Green synthesis and characterization of ZnO nanoparticles using seaweed extract of Halimeda opuntia and their application in seed germination of maize

Achieving uniform and rapid seed germination is essential for economic sustainability and efficient use of production in commercial agriculture. Therefore, in the present study, the potential of zinc oxide nanoparticles (ZnO NPs) synthesized using seaweed extract of Halimeda opuntia was investigated to promote maize seed germination. The characterization results of the ZnO NPs revealed a direct band gap of 3.42 eV (UV–vis) and the presence of functional groups with potential bioactivities (FTIR). XRD confirmed with an average crystallite size below 100 nm. HR-SEM and TEM analyses showed diverse shapes and sizes (rods, hexagonal bodies, and irregular) with diameters ranging from 29.3 to 89.0 nm. EDX confirmed the purity of the synthesized ZnO NPs. Further, different concentrations of ZnO NPs (25, 50, 75, and 100 ppm) were used for seed germination study. The results revealed a significant increase in seed germination percentage compared to the control group. Notably, the highest germination (90%) was observed at 50 ppm. Besides, ZnO NPs at 50 ppm significantly enhanced both root and shoot length, reaching 25.78 cm and 22.95 cm, respectively. In addition, dry matter content of seedlings was also significantly increased at this concentration (4.20 g). Furthermore, seedling analysis revealed a significant increase in antioxidant enzyme activities (SOD, POD, and CAT) in response to ZnO NPs treatment, with the highest activities observed at 50 ppm. Interestingly, malondialdehyde (MDA) content, a marker of oxidative stress, remained unaffected by ZnO nanoparticles. These findings suggest the potential of ZnO NPs at optimized concentrations to promote maize seed germination and seedling growth. Therefore, ZnO NPs synthesized using aqueous extract of Halimeda opuntia can be used as a promising nano priming agent for uniform seed germination and to promote maize growth and productivity.