Foliar application of biosynthetic nano-selenium alleviates the toxicity of Cd, Pb, and Hg in Brassica chinensis by inhibiting heavy metal adsorption and improving antioxidant system in plant

Biosynthetic nano-selenium (bio-SeNP), as a plant growth regulator, has better bioavailability and lower toxicity than selenite and selenate. This study investigated the beneficial role of bio-SeNP in mitigating the adverse effects of multiple heavy metals (HMs, e.g., Cd, Pb, and Hg) on growth and yield of pak choi (Brassica chinensis) grown in slightly or heavily polluted (SP or HP) soil by regulating metabolic and antioxidant systems. The results revealed that foliar application of bio-SeNP (5, 10, 20 mg L^-1 Se) at the 6-leaf stage greatly reduced the levels of Cd, Pb, and Hg in shoots and roots of pak choi. Application of 5 mg L^-1 bio-SeNP significantly (p < 0.05) decreased the translocation factor (TF) of Cd, Pb, and Hg from root to shoot by 9.83%, 44.21%, and 46.99% for SP soil, 24.17%, 56.00%, and 39.36% for HP soil, respectively. Meanwhile, all bio-SeNP treatments led to a significant improvement in plants growth by enhancing the antioxidant defense system (e.g., AsA-GSH) and promoting chlorophyll synthesis as well as suppressed the lipid peroxidation products contents (MDA) in shoots. Moreover, the enhanced levels of mineral nutrient elements (e.g., Ca, Mg, Fe, or Zn) and organic selenium (e.g., selenocystine, Se-methylselenocysteine, and selenomethionine) in the edible shoots of bio-SeNP-treated pak choi plant under multiple HMs stress indicated the positive impacts of bio-SeNP on the improvement of shoot quality and nutritional values. Collectively, our results indicated that bio-SeNP play an important role in the management of multiple HMs-induced adverse effects on pak choi. Foliar application of bio-SeNP at appropriate concentration (≤ 5 mg L^-1 Se) can be considered as a promising agronomic measure for safety leafy vegetable production in multiple HMs polluted soils when bio-SeNP application.

The Unique Substance, Lidocaine and Biological Activity of the Dioscorea Species for Potential Application as a Cancer Treatment, Natural Pesticide and Product

The six Dioscorea species, D. brevipetiolata, D. bulbifera, D. depauperata (Dd), D. glabra (Dg), D. pyrifolia and D. hamiltonii were analyzed for phytochemicals, toxicity in PBMCs, and biological activity in two cancer cell lines by MTT and comet assays, and pesticide efficiency. Via GC-MS, lidocaine was found to be the predominant compound in two of the studied species. To confirm the systematics, lidocaine was also found in lower amounts in 11 species. The MTT assay showed no toxicity in all six of the studied species. The comet assay showed the key result that the ethanol extracts of Dd and Dg violently broke DNA into pieces. Biological activity of these two species’ extracts showed toxicity on HepG2 and no effects on HCT-116. The water extracts of Dd and Dg, applied to Brassica chinensis showed high efficiency as a bioprotectant. In summary, lidocaine seems to be the predominant identifying compound of the genus Dioscorea in Thailand, which is useful in systematics. At least the two species, Dd and Dg, may be used for human hepatocyte cancer treatment and as an alternative pesticide for economically important vegetables. Dioscorea species containing lidocaine or extracted lidocaine have promise for natural product creation.

