Legumes are affected by biotic factors such as insects, molds, bacteria, and viruses. These plants can produce many different molecules in response to the attack of phytopathogens. Protease inhibitors (PIs) are proteins produced by legumes that inhibit the protease activity of phytopathogens. PIs are known to reduce nutrient availability, which diminishes pathogen growth and can lead to the death of the pathogen. PIs are classified according to the specificity of the mechanistic activity of the proteolytic enzymes, with serine and cysteine protease inhibitors being studied the most. Previous investigations have reported the efficacy of these highly stable proteins against diverse biotic factors and the concomitant protective effects in crops, representing a possible replacement of toxic agrochemicals that harm the environment.

The application of green methods in the synthesis of nanoparticles using plants is a cost-effective and eco-friendly approach. Zinc oxide nanoparticles are of great importance due to their versatile properties. The conditions of synthesis strongly influence the characteristics and functionality of the nanoparticles. The present work studied the biological, green synthesis of zinc oxide nanoparticles (ZnONPs) in the presence of different concentrations of ethanolic extract of Larrea tridentata (10, 20, and 30 mg/mL). The time of the formation of nanoparticles was evaluated at different temperatures and pH values of the reaction medium. The formation of ZnONPs was confirmed by ultraviolet-visible (UV-Vis) and Fourier transform infrared spectroscopies (FT-IR), as well as scanning electron microscopy (SEM). X-ray diffraction analysis (XDR) determined the crystallographic structure of the nanoparticles. Obtained ZnONPs had a size range of 18 to 40 nm. The temperature, reaction time, and pH significantly influenced the nanoparticles’ morphology, size, and aggregation. The impact of chosen ZnONPs was tested on the germination of serrano chili seeds (Capsicum annuum). At 100 ppm, the nanoparticles improved germination percentage, vigor, and seedlings’ growth parameters.

Zinc oxide nanoparticles have gained attention in the last decades due to their versatile applications; in agriculture, they have been used for their multiple benefits. In this study, the effects of zinc oxide nanoparticles, obtained via chemical and biological synthesis and of 70–80 nm in size, on the germination and seedling growth of Capsicum annuum and Solanum lycopersicum seed were determined. The physiological parameters, photosynthetic pigments, the content of total phenols, total flavonoids, as well as the antioxidant capacity of 2,2-diphenyl-1-picrylhydrazyl (DPPH), and the enzymatic activity of catalase, peroxidase, and polyphenol oxidase were evaluated. The results indicated that treatment with zinc oxide nanoparticles obtained via green synthesis improved seed germination rate, while chemically synthesized nanoparticles at higher concentrations decreased germination percentage. In general, the parameters of enzymatic and nonenzymatic antioxidants in treated plants showed significant differences with respect to the control. However, the treatments with the bionanoparticles resulted in more beneficial parameters. Zinc oxide nanoparticles obtained via green synthesis are more effective in generating bioactive compounds and activating the enzyme defense system due to being more biocompatible.