If a potential gradient is established Root hair by any means. Water moves centripetally across the epiblema and root hairs and vase then through the cortex to the xylem via endodermis (the passage cells) and pcricycle. The possible pathways of water transport across this regions arc
i. The apoplast pathway
ii. The symplast pathway
iii. The transmembrane pathway.
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The apoplast consists of nonliving components of the root that roughly equates with free space, that is, cell walls, intercellular air spaces and the xylem vessels. The symplast consists of cytoplasm interconnected by plasmodesmata in the symplast pathway water moves from one cell to next via plasmodesmata.
In the transmembrane pathway water enters a cell on one side, exits the cell on the other sides. In other words water crosses at least two membranes for each cell in its path (the plasma membrane on entering and on exiting).
The initial flow of water across the surface layer of root upto innermost layer of cortex is considered to be mainly through apoplast pathway. At the endodermis the apoplast pathway is abstracted by the caesarian strip. Thus the movement of water across the endodermis occurs through the symplast.
In certain cases poorly supersized passage cells allow the entry of water across the endodermis. The vascular cylinder offers little resistance to the movement of water from endodermis. Water on reaching the xylem is translocated upwards.