Water is an essential element in plant life, as it directly participates in the process of photosynthesis and maintains turgor pressure within plant cells. When plants are exposed to water deficiency, a condition known as water stress occurs. This is one of the most important environmental factors that negatively affect plant growth and productivity, especially in arid and semi-arid regions. Concept of Water Stress Water stress is the condition in which the plant is unable to absorb sufficient water to compensate for the loss through transpiration, leading to disruption of vital physiological processes, especially photosynthesis. Concept of Photosynthesis Photosynthesis is the process by which green plants convert light energy into chemical energy stored in the form of sugars, using water and carbon dioxide in the presence of chlorophyll within chloroplasts. General Equation: 6CO₂ + 6H₂O + Light → C₆H₁₂O₆ + 6O₂ Effects of Water Stress on Photosynthesis 1. Stomatal Closure When water is limited, stomata close to reduce water loss, which leads to: Reduced carbon dioxide entry Decreased rate of photosynthesis 2. Reduction in Chlorophyll Content Severe stress may cause: Chlorophyll degradation Reduced light absorption 3. Effect on Light Reactions Water deficiency leads to: Disruption of electron transport Reduced production of ATP and NADPH 4. Increased Oxidative Stress Accumulation of reactive oxygen species (ROS) Damage to cellular membranes and proteins Associated Physiological Changes Leaf wilting Reduced transpiration rate Decreased leaf area Increased production of abscisic acid (ABA), which promotes stomatal closure Plant Adaptation Mechanisms to Water Stress Some plants possess resistance mechanisms such as: Developing deeper roots to absorb water Reducing leaf area Accumulating osmotic substances such as proline Increasing antioxidant enzyme activity Agricultural Importance Water stress directly affects: Reduced agricultural productivity Lower crop quality Increased plant susceptibility to diseases Therefore, studying the effects of drought on photosynthesis is essential for developing resistant plant varieties and improving irrigation management. Water stress is a serious environmental factor that directly and indirectly affects photosynthetic efficiency through stomatal closure, chlorophyll reduction, and increased oxidative stress. Understanding these effects helps improve sustainable agricultural strategies and address climate change challenges.
  الهدف 15 : الحياة في البر   الهدف 11: مدن ومجتمعات محلية مستدامة