Perspiration 1. Water evaporates. 2. Water is usually excreted through petioles , cuticles and lenticels. 3. The process takes place during the day. 4. Exhaust water is always pure. 5. Foliar perfusion is regulated by guard cells. Discharge 1. Water is discharged in liquid form. 2. Water is usually discharged through hydatids or water holes. 3. The process takes place on the last night or early in the morning. 4. Exhaust water may contain sugars. 5. Discharge can never be controlled.