Nanoscale sulfur can be a multifunctional agricultural amendment to enhance crop nutrition and suppress disease. Pristine (nS) and stearic acid coated (cS) sulfur nanoparticles were added to soil planted with tomatoes (Solanum lycopersicum) at 200 mg/L soil and infested with Fusarium oxysporum. Bulk sulfur, ionic sulfate, and healthy controls were included. Orthogonal end points were measured in two greenhouse experiments, including agronomic and photosynthetic parameters, disease severity/suppression, mechanistic biochemical and molecular end points including the time-dependent expression of 13 genes related to two S bioassimilation and pathogenesis-response, and metabolomic profiles. Disease reduced the plant biomass by up to 87%, but nS and cS amendment significantly reduced disease as determined by area-under-the-disease-progress curve by 54 and 56%, respectively. An increase in planta S accumulation was evident, with size-specific translocation ratios suggesting different uptake mechanisms. In vivo two-photon microscopy and time-dependent gene expression revealed a nanoscale-specific elemental S bioassimilation pathway within the plant that is separate from traditional sulfate accumulation. These findings correlate well with time-dependent metabolomic profiling, which exhibited increased disease resistance and plant immunity related metabolites only with nanoscale treatment. The linked gene expression and metabolomics data demonstrate a time-sensitive physiological window where nanoscale stimulation of plant immunity will be effective. These findings provide mechanistic understandings of nonmetal nanomaterial-based suppression of plant disease and significantly advance sustainable nanoenabled agricultural strategies to increase food production.

Phosphorus (P) loss from agro-ecosystems impinges upon P use efficiency by plants and thereby constitutes both agronomic and environmental nuisances. Herein, we report on the potential for controlling P leaching loss and application in crop fertilization through repurposing and nano-functionalizing tripolyphosphate (TPP) as a sole P source. The developed TPP-Chitosan and TPP-Chitosan-ZnO nanofertilizers exhibited positive surface charges, 5.8 and 13.8 mV, and hydrodynamic sizes of 430 and 301 nm, respectively. In soil, nanoformulations of TPP-Chitosan and TPP-Chitosan-ZnO significantly reduced cumulative P leaching during 72 h, reaching 91 and 97% reductions, respectively, compared to a conventional fertilizer, monoammonium phosphate (MAP). Cumulative P leaching after 72 h from these nanofertilizers was, respectively, 84 and 95% lower than from TPP alone. TPP-Chitosan-ZnO was, overall, 65% more effective in reducing P leaching, compared to TPP-Chitosan. Relative to MAP, the wheat plant height was significantly increased by TPP-Chitosan-ZnO by 33.0%. Compared to MAP, TPP-Chitosan and TPP-Chitosan-ZnO slightly increased wheat grain yield by 21 and 30%, respectively. Notably, TPP-Chitosan-ZnO significantly decreased shoot P levels, by 35.5, 47, and 45%, compared to MAP, TPP, and TPP-Chitosan, respectively. Zn release over 72 h from TPP-Chitosan-ZnO was considerably lower, compared to a control, ZnO nanoparticles, and averaged, respectively, 34.7 and 0.065 mg/L, which was 534 times higher for the former. Grain Zn was significantly higher in the TPP-Chitosan treatment, relative to MAP. TPP-Chitosan also significantly mobilized the resident K, S, Mg, and Ca from soil into the plant, helping to improve the overall nutritional quality and supporting the role of chitosan in nutrient mobilization. Taken together, our data highlight the potential for repurposing a non-fertilizer P material, TPP, for agricultural and environmental applications and the effect of applying nanotechnology on such outcomes. Broadly speaking, the reduction in P loss is critical for controlling the eutrophication of water bodies due to nutrient overload and for sustaining the dwindling global P resources.

Little is known about the effect of nano sulfur (NS) under field conditions as a multifunctional agricultural amendment. Pristine and surface coated NS (CS) were amended in soil at 200 mg/kg that was planted with tomato (Solanum lycopersicum) and infested with Fusarium oxysporum f. sp. lycopersici. Foliar exposure of CS (200 μg/mL) was also included. In healthy plants, CS increased tomato marketable yield up to 3.3∼3.4-fold compared to controls. In infested treatments, CS significantly reduced disease severity compared to the other treatments. Foliar and soil treatment with CS increased yield by 107 and 192% over diseased controls, respectively, and significantly increased fruit Ca, Cu, Fe, and Mg contents. A $33/acre investment in CS led to an increase in marketable yield from 4920 to 11,980 kg/acre for healthy plants and from 1135 to 2180 kg/acre for infested plants, demonstrating the significant potential of this nanoenabled strategy to increase food production.

Under a changing climate, cultivating climate-resilient crops will be critical to maintaining food security. Here, we propose the application of reactive oxygen species (ROS)-generating nanoparticles as nanobiostimulants to trigger stress/immune responses and subsequently increase the stress resilience of plants. We established three regimens of silver nanoparticles (AgNPs)-based “stress training”: seed training (ST), leaf training (LT), and combined seed and leaf training (SLT). Trained rice seedlings were then exposed to either rice blast fungus (Magnaporthe oryzae) or chilling stress (10 °C). The results show that all “stress training” regimes, particularly SLT, significantly enhanced the resistance of rice against the fungal pathogen (lesion size reduced by 82% relative to untrained control). SLT also significantly enhanced rice tolerance to cold stress. The mechanisms for the enhanced resilience were investigated with metabolomics and transcriptomics, which show that “stress training” induced considerable metabolic and transcriptional reprogramming in rice leaves. AgNPs boosted ROS-activated stress signaling pathways by oxidative post-translational modifications of stress-related kinases, hormones, and transcriptional factors (TFs). These signaling pathways subsequently modulated the expression of defense genes, including specialized metabolites (SMs) biosynthesis genes, cell membrane lipid metabolism genes, and pathogen–plant interaction genes. Importantly, results showed that the “stress memory” can be transferred transgenerationally, conferring offspring seeds with improved seed germination and seedling vigor. This may provide an epigenetic breeding strategy to fortify stress resilience of crops. This nanobiostimulant-based stress training strategy will increase yield vigor against a changing climate and will contribute to sustainable agriculture by reducing agrochemical use.

Zein nanoparticles (ZNPs) are proposed as effective delivery systems capable of enhancing the translocation of nonsystemic agrochemicals from the roots to the leaves of soybean plants. ZNPs with entrapped methoxyfenozide (MFZ) (209.0 ± 5.6 nm and −42.1 ± 2.1 mV) were formed via emulsion-evaporation and used to facilitate the translocation of MFZ from the roots to the leaves and stems, as measured by liquid chromatography-mass spectrometry (LC-MS), under hydroponic conditions. MFZ concentration increased within the leaves over time from 0.04 to 2.35 μg g −1 at 0.2 mg mL −1 ZNPs exposure, compared to free MFZ (<0.02 μg g −1 ) after 24 h of exposure. The MFZ release from ZNPs, as measured by high-performance liquid chromatography (HPLC), followed pseudo-first-order kinetics at 25 °C, with a faster release at lower ZNP concentrations than at higher concentrations. ZNPs may prove to be a versatile delivery system for other agrochemicals due to their ability to enhance translocation within plants.