Ethylene and Sulfur Coordinately Modulate the Antioxidant System and ABA Accumulation in Mustard Plants under Salt Stress
2021
Mehar Fatma | Noushina Iqbal | Harsha Gautam | Zebus Sehar | Adriano Sofo | Ilaria D’Ippolito | Nafees A. Khan
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 (<i>Brassica juncea</i> L. Czern.) grown under 100 mM NaCl stress. The treatment of ethephon (200 µL L<sup>−1</sup>) and S (200 mg S kg<sup>−1</sup> 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<sup>+</sup>) ion and hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) in salt-stressed plants<sub>.</sub> 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 H<sub>2</sub>O<sub>2</sub> 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.
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