Potential role of phytohormones and plant growth-promoting rhizobacteria in abiotic stresses: consequences for changing environment

Abstract

Plants are sessile beings, so the need of mechanisms to flee from unfavorable circumstances has provided the development of unique and sophisticated responses to environmental stresses. Depending on the degree of plasticity, many morphological, cellular, anatomical, and physiological changes occur in plants in response to abiotic stress. Phytohormones are small molecules that play critical roles in regulating plant growth and development, as well as stress tolerance to promote survival and acclimatize to varying environments. To congregate the challenges of salinity, temperature extremes, and osmotic stress, plants use their genetic mechanism and different adaptive and biological approaches for survival and high production. In the present attempt, we review the potential role of different phytohormones and plant growth-promoting rhizobacteria in abiotic stresses and summarize the research progress in plant responses to abiotic stresses at physiological and molecular levels. We emphasized the regulatory circuits of abscisic acid, indole acetic acid, cytokinins, gibberellic acid, salicylic acid, brassinosteroids, jasmonates, ethylene, and triazole on exposure to abiotic stresses. Current progress is exemplified by the identification and validation of several significant genes that enhanced crop tolerance to stress in the field. These findings will make the modification of hormone biosynthetic pathways for the transgenic plant generation with augmented abiotic stress tolerance and boosting crop productivity in the coming decades possible.

Effects of exogenously applied plant growth regulators in combination with PGPR on the physiology and root growth of chickpea (Cicer arietinum) and their role in drought tolerance

“…It had been previously reported that SA and Putrescine significantly enhance the chlorophyll content in several crop plants (Zhang et al 2009;Rivas-San Vicente and Plasencia 2011;Durmuş and Bekircan 2015). The stimulatory role of PGPR on leaf chlorophyll content had been reported previously (Vafadar et al 2014;Fahad et al 2015). Proline accumulation occurs in plants under various abiotic stresses (Ashraf and Foolad 2007).…”

Application of phytohormones during seed hydropriming and heat shock treatment on sunflower (Helianthus annuus L.) chilling resistance and changes in soluble carbohydrates

“…Salicylic acid (SA), a stress-related signaling compound, may directly or indirectly mediate local and systemic defense responses against pathogens and play a role in plant responses to abiotic stresses including drought, low and high temperatures, heavy metals, and osmotic stress (Janda et al 2014). Jasmonic acid (JA) participates in various processes of plant establishment and performance, like germination of seeds, growth of callus and primary root, flowering, formation of gum and bulb and senescence (Fahad et al 2014). Moreover, JA is involved in plant protection against biotic and stresses, such as insect wounding, attack by various pathogens, drought, chilling and salinity (Fahad et al 2014).…”

“…Jasmonic acid (JA) participates in various processes of plant establishment and performance, like germination of seeds, growth of callus and primary root, flowering, formation of gum and bulb and senescence (Fahad et al 2014). Moreover, JA is involved in plant protection against biotic and stresses, such as insect wounding, attack by various pathogens, drought, chilling and salinity (Fahad et al 2014).…”

Introductory Chapter: Hormonal Regulation in Plant Development and Stress Tolerance

“…IAA plays an important role in plant growth and development as well as in regulating growth under stress factors [14]. IAA plays essential roles in plant adaptation to salinity [15] and heavy metal stresses [16]. Furthermore, auxins induce the transcription of the primary auxin response genes which are identified in various plants such as rice, Arabidopsis and soybean [3,17].…”