Explain ' routes 's for path of water across root cells.

Explanation

Water a first absorbed by root hair and other epidermal cells through imbibtions from soil and moves radially and centripetally across the cortex, endodermis , pericycle and finally reaches xylem element osmotically. There are 3 possible routes of water. i) Apoplast ii) Symplast iii) Transmembrane route .
1. Apoplast : The apoplast ( Greek : apo = away , plast = cell ) consists of everything external to the plasma membrane of the living cell. The apoplast includes cell walls extra cellular spaces and the interior of dead cells such as vessel elements and tracheids. In the apoplast pathway water moves exclusively through the cell wall or the non living part of the plant without crossing any membrane. The apoplast is a continuous system.
Symplast : The symplast ( Greek : sym = within , plast = cell ) consists of the entire mass of cytosol of all the living cells in plant as well as the plasmodesmata the cytoplasmic channel that interconnects them.
In the symplastic route water has to cross plasma membrane to enter the cytoplasm of outer root cell, then it will move within adjoining cytoplasm through plasmodesmata around the vacuoles without the necessity to cross more membrane till it reaches xylem.
3. Transmembrane route :
(i) In transmembrane pathway water sequentially enters a cell on cell on one side and exits from the cell on the other side.
(ii) In this pathway water crosses at least two membranes for each cell.
(iii) Transport across the tonoplast is also involved.