Alterations of Endogenous Hormonal Levels in Plants under Drought and Salinity

Abstract

The phytohormones are pivotal chemical messengers produced within the plant that regulate its growth and development, and responses to environmental stimuli. Drought and salinity are adverse environmental factors that disturb the plant hormonal balance. Accordingly, these hormonal fluctuations modify the cellular dynamic and hence they play a central role in regulating plant growth responses to abiotic stresses such as drought and salinity. The present review gives an update about the alterations of endogenous phytohormones such as abscisic acid (ABA), auxins (Aux), cytokinins (CKs), ethylene (ET), gibberellins (GAs), jasmonates (JAs), salicylic acid (SA), brassinosteroids (BRs), strigolactones (SLs) and nitric oxide (NO) that occur as part of the adaptative responses of plant against drought and salt stresses. Better understanding of the endogenous hormonal changes during the plant response to both abiotic stresses will contribute, in part, to the development of stress-tolerant plants.

Barley Brassinosteroid Mutants Provide an Insight into Phytohormonal Homeostasis in Plant Reaction to Drought Stress

“…Interestingly, the exogenous methylJA was found to repress the expression of the BR signaling and target genes (Gan et al, 2015). As expected (Huang et al, 2008; Llanes et al, 2016), drought stress induced the significant increase in the endogenous JA content in all analyzed genotypes. Interestingly, both the BR-deficient and BR-insensitive barley mutants retain the capacity of the significant increase in the endogenous JA content in reaction to drought, and relatively to even a higher extent when compared with the “Bowman” cultivar.…”

“…In previous studies, mostly exogenous BRs applications were performed, thus the role of the endogenous BRs in the regulation of plant drought response remains controversial and requires further analysis (Jager et al, 2008; Llanes et al, 2016). In the present study the accumulation of two representatives of BRs, CS and 24-epiBL, was found to be significantly stimulated by drought in all analyzed genotypes.…”

“…However, the exact mechanism of SA involvement in drought response is still not fully understood, because the endogenous SA accumulation is modified by various developmental and physiological factors (Llanes et al, 2016). In the present research we demonstrated that alteration in the SA homeostasis and the significant increase in the endogenous SA accumulation is a physiological reaction of barley to drought stress.…”

“…Drought belongs to the major stresses in agriculture (Mahajan and Tuteja, 2005) resulting in serious loss in crop production and shortage of food supplies (Wang et al, 2003; Ferrero-Serrano and Assmann, 2016). Moreover, it is suggested that in several regions of the world crop losses caused by drought will become even more evident (Llanes et al, 2016). During evolution plants have developed a broad range of adaptive reactions, including morphological, physiological and molecular mechanisms allowing a proper response to drought stress (Ahmadi et al, 2010).…”

“…During evolution plants have developed a broad range of adaptive reactions, including morphological, physiological and molecular mechanisms allowing a proper response to drought stress (Ahmadi et al, 2010). One of the most important mechanisms is alteration in endogenous phytohormone concentrations (Llanes et al, 2016). However, in previous studies the influence on plant physiological reactions to drought was analyzed mainly through exogenous BR treatment or application of BR biosynthesis inhibitor, consequently there is still a lack of direct genetic evidence for a role of endogenous BRs in modulation of plant stress responses (Jager et al, 2008; Divi et al, 2010; Zhou et al, 2014).…”