Phytohormones and Abiotic Stresses
Hadi Salek Mearaji, Aida Ansari, Nader Khadem Moghadam Igdelou, Behnam Asgari Lajayer, Mohammad Pessarakli
Abstract
Global climatic change and increasing population necessitate increased crop productivity. Abiotic environmental factors lead to disruption in growth, development, and yield of plants/crops and pose a major threat to food security in the world. Plants are sedentary, so they respond to stresses through various mechanisms, one of which through an alteration in hormone levels. Phytohormones are extremely important for the regulation and coordination of plant growth and development. Changes in phytohormonal concentration and/or hormonal balance could significantly affect the responses of plants to environmental factors. Gibberellins (GAs), auxins (IAA), cytokinins (CKs), ethylene, and abscisic acid (ABA) are five major classes of plant hormones that play crucial roles in the tolerance of plants to abiotic environmental factors. The approaches applied to extend stress-tolerant plants include breeding, genetic engineering, and external application of phytohormones, which lead to hormonal balance under conditions of stress and can be an advantageous tool to reduce the detrimental impacts of undesirable environmental factors. Ameliorating stress tolerance in plants via breeding is arduous because it is a very lengthy process needing a vast amount of resources that are multigenic and quantitative in nature. Various methods are employed for phytohormone use by plants, such as foliar spray and seed priming, especially agronomic crops. The effectiveness of the rate of phytohormone uptake depends on the crop species, stage of growth, and especially the concentration of the applied phytohormones. The type of phytohormones and their use can help plants overcome stressful conditions.