Selection Criteria for Assessment of Drought Tolerance on Physio-morphic Attributes

This chapter discusses the severe impacts of water shortage on plants and their defense mechanisms against drought stress. Climate change is a major factor causing abrupt changes, including sudden rainfall, heat waves, low temperatures, and drought. To cope with these fluctuations, it is crucial to understand the strengths that help plants tolerate these conditions. Prolonged periods of dryness during typically arid seasons are anticipated, increasing drought risks and water scarcity concerns. Drought poses a multifaceted challenge characterized by insufficient water supply, elevated temperatures, and low humidity, disrupting the life cycle of crops for extended periods. Understanding plant responses to drought is essential for developing strategies to mitigate and adapt to its effects. Different species exhibit varied reactions based on their traits, physiology, and environmental context. Several genes are differentially expressed under such conditions, many linked to photosynthesis, metabolic processes, and stress response mechanisms. Plants undergo morphological, physiological, biochemical, anatomical, and molecular changes, such as closing stomata, decreasing photosynthesis activity, detecting root signals, losing turgor pressure, adjusting osmotically, reducing water potential, decreasing CO 2 conductance and internal concentration, increasing root-to-shoot ratio, producing antioxidant species, and activating DREBs transcription factors. An ideal drought-tolerant plant should have a root-to-shoot ratio close to 1, high relative water content, low leaf water loss, high cell membrane stability, high proline content under drought stress, and monitored ethylene levels.