Herbicidal efficacy of harzianums produced by the biofertilizer fungus, Trichoderma brevicompactum

Herbicides are important tools for weed control in modern agriculture. In the search for potential herbicidal natural products from fungal species, harzianum A and B were identified from the biofertilizer fungus, Trichoderma brevicompactum. In the phytotoxicity assays on the dicot species Brassica chinensis, harzianum A and B reduced both shoot and root lengths at low concentrations and inhibited the seed germination at 2 μg mL⁻¹. In addition, harzianum A and B also exhibited phytotoxicity against monocots, Oryza sativa L. cv. Nipponbare and Echinochloa crusgalli L. Beauv.. Compared with a common herbicide, 2,4-dichlorophenoxyacetic acid, harzianum A and B performed similar activity in a pot assay, and were more effective in post-emergence than pre-emergence conditions. Harzianum A and B have potential as efficient herbicide for controlling important dicotyledon and monocotyledon weeds at low concentrations. They can be sprayed in liquid form in both pre- and post-emergence conditions. Our results confirmed the importance of these molecules for the development of new herbicides.

Influence of Soil Phosphate on the Accumulation and Toxicity of Arsenic and Antimony in Choy Sum Cultivated in Individually and Co-contaminated Soils

Fertilizers containing phosphate (PO₄^3- ) are commonly used within the agricultural industry and are known to increase the bioavailability and mobility of metalloids like arsenic (As). This may increase plant uptake of As and hence pose a risk to human health. Arsenic and antimony (Sb) often co-occur in contaminated soils; however, little is known about the interactions between As and Sb with PO₄^3- on their bioavailability, accumulation, and toxicity in plants. The present study investigated individual and combined As and Sb-contaminated soils across 2 soil PO₄^3- concentrations using a commonly consumed leafy vegetable, choy sum (Brassica chinensis var. parachinensis). Increased soil PO₄^3- had no clear influence on the bioavailability of As or Sb (derived from a sequential extraction procedure). At high PO₄^3- concentration, B. chinensis accumulated higher amounts of As in the shoots and roots in both individual and co-contaminated soil, whereas Sb accumulation increased only when Sb was the only contaminant. When As was the only contaminant, the translocation of As from roots to shoots decreased as soil PO₄^3- increased. Increased soil PO₄^3- had no influence on Sb translocation from root to shoot. Although As was toxic (impaired growth) at low PO₄^3- soil concentration, no toxicity was observed in the high-PO₄^3- soil. No toxicity was observed for Sb in either low- or high-PO₄^3- soils. Increased soil PO₄^3- concentration ameliorated or masked As toxicity to plant growth and led to higher As concentration in the plant's edible parts. The addition of high soil PO₄^3- concentrations ameliorated or masked As toxicity to plant growth in both individually and As + Sb co-contaminated soil; however, the plant's edible parts accumulated higher As and Sb concentrations. Environ Toxicol Chem 2020;39:1233-1243. © 2020 SETAC.

Simultaneous attenuation of phytoaccumulation of Cd and As in soil treated with inorganic and organic amendments

A novel FeSiCa rich material (IS), chicken manure (CM) and its biochar were investigated for their efficiency in simultaneous remediation of Cd and As uptake by the vegetable Brassica chinensis L. Wet chemistry analysis and X-ray powder diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy as well as Fourier transform infrared spectroscopy were used to reveal the mechanisms responsible for Cd and As fixation in the amended soils. The IS treatment performed best in reducing Cd uptake, while the combination of IS and CM was the optimal one for As fixation. The precipitation/co-precipitation (in cadmium silicate/phosphate/phosphate hydroxide, cadmium iron and manganese oxides under alkaline conditions, and calcium/magnesium/ferric arsenates) and specific chemisorption (by amorphous iron/manganese oxides) were proved to be more efficient in simultaneously lowering As and Cd phytoavailability than was organic complexation. These findings demonstrate that FeSiCa and FeSiCaC amendments are highly efficient and promising in-situ remediation systems for safe crop production on soils contaminated with Cd and As.

