Search

Key message: Metabolomic and transcriptomic analyses revealed an intensification of energy metabolism in rice grains under DMA stress, possibly causing the consumption of sugars or non-sugars and the development of unfilled grains Excessive dimethylarsinic acid (DMA) causes rice straighthead disease, a physiological disorder typically with erect panicle due to empty grain at maturity. Although the toxicity of DMA and its uptake and transport in rice are well recognized, the underlying mechanism of unfilled grains remains unclear. Therefore, a pot experiment was conducted using a susceptible variety (Ruanhuayou1179, RHY) and a resistant one (Nanjingxiangzhan, NJXZ) via the metabolomic and transcriptomic approaches to explore the mechanisms of empty grains in diseased rice under DMA stress. The results demonstrate an increase in total and methylated As in grains of RHY and NJXZ under DMA addition, with RHY containing higher levels of DMA. DMA addition increased the soluble sugar content in grains of RHY and NJXZ by 17.1% and 14.3% compared to the control, respectively, but significantly reduced the levels of amino acid, soluble protein, and starch. The decrease of grain Zn and B contents was also observed, and inadequate Zn might be a key factor limiting rice grain yield under DMA stress. Notably, DMA addition altered the expression levels of genes involved in the transport of sugar, amino acids, nitrates/peptides, and mineral ions. In sugar and amino acid metabolism, the reduction of metabolites and the upregulated expression of genes reflect positive regulation at the level of energy metabolism, implying that the reduction of grain starch and proteins might be ascribed to generate sufficient energy to resist the stress. This study provides a useful reference for understanding the molecular mechanism of grain emptying under DMA stress. [ABSTRACT FROM AUTHOR]

Neocosmospora solani causes Fusarium wilt disease and root rot, which are serious problems worldwide. To determine the growth inhibition of Neocosmospora solani by Trichoderma hamatum volatile organic compounds (VOCs), the major chemical components of Trichoderma hamatum VOCs and the differences in their contents at different times were analysed, and the activity of these components was evaluated. The antifungal activity of Trichoderma hamatum was measured by a screening test, as Trichoderma hamatum exhibited strong antagonism against Neocosmospora solani in vitro. The double plate technique was used to verify the activity of Trichoderma hamatum VOCs, and the inhibition rate was 63.77%. Neocosmospora solani mycelia were uneven and expanded, the contents of the cells leaked, and the mycelia shrank and presented a diaphragm in the hyphae upon Trichoderma hamatum VOCs treatment. Trichoderma hamatum VOCs and their contents at different times were analysed by using gas chromatography–mass spectrometry. 6-Pentyl-2H-pyran-2-one clearly presented in greater amounts than the other components on day 3, 4, 5, and 6. VOCs from Trichoderma hamatum exhibited evident effects on the percentage of healthy fruit after day 3. Moreover, Trichoderma hamatum can improve the biological control of diseases caused by soilborne pathogens, and can be applied in biocontrol fields. [ABSTRACT FROM AUTHOR]

Manganese toxicity is a major obstacle to agriculture in acid soils. Dark pericarp disease (DPD) is a newly spread physiological disorder induced by excess Mn in litchi, leading to undesirable fruit appearance and substantial economic loss. In this work, broadcast of alkaline soil conditioner in winter, followed by foliar sprays of ascorbic acid and sulfur solution at fruit development, was adopted to examine the effect of these combinations on DPD alleviation in a litchi orchard, with DPD morbidities of 70~85% in recent ten years. The combination of soil conditioner broadcast and foliar water spray was used as the control. At harvest, DPD incidence was significantly decreased by sulfur spray (3.3 ± 1.0%) and slightly reduced by ascorbic acid spray (10.7 ± 8.0%) compared to the control (12.9 ± 7.6%). Soil pH and available Mn were significantly increased and reduced by the soil conditioner broadcast. Sulfur spray significantly inhibited Mn uptake but enhanced the accumulation of Mg, Ca, sugars and cyanidin-3-rutinoside in the pericarp, leading to improved fruit pigmentation. Antioxidase activities were regulated to resist Mn stress by sulfur spray. The spray of ascorbic acid could not mitigate DPD as expected, probably due to the dose used. Conclusively, this study provides a practicable approach to mitigate Mn phytoavailability in acid soils. [ABSTRACT FROM AUTHOR]

