J Plant Ecol ›› 2020, Vol. 13 ›› Issue (6): 683-692.DOI: 10.1093/jpe/rtaa056

• Research Articles • Previous Articles     Next Articles

The decoupling between gas exchange and water potential of Cinnamomum camphora seedlings during drought recovery and its relation to ABA accumulation in leaves

Honglang Duan1,2, *, Defu Wang2 , Xiaohua Wei3 , Guomin Huang2 , Houbao Fan2 , Shuangxi Zhou4 , Jianping Wu5 , Wenfei Liu2 , David T. Tissue6, and Songze Wan7, *   

  1. 1 Institute for Forest Resources & Environment of Guizhou, Key Laboratory of Forest Cultivation in Plateau Mountain of Guizhou Province, College of Forestry, Guizhou University, Guiyang 550025, China, 2 Jiangxi Provincial Key Laboratory for Restoration of Degraded Ecosystems & Watershed Ecohydrology, Nanchang Institute of Technology, Nanchang 330099, China, 3 Department of Earth, Environmental and Geographic Sciences, University of British Columbia Okanagan, Kelowna, BC V1V 1V7, Canada, 4 The New Zealand Institute for Plant and Food Research Ltd., Hawke’s Bay, New Zealand, 5 Laboratory of Ecology and Evolutionary Biology, Yunnan University, Kunming 650500, China, 6 Hawkesbury Institute for the Environment, Hawkesbury Campus, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia, 7 College of Forestry, Jiangxi Agricultural University, Nanchang 330045, China

    *Corresponding author. E-mail: honglangduan@qq.com (H.D.); swan0722@jxau.edu.cn (S.W.)
  • Received:2020-03-21 Revised:2020-08-04 Accepted:2020-08-21 Online:2020-08-26 Published:2020-12-01

Abstract:

Aims

Drought stress and the degree of drought severity are predicted to rise under highly variable patterns of precipitation due to climate change, while the capacity of trees to cope with drought recovery through physiological and biochemical adjustment remains unclear. We aimed to examine the coupling of physiology and biochemistry in trees during drought and the following recovery.

Methods

Potted seedlings of Cinnamomum camphora were grown under well watered conditions prior to the experimental drought stress, which was initiated by withholding water. Seedlings were rewatered following attainment of two drought severities: mild drought (stomatal closure) and moderate drought (ψxylem = −1.5 MPa). We measured leaf-level water potential, gas exchange (photosynthesis and stomatal conductance), abscisic acid (ABA), proline and non-structural carbohydrates (NSCs) concentrations in seedlings of C. camphora during drought and a 4-day recovery.

Important Findings

We found that drought severity largely determined physiological and biochemical responses and affected the rate of recovery. Stomatal closure occurred at the mild drought stress, accompanied with ABA accumulation in leaves and decline in water potential, while leaf proline accumulation and variable NSC were evident at the moderate drought stress. More severe drought stress led to delayed recovery of gas exchange, but it did not have significant effect on water potential recovery. The relationships of water potential and gas exchange differed during drought stress and post-drought recovery. There was tight coupling between water potential and gas exchange during drought, but not during rewatering due to high ABA accumulation in leaves, thereby delaying recovery of stomatal conductance. Our results demonstrate that ABA could be an important factor in delaying the recovery of stomatal conductance following rewatering and after water potential recovery of C. camphora. Furthermore, greater drought severity had significant impacts on the rate of recovery of tree physiology and biochemistry.

Key words: drought, recovery, gas exchange, ABA, NSC, proline

摘要:

气候变化将改变降雨格局,从而导致极端干旱事件增多。然而,树木如何协调生理和生化响应来应对干旱-恢复的机制仍不清楚。本 研究探讨了干旱-恢复过程中树木生理与生化特征的耦联关系。我们首先将香樟(Cinnamomum camphora)盆栽幼苗种植在水分充足的条件下,然后通过停止浇水以达到干旱处理的目的。当幼苗胁迫至轻度干旱(气孔关闭)和中度干旱(ψxylem = −1.5 MPa)时,分别对其进行复水处理。在干旱及复水4天过程中,我们测定了香樟叶片水势、气体交换、脱落酸以及非结构性碳水化合物的变化规律。我们发现干旱强度在很大程度上决定了香樟的生理与生化响应,并影响其干旱后恢复。轻度干旱导致气孔关闭,并引起叶片脱落酸累积和水势下降,而中度干旱可进一步引起叶片脯氨酸累积和非结构性碳水化合物的变化。干旱强度的增加会导致气体交换恢复滞后,但对水势的恢复无显著影响。另外,干旱与复水过程中水势与气体交换之间的关系存在较大差异: 即干旱过程中水势与气体交换存在很强的耦联关系,而这种耦联关系在复水过程中并不存在,其主要原因是由于叶片脱落酸累积,从而延缓了气孔导度的恢复。综上,本研究结果表明,脱落酸可能是导致香樟旱后气孔导度恢复滞后的主要影响因素。此外,干旱强度对树木生理和生化的恢复具有显著影响。

关键词: 干旱, 恢复, 气体交换, 脱落酸, 非结构性碳水化合物, 脯氨酸