Ethylene and Sulfur Coordinately Modulate the Antioxidant System and ABA Accumulation in Mustard Plants under Salt Stress.

Mehar Fatma,Zebus Sehar,Adriano Sofo,Harsha Gautam,Nafees A Khan,Ilaria D’Ippolito,Noushina Iqbal

doi:10.3390/plants10010180

Mehar Fatma, Zebus Sehar + Show 5 more

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https://doi.org/10.3390/plants10010180

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Abstract

This study explored the interactive effect of ethephon (2-chloroethyl phosphonic acid; an ethylene source) and sulfur (S) in regulating the antioxidant system and ABA content and in maintaining stomatal responses, chloroplast structure, and photosynthetic performance of mustard plants (Brassica juncea L. Czern.) grown under 100 mM NaCl stress. The treatment of ethephon (200 µL L−1) and S (200 mg S kg−1 soil) together markedly improved the activity of enzymatic and non-enzymatic components of the ascorbate-glutathione (AsA-GSH) cycle, resulting in declined oxidative stress through lesser content of sodium (Na+) ion and hydrogen peroxide (H2O2) in salt-stressed plants. These changes promoted the development of chloroplast thylakoids and photosynthetic performance under salt stress. Ethephon + S also reduced abscisic acid (ABA) accumulation in guard cell, leading to maximal stomatal conductance under salt stress. The inhibition of ethylene action by norbornadiene (NBD) in salt- plus non-stressed treated plants increased ABA and H2O2 contents, and reduced stomatal opening, suggesting the involvement of ethephon and S in regulating stomatal conductance. These findings suggest that ethephon and S modulate antioxidant system and ABA accumulation in guard cells, controlling stomatal conductance, and the structure and efficiency of the photosynthetic apparatus in plants under salt stress.

Highlights

Every year, 1.5 million hectares of lands are becoming inappropriate for agricultural production due to salinity [1,2]
Data are presented as means ± SE (n = 4)
Data followed by same letter are not significantly different by Least significant difference (LSD) test at p < 0.05

Summary

Introduction

1.5 million hectares of lands are becoming inappropriate for agricultural production due to salinity [1,2]. Plants regulate the thylakoid membrane fluidity and membrane lipid composition by involving various mechanisms in a way to maintain a suitable environment for the functioning of integral proteins [8]. In such efforts, various salt-responsive genes are synthesized that encode for protein mainly involved in the scavenging of ROS, organization of thylakoid membrane, the activity of pigment system II (PSII), assimilation of carbon dioxide (CO2 ), biosynthesis and signaling of abscisic acid (ABA), together with osmotic and ionic homeostasis [9]. It is essential to maintain the thylakoid structure and stomatal regulation together with the antioxidants involved in the AsA-GSH cycle to scavenge ROS, so and alleviating the deleterious effects of salt stress. Akyol et al [10] reported that antioxidant metabolism helps the plant to deal with salinity-induced oxidative stress

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