Question

explain suction pressure theory

Answer 1

The term diffusion pressure deficit (DPD) was coined by B.S Meyer in 1938. Originally DPD was described as suction pressure by Renner (1915). It is reduction in the diffusion pressure of water in solution or cell over its pure state due to presence of solutes in it and forces opposing diffusion. Diffusion pressure of water is maximum and its theoretical value is 1236 atm. DPD of a solution is equal to its osmotic pressure i.e. DPD = OP(of solution). DPD of a cell is influence by both osmotic pressure and wall pressure (turgor pressure) which opposes the endosmotic entry of water, i.e. DPD = OP - Wall pressure. DPD is directly proportional to the concentration of the solution. DPD decreases with dilution of solution. The actual pressure with which cell absorbs water is called "suction pressure".

Answer 2

suction pressure is equal to diffusion pressure defficit
the actual pressure with which a cell absorb water is suction pressure