Falchi Rachele, Bonghi Claudio, Drincovich María F, Famiani Franco, Lara María V, Walker Robert P, Vizzotto Giannina
Department of Agricultural, Food, Environmental, and Animal Sciences, University of Udine, Udine, Italy.
Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova Agripolis, Legnaro, Italy.
Front Plant Sci. 2020 Nov 13;11:573982. doi: 10.3389/fpls.2020.573982. eCollection 2020.
The partitioning of assimilates in fruits, which are economically important sink organs, is ruled by different physiological processes and affected by both environmental and agronomical factors. The bulk of the water and solutes, required for growth, is imported into fruits and seeds through xylem and phloem. In the stone fruits, five vascular bundles enter the base of the fruit, then dividing to supply either the flesh or the seed. The main sugars accumulated in stone fruits include fructose, glucose, and sucrose, along with other minor saccharides. The mechanisms of phloem loading in these fruit species have not been fully elucidated yet, but the available data hint either an apoplastic or a symplastic type or possibly a combination of both, depending on the species and the sugar considered. Similarly, phloem unloading mechanisms, elucidated for a small number of species, depend on genotype and developmental stage. Remarkably, key enzymes and transporters involved in the main sugars-conversion and transport pathways have received considerable attention. In stone fruit trees, the presence of an elevated number of fruits alters the source-sink balance, with a consequent intensification of competition among them and between vegetative and reproductive growth. The main environmental factors affecting this balance and the agronomical/artificial manipulations of source-sink relationships to achieve adequate fruit production and quality are reviewed.
果实作为经济上重要的库器官，同化物在其中的分配受不同生理过程支配，并受到环境和农艺因素的影响。生长所需的大量水分和溶质通过木质部和韧皮部进入果实和种子。在核果类中，五条维管束进入果实基部，然后分支以供应果肉或种子。核果类中积累的主要糖类包括果糖、葡萄糖和蔗糖，以及其他少量糖类。这些果实物种中韧皮部装载的机制尚未完全阐明，但现有数据表明，根据物种和所考虑的糖类不同，可能是质外体类型、共质体类型，或者两者兼而有之。同样，少数物种中阐明的韧皮部卸载机制取决于基因型和发育阶段。值得注意的是，参与主要糖类转化和运输途径的关键酶和转运蛋白受到了相当多的关注。在核果类果树中，果实数量增加会改变源 - 库平衡，从而加剧果实之间以及营养生长和生殖生长之间的竞争。本文综述了影响这种平衡的主要环境因素以及源 - 库关系的农艺/人工调控措施，以实现充足的果实产量和品质。