Immobilization of soil cadmium using combined amendments of illite/smectite clay with bone chars

The widespread use of cadmium (Cd)-containing organic fertilizers is a source of heavy metal inputs to agricultural soils in suburban areas. Therefore, the research and development of new materials and technologies for the remediation of Cd-contaminated soil is of great significance and has the potential to guarantee the safety of agricultural products and the protection of human health. We performed pot experiments to determine the potential of combined amendments of illite/smectite (I/S) clay with bone chars for the remediation of Cd-contaminated agricultural soils in a suburban area of Beijing, China. The results showed that both diethylene triamine pentaacetic acid (DTPA)-extractable Cd in soil and the Cd in Brassica chinensis were significantly decreased by the application of 1, 2, or 5% combined amendments with various I/S and bone char (BC) ratios. The higher proportions of BC used in the combined amendments resulted in a better immobilization of soil Cd. The application of the 5% amendment that combined I/S with either pig or cattle BC resulted in the best immobilization. All of the combined amendments, regardless of the composition and ratio of the components, had no negative effects on the growth of B. chinensis. Therefore, it was concluded that combined amendments of I/S and BC have a good potential for remediating Cd-contaminated soils.

[Effect of Foliar Zinc Application on Bioaccessibility of Cadmium and Zinc in Pakchoi]

Two cultivars of pakchoi with different cadmium (Cd) accumulation were grown in nutrient solutions containing low and sufficient zinc (Zn) levels. ZnSO₄ and ZnNa₂ EDTA were applied as foliar fertilizers. The bioaccessibilities of Cd and Zn in pakchoi were assessed by the in vitro digestion method, and the bioaccessible established daily intakes (BEDI) of Cd and Zn from pakchoi were calculated. The effect of foliar zinc application on concentrations, bioaccessibilities, and BEDIs of Cd and Zn in pakchoi was evaluated. Results show that the Cd concentrations in shoots of the tested pakchoi cultivars under sufficient Zn condition were significantly lower than those under low Zn condition, and foliar application of ZnNa₂ EDTA significantly decreased the Cd concentrations of pakchoi. The tested pakchoi cultivars with sufficient Zn had a significantly higher mean shoot Zn concentration than those with low Zn. Foliar Zn treatments significantly increased shoot Zn concentrations of pakchoi, with the highest in the ZnSO₄ treatment. Cd bioaccessibility in the tested pakchoi cultivars with sufficient Zn was significantly lower than that with low Zn. Foliar applied Zn could significantly reduce Cd bioaccessibility in the gastric phase, with a maximal reduction of 35.81% compared to the control. Foliar treatment with ZnSO₄ could significantly decrease Cd bioaccessibility in the small intestinal phase, with a maximal reduction of 59.24% compared to the control. Foliar Zn treatments reduced significantly the Zn bioaccessibility of pakchoi in the gastric and small intestinal phases, with a maximal reduction of 68.90% compared to the control. The reduction of Zn bioaccessibility was higher in the ZnSO₄ treatment than in the ZnNa₂ EDTA treatment. Via the consumption of the Cd-contaminated common cultivar Hanlv, the BEDI values of Cd were higher than that of the provisional tolerable daily intake (PTDI) standard of WHO [0.83 μg·(kg·d)^-1]. However, via the consumption of the low-Cd accumulating cultivar Huajun or pakchoi with foliar application of ZnSO₄, the BEDI values of Cd decreased significantly and were below the PTDI value. Via the consumption of pakchoi in the control or low-level ZnNa₂ EDTA treatments, the BEDI values of Zn were below that of the recommended nutrient intake for Zn. However, via the consumption of pakchoi with foliar application of ZnSO₄ or high-level ZnNa₂ EDTA, the BEDI values of Zn were higher than that of the recommended nutrient intake and met the human needs for Zn from vegetables. Under the ZnSO₄ treatment, the BEDI values of Zn from pakchoi were the highest. In conclusion, foliar zinc application could significantly reduce the bioaccessibilities of Cd and Zn in pakchoi and the BEDI values of Cd and increase the BEDI values of Zn. Foliar application with ZnSO₄ was the most suitable treatment to reduce Cd intake and increase Zn intake from pakchoi.

