Different forms of copper and kinetin impacted element accumulation and macromolecule contents in kidney bean (Phaseolus vulgaris) seeds

Analysis of multiple biomarkers revealed the size matters of Cu particles for barley response under foliar exposure

The impact of particle size of engineered nanoparticles (ENPs) on plant response has marginally been investigated under the foliar application so far. Concerning the significance of particle diameter for their properties and interaction with plants, the effect of size should be considered in the analysis of the effect of micronutrient-based ENPs on plants. It is of particular importance for ENPs containing Cu due to plants needing a relatively low amount of this element, thus there is a risk of overdosing during application as a fertilizer or pesticide. Here, we examined the biochemical and transcriptional response of barley (Hordeum vulgare L.) to Cu nanoparticles (nano-Cu) with different diameters (25 nm, 50 nm, 70 nm), microparticles (micro-Cu), and chelated Cu (EDTA-Cu). The plants suffering from Cu deficiency were foliar sprayed with Cu compounds at 1000 mg/L during the tillering stage. 1- and 7-day plants were analyzed in terms of biomass, Cu content, the activity of enzymes involved with antioxidant response, the content of low molecular weight compounds, and the expression of genes regulated metal homeostasis, aquaporins, and defense. The results showed that the Cu leaf level was differentiated over time and after 7 days it was higher under exposure to the smallest nano-Cu than other particulate Cu. Regardless of the duration of exposure, the Cu content was highest in plants treated with Cu-EDTA. The cluster analysis of all markers revealed a clear distinct response to the smallest nano-Cu and other particulate and ionic treatments. The bigger nano-Cu, depending on the markers, caused the medium effects between the nano-Cu 25 nm and micro-Cu and Cu-EDTA. The found size thresholds at the nanoscale will be useful for the fabrication of safe-by-design agrochemicals to provide crop security and attenuate environmental impact.

Responses of non-structural carbohydrates and biomass in plant to heavy metal treatment

The contamination of heavy metals profoundly impacts plant metabolic processes and various physiological indicators, such as non-structural carbohydrates (NSC). However, a comprehensive understanding of how NSC in plants respond to heavy metal treatment and how different experimental setting and plant types affect the response of plant NSC is still lacking. Here, we compiled data of 2084 observations of NSC from 85 published studies and conducted a meta-analysis to investigate the responses of soluble sugars, starch, the ratio of soluble sugar to starch, and total non-structural carbohydrates (TNSC) to heavy metal treatment. Our results showed that, under heavy metal treatment, foliar soluble sugars, foliar TNSC, and the ratio of soluble sugars to starch in both foliage and root increased significantly by 21.6 %, 11.6 %, 55.9 %, and 65.1 %, respectively; and foliar starch, root starch, and root TNSC decreased significantly by 10 %, 23.3 %, and 11 %, respectively; while root soluble sugars remained unchanged. The treatment of heavy metals significantly diminished the biomass of foliage, above-ground, and root by 12.3 %, 29.5 %, and 34.3 %, respectively. The responses of foliar NSC to heavy metal treatment were strongly dependent on leaf habit, the duration and concentration of heavy metal treatment, and soil pH value. The magnitude of the response of NSC to heavy metals increased with the duration and concentration of heavy metal treatment. Furthermore, the types of heavy metals modulated the magnitude of the response of foliar NSC to heavy metal treatment. Overall, our findings provide valuable insights into the responses of plant NSC to heavy metal stress and contribute to a comprehensive understanding of this crucial aspect of plant physiology.

Effects of nano-enabled agricultural strategies on food quality: Current knowledge and future research needs

It is becoming more feasible to use nano-enabled agricultural products such as nanofertilizers and nanopesticides to improve the efficiency of agrochemical delivery to crop plants. Experimental results have shown that nano-agrochemicals have great potential for reducing the environmental impact of traditional agrochemicals while simultaneously significantly increasing crop production. However, emerging data suggest that nano-enabled products are not only capable of increasing yield, but also result in alterations in crop quality. Variation in proteins, sugars, starch content, as well as in metallic essential elements have been reported. Verbi gratia, albumin, globulin, and prolamin have been significantly increased in rice exposed to CeO₂ engineered nanoparticles (ENPs), while CeO₂, CuO, and ZnO ENPs have increased Ca, Mg, and P in several crops. Conversely, reductions in Mo and Ni have been reported in cucumber and kidney beans exposed to CeO₂ and ZnO engineered nanomaterials, respectively. However, reports on specific effects in human health due to the consumption of agricultural products obtained from plants exposed to nano-agrochemicals are still missing.

