The decreased crop productivity is the result of altered physiological and biochemical status of the plants under stress conditions. Abiotic stress tolerance is a complex phenomenon that depends upon interactive effect of different biochemical pathways that are activated/modulated in response to stress. Major biochemical events affected under abiotic stress conditions are reserve mobilization, source–sink relationship, membrane permeability, altered endogenous hormonal level, accumulation of free radicals, antioxidative defense system and osmolyte accumulation in plants. Gibberellins are the key regulators of the translocation from source to the developing sink through which the extracellular invertase involved in phloem unloading, carbohydrate partitioning and growth of sink tissues is induced. ABA is involved in maintaining antioxidant potential and detoxification of cellular damage under stress conditions. The tolerant genotypes have better capacity to induce the antioxidant enzyme system to face abiotic stress conditions. Abiotic stresses lead to oxidative stress in plants due to higher leakage of electrons towards O2 during photosynthetic and respiratory processes. Enzymes of anaerobic metabolism such as alcohol dehydrogenase, pyruvate dehydrogenase and aldehyde dehydrogenase are upregulated under water logging in tolerant cultivars. Sugars such as sucrose, raffinose series oligosaccharides and fructans are also involved in direct ROS quenching. Glycine betaine and proline help the plant in maintaining osmotic adjustment in plants under stress conditions. Development of genotypes tolerant to different stresses is considered a promising approach for meeting growing food demands.
Abiotic stress, Antioxidative defence system, Carbohydrates, Drought, Temperature, Plant growth regulators, Salt stress
