Girdling is the removal of a ring of outer up to the depth of the plant of the phloem layer in a woody trunk.Phloem is responsible for downward movement of food, which is stopped bt gridling. The roots will not be able to get food and die first.

The plants survive under flooded condition by losing excess water through transpiration (increased (increased transpiration rate.) It is seen that in prolonged flooded conditions, roots die because of lack oxygen and plants eventually dies.

Various ions from the soil are actively absorbed and accumulated in the root tissues.This accumulation of ions causes a decrease in water potential.So water is absorbed passively through osmosis by the root, which results in hydrostatic pressure.Since, ions are absorbed actively, there is a need for energy to develop root pressure.

An analysis of the xylem exudates shows that through some of the nitrogen travels as inorganic travels as inorganic ions, much of it is carried in the organic form as amino acids and related compounds. Similarly, small amount of phosphorus and sulphur are carried as organic compunds.In addition, small amount of exchange of materials does take between xylem and phloem.

In such condition, the sugar solution known to be osmotically active because the sugar solution possesses low water potential due to which it causes osmotic entry of water into it.