干旱胁迫下毛白杨和元宝槭的水力学调控

doi:10.17521/cjpe.2021.0495

摘要/Abstract

摘要：

毛白杨(Populus tomentosa)和元宝槭(Acer truncatum)是华北平原人工林的主要树种, 研究两者水力结构和干旱-复水过程中茎非结构性碳水化合物(NSC)含量动态, 可揭示其水力学调控策略, 为全球气候变化背景下华北人工林水分平衡的科学管理提供理论依据。该研究以相同生境下分布的毛白杨和元宝槭幼树为研究材料, 测量两者的茎抗栓塞能力与水力安全阈、水力面积、叶膨压损失点等水力结构参数; 开展干旱-复水实验, 测定茎NSC含量动态以及干旱胁迫解除后复水阶段的木质部栓塞修复能力。结果表明: 毛白杨导水率损失50%对应的水势(-1.289 MPa)高于元宝槭(-2.894 MPa), 且膨压损失点时的渗透势低, 水力安全阈小, 木材密度小, 气孔调节偏向于变水行为, 表现为易栓塞的低水势忍耐脱水耐旱特性, 水分调节对策趋于冒险; 元宝槭则倾向于不易栓塞的高水势延迟脱水耐旱特性, 水分调节对策趋于保守。在干旱-复水实验中, 毛白杨可溶性糖、淀粉和茎NSC含量先减后增, 元宝槭则先增后减; 并且毛白杨表现出比元宝槭更高的栓塞修复能力, 这与植物体内茎NSC含量变化差异具有一定联系。毛白杨较高的栓塞修复能力也为其易栓塞的低水势忍耐脱水耐旱特性及冒险的水分调节对策提供水力安全保障。两树种在水力学调控上表现出的较大差异可能与其生活史特性相关。

关键词: 水力学调控, 水分调节对策, 非结构性碳水化合物, 栓塞修复, 耐旱特性

Abstract:

Aims The tree decline and death caused by drought stress under global climate change is a topic of general interest in ecological research. Different tree species in the same habitat can adopt various hydraulic strategies to maintain water balance in order to deal with drought stress. Populus tomentosa and Acer truncatum are the main tree species in plantations in the North China Plain. Studies on their hydraulic structure and dynamics of non-structural carbohydrate (NSC) content during drought-rehydration can reveal their hydraulic regulation strategies and provide theoretical basis for scientific management of water balance in plantations in north China under the background of global climate change.

Methods By using the saplings of P. tomentosa and A. truncatum distributed in the same habitat, we measured the hydraulic structure parameters, such as the resistance to embolism and hydraulic safety margin of stem, hydraulic areas, osmotic potential at leaf turgor pressure loss point, etc. Dehydration and rehydration were carried out to investigate the dynamics of stem NSC content, and to examine the repair capacity of xylem embolism in the rehydration stage after drought stress removel.

Important findings The results showed that the water potential of P. tomentosa (-1.289 MPa) when xylem hydraulic conductivity lost 50% was higher than that of A. truncatum(-2.894 MPa). Populus tomentosa also presented lower osmotic potential at turgor pressure loss point, narrower hydraulic safety margin, smaller wood density, and tended to have anisohydry behavior of stomatal regulation, indicating that it was prone to embolism characterized with dehydration and drought tolerance at low water potential, and tended to have more risky water regulation strategies. Acer truncatum survived drought stress by “delayed dehydration” at high water potentials, and tended to have conservative water regulation strategy. In the dehydration-rehydration experiment, the contents of soluble sugar, starch and non-structural carbohydrate in stem of P. tomentosa decreased first and then increased, while those of A. truncatum increased first and then decreased, and P. tomentosa showed a higher embolic repair ability than A. truncatum, which was related to the difference of stem NSC content. The higher embolism repair ability of P. tomentosa can provide hydraulic safety guarantee for risky water regulation strategies and drought tolerance strategy. There were significant differences between P. tomentosa and A. truncatum in the regulation of hydraulics, which might be related to the characteristics of life history.

