The nutrient transported from dorsal vascular bundles first unloaded into apoplast via nucellar projection, then was absorbed by aleurone layer cells;

Symplast pathway and transcelluar pathway is difficultly distinguished by Experiment methods, and have no valid ways to make distinction between apoplast and cell to cell pathway.

The apoplast is of essential significance in cell communication and identification; the apoplast signal molecules, too, plays an important role in the growth and development of plant cells.