The coexistence of heavy metals and antibiotics in the environment always results in greater toxicity compared to the individual precursors. Therefore, efficient and economic technology for the simultaneous removal of antibiotics and heavy metals is essential. Herein, litchi leaves biochar carbonized at 550 °C (L550) demonstrated high efficiency in co-removal of CTC (1838.1 mmol/kg) and Cu (II) (1212.9 mmol/kg) within wide range of pH (pH 4–7). Ionic strength obviously enhanced the Cu (II) removal but showed no significant effect on CTC removal. Although Al3+ and HPO42− decreased the adsorption capacities of CTC and Cu (II) on L550, the coexistence of Na+, K+, Mg2+, Cl−, NO3−, CO32− and SO42− showed a negligible effect on the simultaneous removal of CTC and Cu (II). Moreover, the adsorption capacities of CTC and Cu (II) on L550 were excellent in the river water, tap water, and lake water. In addition to electrostatic interactions, ion exchange governed Cu (II) adsorption, while surface complexation played a key role in CTC adsorption on L550. Our results demonstrated that litchi leaves biochar could be a promising adsorbent for remediating multi-contaminated environments. [ABSTRACT FROM AUTHOR]

Rice straighthead disease substantially reduces crop yield, posing a significant threat to global food security. Dimethylarsinic acid (DMA) is the causal agent of straighthead disease and is highly toxic to the reproductive tissue of rice. However, the precise physiological mechanism underlying DMA toxicity remains unknown. In this study, six rice varieties with varying susceptibility to straighthead were utilized to investigate the growth performance and element distribution in rice panicles under DMA stress through pot experiments, as well as to explore the physiological response to DMA using transcriptomic methods. The findings demonstrate significant variations in both DMA accumulation and straighthead sensitivity among cultivars. The susceptible varieties exhibited higher DMA accumulation indices and displayed typical symptoms of straighthead disease, including erect panicles, deformed rachides and husks, and reduced seed setting rate and grain yield when compared to the resistant varieties. Moreover, DMA addition promoted mineral nutrients to accumulate in rachides and husks but less in grains. DMA showed preferential accumulation in rice grains with a distribution pattern similar to that of Copper (Cu) and zinc (Zn) within the panicle. Transcriptome analyses underscored the substantial impact of DMA on gene expression related to mineral metabolism. Notably, DMA addition significantly up‐regulated the expression of pectin methylesterase, pectin lyase, polygalacturonase, and exogalacturonase genes in Nanjingxiangzhan, while these genes were down‐regulated or weakly expressed in Ruanhuayou 1179. The alteration of pectin metabolic pathways induced by DMA may lead to abnormality of cell wall assembly and modification, thereby resulting in deformed rice panicles. [ABSTRACT FROM AUTHOR]