Effect of copper oxide nanoparticles on two varieties of sweetpotato plants

Little information is available on the interaction of CuO nanoparticles (nCuO) with tuberous roots. In this study, Beauregard-14 (B-14, low lignin) and Covington (COV, high lignin) sweetpotato varieties were cultivated until maturity in soil amended with nCuO, bulk copper oxide (bCuO) and CuCl2 at 25-125 mg/kg. The Cu treatments had no significant influence on chlorophyll content. Gas exchange parameters were not affected in B-14. In COV, however, at 125 mg/kg treatments, bCuO reduced the intercellular CO2 (11%), while CuCl2 increased it by 7%, compared with control (p ≤ 0.035). At 25 mg/kg nCuO increased the length of COV roots (20.7 ± 2.0 cm vs. 14.6 ± 0.8 cm, p ≤ 0.05). In periderm of B-14, nCuO, at 125 mg/kg, increased Mg by 232%, while the equivalent concentration of CuCl2 reduced P by 410%, compared with control (p ≤ 0.05). The data suggest the potential application of nCuO as nanofertilizer for sweetpotato storage root production.

Effect of metal oxide nanoparticles on amino acids in wheat grains (Triticum aestivum) in a life cycle study

Engineered nanoparticles (NPs) are now used as additives in pesticides and fungicides and as novel fertilizers in agriculture so there is an urgent need to explore their effects on crop yield and quality in a full life cycle study. In the present study, three widely used NPs (TiO₂, Fe₂O₃ and CuO NPs applied at doses of 50 and 500 mg/kg) were selected to investigate their long-term impact on wheat growth. TiO₂ NPs did not affect the growth and development of wheat, but Fe₂O₃ NPs promoted wheat precocity and CuO NPs inhibited the growth and development of the wheat grains. The Cu content in grains treated with CuO NP increased by 18.84%-30.45% compared with the control. However, the contents of Fe and Zn were both significantly lower in the CuO NP treatments. Univariate and multivariate analyses were used to analyze the effect of different NPs on the composition of amino acids in wheat grains. Exposure to TiO₂ NPs at dose of 500 mg/kg increased the overall amino acid nutrition in the edible portion of wheat. Fe₂O₃ NPs at both doses increased the contents of cysteine (Cys) and tyrosine (Tyr). The addition of CuO NPs reduced the level of some essential amino acids in wheat grains, isoleucine (Ile), leucine (Leu), threonine (Thr) and histidine (His). Overall, evaluation of the potential impacts of metal-based NPs on the nutritional quality of wheat grains could provide important information for their safe use when incorporated into agrichemicals in sustainable agriculture.

Metallic nanoparticles influence the structure and function of the photosynthetic apparatus in plants

The applications of nanoparticles continue to expand into areas as diverse as medicine, bioremediation, cosmetics, pharmacology and various industries, including agri-food production. The widespread use of nanoparticles has generated concerns given the impact these nanoparticles - mostly metal-based such as CuO, Ag, Au, CeO₂, TiO₂, ZnO, Co, and Pt - could be having on plants. Some of the most studied variables are plant growth, development, production of biomass, and ultimately oxidative stress and photosynthesis. A systematic appraisal of information about the impact of nanoparticles on these processes is needed to enhance our understanding of the effects of metallic nanoparticles and oxides on the structure and function on the plant photosynthetic apparatus. Most nanoparticles studied, especially CuO and Ag, had a detrimental impact on the structure and function of the photosynthetic apparatus. Nanoparticles led to a decrease in concentration of photosynthetic pigments, especially chlorophyll, and disruption of grana and other malformations in chloroplasts. Regarding the functions of the photosynthetic apparatus, nanoparticles were associated with a decrease in the photosynthetic efficiency of photosystem II and decreased net photosynthesis. However, CeO₂ and TiO₂ nanoparticles may have a positive effect on photosynthetic efficiency, mainly due to an increase in electron flow between the photosystems II and I in the Hill reaction, as well as an increase in Rubisco activity in the Calvin and Benson cycle. Nevertheless, the underlying mechanisms are poorly understood. The future mechanistic work needs to be aimed at characterizing the enhancing effect of nanoparticles on the active generation of ATP and NADPH, carbon fixation and its incorporation into primary molecules such as photo-assimilates.