Sustainable
agriculture is a key component of the effort to meet
the increased food demand of a rapidly increasing global population.
Nano-biotechnology is a promising tool for sustainable agriculture.
However, rather than acting as nanocarriers, some nanoparticles (NPs)
with unique physiochemical properties inherently enhance plant growth
and stress tolerance. This biological role of nanoparticles depends
on their physiochemical properties, application method (foliar delivery,
hydroponics, soil), and the applied concentration. Here we review
the effects of the different types, properties, and concentrations
of nanoparticles on plant growth and on various abiotic (salinity,
drought, heat, high light, and heavy metals) and biotic (pathogens
and herbivores) stresses. The ability of nanoparticles to stimulate
plant growth by positive effects on seed germination, root or shoot
growth, and biomass or grain yield is also considered. The information
presented herein will allow researchers within and outside the nano-biotechnology
field to better select the appropriate nanoparticles as starting materials
in agricultural applications. Ultimately, a shift from testing/utilizing
existing nanoparticles to designing specific nanoparticles based on
agriculture needs will facilitate the use of nanotechnology in sustainable
agriculture.
Engineered nanoparticles (NPs) are being released into aquatic environments with their increasing applications. In this work, we investigated the interaction of CuO NPs with a floating plant, water hyacinth (Eichhornia crassipes). CuO NPs (50 mg/L) showed significant growth inhibition on both roots and shoots of E. crassipes after 8-day exposure, much higher than that of the bulk CuO particles (50 mg/L) and their corresponding dissolved Cu ions (0.30 mg/L). Scanning electron and light microscopic observations showed that the root caps and meristematic zone of E. Crassipes were severely damaged after CuO NP exposure, with disordered cell arrangement and a destroyed elongation zone of root tips. It is confirmed that CuO NPs could be translocated to shoot from both roots and submerged leaves. As detected by X-ray absorption near-edge spectroscopy analysis (XANES), CuO NPs were observed in roots, submerged leaves, and emerged leaves. CuS and other Cu species were also detected in these tissues, providing solid evidence of the transformation of CuO NPs. In addition, stomatal closure was observed during CuO NPs-leaf contact, which was induced by the production of HO and increased Ca level in leaf guard cells. These findings are helpful for better understanding the fate of NPs in aquatic plants and related biological responses.
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