With respect to influence on plant growth and health, it is the amount and frequency of rainfall received during the growing season that is of greater significance than the total amount of precipitation in a given year. When defining a drought year, the pattern and frequency of rainfall are clearly more important than the total amount of rain. Water relations in plants To understand the impact of drought on plants, a review of water relations can be helpful. Without water, there is no plant life. It is the milieu in which chemical reactions inside a plant cell take place.
Water is the major component of the protoplasm which makes up the content of cells.
Water also serves as a raw material for many metabolic processes, including photosynthesis. Aside from its role in photosynthesis and other chemical reactions, water plays a significant role in the physical processes of plant growth. As new cells form, they expand in response to turgor pressure, that is, the pressure exerted on the cell membranes and walls by water entering the cells. Following this expansion, the cell adds additional layers of cellulose to form a more permanent cell structure. This is a fundamental process in the elongation of newly formed cells and the growth of woody plants.