Department of Environmental Sciences - Botany, University of Basel, Schönbeinstrasse 6, Basel, 4056, Switzerland.
Max-Planck Institute for Biogeochemistry, Hans Knöll Strasse 10, Jena, 07745, Germany.
New Phytol. 2018 Apr;218(1):107-118. doi: 10.1111/nph.14987. Epub 2018 Feb 9.
The usage of nonstructural carbohydrates (NSCs) to indicate carbon (C) limitation in trees requires knowledge of the minimum tissue NSC concentrations at lethal C starvation, and the NSC dynamics during and after severe C limitation. We completely darkened and subsequently released seedlings of two deciduous and two evergreen temperate tree species for varying periods. NSCs were measured in all major organs, allowing assessment of whole-seedling NSC balances. NSCs decreased fast in darkness, but seedlings survived species-specific whole-seedling starch concentrations as low as 0.4-0.8% per dry matter (DM), and sugar (sucrose, glucose and fructose) concentrations as low as 0.5-2.0% DM. After re-illumination, the refilling of NSC pools began within 3 wk, while the resumption of growth was delayed or restricted. All seedlings had died after 12 wk of darkness, and starch and sugar concentrations in most tissues were lower than 1% DM. We conclude that under the applied conditions, tree seedlings can survive several weeks with very low NSC reserves probably also using alternative C sources like lipids, proteins or hemicelluloses; lethal C starvation cannot be assumed, if NSC concentrations are higher than the minimum concentrations found in surviving seedlings; and NSC reformation after re-illumination occurs preferentially over growth.
非结构性碳水化合物（NSC）的使用表明树木受到碳（C）限制，这需要了解在致命的 C 饥饿下组织中最小的 NSC 浓度，以及在严重 C 限制期间和之后的 NSC 动态。我们将两种落叶树和两种常绿温带树种的幼苗完全遮暗，然后释放不同时间。在所有主要器官中测量 NSCs，从而可以评估整个幼苗的 NSC 平衡。在黑暗中，NSC 迅速减少，但幼苗能够在特定物种的整个幼苗淀粉浓度低至 0.4-0.8%干物质（DM）和糖（蔗糖、葡萄糖和果糖）浓度低至 0.5-2.0% DM 下存活。重新光照后，NSC 池的填充在 3 周内开始，而生长的恢复则延迟或受到限制。在黑暗 12 周后，所有幼苗都死亡，大多数组织中的淀粉和糖浓度都低于 1% DM。我们得出结论，在应用条件下，如果 NSC 浓度高于存活幼苗中发现的最低浓度，则树木幼苗可以在非常低的 NSC 储备下存活数周，可能还会利用替代 C 源，如脂质、蛋白质或半纤维素；不能假设致命的 C 饥饿，如果 NSC 浓度高于存活幼苗中发现的最低浓度；并且 NSC 在重新光照后的重新形成优先于生长。
