Q.If a cell in the cortex with DPD of 5 atm is surrounded by hypodermal cells with DPD of 2 atm, what will be the direction of movement of water ?

Since DPD of the hypodermal cells (2 atm) is lower than that of the cortical cell (5 atm), water moves from the hypodermal cells into the cortical cell.

Diffusion Pressure Deficit (DPD), also called suction pressure, is the amount by which the diffusion pressure of water in a cell (or solution) is less than the diffusion pressure of pure water at the same temperature and pressure. A cell with a HIGHER DPD has a greater 'thirst' or pulling power for water (it is drawing water in more strongly), while a cell with a LOWER DPD has less pulling power.

The rule governing osmotic water movement between adjacent cells is that water always moves from the cell/region with the LOWER DPD to the cell/region with the HIGHER DPD (i.e., water moves toward the cell that has the greater deficit/pulling power for water), until the DPDs of the two cells become equal (equilibrium).

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