Root growth and development need proper carbon partitioning between sources and sinks. Photosynthesis products are unloaded from the phloem and enter the root meristem cell by cell. While sugar transporters play a major role in phloem loading, phloem unloading occurs via the plasmodesmata in growing root tips. The aperture and permeability of plasmodesmata strongly influence symplastic unloading. Recent research has dissected the symplastic path for phloem unloading and identified several genes that regulate phloem unloading in the root. Callose turnover and membrane lipid composition alter the shape of plasmodesmata, allowing fine-tuning to adapt phloem unloading to the environmental and developmental conditions. Unloaded sugars act both as an energy supply and as signals to coordinate root growth and development. Increased knowledge of how phloem unloading is regulated enhances our understanding of carbon allocation in plants. In the future, it may be possible to modulate carbon allocation between sources and sinks in a manner that would contribute to increased plant biomass and carbon fixation.

中文翻译：

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控制韧皮部卸载和根发育

根的生长和发育需要在源和汇之间进行适当的碳分配。光合作用产物从韧皮部卸载并逐个细胞地进入根分生组织。虽然糖转运蛋白在韧皮部装载中起主要作用，但韧皮部卸载是通过生长的根尖中的胞连丝发生的。胞间连丝的孔径和渗透性强烈影响共质卸载。最近的研究剖析了韧皮部卸载的共生路径，并鉴定了几个调节根部韧皮部卸载的基因。胼胝质周转和膜脂组成改变胞间连丝的形状，从而可以进行微调以使韧皮部卸载适应环境和发育条件。卸载的糖既充当能量供应，又充当协调根生长和发育的信号。对韧皮部卸载如何调节的了解的增加增强了我们对植物碳分配的理解。未来，有可能以有助于增加植物生物量和碳固定的方式调节源和汇之间的碳分配。