abstract

摘要： [目的] 通过分析刺槐在干旱和复水过程中水力学性状和非结构碳(NSC)储藏的变化,研究在水力学失败和碳饥饿对刺槐苗木的影响,以探讨在经历导致落叶的严重干旱胁迫之后叶片恢复的影响因素。研究的结果可以阐明刺槐干旱和复水过程中水力学结构和碳代谢的交互作用方式,同时为揭示干旱半干旱地区刺槐衰败死亡的生理学机制提供思路和试验证据。[方法] 测定3年生刺槐苗在严重干旱导致落叶后和复水后叶片长成时的小枝凌晨和正午水势、枝条正午气穴栓塞、叶片最大光合速率和气孔导度、单株叶面积、枝条和根的非结构碳含量,测定严重干旱后刺槐枝条的栓塞脆弱性,并比较复水后茎干基部和上部新发叶片的叶面积、比叶质量和光合作用及新发小枝的凌晨和正午水势、枝条气穴栓塞。[结果] 在干旱导致全部落叶时,凌晨和正午水势分别达到-3.01和-3.73 MPa,显著低于对照;正午导水损失率(PLC)达到91%,显著高于对照;干旱导致刺槐90%以上落叶时其叶片的光合速率为负值,气孔导度也降低到趋近于0。在复水后30天叶片长成时,枝条正午PLC为81%,仍显著高于对照。经历干旱和复水处理的枝条P₅₀(栓塞为50%时的枝条水势)为-1.09 MPa,比对照高0.37 MPa,经历干旱胁迫的枝条抗气穴栓塞能力显著降低。干旱和复水过程均显著降低了刺槐枝条和根的NSC含量,复水过程NSC降低程度更大。复水后的单株总叶面积仅为对照的38%。复水后叶片恢复的主要部位是茎基部和枝条上部,茎基部恢复叶片的叶面积、光合速率、气孔导度均显著大于枝条上部恢复叶片,茎基部新发小枝的凌晨和正午水势显著高于上部新发小枝。[结论] 严重干旱导致水势降低,木质部导管栓塞加重,限制了刺槐的水分输导,进而抑制叶片光合作用,导致出现负的碳平衡。在复水阶段,前期严重干旱导致木质部导水能力下降和NSC含量下降限制了复水后新叶的生长,NSC含量降低可能会影响木质部栓塞的即时修复,水力学失败和碳饥饿的交互作用加重了干旱对刺槐的影响。

关键词: 刺槐, 干旱, 复水, 水力学结构, 非结构性碳, 叶片恢复

Abstract: [Objective] The ability of maintaining hydraulic structure and carbon balance is a key factor for plants to affect the survival and recovery from drought under drought stress. The main purposes of this study were to explore the interaction of hydraulic failure and carbon starvation on black locust(Robinia pseudoacacia) seedlings by monitoring the changes of hydraulic traits and nonstructural carbohydrates (NSC) reserves during drought and rewatering periods, with a particularly interest in the seedling's performances during the rewatering period after experiencing severe drought stress to explore the major factors limiting leaf recovery from drought. Results can illustrate the interaction pattern of hydraulic traits and carbon metabolism during drought and rewatering periods, meanwhile provide research idea and experimental evidence for revealing physiological mechanism of decline and die-off for black locust in arid and semi-arid region.[Method] We measured predawn and midday twig water potential, midday branch percentage loss of conductivity (PLC), net photosynthetic rate, stomatal conductance, leaf area of individual plant, and NSC concentration of branches and roots after drought-induced severe defoliation and with having regenerated leaves after rewatering. Stem vulnerability curve after severe drought was determined. Leaf area, specific leaf weight and net photosynthetic rate of leaves resprouting on stem base and top after rewatering were compared. Predawn and midday twig water potential, and midday PLC of branches resprouting on stem base and top after rewatering were also compared. [Result] At the time of drought-induced complete defoliation, predawn and midday twig water potential were -3.01 MPa and -3.73 MPa respectively, and they were significantly lower than those of control. The midday PLC defoliated seedlings reached to 91%, and was significantly higher compared to control. At the time of more than 90% leaves defoliation, leaf net photosynthetic rate was negative with near-zero of stomatal conductance. Midday branch PLC was 81% in 30 days after rewatering, still significantly higher than that of control. P₅₀ (the water potential causing a 50% conductivity loss) was -1.09 MPa for branches subjected to drought and rewatering, which was 0.37 MPa higher compared to control. Cavitation resistance in branch segments was significantly reduced by drought. NSC concentration in branches and roots markedly declined during drought and rewatering periods, and NSC concentration dropped more severe during rewatering. Total leaf area per individual resprouting plant was only 38% of the control. Leaves resprouted mainly on stem base and top, but leaf area, net photosynthetic rate and stomatal conductance of leaves on stem base was significantly greater than those of leaves on the top. Predawn and midday water potential of twigs resprouting on stem base was also significantly higher than that of twigs resprouting on the top.[Conclusion] Severe drought lowered water potential, increased xylem embolism, and constrained water transport, then reduced photosynthetic rate resulting in negative carbon balances. Severe drought induced cavitation fatigue, and the lowered NSC reserves limited resprouting ability during rewatering period. Reduced NSC reserves may also have impact on instant xylem cavitation repair. The interaction of hydraulic failure and carbon starvation exacerbated the effect of drought on black locust seedlings.

Key words: Robinia pseudoacacia, drought, rewatering, hydraulic structure, nonstructural carbohydrates (NSC), foliage recovery

中图分类号:

S718.43

王林, 代永欣, 郭晋平, 高润梅, 万贤崇. 刺槐苗木干旱胁迫过程中水力学失败和碳饥饿的交互作用[J]. 林业科学, 2016, 52(6): 1-9.

Wang Lin, Dai Yongxin, Guo Jinping, Gao Runmei, Wan Xianchong. Interaction of Hydraulic Failure and Carbon Starvation on Robinia pseudoacacia Seedlings During Drought[J]. Scientia Silvae Sinicae, 2016, 52(6): 1-9.

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