Green nanotechnology has made the synthesis of nanoparticles a possible approach. Nanotechnology has a significant impact on several scientific domains and has diverse applications in different commercial areas. The current study aimed to develop a novel and green approach for the biosynthesis of silver oxide nanoparticles (Ag₂ONPs) utilizing Parieteria alsinaefolia leaves extract as a reducing, stabilizing and capping agent. The change in color of the reaction mixture from light brown to reddish black determines the synthesis of Ag₂ONPs. Further, different techniques were used to confirm the synthesis of Ag₂ONPs, including UV-Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), zeta potential and dynamic light scattering (DLS) analyses. The Scherrer equation determined a mean crystallite size of ~22.23 nm for Ag₂ONPs. Additionally, different in vitro biological activities have been investigated and determined significant therapeutic potentials. Radical scavenging DPPH assay (79.4%), reducing power assay (62.68 ± 1.77%) and total antioxidant capacity (87.5 ± 4.8%) were evaluated to assess the antioxidative potential of Ag₂ONPs. The disc diffusion method was adopted to evaluate the antibacterial and antifungal potentials of Ag₂ONPs using different concentrations (125–1000 μg/mL). Moreover, the brine shrimp cytotoxicity assay was investigated and the LC₅₀ value was calculated as 2.21 μg/mL. The biocompatibility assay using red blood cells (<200 μg/mL) confirmed the biosafe and biocompatible nature of Ag₂ONPs. Alpha-amylase inhibition assay was performed and reported 66% inhibition. In conclusion, currently synthesized Ag₂ONPs have exhibited strong biological potential and proved as an attractive eco-friendly candidate. In the future, this preliminary research work will be a helpful source and will open new avenues in diverse fields, including the pharmaceutical, biomedical and pharmacological sectors.

Abiotic stresses, including drought and heavy metals, are detrimental to plant growth and development and enormously reduce agricultural yields. Plants may quickly change their transcriptome in response to various stressful conditions. Plants develop many defense mechanisms to respond to various stresses that can be classified into morphological, physiological, and biochemical responses. Polyphenol oxidases (PPOs) are one of the self-protective enzymes found in plants except for Arabidopsis. Currently, drought and heavy metals were applied exogenously to transgenic A. thaliana lines (transformed with Oryza sativa PPO promoter fused to the GUS reporter gene). The current study mainly focused on the systematic pathway by which plants respond to stressors. The aim of this study is to investigate the effect/expression of PPO and antioxidant defense system against abiotic stresses. A. thaliana was treated with different concentrations of polyethylene glycols. At 30% PEG, maximum fold induction (1.9) was seen after 12 h. Overall, various concentrations (5%, 20%, and 30%) induced PPO expression after 6, 12, and 24 h. Moreover, three different concentrations of Cu (50 µM, 100 µM, 200 µM) and Ni (50 µM, 100 µM, 200 µM) for 6, 12, and 24 h were also applied. It was observed that the expression profiling of the OsPPO promoter induced GUS gene expression in response to Cu and Ni treatments. The maximum fold induction (15.03) of GUS was observed in 100 µM of Cu after 24 h. In the case of Ni, maximum fold induction of (7.78) was observed at 100 µM after 24 h. So, both Cu and Ni showed a similar pattern of induction at 100 µM after 24 h. In conclusion, the efficiency of the PPOGUS promoter can be operated to assess the response of plants to various abiotic stimuli.

Heavy metal stress, including lead, adversely affects the growth and yield of several economically important crops, leading to food challenges and significant economic losses. Ameliorating plant responses to various environmental stresses is one of the promising areas of research for sustainable agriculture. In this study, we evaluated the effect of aspartic acid-functionalized copper nanoparticles on the photosynthetic efficiency and antioxidation system of maize plants under Pb toxicity. The ion reduction method was employed for the synthesis of CuNPs, using ascorbic acid as the reducing agent and aspartic acid as the surface functionalizing agent. Isolated experiments under laboratory and field conditions were performed using a randomized complete block design (RCBD). Seeds primed in water, 1.0, 5.0, and 10 µg/mL of Asp-CuNPs were sown under 0, 500, and 1000 mg/L Pb stress in laboratory conditions, while primed seeds along with foliar-applied Asp-CuNP plants were grown in a field under applied Pb stress, and the obtained data were statistically analyzed using TWANOVA. The laboratory experiment shows that Asp-CuNPs act both as a plant growth regulator (PGR) and plant growth inhibitor (PGI), depending upon their concentration, whereby Asp-CuNPs act as a PGR at a concentration of 1 µg/mL ≤ X ≤10 µg/mL. The field experiment confirms that seed priming and foliar spraying with Asp-CuNPs activate embryos and enhance plant growth in a dose-dependent manner. In addition, Asp-CuNPs (10 µg/mL) significantly increase chlorophyll content to 0.87 mg/g from 0.53 mg/g (untreated) when plants were exposed to Pb toxicity at 1000 mg/kg of soil. It is noteworthy that Asp-CuNPs induce resilience to Pb toxicity (1000 mg/kg of soil) in plants by reducing its root absorption from 3.68 mg/kg (0 µg/mL Asp-CuNPs) to 1.72 mg/kg with the application of 10 µg/mL Asp-CuNPs. Additionally, histochemical analyses with NBT and hydrogen peroxide revealed that ROS accretion in plants treated with Asp-CuNPs declined because of the augmentation of antioxidant enzyme (POD, SOD, APOX, etc.) activities under Pb toxicity. Our findings suggest that amino acid-functionalized copper nanoparticles regulate plant defensive mechanisms related to lead tolerance, which is a promising approach for the induction of resistivity to heavy metal stress.

Climate variability has been a catalytic factor in inducing both biotic and abiotic stresses, exerting detrimental impacts on crop yields. This, in turn, leads to the manifestation of biochemical and physiological impairments within plant systems. This study aimed to evaluate the effects of different concentrations of resorcinol and biochar on tomato (Lycopersicon esculentum Mill.) growth, primary and secondary metabolites, and antioxidant enzyme content levels. Biochar was synthesized from Cedrus deodara (Roxb. ex D. Don) G. Don, sawmill shavings using pyrolysis and subjected to comprehensive characterization employing contemporary techniques including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and UV-vis spectroscopy (UV). Both resorcinol at 0.1 μM/L and biochar at 30 mg/L significantly enhanced tomato seed germination and plant growth, promoting increased shoot/root length and fresh/dry weights in tomato plants compared to controls. This supplementation also amplifies tomato chlorophyll contents, growth metabolites, and antioxidant enzyme activities, contributing to robust plant development. Resorcinol at 0.1 μM/L concentration significantly enhanced total protein (79.9 μg/g), total phenol (58.8 μg/g), total proline (0.03 μg/g), total lipid (3.8 μg/g), total soluble sugar (42.5 μg/g), and flavonoid (0.09 μg/g) as compared to control. Biochar at 30 mg/L concentration showed maximum values of total protein (92.1 μg/g), total phenol (61.3 μg/g), total proline (0.03 μg/g), total lipid (5.5 μg/g), total soluble sugar (48.9 μg/g), and flavonoid (0.08 μg/g). This research indicated that foliar application of these specific concentrations of resorcinol and biochar has the ability to improve tomato plant growth, osmolytes, and antioxidant activity.