The plant continuously lose water in the vapour form from its body surfaces. It creates a transpiration pull to absorb more and more water from soil through roots. If the plant does not get water in soil, even then loss through transpiration is not stopped, so plant shows wilting sometimes it leads to the physiological wilting (non-recoverable) and plant dies. So, the transpiration is necessary evil.

The three physical properties of water that helps in ascent up to xylem are as given

Cohesive properties	Mutal attraction between molecules
Adhesive properties	Attraction of water molecules to polar surfaces (of tracheids)
Surface tension	Water molecules get attracted to each other more in liquid phase than in gas phase.

If gardener forgets to water the plants, it will start it wilting (a physiological state of plant in which plant leaves droop down). If watered in time, the plant may recover and become normal. But in second condition, if watering is delayed, the plant will not recover as if it reaches at physiological wilting stage, it will not recover and dies.

Facilitated diffusion's is the mechanism which is highly selective passive process. In facilitated diffusion special proteins help in movement of substances across the membrane without expenditure of ATP energy because facilitated diffusion cause net transport of molecules from a low to high concentration and this would not require input of energy.

(a) The cell swell in hypotonic solution and shrink in hypertonic solution.

(b) Imbibition is a special type of diffusion when water is adsorbed by living cells.

(c) Most of the water flow in roots occurs via the apoplast way.