Insight into phytohormonal modulation of defense mechanisms to salt excess in a halophyte and a glycophyte from Asteraceae family

Alina Wiszniewska,Michał Dziurka,Kinga Dziurka,Aleksandra Koźmińska,Ewa Hanus-Fajerska

doi:10.1007/s11104-021-04889-x

Abstract

AimsThe aim of this study was to compare the efficiency of three defense mechanisms (ionic balance, osmotic adjustment and counteracting oxidative stress) under low, moderate and high soil salinity in two related species of contrasting tolerance to salinity: the halophyte Aster tripolium and the glycophyte Aster alpinus, and to elucidate their phytohormone-mediated regulation.MethodsThe phytohormonal profiling was performed to asses correlations between the pool of plant growth regulators and parameters depicting ionic homeostasis, osmotic adjustment and antioxidant system.ResultsDefense mechanisms in both species were based on accumulation/activity of distinct compounds (Na+ and K+ ions, antioxidants), but differences among species concerned particularly soluble carbohydrates and betaines. The halophyte accumulated mannitol, uronic acids and sucrose, while the glycophyte mostly glucose and proline-betaine. The halophyte responses also correlated with changes in the content of plant growth promoting PGRs, as well as jasmonates and benzoic acid. The glycophyte responses corresponded with changes in content of abscisic acid and ethylene precursor, as well as salicylic acid.ConclusionsWe provided evidence that benzoic acid rather than salicylic acid is involved in salt tolerance in the halophyte and elevated SA content may enhance vulnerability to salt excess. An important element of tolerance trait is also JA-GA network that influences the intensity of defense responses. This study uncovers new aspects of internal phytohormonal regulation of plant reaction to soil salinity and enables further insight into extremophyte biology.

Highlights

Excessive soil salinity is a destructive environmental factor that greatly reduces plant growth and productivity
We provided evidence that benzoic acid rather than salicylic acid is involved in salt tolerance in the halophyte and elevated Salicylic acid (SA) content may enhance vulnerability to salt excess
A. tripolium was capable of maintaining constant content of active and inactive Aux under low and moderate salinity in comparison to control conditions

Summary

Introduction

Excessive soil salinity is a destructive environmental factor that greatly reduces plant growth and productivity. General plant tolerance to suboptimal salinity mostly depends on the activation of a series of conserved mechanisms, among which three are important: control of ion homeostasis, accumulation of osmolytes to maintain cellular osmotic balance, and activation of antioxidant system to counteract oxidative stress (Flowers and Colmer 2015; Rozema and Schat 2013). Extended knowledge has been gathered considering physiological performance of halophytes in saline areas These plants are extremely salt tolerant – they usually grow and survive in environments with salt concentrations as high as 5 g·l −1 (Joshi et al 2015), being capable of surviving under a salt shock, for example due to tidal or rainfall events.

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