Source–sink balance is a major determinant of carbon partitioning within plants. Thinning is an agronomic practice that consists of changing the ratio between leaves and fruits, the source and sink plant organs, respectively. Decreasing the fruit load on a peach tree is supposed to lead to an increase in fruit size and sometimes in soluble solid content in the remaining fruit. However, this response would change in early and late harvest peach varieties when considering the reduction in sink organs and decrease in photosynthetic process. The aim of this work was to study the effects of source–sink balance on physiological and metabolic parameters of two nectarine varieties with different fruit time development and harvest. Differential thinning was concurrently performed in trees of both varieties. Fruit development kinetics in addition to physiological parameters, such as chlorophyll fluorescence, gas-exchange, and leaf sugar composition, were determined over two harvest seasons. The decrease in photosynthetic rate in thinned trees was associated with stomata limitation and transitory sugar accumulation in leaves with sorbitol as the most abundant sugar. On the other hand, most photochemical processes remained constant in leaves of both varieties regardless of the thinning treatment. We suggest that increasing the source–sink ratio via thinning treatment leads to transient soluble sugar accumulation in the leaves and indicates an imbalance in drain capacity resulting in reduced photosynthesis and stomatal closure. In these nectarine varieties, thinning led to lower net photosynthesis but had no significant impact on final fruit size. Fruit thinning also allowed the development of other sink organs (such as vegetative suckers) and probably occurred as an acclimation process in order to maintain source–sink balance within the tree.

中文翻译：

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不同的源-库操纵方式影响早熟和晚收油桃品种的叶片碳水化合物和光合作用

源库平衡是植物内碳分配的主要决定因素。间苗是一种农艺实践，包括改变叶片和果实，植物的源器官和汇的器官之间的比例。减少桃树上的果实负荷可能会导致果实尺寸增加，有时还会增加其余果实中的可溶性固体含量。但是，当考虑减少水槽器官和减少光合过程时，这种反应在早收桃和晚收桃品种中都会改变。这项工作的目的是研究源库平衡对两个具有不同果实发育和收获时间的油桃品种的生理和代谢参数的影响。同时在两个品种的树木中进行差异性间伐。除了生理参数（例如叶绿素荧光，气体交换和叶糖成分）外，还确定了两个收获季节的果实发育动力学。以山梨糖醇为最丰富糖的叶片间伐树木光合速率的下降与气孔限制和叶片中短暂糖的积累有关。另一方面，不管间苗处理如何，大多数光化学过程在两个品种的叶片中都保持不变。我们建议通过稀疏处理增加源库比，导致叶片中可溶性糖的瞬时积累，并表明排水能力的失衡导致光合作用减少和气孔关闭。在这些油桃品种中，间伐导致较低的净光合作用，但对最终果实的大小没有显着影响。