1. Excess water getting into the plant might decay the cells. Transpiration prevents it by removing the extra water.
2. Extra quantity of water, if retained would disturb the osmotic relationship between cells. This is prevented by transpiration.
3. Transpiration stream helps in the distribution of nutrients to all the parts of the plant body.
4. Fresh and cool water reaches all the parts of the plant body and this reduces the metablic heat acting as a coolant.