干旱及复水条件下侧柏幼苗可溶性糖含量与光合生理特性

Soluble sugar content and physiological characteristics of Platycladus orientalis seedlings under drought and rewatering conditions

摘要

【目的】量化干旱及复水过程中侧柏幼苗可溶性糖含量及光合生理特性的动态变化，解析不同水分条件下可溶性糖及其组分与光合生理特性的相关关系，以期为科学规划干旱气候下北京地区绿化树种以及旱后植被恢复与重建提供科学依据与理论支撑。【方法】基于预实验确定的生理萎蔫点，以北京地区侧柏幼苗为材料，设置逐步干旱（TD，取样于干旱第 0、2、6、10、15、18 天）、旱后复水（TW，取样于旱后复水第 3、5、10、13、17、25 天）试验组与对照组（CK，维持 80% ~ 90% 田间持水量）；同步监测土壤体积含水量与叶水势以量化各节点胁迫强度，于关键节点测定光合、荧光参数及各器官可溶性糖及其组分含量；通过恢复度指数量化旱后修复程度，并运用 Pearson 相关分析解析糖−光合关联随水分条件的动态转变。【结果】（1）光合生理指标在干旱及复水过程中呈显著阶段响应特征。干旱阶段，侧柏光合生理指标均在干旱中期（TD₆ ~ TD₁₀）达到峰值后降低；复水后胞间 CO₂ 浓度（ C_i）、蒸腾速率（ T_r）及荧光参数率先恢复，净光合速率（ A_n）、气孔导度（ G_s）随后恢复。（2）可溶性糖及其组分的器官分配存在明显的干旱响应差异。干旱阶段，叶可溶性糖及其组分含量增加（总糖提高 247.7%、葡萄糖提高 203.6%、果糖提高 264.9%），小枝、主干降低，光合产物优先向叶片分配；地下器官可溶性糖及其组分含量均呈先升后降趋势。从糖组分看，地上、地下器官蔗糖占比均较低，葡萄糖、果糖占比均较高，蔗糖合成与运输受抑，主要依赖葡萄糖、果糖进行渗透调节。旱后复水阶段，除蔗糖和主干葡萄糖外，地上器官及地下器官糖含量均在第 3 天恢复至 CK。（3）可溶性糖与光合生理特性的相关性随水分条件发生方向性转变。干旱阶段，叶蔗糖与 A_n、 G_s 呈显著负相关（ P < 0.05）；除蔗糖外，细根可溶性糖及其组分与 G_s 呈正相关，根系糖含量变化与气孔导度协同；旱后复水阶段，叶蔗糖含量与 G_s 转为正相关，蔗糖回升伴随气孔导度恢复；叶、小枝、粗根可溶性总糖、葡萄糖以及小枝、主干、粗根果糖与最大光化学效率（ F_v/ F_m）呈显著负相关（ P < 0.05），糖含量变化伴随光系统修复。【结论】侧柏通过光合生理的阶段性调整与可溶性糖的器官分配重塑以应对水分胁迫。干旱阶段光合碳优先向叶片集中，葡萄糖和果糖主导渗透调节；复水后光合、荧光参数恢复进程存在差异，气孔导度与蔗糖代谢同步回升。本研究揭示了侧柏在水分胁迫下的生理适应机制，可为北京地区侧柏林水分管理与旱后植被恢复提供理论依据。

Abstract

[Objective] This study aimed to quantify the dynamic changes in soluble sugar content and photosynthetic physiological characteristics of Platycladus orientalis seedlings during progressive drought and subsequent rewatering, and to elucidate the correlations between soluble sugars (and their components) and photosynthetic traits under different water conditions. The findings are expected to provide scientific basis and theoretical support for scientifically planning greening tree species in Beijing under drought climate and for post-drought vegetation restoration and reconstruction. [Method] Based on the physiological wilting point identified in preliminary experiments, P. orientalis seedlings in the Beijing area were subjected to progressive drought (TD, sampled on the 0, 2nd, 6th, 10th, 15th, and 18th days), post-drought rewatering (TW, sampled on the 3rd, 5th, 10th, 13th, 17th, and 25th days), and control (CK, maintained at 80%−90% field capacity). Soil volumetric water content and leaf water potential were synchronously monitored to quantify stress intensity at each sampling node. At critical nodes, photosynthetic and chlorophyll fluorescence parameters were measured, and soluble sugars and their components were determined in various organs. A recovery index was established to quantify post-drought restoration, and Pearson correlation analysis was used to reveal the dynamic shift in sugar-photosynthesis relationships under different water conditions. [Result] (1) Photosynthetic physiological indices showed significant stage-responsive characteristics during the drought and rewatering phases. During the drought phase, photosynthetic indices of P. orientalis peaked at mid-drought (TD₆−TD₁₀) and then declined. During the rewatering phase, intercellular CO₂ concentration (C_i), transpiration rate (T_r), and chlorophyll fluorescence parameters recovered first, followed by net photosynthetic rate (A_n) and stomatal conductance (G_s). (2) Organ-specific allocation of soluble sugars and their components exhibited marked drought-responsive differences. During the drought phase, leaf soluble sugar and its component contents increased (total sugars increased by 247.7%, glucose by 203.6%, and fructose by 264.9%), while those in twigs and stems decreased, indicating that photosynthates were preferentially allocated to leaves. Underground organs showed an initial increase followed by a decrease in soluble sugar and component contents. Regarding sugar components, the proportion of sucrose was relatively low in both aboveground and belowground organs, whereas glucose and fructose proportions were high, suggesting that sucrose synthesis and transport were inhibited and that osmotic adjustment mainly relied on glucose and fructose. During the rewatering phase, except for sucrose, sugar contents in aboveground and underground organs recovered to CK levels by day 3. (3) The correlations between soluble sugars and photosynthetic physiological characteristics underwent directional shifts with changing water conditions. During the drought phase, leaf sucrose was significantly negatively correlated with A_n and G_s (P < 0.05); except for sucrose, soluble sugars and their components in fine roots were positively correlated with G_s, indicating that root sugar changes were coordinated with stomatal conductance. During the rewatering phase, leaf sucrose content shifted to a positive correlation with G_s, with sucrose recovery accompanying stomatal conductance restoration. Soluble total sugars and glucose in leaves, twigs, and coarse roots, as well as fructose in twigs, stems, and coarse roots, were significantly negatively correlated with maximum photochemical efficiency (F_v /F_m) (P < 0.05), with sugar changes accompanying photosystem repair. [Conclusion] P. orientalis copes with water stress through stage-specific adjustments in photosynthetic physiology and reorganization of soluble sugar allocation among organs. During the drought phase, photosynthetic carbon is preferentially concentrated in leaves, with glucose and fructose dominating osmotic adjustment; during the rewatering phase, recovery of photosynthetic and chlorophyll fluorescence parameters proceeds at different rates, while stomatal conductance and sucrose metabolism recover in tandem. This study reveals the physiological adaptation mechanisms of P. orientalis under water stress, providing a theoretical basis for water management and post-drought vegetation restoration of Platycladus forests in Beijing.

关键词

侧柏 / 干旱 / 复水 / 可溶性糖 / 光合能力 / 水分管理 / 旱后植被恢复

Key words

Platycladus orientalis / drought / rehydration / soluble sugar / photosynthetic capacity / water management / post-drought vegetation restoration

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基金资助

北京市农林科学院林业果树研究所基金项目(LGSSZJJ202508)

国家自然科学基金面上项目(32571805)