Study the following table showing the components of water potential of four cells of an actively transpiring plant.
Identify the four cells as root hair, cortical cell, endodermal cell (lacking casparian strips) and pericycle cell respectively in the young root (assuming symplastic water flow through them).
B, D, C, A
D, A, C, B
A, D, C, B
A, C, B, D
A, D, C, B
The movement of water from one cell to another cell through the plasmodesmata is called the symplast pathway. It occurs in the following sequence:
Root hair → Epidermis → Cortex → Endodermis → Pericycle → Xylem
Solute potential (ψs) and pressure potential (ψp) are two components of water potential. Water potential can be calculated using the formula:
Water always flows from higher potential to lower potential. The water potential values of the four given cells are:
A → - 0.68 + 0.42 = - 0.26
B → -0.75 + 0.36= - 0.39
C → - 0.83 + 0.47 = - 0.36
D → - 0.57 + 0.29 = - 0.28
So, the correct sequence of the flow of water is A → D → C → B.
Thus, A, D, C and B respectively are the root hair, cortical cell, endodermal cell and pericycle cell.