Main conclusion: Sunlight boosts anthocyanin synthesis/accumulation in sunny pericarp of litchi fruit, directly leading to uneven pigmentation. Distribution discrepancy of mineral element aggravates uneven coloration by modulating synthesis/accumulation of anthocyanin and sugar. Uneven coloration, characterized by red pericarp on sunny side and green pericarp on shady side, impacts fruit quality of ‘Feizixiao’ (cv.) litchi. The mechanisms of this phenomenon were explored by investigating the distribution of chlorophyll, flavonoids, sugars, and mineral elements in both types of pericarp. Transcriptome analysis in pericarp was conducted as well. Sunny pericarp contained higher anthocyanins in an order of magnitude and higher fructose, glucose, co-pigments (flavanols, flavonols, ferulic acid), and mineral elements like Ca, Mg and Mn, along with lower N, P, K, S, Cu, Zn and B (P < 0.01), compared to shady pericarp. Sunlight regulated the expression of genes involved in synthesis/accumulation of flavonoids and sugars and genes functioning in nutrient uptake and transport, leading to asymmetric distribution of these substances. Anthocyanins conferred red color on sunny pericarp, sugars, Ca and Mg promoted synthesis/accumulation of anthocyanins, and co-pigments enhanced color display of anthocyanins. The insufficiencies of anthocyanins, sugars and co-pigments, and inhibition effect of excess K, S, N and P on synthesis/accumulation of anthocyanins and sugars, jointly contributed to green color of shady pericarp. These findings highlight the role of asymmetric distribution of substances, mineral elements in particular, on uneven pigmentation in litchi, and provide insights into coloration improvement via precise fertilization. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) is one of the most important staple food crops worldwide. For people fed on rice, toxic elements cadmium (Cd) and arsenic (As) and mineral nutrients in rice are pivotal to evaluate potential risks of harmful element intake and malnutrition. We collected rice samples of 208 cultivars (83 inbred and 125 hybrid) from fields in South China and determined Cd, As, As species, and mineral elements in brown rice. Chemical analysis shows that the average content of Cd and As in brown rice were 0.26 ± 0.32 and 0.21 ± 0.08 mg·kg−1, respectively. Inorganic As (iAs) was the dominative As species in rice. Rice Cd and iAs in 35.1% and 52.4% of the 208 cultivars exceeded rice Cd and iAs limits, respectively. Significant variations of rice subspecies and regions were found for Cd, As, and mineral nutrients in rice (P < 0.05). Inbred rice had lower As uptake and more balanced mineral nutrition than hybrid species. Significant correlation was observed between Cd, As versus mineral elements like Ca, Zn, B, and Mo (P < 0.05). Health risk assessment indicates that high risks of non-carcinogenic and carcinogenic of Cd and iAs, and malnutrition, in particular Ca, protein and Fe deficiencies, might be caused by rice consumption in South China. [ABSTRACT FROM AUTHOR]

Foliar nutrient diagnosis is a potent tool for nutrient management in crops. Litchi (Litchi chinensis Sonn.) plantation in China dominates the worldwide litchi cultivation, and Feizixiao is the most widely cultivated species in China. Herein, 538 leaf samples were collected at fruit swelling stage and the terminal shoot maturing stage during 2016–2017, and the fruit yields of all the sampled trees were recorded. The suitability of four nutrient diagnosis methods including critical value approach (CVA), sufficiency range approach (SRA), modified diagnosis and recommendation integrated system (M-DRIS), and compositional nutrient diagnosis (CND) in Feizixiao were compared. Only a few of foliar nutrients could be diagnosed by CVA. Similar evaluations were achieved by both M-DRIS and CND, but the diagnosis accuracy highly varied with the severity of nutrient deficiency or abundance and the diagnosis year. Finally, SRA was accepted to establish the diagnosis norms due to its stable assessments for all nutrients. The optimal foliar nutrient range for Feizixiao is recommended as N 16.7–19.2, P 1.06–1.25, K 5.1–6.7, Ca 7.7–11.0, Mg 2.5–3.7 and S 1.51–1.81 g kg−1, and Zn 19.6–32.6 and B 11.5–19.2 mg kg−1 at the fruit swelling stage , and N 19.7–22.0, P 1.69–1.95, K 10.8–12.7, Ca 3.0–4.1, Mg 2.5–2.9 and S 1.38–1.57 g kg−1, and Zn 15.0–18.9 and B 10.8–16.8 mg kg−1 at the terminal shoot maturing stage. [ABSTRACT FROM AUTHOR]

