what is DPD? PLZ EXPLAIN...

DPD is diffusion pressure deficit. It is also called suction pressure. 

Diffusion pressure of the pure solvent is maximum. Addition of solutes result in a decrease in the diffusion pressure. The deficit was termed diffusion pressure deficit. The greater the concentration of a solution, the greater is its DPD. Such a solution will tend to take up water and become normal, therefore water moves from low DPD to high DPD. Value of DPD is always positive. DPD for a cell is DPD=OP-TP. DPD is an index of water absorbing capacity of cell.