Key message Non-structural carbohydrates (NSC) are the main form of carbon storage in broadleaved trees; precise NSC quantification is relevant to predict forest resilience. Sample microwaving before drying is considered to reduce NSC losses; however, evidence is scarce. We demonstrate that microwaving leaf and branch sapwood samples before drying did not significantly reduce NSC losses with respect to freezing or direct stove-drying. Context Non-structural carbohydrates (NSC) mediate tree survival, but precise determinations of NSC concentrations remain challenging. An unclear aspect is whether carbohydrate losses during sample processing can be reduced by different sample treatments. Aims We postulated that due to higher metabolic rates, leaves should be more responsive to sample treatments than branch sapwood, and resource-acquisitive species should be more responsive to sample treatment than resource-conservative species. Methods In leaves and branch sapwood of six tree species, we compared the effects of three sample treatments on the concentrations of NSC, starch, and low-molecular weight sugars: sample microwaving before drying (microwave), sample freezing at − 20 °C before drying (freezing), and only drying (stove). Results We found that across species and tissues, freezing led to significantly higher NSC and sugar concentrations than microwave and stove. This effect was, however, entirely driven by the leaves. Although the effect of sample treatments on NSC, starch, and sugar concentrations differed among species, resource-acquisitive species were not necessarily more affected by sample treatments than resource-conservative species. Conclusion Results suggest that either freezing or microwaving does not reduce carbohydrate losses in branch sapwood during sample handling and processing; however, freezing reduces leaf sugar and NSC losses when compared with microwave or direct stove-drying (194 words).

中文翻译：

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微波或冷冻是否会减少植物样品处理过程中非结构性碳水化合物的损失？

关键信息 非结构性碳水化合物 (NSC) 是阔叶树碳储存的主要形式；精确的 NSC 量化与预测森林恢复力有关。干燥前样品微波被认为可以减少 NSC 损失；然而，证据很少。我们证明，干燥前微波处理叶和树枝边材样品并没有显着减少冷冻或直接炉干干燥的 NSC 损失。背景 非结构性碳水化合物 (NSC) 介导树木存活，但精确测定 NSC 浓度仍然具有挑战性。一个不清楚的方面是样品处理过程中的碳水化合物损失是否可以通过不同的样品处理来减少。目标 我们假设由于更高的代谢率，叶子应该比枝边材对样品处理更敏感，资源获取性物种应比资源保守性物种对样本处理更敏感。方法 在 6 种树种的叶和枝边材中，我们比较了三种样品处理对 NSC、淀粉和低分子量糖浓度的影响：样品在干燥前微波（微波），样品在 - 20 °C 冷冻前干燥（冷冻），只有干燥（炉子）。结果我们发现，在物种和组织中，冷冻导致的 NSC 和糖浓度显着高于微波和炉子。然而，这种效果完全是由叶子驱动的。尽管样品处理对 NSC、淀粉和糖浓度的影响因物种而异，但资源获取性物种不一定比资源保护性物种更受样品处理的影响。结论 结果表明，在样品处理和加工过程中，冷冻或微波都不会减少树枝边材中碳水化合物的损失；然而，与微波或直接炉子干燥相比，冷冻减少了叶糖和 NSC 的损失（194 字）。