Key words: hydraulic regulation, water regulation countermeasure, non-structural carbohydrate, embolism repair, drought tolerance characteristic

伍敏, 田雨, 樊大勇, 张祥雪. 干旱胁迫下毛白杨和元宝槭的水力学调控. 植物生态学报, 2022, 46(9): 1086-1097. DOI: 10.17521/cjpe.2021.0495

WU Min, TIAN Yu, FAN Da-Yong, ZHANG Xiang-Xue. Hydraulic regulation of Populus tomentosa and Acer truncatum under drought stress. Chinese Journal of Plant Ecology, 2022, 46(9): 1086-1097. DOI: 10.17521/cjpe.2021.0495

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2021.0495

https://www.plant-ecology.com/CN/Y2022/V46/I9/1086

图/表 9

图1 毛白杨与元宝槭木质部脆弱性曲线(平均值±标准误, n = 6)。垂直虚线表示计算出的毛白杨的导水率损失50%对应的木质部水势值(Ψxylem-50); 垂直实线表示计算出的元宝槭的Ψxylem-50。

Fig. 1 Stem vulnerability curves of Populus tomentosa and Acer truncatum (mean ± SE, n = 6). Vertical dashed lines represent calculated xylem water potential when hydraulic conductivity lost 50% (Ψxylem-50) in P. tomentosa; vertical solid lines represent calculated Ψxylem-50 of A. truncatum.

表1 毛白杨与元宝槭的脆弱性参数

Table 1 Vulnerability parameters of Populus tomentosa and Acer truncatum

树种 Tree species	导水率损失50% 对应的木质部水势 Xylem water potential corresponding to 50% loss of hydraulic conductivity (Ψ_xylem-50)(MPa)	水力安全阈 Hydraulic safety margin (HSM) (MPa)	木质部修复系数 Xylem recovery index (XRI)	相对于干旱期间的木质部修复系数 Xylem recovery index-drought (XRID)	导水率损失百分比的日变化 Diurnal changes in percentage loss of hydraulic conductivity (ΔPLC)(%)
毛白杨 P. tomentosa	-1.289	0.350	0.740	0.362	40.450
元宝槭 A. truncatum	-2.894	2.750	0.529	0.077	3.237

图2 毛白杨与元宝槭水力面积图。灰色区域表示水力面积区域; 括号内的数字是计算出的水力面积。

Fig. 2 Hydraulic area maps of Populus tomentosa and Acer truncatum. Gray areas indicate hydraulic area regions, numbers in parentheses are calculated hydraulic areas. Ψleaf-md, leaf water potential in the midday; Ψleaf-pd, leaf water potential predawn.

表2 毛白杨与元宝槭的茎水力结构参数(平均值±标准误)

Table 2 Stem hydraulic structure parameters of Populus tomentosa and Acer truncatum (mean ± SE)

树种 Tree species	胡伯尔值 Huber value (Hv) (cm²·g^-1)	最大导水率 Maximum hydraulic conductivity (K_hmax) (kg·MPa^-1·m^-1·s^-1)	最大比导水率 Maximum specific conductivity (K_s) (kg·MPa^-1·m^-1·s^-1)	最大比叶导水率 Maximum leaf specific conductivity (LSC) (kg·MPa^-1·m^-1·s^-1)	最大导管长度 Maximum vessel length (MVL) (cm)	木材密度 Wood density (WD)(g·cm^-1)
毛白杨 P. tomentosa	0.031 ± 0.002^a	13.43 ± 4.65^a	10.17 ± 2.25^a	0.0017 ± 0.0003^a	22.29 ± 1.72^a	0.235 ± 0.009^a
元宝槭 A. truncatum	0.026 ± 0.001^a	1.30 ± 0.74^b	1.49 ± 0.57^b	0.0004 ± 0.0001^b	7.83 ± 0.77^b	0.361 ± 0.023^b

表3 毛白杨与元宝槭的叶水力结构参数(平均值±标准误)

