Plant Response to Water-deficit Stress

Drought, a period of abnormally dry weather, results in soil-water deficit and subsequently plant-water deficit. The lack ofwater in the environment constitutes a stresswhen it induces an injury in the plant. Water deficit in the plant disrupts many cellular and whole plant functions, having a negative impact on plant growth and reproduction. Crop yields are reduced by 69% on average when plants are exposed to unfavourable conditions in the field (Boyer, 1982). Availability of water is the most important factor in the environment that reduces the production of our crops. Aswater is increasingly needed for humanpopulations and prime agricultural lands are used for housing, the availability of water will have a greater impact on our ability to produce crops. In nature, certain species are adapted to dry environments. The genotype determines the ability of the plant to survive and thrive in environments with low water availability. In addition, the duration of the water-deficit stress, the rate of stress imposition, and the developmental stage of the plant at the time of stress imposition also affect plant growth. Whether the amount of water present in the environment is a stress is different for each species. A sensing mechanism initiates the responses to water deficit, which occur at themolecular, metabolic, physiological and developmental levels. Many of these responses are driven by changes in gene expression.