What is the process by which plants lose water vapor called?

Transpiration is the process by which plants lose water vapor, primarily from small openings in their leaves known as stomata. This process is essential for several reasons. It helps in the regulation of temperature within the plant, maintains nutrient flow from roots to leaves, and aids in the uptake of minerals from the soil. When water evaporates from the leaf surface, it creates a negative pressure that helps pull more water up through the plant's vascular system, which is crucial for maintaining hydration and overall plant health.

In contrast, evaporation refers to the process of water turning from liquid to vapor and can occur from various surfaces, not just in plants. Condensation is the process where water vapor cools and turns back into liquid, usually forming droplets. Photosynthesis is a biochemical process in plants that converts carbon dioxide and water into glucose and oxygen, utilizing sunlight, and is not directly related to the loss of water vapor. Thus, transpiration specifically defines the loss of water through plant surfaces, making it the correct answer.