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 (ψ_xylem = −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.

中文翻译：

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樟树幼苗干旱恢复过程中气体交换与水势的解耦及其与ABA积累的关系

摘要

目的

由于气候变化，干旱压力和干旱严重程度预计会在高度变化的降水模式下上升，而树木通过生理和生化调整应对干旱恢复的能力仍不清楚。我们旨在研究干旱和随后的恢复过程中树木的生理生化耦合。

方法

在试验干旱胁迫之前，樟树的盆栽幼苗在灌溉条件良好的条件下生长，该干旱是通过保留水分开始的。达到两个干旱严重程度后，对幼苗重新浇水：轻度干旱（气孔闭合）和中度干旱（ψ_木质部= -1.5 MPa）。我们在干旱和4天恢复期间测量了樟树幼苗中的叶水平水势，气体交换（光合作用和气孔导度），脱落酸（ABA），脯氨酸和非结构性碳水化合物（NSCs）浓度。

重要发现

我们发现干旱的严重程度在很大程度上决定了生理和生化反应，并影响了恢复速度。在轻度干旱胁迫下发生气孔关闭，伴随着叶片中ABA的积累和水势的下降，而在中度干旱胁迫下叶片脯氨酸的积累和可变的NSC明显。更为严重的干旱胁迫导致气体交换的恢复延迟，但对水势恢复没有显着影响。在干旱胁迫和干旱后恢复期间，水势和气体交换的关系有所不同。在干旱期间，水势与气体交换之间存在紧密的耦合，但在复水期间却没有，因为叶片中的ABA含量高，从而延迟了气孔导度的恢复。C.樟脑。此外，更大的干旱严重程度对树木生理和生化的恢复速率有重大影响。