School of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff, AZ 86011, USA.
Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA.
Tree Physiol. 2021 Mar 6;41(3):388-402. doi: 10.1093/treephys/tpaa149.
In trees, large uncertainties remain in how nonstructural carbohydrates (NSCs) respond to variation in water availability in natural, intact ecosystems. Variation in NSC pools reflects temporal fluctuations in supply and demand, as well as physiological coordination across tree organs in ways that differ across species and NSC fractions (e.g., soluble sugars vs starch). Using landscape-scale crown (leaves and twigs) NSC concentration measurements in three foundation tree species (Populus tremuloides, Pinus edulis, Juniperus osteosperma), we evaluated in situ, seasonal variation in NSC responses to moisture stress on three timescales: short-term (via predawn water potential), seasonal (via leaf δ13C) and annual (via current year's ring width index). Crown NSC responses to moisture stress appeared to depend on hydraulic strategy, where J. osteosperma appears to regulate osmotic potentials (via higher sugar concentrations), P. edulis NSC responses suggest respiratory depletion and P. tremuloides responses were consistent with direct sink limitations. We also show that overly simplistic models can mask seasonal and tissue variation in NSC responses, as well as strong interactions among moisture stress at different timescales. In general, our results suggest large seasonal variation in crown NSC concentrations reflecting the multiple cofunctions of NSCs in plant tissues, including storage, growth and osmotic regulation of hydraulically vulnerable leaves. We emphasize that crown NSC pool size cannot be viewed as a simple physiological metric of stress; in situ NSC dynamics are complex, varying temporally, across species, among NSC fractions and among tissue types.
在树木中，非结构性碳水化合物（NSC）如何响应自然完整生态系统中水分供应的变化，仍然存在很大的不确定性。NSC 库的变化反映了供应和需求的时间波动，以及树木器官之间的生理协调，这种协调在不同物种和 NSC 分数（例如，可溶性糖与淀粉）之间存在差异。我们使用三种基础树种（颤杨、白皮松、刺柏）树冠（叶片和嫩枝）NSC 浓度的景观尺度测量值，评估了 NSC 对水分胁迫的短期（通过黎明前水势）、季节性（通过叶片 δ13C）和年度（通过当年的年轮宽度指数）三种时间尺度的响应。树冠 NSC 对水分胁迫的响应似乎取决于水力策略，其中 J. osteosperma 似乎通过更高的糖浓度来调节渗透势，P. edulis 的 NSC 响应表明呼吸作用枯竭，而 P. tremuloides 的响应与直接的汇限制一致。我们还表明，过于简单的模型可能会掩盖 NSC 响应的季节性和组织变化，以及不同时间尺度的水分胁迫之间的强烈相互作用。总的来说，我们的结果表明，树冠 NSC 浓度存在很大的季节性变化，反映了 NSCs 在植物组织中的多种共同功能，包括作为储存物质、促进生长和调节对水力敏感的叶片的渗透作用。我们强调，不能将树冠 NSC 库大小视为应激的简单生理指标；原位 NSC 动态是复杂的，随时间变化，在不同物种之间、不同 NSC 分数之间以及不同组织类型之间存在差异。
