The following three points will highlight the three major pathways of water movement in roots with diagram.
This allows direct cytoplasm-to-cytoplasm flow of water and other nutrients along concentration gradients. In particular, it is used in the root systems to bring in nutrients from soil.
It moves these solutes from epidermis cells through the cortex into the endodermis and eventually the pericycle, where it can be moved into the xylem for long distance transport.
Specifically there are three pathways of water passage from root hairs to xylem inside the root:
(i) Apoplast,
(ii) Nonvascular symplast
(iii) Vacuolar symplast.
(i) Apoplast Pathway:
Here water passes from root hair to xylem through the walls of intervening cells without crossing any membrane or cytoplasm. This pathway provides the least resistance to movement of water. However, it is interrupted by the presence of impermeable lignosuberin casparian strips in the walls of endodermal cells.
(ii) Non-vacuolar Symplast Pathway:
Water passes from cell to cell through their protoplasm. It does not enter cell vacuoles. The cytoplasm of the adjacent cells are connected through through bridges called plasmodesmata. For entering into symplast, water has to pass through plasma lemma (cell membrane) at-least at one place. It is also called trans-membrane pathway,
(iii) Vacuolar Symplast Pathway:
Here individual root cells function as tiny osmotic systems. The first osmotic system operates at root hair cell. It absorbs water from soil through osmosis. The pathway is cell wall, plasma-lemma, cytoplasm, tonoplast and central vacuole. From root hair eel, water passes into vacuoles of adjacent cortical cell through osmosis.
The process continues till water reaches the xylem parenchyma cells. However, vacuolar pathway provides a lot of resistance. It is used only when individual cells are to pick up water. Otherwise, the usual pathway of water movement is partly apoplastic and partly symplastic.