Institute of Plant Sciences, Agricultural Research Organization, Gilat, 85280, Negev, Israel.
Environmental Studies Program, Department of Geography, Institute of Ecology and Evolution, University of Oregon, Eugene, OR, 97403, USA.
Sci Rep. 2017 Jun 12;7(1):3265. doi: 10.1038/s41598-017-03608-w.
Trees experience two distinct environments: thermally-variable air and thermally-buffered soil. This generates intra-tree temperature gradients, which can affect carbon metabolism and water transport. In this study, we investigated whether carbohydrate allocation within trees is assisted by temperature gradients. We studied pistachio (Pistacia integerrima) to determine: (1) temperature-induced variation in xylem sugar concentration in excised branches; (2) changes in carbon allocation in young trees under simulated spring and fall conditions; and (3) seasonal variability of starch levels in mature orchard trees under field conditions. We found that warm branches had less sugar in perfused sap than cold branches due to increasing parenchyma storage. Simulated spring conditions promoted allocation of carbohydrates from cold roots to warm canopy and explained why starch levels surged in canopies of orchard trees during early spring. This driving force of sugar transport is interrupted in fall when canopies are colder than roots and carbohydrate redistribution is compartmentalized. On the basis of these findings, we propose a new mechanistic model of temperature-assisted carbohydrate allocation that links environmental cues and tree phenology. This data-enabled model provides insights into thermal "fine-tuning" of carbohydrate metabolism and a warning that the physiological performance of trees might be impaired by climatic changes.
温度多变的空气和温度缓冲的土壤。这会在树内产生温度梯度，从而影响碳代谢和水分运输。在这项研究中，我们研究了树木内的碳水化合物分配是否受到温度梯度的辅助。我们研究了开心果（Pistacia integerrima），以确定：(1) 离体枝条木质部糖浓度受温度诱导的变化；(2) 在模拟的春季和秋季条件下，幼树的碳分配变化；(3) 在田间条件下，成熟果园树木的淀粉水平的季节性变化。我们发现，温暖的枝条在灌注液中的糖含量比寒冷的枝条少，这是由于薄壁组织储存增加所致。模拟的春季条件促进了从冷根到暖树冠的碳水化合物分配，这解释了为什么在早春，果园树木的树冠中淀粉水平会激增。当树冠比根冷时，糖运输的驱动力在秋季中断，碳水化合物重新分配被分隔。基于这些发现，我们提出了一个新的温度辅助碳水化合物分配的机制模型，该模型将环境线索和树木物候学联系起来。这个数据驱动的模型提供了对碳水化合物代谢的热“微调”的深入了解，并警告说，气候变化可能会损害树木的生理性能。