Comparison of DGT with traditional extraction methods for assessing arsenic bioavailability to Brassica chinensis in different soils

Several predictive models and methods have been used for heavy metals bioavailability, but there is no universally accepted approach in evaluating the bioavailability of arsenic (As) in soil. The technique of diffusive gradients in thin-films (DGT) is a promising tool, but there is a considerable debate with respect to its suitability. The DGT method was compared with other traditional chemical extractions techniques (soil solution, NaHCO₃, NH₄Cl, HCl, and total As method) for estimating As bioavailability in soil based on a greenhouse experiment using Brassica chinensis grown in various soils from 15 provinces in China. In addition, we assessed whether these methods are independent of soil properties. The correlations between plant and soil As concentration measured with traditional extraction techniques were pH and iron oxide (Fe_ox) dependent, indicating that these methods are influenced by soil properties. In contrast, DGT measurements were independent of soil properties and also showed a better correlation coefficient than other traditional techniques. Thus, DGT technique is superior to traditional techniques and should be preferable for evaluating As bioavailability in different type of soils.

Effects of glucose on the uptake and metabolism of glycine in pakchoi (Brassica chinensis L.) exposed to various nitrogen sources

BACKGROUND

Plants can absorb amino acids as a nitrogen (N) source, and glucose is an important part of root rhizodeposition and the soil sugar pool, which participates in the regulation of plant growth and uptake. In pakchoi, the effect of glucose concentration on the glycine N uptake from a nutrient mixture composed of glycine, ammonium, and nitrate, or from a single N solution of glycine alone was studied using specific substrate 15N-labeling and 15N-gas chromatography mass spectrometry.

RESULTS

The optimal glucose concentration for plant growth was 4.5 μM or 25 μM when supplied with glycine alone or the N mixture, respectively, and resulted in a >25% increase in seedling biomass. The addition of glucose affected the relative contribution from organic or inorganic sources to overall N uptake. When glucose was added at optimal concentrations, glycine was preferentially used as an N source, while the relative contribution from nitrate was reduced. The limiting step for glycine N contribution was active uptake in the roots in high glucose and single-N-source conditions; however, root metabolism of glycine to serine was limiting in high-glucose and mixed-N-source conditions.

CONCLUSIONS

The addition of low concentrations of glucose increased the relative uptake of organic nitrogen and reduced the uptake of nitrate, suggesting a feasible way to decrease nitrate content and increase the edible quality of vegetables.

Improved Discrimination for Brassica Vegetables Treated with Agricultural Fertilizers Using a Combined Chemometric Approach

Multielement and stable isotope (δ(13)C, δ(15)N, δ(2)H, δ(18)O, (207)Pb/(206)Pb, and (208)Pb/(206)Pb) analyses were combined to provide a new chemometric approach to improve the discrimination between organic and conventional Brassica vegetable production. Different combinations of organic and conventional fertilizer treatments were used to demonstrate this authentication approach using Brassica chinensis planted in experimental test pots. Stable isotope analyses (δ(15)N and δ(13)C) of B. chinensis using elemental analyzer-isotope ratio mass spectrometry easily distinguished organic and chemical fertilizer treatments. However, for low-level application fertilizer treatments, this dual isotope approach became indistinguishable over time. Using a chemometric approach (combined isotope and elemental approach), organic and chemical fertilizer mixes and low-level applications of synthetic and organic fertilizers were detectable in B. chinensis and their associated soils, improving the detection limit beyond the capacity of individual isotopes or elemental characterization. LDA shows strong promise as an improved method to discriminate genuine organic Brassica vegetables from produce treated with chemical fertilizers and could be used as a robust test for organic produce authentication.

