Abstract
Selenium Nanoparticles (SeNPs) exhibit tremendous application in agriculture as antimicrobials or as nano fertilizer. Present work reports the eco-friendly synthesis of SeNPs by using Allamanda cathartica L. flower extract (aqueous) as a reducing/capping agent and selenium dioxide as a precursor. The method used here is free of any toxic reducing agents and organic solvents. The synthesis process of SeNPs took 5 h at 60 °C, confirmed by the brick red colour of the solution followed by UV-Vis spectroscopy and further characterized by XRD, FTIR, EDX and SEM. The average size (diameter) of the SeNPs were found to be 60.31 nm by DLS. It has shown strong antimicrobial activity against Pseudomonas marginalis and P. aeruginosa at 2.5, 5 and 10 mg/mL concentrations. Besides, its application improved seed germination and growth parameters of Brassica campestris (TS 36 variety) under salt stress. 25 mg/L SeNPs has improved the germination percentage by around 31%, shoot length by 92%, root length by 78% and total chlorophyll content by 49% under 200 mM NaCl stress. This SeNPs could be a potential antimicrobial agent in treating plant diseases caused by the mentioned phytopathogens, having no or minimum toxicity, in fact having positive impacts on plant growth.
Highlights
Selenium Nanoparticles (SeNPs) have been proved to be an essential element in human as well as in lower plants such as algae, but in higher plants, though some beneficial activity has been observed still it is not proved to be essential (Araie and Shiraiwa 2009; El-Ramady et al, 2016; Sarkar et al, 2021a)
Synthesis of SeNPs by A. cathartica L. flower extract has been first detected by the colloidal brick-red colouration of the reaction solution (Figure 2A, Figure 2B) and confirmed by UV absorbance peak of the synthesis solution (SeO2 þ Flower extract) at the wavelength of 287 nm (Figure 2C), whereas there was no absorbance peak observed for the flower extract or the precursor SeO2 at that wavelength
In the process of optimization of flower extract concentration required for the synthesis of SeNPs from SeO2, keeping constant SeO2 concentration of 20 mM, it has been revealed that synthesis is increased while increasing flower extract concentration from 10% to 15% and 15%–20% but further increasing flower extract to 25% and 30% could not increase it significantly (Figure 3a)
Summary
Selenium Nanoparticles (SeNPs) have been proved to be an essential element in human as well as in lower plants such as algae, but in higher plants, though some beneficial activity has been observed still it is not proved to be essential (Araie and Shiraiwa 2009; El-Ramady et al, 2016; Sarkar et al, 2021a). Its flower contains quercetin (a strong reducing agent), kaempferol, hesperetin and some other flavonoid compounds (Ghosh et al, 2019) which may have a potential role in the synthesis of SeNPs and its stabilization Phytopathogens such as Pseudomonas aeruginosa strains present in soil interact with plant roots and causes necrosis (Walker et al, 2004) and Pseudomonas marginalis causes severe stalk rot disease in mustard (Singh et al, 2016), Fusarium oxysporum (Williams and Saha 1993) and Sclerotinia sclerotiorum (Bharti et al, 2016) causes severe harm to mustard cultivation. The present work mainly focuses on the optimized biosynthesis of SeNPs by using A. cathartica L. flower extract; evaluation of its potential in promoting Brassica campestris seed germination under salt stress and in inhibiting the growth of phytopathogenic microorganisms, especially pathogens that cause diseases of the mustard crop
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