Zinc oxide nanoparticles alleviate drought-induced alterations in sorghum performance, nutrient acquisition, and grain fortification.

Drought is a major environmental event affecting crop productivity and nutritional quality, and potentially, human nutrition. This study evaluated drought effects on performance and nutrient acquisition and distribution in sorghum; and whether ZnO nanoparticles (ZnO-NPs) might alleviate such effects. Soil was amended with ZnO-NPs at 1, 3, and 5 mg Zn/kg, and drought was imposed 4 weeks after seed germination by maintaining the soil at 40% of field moisture capacity. Flag leaf and grain head emergence were delayed 6-17 days by drought, but the delays were reduced to 4-5 days by ZnO-NPs. Drought significantly (p < 0.05) reduced (76%) grain yield; however, ZnO-NP amendment under drought improved grain (22-183%) yield. Drought inhibited grain nitrogen (N) translocation (57%) and total (root, shoot and grain) N acquisition (22%). However, ZnO-NPs (5 mg/kg) improved (84%) grain N translocation relative to the drought control and restored total N levels to the non-drought condition. Shoot uptake of phosphorus (P) was promoted (39%) by drought, while grain P translocation was inhibited (63%); however, ZnO-NPs lowered total P acquisition under drought by 11-23%. Drought impeded shoot uptake (45%), grain translocation (71%) and total acquisition (41%) of potassium (K). ZnO-NP amendment (5 mg/kg) to drought-affected plants improved total K acquisition (16-30%) and grain K (123%), relative to the drought control. Drought lowered (32%) average grain Zn concentration; however, ZnO-NP amendments improved (94%) grain Zn under drought. This study represents the first evidence of mitigation of drought stress in full-term plants solely by exposure to ZnO-NPs in soil. The ability of ZnO-NPs to accelerate plant development, promote yield, fortify edible grains with critically essential nutrients such as Zn, and improve N acquisition under drought stress has strong implications for increasing cropping systems resilience, sustaining human/animal food/feed and nutrition security, and reducing nutrient losses and environmental pollution associated with N-fertilizers.

DQF J-RES NMR: Suppressing the singlet signals for improving the J-RES spectra from complex mixtures.

Two-dimensional J-RESolved spectroscopy (J-RES) finds routine use in metabolomics for reducing signal overlap as it separates chemical shift and multiplet information along two frequency axes. However, only magnitude mode of the experiment is practical which prevents exploitation of its full resolving power. Tailing from high-intensity metabolite peaks often obscure nearby low-intensity metabolite peaks which leads to ambiguity in assignment of metabolites. Absorptive mode J-RES spectroscopy offers better-resolving power but comes at the cost of either sensitivity or complicated post-processing. Quite often for certain complex mixtures such as bio-fluids some components of the mixture display intense singlet signals which dominate the whole spectrum resulting in less reliable detection of weaker metabolite signals. Multi-frequency presaturation could suppress these intense singlets but will also remove the useful weaker multiplet peaks which are either totally eclipsed with the intense singlets or very close in frequency. We show that by using a double quantum filter (DQF) in magnitude mode J-RES technique, the intensity of the strong singlet metabolite peaks can be reduced relative to the intensity of the sparsely present multiplet metabolite signals. This approach leads to the identification of many weak intensity multiplet peaks which are otherwise undetected due to their overlap with intense singlet peaks in regular J-RES as well as 1D 1H spectra. Although the improved intensity of most of the weaker peaks relative to the strong singlet peaks is observed, some multiplets can disappear due to the delay-dependent modulation of the signals by the DQF. A few DQF J-RES spectra recorded with different DQF delays, therefore, produce better assignment when analyzed together. The technique is demonstrated on a mixture of eight compounds, human urine, and plant extract samples.