Plant Stress and Water Stress Effects

Physiology of Plant Stress and Water Stress Effects

• Stress is defined as an external factor that negatively affects plant survival, crop yield, biomass accumulation, and primary processes related to growth.
• Stress tolerance is the plant's ability to cope with an unfavorable environment, and it varies among plants.
• Acclimation is when the plant's tolerance increases due to prior stress exposure, while adaptation refers to a genetically determined level of resistance.
• Plants are frequently exposed to stress under natural and agricultural conditions, and some environmental factors may take days, weeks, or even months to become stressful.
• Water stress results in stomatal closure, which happens when guard cells directly lose water to the atmosphere or have a lowered solute content.
• Water-stressed plants have smaller leaves due to cell shrinkage, cell wall relaxation, and senescence, which reduces water loss by transpiration.
• Root extension is enhanced in water-stressed plants due to a smaller leaf area, allowing more assimilates to be distributed to the root system, supporting deeper soil penetration.
• Photosynthesis is decreased during water stress due to stomatal closure and desiccation of mesophyll cells, which negatively affects metabolism.
• Transpiration is crucial for cooling leaf surfaces and the atmosphere, and less transpiration during water stress leads to increased leaf temperatures.
• Water uptake and movement are reduced during water stress due to water molecules clinging more tightly to soil particles, root shrinkage, damage to root hairs, and suberin covering mature roots.
• Large xylem vessels cavitate during water stress, but smaller vessels and tracheids can continue water transport.
• Water stress during reproduction is more sensitive, as assimilates are directed to the fruit rather than the roots.