Aims: A new physiological disorder, dark pericarp disease (DPD) in litchi fruit is recently observed in South China. DPD occurs after heavy rain and is aggregated by insolation, leading to undesirable fruit appearance. This work aims to reveal the cause of DPD, and seek efficient solutions for it. Methods: A field experiment was conducted to investigate the link between pericarp nutrients and DPD occurrence in litchi grown in soil with abundant available Mn. The antioxidase activities, subcellular location of dark materials, phenol compounds in dark pericarp fruit (DPF) and soil properties affected by dolomite broadcast and dolomite broadcast plus foliar K2SiO3 spray were examined as well. Results: Mn contents in tissues significantly decreased in the order: dark pericarp of DPF > normal pericarp of DPF > pericarp of normal fruit (P < 0.01), indicating that DPD is associated with excessive Mn. Dark materials dominated in the upper mesocarp of DPF. Nanoparticles of dark materials were formed from phenol grains in vacuole, and sequestered into vesicle from vacuole, then excreted to cytoplasm. Dolomite broadcast significantly mitigated DPD by raising soil pH, lowering soil available Mn and regulating antioxidase activities in pericarp (P < 0.05). However, it is unexpected that additional Si spray significantly offset the role of dolomite application, probably due to its alkality. Conclusions: This study first reports that DPD is caused by excessive Mn in litchi. Dark materials are probably comprised of oxidized and/or polymerized phenols in pericarp of DPF. Dolomite application efficiently alleviates DPD, but extra foliar alkaline Si spray counteracts its role. [ABSTRACT FROM AUTHOR]

Fruit color is a decisive factor in consumers' preference. The bright red color of litchi fruit is associated with its high anthocyanin; however, poor fruit coloration is a major obstacle in litchi plantation. The role of spraying mineral nutrient salts such as KH2PO4, KCl, K2SO4, and MgSO4 on litchi pericarp pigmentation was examined by a field trial, and the relation between human visual color preference versus pericarp pigments and hue-saturation-brightness (HSB) color parameters was investigated. K2SO4-sprayed litchi fruit gained the maximum popularity for its attractive red color. Spray of K and Mg salts decreased the buildup of yellowish pigments, but increased the accumulation of red ones, with the exception of slightly reduced anthocyanins in KH2PO4-sprayed fruit, by regulating the activities of enzymes involved in anthocyanidin metabolism and decreasing pericarp pH, leading to varied pericarp pigment composition. K2SO4 spray generated the highest percentage of cyanidin-3-glucoside over all pigments in pericarp. Correlation analysis shows the percent of cyanidin-3-glucoside, superior to anthocyanin concentration and HSB color parameters, was a reliable indicator to fruit color preference. This work demonstrates that spray of suitable mineral salt can regulate pericarp pigment profile, and is an effective approach to improve fruit pigmentation and promote its popularity. [ABSTRACT FROM AUTHOR]

The environmental and human health risk posed by veterinary antibiotics is of global concern. Antibiotic uptake by herbal plants has been studied, but little is known about perennial woody fruit crops. Litchi (Litchi chinensis Sonn.), a longevial fruit tree, is routinely fertilized with animal manure and, therefore, may be at risk of antibiotic uptake into its fruits. This study investigated the degradation of chlortetracycline and doxycycline present in manure used to amend orchard soil, and their subsequent assimilation by litchi plant, as affected by manure application rate. The results show that half-lives of chlortetracycline and doxycycline in soil were decreased by increased manure rate, with an average of 27 and 59 days, respectively. Chlortetracycline was readily transported to litchi shoots and increased with the growth of litchi plants. Doxycycline predominantly remained in the roots, and underwent growth dilution in the plants. The two tetracyclines could not be detected in fruits from litchi trees when applied with manures, at various rates, over 2 years. For litchi, chlortetracycline may pose human health risk through manure application, but doxycycline is unlikely to do so. Long-term field experiments are required to monitor antibiotic accumulation in fruits of perennial fruit trees fertilized with animal manure. [ABSTRACT FROM AUTHOR]