Table 3 Leaf hydraulic structure parameters of Populus tomentosa and Acer truncatum (mean ± SE)

树种 Tree species	比叶质量 Specific leaf mass (LMA)(g·cm^-2)	叶密度 Leaf density (LD)(g·cm^-1)	叶干物质含量 Leaf dry matter content (LDMC)
毛白杨 P. tomentosa	0.006 5 ± 0.000 3^a	0.149 ± 0.006^a	0.313 ± 0.007^a
元宝槭 A. truncatum	0.005 5 ± 0.000 2^b	0.240 ± 0.009^b	0.331 ± 0.008^a

表4 毛白杨与元宝槭压力-体积曲线参数比较(平均值±标准误)

Table 4 Comparison of pressure volume curve parameters between Populus tomentosa and Acer truncatum (mean ± SE)

树种 Tree species	饱和渗透势 Saturated osmotic potential (Ψ_sat) (-MPa)	膨压损失点时渗透势 Osmotic potential of turgor loss point (Ψ_tlp)(-MPa)	膨压损失点相对含水量 Relative water content of turgor loss point (RWC_tlp)(%)	最大弹性模量 Maximum modulus of elasticity (ε_max)(MPa)	水容 Water capacitance (C_leaf) (mol·m^-2·MPa^-1)	\|Ψ_sat - Ψ_tlp\| (MPa)
毛白杨 P. tomentosa	1.82 ± 0.30^a	2.44 ± 0.54^a	88.08 ± 1.02^a	13.70 ± 1.06^a	0.280 ± 0.009^a	0.62 ± 0.34^a
元宝槭 A. truncatum	1.51 ± 0.10^a	1.76 ± 0.10^b	86.41 ± 0.98^a	11.55 ± 1.43^a	0.557 ± 0.096^b	0.25 ± 0.06^b

图3 毛白杨与元宝槭干旱-复水过程木质部水势(Ψxylem)变化(平均值±标准误, n = 6)。与对照组相比, 干旱-复水组在干旱处理过程中, Ψxylem下降。当干旱至第5天和第11天, 毛白杨与元宝槭的Ψxylem分别达到导水率损失50%对应的木质部水势值(Ψxylem-50), 随后进行复水, Ψxylem恢复。

Fig. 3 Changes of xylem water potential (Ψxylem) of Populus tomentosa and Acer truncatum during dehydration-rehydration (mean ± SE, n = 6). Compared with the control group, Ψxylem decreased during the drought treatment in the dehydration-rehydration group. In the 5th and 11th days of dehydration, the Ψxylem of P. tomentosa and A. truncatum reached the water potential when hydraulic conductivity lost 50% respectively, and then Ψxylem recovered when treated with rehydration.

图4 不同水分条件下毛白杨与元宝槭枝条非结构性碳水化合物(NSC)及其组分含量变化(平均值±标准误, n = 6)。不同大写字母表示同一水分状况下同一物质在两树种之间差异显著, 不同小写字母表示同一树种下同一物质在不同处理之间差异显著(p < 0.05)。Ψxylem-50, 导水率损失50%对应的木质部水势值。

Fig. 4 Changes of non-structural carbohydrates (NSC) and its components in the stems of Populus tomentosa and Acer truncatum under different water conditions (mean ± SE, n = 6). Different uppercase letters indicate the same substance has significant differences between the two tree species under the same moisture, and different lowercase letters indicate the same substance has significant differences among the treatments under the same tree species (p < 0.05). Ψxylem-50, water potential when hydraulic conductivity lost 50%.

图5 毛白杨与元宝槭茎可溶性糖含量/淀粉含量对不同水分阶段的响应(平均值±标准误, n = 6)。Ψxylem-50, 导水率损失50%对应的木质部水势值。

Fig. 5 Response of soluble sugar content/starch content of Populus tomentosa and Acer truncatum stems to different moisture conditions (mean ± SE, n = 6). Ψxylem-50, water potential when hydraulic conductivity lost 50%.

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