Effect of biofabricated zinc oxide nanoparticles on callus and in vitro regenerated shoots of Reseda lutea, and assessment of biochemical responses, polyphenolic content, and genetic stability.

Abstract

The conservation of rare and endangered plant species has progressed with the advent of nanotechnology, enabling their large-scale production with desirable traits. The present study was focused on the synthesis of zinc oxide nanoparticles (ZnO-NPs) using the aqueous extract of Convolvulus arvensis and their characterization using various techniques (UV spectra, FTIR, transmission electron microscopy (TEM), and zeta potential), and further, their impact was assessed on callus and in vitro raised shoots of Reseda lutea. Low concentrations of ZnO-NPs (15 and 30 mg/L) increased the fresh weight of shoots by 35.38% and 17.43%, respectively. In contrast, a high concentration of ZnO-NPs (60 mg/L) in MS medium resulted in a 29% decrease in shoot biomass. The different concentrations of ZnO-NPs (15, 30, and 60 mg/L) increased the callus biomass by 70.7%, 62.6%, and 24.8%, respectively, compared to the control. The total phenolic content (TPC) and flavonoid content (TFC) in both regenerated stages were varied, and they were increased in callus by 15.5% with 60 mg/L of ZnO-NPs, whereas TPC and TFC were reduced in shoot, and a greater reduction was observed in TFC with the same concentration of ZnO-NP treatment than the control. The biochemical analysis performed on callus and shoot revealed a dose-dependent accumulation of proline and TBARS content. The accumulation of total soluble protein improved in both regeneration stages, and its content varied with different treatment doses of ZnO-NPs. A close relationship was observed in protein accumulation by 26.24%, and chlorophyll contents by 36.4% in shoots with 15 mg/L ZnO-NPs than the control, while both parameters decreased with 60 mg/L ZnO-NPs. The activities of antioxidant enzymes, including GR, SOD, and APX, varied under different treatment doses of ZnO-NPs. The flow cytometry (FCM) results of callus and shoot with ZnO-NPs treatment confirmed the genetic stability by genome size (2C DNA content). The results of this study show that biogenic ZnO-NPs positively influence various attributes of the callus and shoot stages and may support the mass production of R. lutea with abiotic stress tolerance.