This document discusses the importance of water for plants. It outlines how water is used in photosynthesis, as a solvent, for chemical transport, and generating water pressure. The document also examines how water is present in the atmosphere through relative humidity, and how it regulates transpiration and photosynthesis. Factors that impact transpiration like wind speed, humidity, light intensity and temperature are explored. The document also looks at different forms of precipitation, how plants are classified based on their water relations, and the key roles water plays in plant growth and reproduction through processes like photosynthesis, transpiration and providing turgor pressure.