Question

why the guard cell swell if it not swell what will happen and why guard cell shrink

Answer 1

when the water is fill in guard cell it will swell so that stomata is open and gas can exchange and when water in released the cell gets shrink

Answer 2

The guard cell swell due to filling of water inside them, which enables the stomatal pore to get exposed to the outer envirinment. All the gaseous exchange takes place through the stoamtal pore and hence if the guard cells does not let the pore be exposed,no gaseous exchange will ever take place.

The guard cells shrink due to the moving out of water from them.This mechanism is important so that not much of the sunlight should be able to enter the cell,which if happens,can cause serious damage to the plant cells.Hence with the shrinking of the guard cells,the stomatal pore is covered .

hope it helps u my frnd:)