USDA Forest Service, Forestry Sciences Laboratory, Corvallis, OR 97331, USA.
Plant Cell Environ. 2011 Nov;34(11):1920-30. doi: 10.1111/j.1365-3040.2011.02388.x. Epub 2011 Jul 25.
We analysed concentrations of starch, sucrose, glucose and fructose in upper branch wood, foliage and trunk sapwood of Douglas-fir trees in height classes ranging from ~2 to ~57 m. Mean concentrations of non-structural carbohydrates (NSC) for all tissues were highest in the tallest height class and lowest in the lowest height class, and height-related trends in NSC were most pronounced in branches. Throughout a 17-month sampling period, mean values of branch NSC from the 57 m trees ranged between 30 and 377% greater than the 2 m trees. Branch NSC was inversely correlated with midday shoot water potential (Ψ(l)), shoot osmotic potential at full turgor (Ψ) and shoot extension. Temporal fluctuation in branch NSC was inversely correlated with height, and positively correlated with midday Ψ(l) , Ψ and shoot extension. The positive correlation between height and storage of NSC, and the negative correlation between NSC storage and shoot extension provide evidence that size-related growth decline in trees is not strongly associated with constraints on photosynthesis. The negative correlation between height and fluctuation in NSC suggests that mobilization of photosynthate in taller trees is constrained by some factor such as reductions in turgor-driven cell expansion or constraints on phloem transport.
我们分析了从2 米到57 米高度级别的花旗松树干木质部、叶片和树枝中淀粉、蔗糖、葡萄糖和果糖的浓度。所有组织中非结构性碳水化合物（NSC）的平均浓度在最高的高度级中最高，在最低的高度级中最低，NSC 的高度相关性在树枝中最为明显。在 17 个月的采样期内，57 米树的树枝 NSC 平均值比 2 米树高出 30%至 377%。树枝 NSC 与中午 shoot 水势（Ψ(l)）、shoot 膨压下的渗透势（Ψ）和 shoot 伸长呈负相关。树枝 NSC 的时间波动与高度呈负相关，与中午 Ψ(l)、Ψ 和 shoot 伸长呈正相关。NSC 储存量与高度呈正相关，与 shoot 伸长呈负相关，这表明与树木大小相关的生长下降与光合作用的限制没有很强的关联。NSC 与高度之间的负相关表明，在较高的树木中，光合产物的动员受到某种因素的限制，例如膨压驱动的细胞扩张减少或韧皮部运输的限制。