Effects of Dissolved Organic Matter on Uptake and Translocation of Lead in Brassica chinensis and Potential Health Risk of Pb

Dissolved organic matter (DOM) can affect the bioavailability of heavy metals in soil, especially in soils used for vegetable production, where intensive organic fertilization is applied. The present study examined the effects of DOM derived from commercial organic fertilizers (COF), cow manure (COM) and chicken manure (CHM), on uptake and translocation of lead (Pb) in Brassica chinensis in a pot experiment. The results indicate that DOM derived from CHM (DOM_CHM) significantly increased Pb concentrations in roots of B. chinensis (p < 0.05). By contrast, there was no significant increase in shoot Pb concentration for all the DOM treatments except the high DOM_CHM treatment in the soil with 800 mg·kg⁻¹ Pb. Consistent with the Pb concentrations in shoots, translocation factor of Pb from soil to shoot and specific lead uptake (SLU) by B.chinensis were significantly increased for the high DOM_CHM treatment in the high Pb soil, but not for other DOM treatments. Based on the results of this study, the application of DOM to the soil with 800 mg·kg⁻¹ Pb could result in an increase in total Pb annually ingested by the inhabitants of Nanjing City in the range of 2018–9640 kg, with the highest estimates resulting from the high DOM_CHM treatment. This study suggests the risk may rise under some conditions as indicated in the high DOM_CHM treatment and high Pb pollution level.

Effects of inorganic and organic amendments on the uptake of lead and trace elements by Brassica chinensis grown in an acidic red soil

A greenhouse study was conducted to investigate the effects of inorganic (phosphate rock, single superphosphate and calcium magnesium phosphate) and organic amendments (peat, straw manure and pig manure) on the uptake of lead (Pb) and trace elements by Chinese Cabbage (Brassica chinensis) grown in an acidic red soil. The application of all organic amendments increased the soil pH while inorganic amendments such as single superphosphate did not. Both inorganic and organic amendments decreased the availability and uptake of Pb while the organic amendments were superior to the inorganic (phosphate) amendments in reducing the availability of the more labile (soluble and exchangeable Pb) forms of soil Pb. More Pb was taken up by roots than shoots with all soil amendments. Among the organic amendments, straw manure and pig manure caused the largest decrease in Pb availability at 456.5 and 457.3 mg kg(-1), respectively, when a high level of 30 g organic amendments kg(-1) was applied. The organic amendments greatly increased the fraction D targeted to Fe-Mn oxides bound Pb, and decreased the fraction A (water-soluble), B (exchangeable), and C (carbonate-bound), thereby decreasing the solubility and mobility of Pb in soil. The organic amendments also significantly improved the concentrations of Fe, Mn, Cu and Zn in the soil and shoots (except Fe in shoots and/or roots), which are essential for plant nutrition. The organic amendments of straw and pig manure lowered the availability and uptake of Pb but not that of other trace metals. Thus, these amendments have the potential to remediate Pb-contaminated soils in situ.

Responses of Some Common Cruciferae to Root-knot Nematodes

Ten cultivated plants of the family Cruciferae were evaluated for susceptibility to Meloidogyne arenaria race 1, M. incognita races 1 and 3, and M. javanica in a series of four separate greenhouse tests. After 62-64 days, or 1,032-1,072 degree days (10 C base), several of the crops evaluated showed moderate to severe levels of galling (> 3.0 on 0-5 scale) and moderate numbers of egg masses (>2.0 on 0-5 scale) in response to each of the nematode species and races. Among the plants tested, collard (Brassica oleracea var. acephala) cv. Georgia Southern was the least susceptible (fewest galls and egg masses) to each of the four nematode isolates. Similar low levels of infection were obtained with broccoli (B. oleracea var. botrytis) cv. De Cicco in response to M. incognita race 1 and M. arenaria. Numbers of second-stage juveniles hatched from eggs per root system were variable in the test with M. arenaria, but lowest on collard for each of the other nematodes. Some commonly grown crucifers are hosts to several different species and races of Meloidogyne, which should be considered if these crops are included in cropping systems.