Crop plants are exposed to several environmental stresses, all affecting plant growth and development, which consequently hamper crop productivity. Among all stresses drought is considered the single most devastating environmental stress. During germination phase, the water absorbed is required for several enzymatic reactions, for solubilization and transport of metabolites and as a reagent in the hydraulic digestion of proteins, carbohydrates and lipids from the tissue reserve of the seed towards the embryo. Drought stress negatively impacts growth, yield, membrane integrity, pigment content, osmotic adjustment, water relationsand photosynthetic activity. It causes not only a significant damage to photosynthetic pigments, but also affects thylakoid membranes. The generation of reactive oxygen species (ROS) is one of the earliest biochemical responses of eukaryotic cells to biotic and abiotic stresses. Being highly reactive, ROS can seriously damage plants by increasing lipid peroxidation, protein degradation, DNA fragmentation and ultimately cell death. Escape from drought is attained when phenological growth is effectively coordinated with periods of water availability, where the growing season is shorter and terminal drought stress predominates. Drought avoiders maintain water status through stomatal closure to minimize transpirational water loss and maintains water uptake through an extensive and prolific root system, osmoregulation and anti-oxidant enzymes. Both conventional and molecular breeding have paved the way towards tolerance and plant scientists have developed new line of crop plants that can cope with water stressed environment without sacrificing yield.
Prof. Dr. Bilal BİLGİN