In this Review, an effort is made to discuss the most recent progress and future trend in the two‐way traffic of the interactions between plants and nanoparticles (NPs). One way is the use of plants to synthesize NPs in an environmentally benign manner with a focus on the mechanism and optimization of the synthesis. Another way is the effects of synthetic NPs on plant fate with a focus on the transport mechanisms of NPs within plants as well as NP‐mediated seed germination and plant development. When NPs are in soil, they can be adsorbed at the root surface, followed by their uptake and inter/intracellular movement in the plant tissues. NPs may also be taken up by foliage under aerial deposition, largely through stomata, trichomes, and cuticles, but the exact mode of NP entry into plants is not well documented. The NP–plant interactions may lead to inhibitory or stimulatory effects on seed germination and plant development, depending on NP compositions, concentrations, and plant species. In numerous cases, radiation‐absorbing efficiency, CO2 assimilation capacity, and delay of chloroplast aging have been reported in the plant response to NP treatments, although the mechanisms involved in these processes remain to be studied.

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metal solution, reduction of the metal ions leads to the generation of metal atom clustering generating nanosized particles. A characteristic of biosynthetic NPs is their high stability as the organisms provide their own biomolecular capping agent(s). [1] While plant-based production of NPs is now considered a scientific curiosity rather than a promising biotechnology, [2] bacteriamediated NP biosynthesis offers better chances, in light of the poorly characterized microbial diversity and the complex chemistry of enzymes in metal-reducing bacteria. Two recent works focused on directed biofabrication of CdSe-nanoparticles through regulating extracellular electron transfer [3] and the biosynthesis of highly active copper NPs (CuNP) by Shewanella oneidensis. [4] However, the description of molecular mechanism(s) involved in the biosynthesis of NPs has received little attention, which is the focus of this review.The CFCF or culture supernatants (CS) of bacteria mediate the synthesis of AgNPs [5] as presented in this section. The CFCF from the family Enterobacteriaceae reduce silver ions to AgNPs ( Table 1). CFCF of Klebsiella pneumoniae, Escherichia coli, and Metal nanoparticles (NPs), chalcogenides, and carbon quantum dots can be easily synthesized from whole microorganisms (fungi and bacteria) and cell-free sterile filtered spent medium. The particle size distribution and the biosynthesis time can be somewhat controlled through the biomass/metal solution ratio. The biosynthetic mechanism can be explained through the ionreduction theory and UV photoconversion theory. Formation of biosynthetic NPs is part of the detoxification strategy employed by microorganisms, either in planktonic or biofilm form, to reduce the chemical toxicity of metal ions. In fact, most reports on NP biosynthesis show extracellular metal ion reduction. This is important for environmental and industrial applications, particularly in biofilms, as it allows in principle high biosynthetic rates. The antimicrobial and antifungal effect on biosynthetic NPs can be explained in terms of reactive oxygen species and can be enhanced by the capping agents attached to the NP during the biosynthesis process. Industrial applications of NP biosynthesis are still lagging, due to the difficulty of controlling NP size and low titer. Further, the environmental assessment of biosynthetic NPs has not yet been carried out. It is expected that further advancements in biosynthetic NP research will lead to applications, particularly in environmental biotechnology.

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