Photosynthesis, Antioxidant Protection, and Drought Tolerance in Plants

Drought stress usually leads to reductions in crop yield, which can result from many drought-induced morphological, physiological, and metabolic changes that occur in plants. In this chapter, we review the most recent reports on drought-induced responses in plants, focusing on the role of oxidative stress as well as on other possible mechanisms. A key sign of drought stress at the molecular level is the accelerated production of reactive oxygen species. Levels of leaf and root enzymatic antioxidants (peroxidase, catalase, and glutathione reductase), nonenzymatic antioxidants (glycine betaine), and stress parameters (hydrogen peroxide and malondialdehyde) were determined under watered and drought stress conditions in two durum wheat genotypes differing in drought resistance. The dehydration of wheat leaves and roots was accompanied by the accumulation of H2O2, MDA, and GB, a phase change in the activity of antioxidant enzymes, indicating the development of oxidative stress. Activities of antioxidant enzymes under drought stress were shown to relate de novo synthesis of some isoenzymes. The activity, some physicochemical and kinetic parameters of carbonic anhydrase were comparatively studied in the flag leaves, ear elements, and root systems of wheat genotypes during ontogenesis. TRAP markers linked to the QTL for the drought tolerance were used for the molecular assessment of drought tolerance of wheat genotypes.