Kebede Nanesa Tufa
Water stress is a severe environmental constraint to plant productivity. Water stress induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. This Seminar describes the effects of water stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants, and the mechanism of Water stress resistance in plants on a morphological, physiological and molecular basis. Water stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Water stress effects can be managed by production of the most appropriate plant genotypes together with adjustment of agronomic practices (sowing time, plant density and soil management). Stress measurement is the quantification of the effects of environmental stresses on growth, productivity and survival of plants; Visual assessment of damages incurred Strain and measurement using different tools and protocols. Thermal sensing for plant water status, Leaf chlorophyll fluorescence, Measuring Plant Stress with an Infrared Thermometer and determination of water stress with spectral reflectance are among plant water stress measuring devices and techniques.
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