The process by which plants lose water vapor is called transpiration. This process occurs primarily through small openings on the undersides of leaves known as stomata. Transpiration helps to regulate temperature within the plant and aids in the uptake of nutrients and minerals from the soil. As water vapor escapes from the plant, it creates a negative pressure that draws more water and nutrients up through the plant's roots and stem. Transpiration is an essential part of the water cycle and plays a crucial role in maintaining plant health and ecosystems.