Université Clermont Auvergne, INRAE, PIAF, Clermont-Ferrand, France.
Université de Montpellier, INRAE, CIRAD, Institut Agro, AGAP, Montpellier, France.
J Exp Bot. 2021 Feb 27;72(5):1933-1945. doi: 10.1093/jxb/eraa559.
Photosynthetic carbon assimilation rates are highly dependent on environmental factors such as light availability and on metabolic limitations such as the demand for carbon by sink organs. The relative effects of light and sink demand on photosynthesis in perennial plants such as trees remain poorly characterized. The aim of the present study was therefore to characterize the relationships between light and fruit load on a range of leaf traits including photosynthesis, non-structural carbohydrate content, leaf structure, and nitrogen-related variables in fruiting ('ON') and non-fruiting ('OFF') 'Golden Delicious' apple trees. We show that crop status (at the tree scale) exerts a greater influence over leaf traits than the local light environment or the local fruit load. High rates of photosynthesis were observed in the ON trees. This was correlated with a high leaf nitrogen content. In contrast, little spatial variability in photosynthesis rates was observed in the OFF trees. The lack of variation in photosynthesis rates was associated with high leaf non-structural carbohydrate content at the tree level. Taken together, these results suggest that low carbon demand leads to feedback limitation on photosynthesis resulting in a low level of within-tree variability. These findings provide new insights into carbon and nitrogen allocations within trees, which are heavily dependent on carbon demand.
光合作用碳同化速率高度依赖于环境因素，如光照可用性，以及代谢限制，如碳在汇器官中的需求。在树木等多年生植物中，光和汇需求对光合作用的相对影响仍未得到很好的描述。因此，本研究的目的是描述光照和果实负载对一系列叶片特性的关系，包括光合作用、非结构性碳水化合物含量、叶片结构和氮相关变量，在结果（“ON”）和非结果（“OFF”）的“金冠”苹果树上。我们表明，作物状态（在树的尺度上）对叶片特性的影响大于局部光照环境或局部果实负载。在 ON 树上观察到高的光合作用速率。这与高的叶片氮含量有关。相比之下，在 OFF 树上观察到光合作用速率的空间变化很小。在 OFF 树上光合作用速率的缺乏变化与高水平的叶片非结构性碳水化合物含量有关。这些结果表明，低的碳需求导致光合作用的反馈限制，导致低的树内变异性。这些发现为树木内的碳和氮分配提供了新的见解，这在很大程度上取决于碳需求。
