The process by which plants lose water through their leaves is called transpiration. During transpiration, water vapor is released from tiny openings on the underside of leaves known as stomata. This loss of water creates a negative pressure within the plant, which helps draw up water and nutrients from the roots through the xylem. Transpiration is essential for maintaining plant hydration, regulating temperature, and facilitating the carbon dioxide uptake necessary for photosynthesis. It plays a crucial role in the water cycle, contributing to atmospheric moisture and weather patterns.