Roxarsone (ROX), a widely used feed organoarsenic additive, occurs as itself and its metabolites in animal manure that is commonly land used as fertilizer. Soil property impacts arsenic (As) speciation and bioavailability. Fourteen soils across China were used to conduct culture experiments to investigate As uptake by garland chrysanthemum ( ChrysanthemumL coronarium), with the soils fertilized with chicken manure bearing ROX and its metabolites. The results show As(III) was the sole As form in garland chrysanthemum shoots, and As(III) and As(V) occurred in roots. Only inorganic As was detected in all soils when the plants were harvested. Stepwise regression analysis shows soil-exchangeable Ca predominated shoot As(III) concentration (shoot As(III) = 1.60030 soil Ca, R = 0.8832***). Therefore, ROX is transferred into the human food chain finally as inorganic As in plants. Application of animal manure bearing ROX and its metabolites is not recommended in Ca-rich soils to avoid excess inorganic As dietary exposure. [ABSTRACT FROM AUTHOR]

Surfactant-free tiny Pt clusters were successfully encapsulated within MOFs with controllable size and spatial distribution by a novel kinetically modulated one-step strategy. Our synthesis relies on the rational manipulation of the reduction rate of Pt ions and/or the growth rate of MOFs by using H2 as assistant reducing agent and/or acetic acid as MOF-formation modulator. The as-prepared Pt@MOF core-shell composites exhibited exceedingly high activity and excellent selectivity in the oxidation of alcohols as a result of the ultrafine 'clean' Pt clusters, as well as interesting molecular-sieving effects derived from the outer platinum-free MOF shell. [ABSTRACT FROM AUTHOR]

Surfactant-free tiny Pt clusters were successfully encapsulated within MOFs with controllable size and spatial distribution by a novel kinetically modulated one-step strategy. Our synthesis relies on the rational manipulation of the reduction rate of Pt ions and/or the growth rate of MOFs by using H2 as assistant reducing agent and/or acetic acid as MOF-formation modulator. The as-prepared Pt@MOF core-shell composites exhibited exceedingly high activity and excellent selectivity in the oxidation of alcohols as a result of the ultrafine 'clean' Pt clusters, as well as interesting molecular-sieving effects derived from the outer platinum-free MOF shell. [ABSTRACT FROM AUTHOR]

A simple and highly efficient nanostructured catalyst system comprising magnetic Co nanoparticles stabilized by N-doped carbon composite (Co/C–N) was synthesized by one-pot thermal decomposition of a Co-containing MOF. The catalysts were characterized by temperature programmed desorption (TPD), N2 physical adsorption, powder X-ray diffraction (PXRD), Raman spectroscopy, transmission electron microscopy (TEM), scanning electronic microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The catalytic activity of Co/C–N materials was investigated in the selective aerobic oxidation of alcohols in neat water under an atmospheric pressure of air and base-free conditions. As compared to those prepared by traditional impregnation methods, Co/C–N exhibited an efficient performance with significantly improved catalytic activities. Besides conferring high activity and selectivity to the target products, the proposed catalytic system featured a broad substrate scope for both aryl and alkyl alcohols. Furthermore, the magnetically recoverable Co/C–N catalyst could be easily separated from the reaction system by using an external magnetic field and reused at least five times without any significant loss in catalytic efficiency under the investigated conditions. [ABSTRACT FROM AUTHOR]

The control over the size and location of metal nanoparticles (MNPs) within metal–organic frameworks (MOFs) is achieved in one step through a cooperative in situ metal precursor incorporation and on-site moderate reduction process, which is operated by a temperature control program. The choice of operation temperatures is based on the MOF assembly temperature (T1), and an elevated temperature (T2) to elicit the reducibility of DMF solvent to fabricate MNPs. Such a rational design could effectively introduce metal precursors into the pores of MOFs and on-site moderately reduce the embedded metal ions to generate tiny MNPs by the penetrated DMF, which could not be achieved by a quick heating process. The proposed methodology has been successfully applied to the one-step fabrication of ultrafine Pd NPs selectively encapsulated inside the pores of UiO-67 without any external reducing agents. The obtained Pd-in-UiO-67 shows superior catalytic activity and selectivity in the hydrogenation of styrene even at room temperature and atmospheric pressure of H2. [ABSTRACT FROM AUTHOR]