Abstract
Cadmium (Cd) accumulation is an emerging environmental hazard and has detrimental effects on plant growth and development. Salicylic acid (SA) is a well-known plant growth regulator that can initiate various molecular pathways to ameliorate Cd toxicity. The experiment was executed to scrutinize the mediatory role of SA to accelerate the defensive mechanism of mung bean in response to Cd stress. Mung bean plants were exposed to 0, 5, 10 and 15 mg Cd kg-1 of soil. Exogenous application of SA 0, 10-6 and 10-3 M was added prior flowering. Results exhibited that Cd stress considerably reduced the growth-related attributes i.e. shoot length, root length, fresh and dry biomass, total soluble protein, total amino acids, relative water contents and photosynthetic pigments. Cadmium stress showed a significant increase in antioxidants levels such as peroxidase (POD), ascorbate peroxidase (APX), ascorbic acid (AsA), and catalase (CAT) and promoted the accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents. However, exogenously applied SA significantly improved plant biomass and photosynthetic pigments under Cd stress. Moreover, SA improved the defensive system by enhancing antioxidants’ activities under the increasing concentration of Cd stress. Furthermore, SA reduced the Cd uptake, membrane damage and, H2O2 and MDA accumulation. The study's findings concluded that exogenous-applied SA enhanced plant growth, promoted the antioxidant activities, and reduced the oxidative damage in mung bean seedlings under Cd stress.
Highlights
Shoot and root length were reduced by 34% and 40% respectively at higher Cd concentration (15 mg Cd kg-1) as related to control treatment
Outcomes of this study can be related to previous studies where researchers identified that Salicylic acid (SA) ameliorated the harmful effects of Cd and showed positive effects on mung bean growth which may be accompanied by maximum induction of indole acetic acid (IAA) activity that promote the rapid cell division in the apical meristematic region (Shakirova et al, 2007)
This study revealed that Cd stress significantly decreased the growth of mung bean seedlings mainly by altering physiological and biochemical processes
Summary
The natural environment has frequently acquiring metal pollution from the anthropogenic fonts comprising sewage expulsions, mining manoeuvres, phosphate fertilizers and overflows from metal refining industries and other industries (Yang et al, 2006; Liu et al, 2007; Seleiman et al, 2012; Seleiman et al, 2013; Seleiman et al, 2017; Hassan et al, 2019; Seleiman et al, 2020a; Seleiman et al, 2020b; Hassan et al, 2021; Seleiman et al, 2021a). Plants have a scavenging mechanism including enzymatic (i.e. POD, SOD, APX and CAT) and non-enzymatic antioxidants (i.e. anthocyanin and ascorbic acid) against different stress conditions (Al-Ashkar et al, 2020; Hassan et al, 2020; Seleiman et al, 2021a; Seleiman et al, 2021b). They protect the plants from different abiotic stresses, but their activity is reduced due to metal ion interaction (Noriega et al, 2012, Sofy et al, 2020)
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