Abstract

ABSTRACTThis study examined the protective effect of Zn on salt-stressed Brassica juncea plants using some key morphological and biochemical attributes at different developmental stages (30, 60, and 90 days after treatment [DAT]). Salt stress (200 mM) caused suppression in plant height, root length, and dry weight by 58.35%, 41.15%, and 53.33%, respectively, at 90 DAT, but Zn application improved these variables by 15.52%, 16.59%, and 11.45%, respectively. Furthermore, 200 mM NaCl decreased total chlorophyll by 45.32% and relative water content by 27.62% at 90 DAT, whereas Zn application compensated the decrease in the levels of both variables. NaCl (200 mM) increased H2O2, malondialdehyde, and electrolyte leakage by 70.48%, 35.25%, and 68.39%, respectively, at 90 DAT, but Zn supplementation appreciably reduced these variables. Except for catalase, enzymatic antioxidant activity increased under NaCl stress. Zn application with salt further increased the activities of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and glutathione-S-transferase by 33.51%, 9.21%, 10.98%, 17.46%, and 12.87%, respectively, at 90 DAT. At 90 DAT, salt stress increased flavonoids by 24.88%, and Zn supply by a further 7.68%. Overall, Zn mitigated the adverse effects of salt stress through osmotic adjustment, as well as by modulating the oxidative defense system and flavonoid contents.

Highlights

  • Salinity is a major environmental cue, which considerably suppresses crop production worldwide through its injurious effects on plant growth and development (Ashraf and McNeilly 2004; Ahanger and Agarwal 2017)

  • Heights of plants treated with 100 mM NaCl decreased by 13.18%, 17.85%, and 21.75% at 30, 60, and 90 days after treatment (DAT), respectively

  • The treatment with 200 mM NaCl decreased plant height by 25.75%, 39.68%, and 58.35% compared with the control heights at 30, 60, and 90 DAT, respectively

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Summary

Introduction

Salinity is a major environmental cue, which considerably suppresses crop production worldwide through its injurious effects on plant growth and development (Ashraf and McNeilly 2004; Ahanger and Agarwal 2017). Salinity stress hampers plant growth via diminishing cell division and expansion, reducing photosynthetic efficiency, modifying metabolic processes, as well as causing ion toxicity, osmotic stress, oxidative stress, genotoxicity, and other physiological disorders (Ibrahim et al 2012; Wani et al 2013; Yan et al 2013; Ahmad et al 2016b; Anjum et al 2015; Hussein et al 2017). Upregulated osmolytes’ (e.g. proline, glycine betaine, and soluble sugars) synthesis and accumulation protect proteins, enzymes, and other biologically important molecules (Hayat et al 2012; Ahanger and Agarwal 2017) These osmotically active solutes act as antioxidants and contribute to water content maintenance for optimal cellular functioning (Ahanger et al 2014, 2015; Anjum et al 2014)

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