Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA.
Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, Arizona, USA.
Plant Cell Environ. 2020 Jun;43(6):1467-1483. doi: 10.1111/pce.13749. Epub 2020 Mar 10.
Non-structural carbohydrates (NSCs) are necessary for plant growth and affected by plant water status, but the temporal dynamics of water stress impacts on NSC are not well understood. We evaluated how seasonal NSC concentrations varied with plant water status (predawn xylem water potential, Ψ) and air temperature (T) in the evergreen desert shrub Larrea tridentata. Aboveground sugar and starch concentrations were measured weekly or monthly for ~1.5 years on 6-12 shrubs simultaneously instrumented with automated stem psychrometers; leaf photosynthesis (A ) was measured monthly for 1 year. Leaf sugar increased during the dry, premonsoon period, associated with lower Ψ (greater water stress) and high T. Leaf sugar accumulation coincided with declines in leaf starch and stem sugar, suggesting the prioritization of leaf sugar during low photosynthetic uptake. Leaf starch was strongly correlated with A and peaked during the spring and monsoon seasons, while stem starch remained relatively constant except for depletion during the monsoon. Recent photosynthate appeared sufficient to support spring growth, while monsoon growth required the remobilization of stem starch reserves. The coordinated responses of different NSC fractions to water status, photosynthesis, and growth demands suggest that NSCs serve multiple functions under extreme environmental conditions, including severe drought.
非结构性碳水化合物（NSCs）是植物生长所必需的，受植物水分状况的影响，但水分胁迫对 NSCs 的时间动态影响还不太清楚。我们评估了常绿沙漠灌木三角叶滨藜的非结构性碳水化合物浓度如何随植物水分状况（晨前木质部水势，Ψ）和空气温度（T）的季节性变化而变化。同时用自动茎液流计对 6-12 株灌木进行了约 1.5 年的每周或每月的地上糖和淀粉浓度测量；1 年内每月测量叶片光合作用（A）。在旱季和前季风期，叶片糖含量增加，与较低的 Ψ（更大的水分胁迫）和较高的 T 有关。叶片糖的积累与叶片淀粉和茎糖的下降相吻合，表明在低光合作用吸收期间优先积累叶片糖。叶片淀粉与 A 强烈相关，在春季和季风季节达到峰值，而茎淀粉除季风期间耗尽外相对保持稳定。最近的光合作用产物似乎足以支持春季生长，而季风生长需要动员茎淀粉储备。不同 NSC 分数对水分状况、光合作用和生长需求的协调响应表明，NSCs 在极端环境条件下具有多种功能，包括严重干旱。
