Abstract
Rice is one of the most widely cultivated crops worldwide; however, it is not amenable to genetic manipulations, owing to its poor response to tissue culture and regeneration in vitro. To improve its response to tissue culture, we evaluated the influence of biosynthesized silver nanoparticles on callus induction, regeneration and rhizogenesis in Indica rice cv. IR64. Silver nanoparticles were biosynthesized by using silver nitrate and Parthenium hysterophorus plant extract, and were characterized by UV-visible spectroscopy, Fourier-transform infrared spectroscopy, Transmission electron microscopy and X-ray diffraction. The biosynthesized silver nanoparticles (PHAgNPs), when supplemented in tissue culture medium, promoted callus induction frequency, callus regeneration and rhizogenesis at concentrations of 10 mg l −1, 5 mg l−1 and 10 mg l−1, respectively. Further examination of the endogenous hormonal levels in regenerating calli revealed that AgNPs enhanced regeneration by alleviating abscisic acid and ethylene levels in the plant tissue. The stimulatory influence eliciting the regeneration response was found to be optimal with the supplementation of 5 mg l−1 PHAgNPs in the regeneration medium; the malondialdehyde, proline and hydrogen peroxide levels were also lower than those in the control, thus suggesting improved antioxidant status. Our results indicated that biosynthesized PHAgNPs may have the potential to positively influence tissue culture of recalcitrant varieties.
Highlights
Indica Rice is prominently cultivated in the tropical and subtropical regions of Asia, and it accounts for 80% of the rice cultivated worldwide
The biosynthesized AgNPs were validated with Fourier-transform infrared spectroscopy (FTIR), which analysed the displacement in the absorbance rate of biomolecules in PHAgNPs compared with that of biomolecules in Parthenium hysterophorus (PH) plant extract
The X-ray diffraction (XRD) pattern of PHAgNPs was determined by using JCPDS intensities (JCPDS files No 893722), which suggested that the biosynthesized NPs have a face centred cubic structure, and the biosynthesized NPs have an average size of ~25 nm and a mostly spherical shape, as evidenced by Transmission electron microscopy (TEM) and calculations with Debye–Scherrer’s equation
Summary
Indica Rice is prominently cultivated in the tropical and subtropical regions of Asia, and it accounts for 80% of the rice cultivated worldwide. The interaction of auxin and cytokinin is crucial for the development of plants, and these hormones are commonly employed in in vitro plant tissue culture to regulate differentiation in explants. Flowering, and it is part of a complex regulatory network that includes auxins and cytokinins and is imperative for embryogenesis and shoot regeneration Another important PGR is ethylene, a gaseous hormone that primarily influences ripening of fruits and senescence in plants[5,6]. In the present study, we attempted to correlate the influence of exogenously supplemented AgNPs on endogenous ROS as well as PGR levels in regenerating calli, to better understand the influence of AgNPs on plant development. AgNPs, because of their small size (1–100 nm) possess unique optical and physiochemical properties, and are used in various fields for conduction, biological detection, catalysis, wound healing, anti-microbial activity and phytostimulation[14]
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