Water Loss - Plant Water Relation

Plants lose about 98% of water to the atmosphere by transpiration. Often water loss by transpiration exceeds gain by absorption and results in negative water balance within the plant. Small and moderate deficit that occur due to high temperature during the day are compensated during the night but prolonged deficit causes irreversible damages and threatens the plant's survival. Transpiration is essentially evaporation of water from the aerial portion of the plant.

However, evaporation of water from open surface meets less resistance while evaporation of water from leaves faces considerable resistance. Transpiration occurs mainly through stomata of the leaves. This is called stomata transpiration. About 5% of the water is lost from the leaf through the cuticle. This is called cuticular transpiration. In woody plants there are lenticels opening within the bark that function in gas exchange. The water loss through these cells is called lenticular transpiration.