Progress in phloem Ioading and unloading of plant photoassimiate
Gong Yue · Xibei zhiwu xuebao · 1999
The research of recent years shows that phloem loading and unloading of plant photoassimi1ate both have symplasmic and apoplasmic pathways. Sugars transported by loading main1y are: (1) raf finose and its analogue (in symplasmic pathway), (2) sucrose (in apoplasmic). Symplasmic unloadlng of photoassimilate occurs through bulk flow and diffusion,but apoplasmic unloading is clarified into two types according whether sucrose is hydrolysable or not. The mechanisms of loading and unloading are different with plant species and the sink－source relationship of the whole plant. They also adapted with growth stages and the change of enviroment. It has important significance for theory development and practice of high－yie1d agriculture to study in advance the control mechanism of phloem loading and unloading.