The potential of green synthesized zinc oxide nanoparticles as nutrient source for plant growth

In this work, the green ZnO NPs were synthesized using plant leaf extract (Aloe barbadensis Mill). Their formation was validated using a number of optical spectroscopic and electron microscopic techniques. The particle size of green ZnO NPs averaged as 35 nm which was far smaller than that prepared by conventional chemical methods for comparison purpose (e.g., 48 nm). Although both types of ZnO NPs were spherical with high crystallinity, the former is likely to better reflect the strong reducing and capping capability of the leaf extract. The suitable concentrations of ZnO NPs for seedling emergence and germination of wheat (Triticum aestivum L.) were then explored at varying NP levels (0, 15, 62, 125, 250, and 500 mg/L). Accordingly, the ones treated with green ZnO NPs grew better than the control seeds. Moreover, the wheat seed samples treated with a moderate amount (e.g., 62 mg/L) of green ZnO NPs showed most significant enhancement (P < 0.005) in their root and shoot length relative to other concentration levels or to the chemically synthesized ones (e.g., by 50% and 105%, respectively). As such, the potential of green synthesized ZnO NPs has been recognized as a nano-based nutrient source for agricultural applications.