Spinach Leaf Research Articles

Features of the Functioning of Succinate Dehydrogenase and Malate Dehydrogenase in Leaves of Spinach (Chenopodium foliosum L.) and Amaranth (Amaranthus caudatus L.) under Salt Stress Conditions

Salt stress was shown to cause changes in the activity and isozyme composition of mitochondrial malate dehydrogenase (MDH) in leaves of amaranth (C4-type); these changes were manifested in the induction of an additional MDH isoform. Exposure of spinach plants (C3-type) to a NaCl solution did not cause significant changes in the isozyme composition and activity of the enzymes studied. Succinate dehydrogenase (SDH) activity in amaranth leaves under salt stress conditions increased several times, while the isoenzyme composition of SDH remained unchanged. The levels of gene transcripts in leaves of amaranth and spinach clearly correlated with changes in the MDH and SDH activity. Salt stress enhanced expression of the mdh-mtx (mitochondrial) and mdh-cyt (cytoplasmic) genes in amaranth leaves during the whole experiment. In the case of the sdha gene, a decrease in the content of transcripts was observed that clearly correlated with the reduction in SDH activity.

Three New Fungal Leaf Spot Diseases of Spinach in the United States and the Evaluation of Fungicide Efficacy for Disease Management.

Leaf spot diseases of spinach, caused by Colletotrichum spinaciae, has become a major production constraint in several production areas, including Texas, in recent years. Leaf spot symptoms were observed in several fields in Texas in 2016 and 2017, with typical anthracnose-like symptoms and leaves with small, circular, and sunken lesions that appeared similar to injury from windblown sand. The lesions were plated on potato dextrose agar, from which fungal cultures were recovered. The fungi were identified based on morphology and sequence analysis of the introns of glutamate synthetase and glyceraldehyde-3-phosphate dehydrogenase (for isolates determined to be Colletotrichum spp.) and the internal transcribed spacer ribosomal DNA (for isolates determined to be Myrothecium spp.). Based on foliar symptoms, fungal colony and spore morphology, pathogenicity tests of fungal isolates on the spinach cultivar 'Viroflay', and DNA sequence analysis of the isolates, the symptoms on spinach leaves for two sets of samples were caused by Colletotrichum coccodes and Colletotrichum truncatum, and leaf spots resembling damage from windblown sand were caused by Myrothecium verrucaria. This is the first report of spinach leaf spot diseases caused by C. coccodes, C. truncatum, and M. verrucaria in the United States. C. coccodes and C. truncatum caused severe symptoms on the spinach cultivar 'Viroflay', whereas M. verrucaria caused symptoms of intermediate severity. Fungicide efficacy tests demonstrated that chlorothalonil, mancozeb, pyraclostrobin, fluxapyroxad + pyraclostrobin, and penthiopyrad were completely effective at preventing leaf spots caused by any of these pathogens when applied 24 h before inoculation of 'Viroflay' plants in greenhouse trials.

Novel Method for Fire Retardancy of Cotton Fabrics Coated by Spinach Leaf Extract Assisted by Corona Discharge Plasma

The application of material physics in the functional textile field has been widely applied, one of which is plasma technology. In this research, the fire-retardant properties have been developed in the cotton fabric textile material using spinach leaf extract and comparison of fire-retardant resin on the market using plasma technology. The flame-retardant is applied to the cotton fabric using the atmospheric-pressure plasma method with a tip-cylinder electrode. The cotton fabric used is a cotton fabric that has undergone a process of bleaching and mercerization. In this research, two types of methods have been carried out, namely the immersion method on the fire-retardant resin substance with atmospheric pressure plasma pre-treatment and the immersion method on spinach leaf extract with atmospheric pressure plasma treatment. Research shows that there is an increase in the fire-retardant properties of cotton fabrics that have been given treatment. The assessment of fire-retardant properties was tested using the standard method of fire-retardant ASTM D6413-08 vertical method. In this research, atmospheric-pressure plasma treatment with a time variation of 2 minutes and 4 minutes has been carried out. The results showed that the cotton fabric treated with the immersion method on spinach leaf extract and atmospheric pressure plasma pre-treatment had better fire-retardant properties. It has also been found that the length of time the plasma treatment will affect the fire-retardant properties of cotton fabrics.

Methodology: an optimized, high-yield tomato leaf chloroplast isolation and stroma extraction protocol for proteomics analyses and identification of chloroplast co-localizing proteins

BackgroundChloroplasts are critical organelles that perceive and convey metabolic and stress signals to different cellular components, while remaining the seat of photosynthesis and a metabolic factory. The proteomes of intact leaves, chloroplasts, and suborganellar fractions of plastids have been evaluated in the model plant Arabidopsis, however fewer studies have characterized the proteomes of plastids in crops. Tomato (Solanum lycopersicum) is an important world-wide crop and a model system for the study of wounding, herbivory and fruit ripening. While significant advances have been made in understanding proteome and metabolome changes in fruit ripening, far less is known about the tomato chloroplast proteome or its subcompartments.ResultsWith the long-term goal of understanding chloroplast proteome dynamics in response to stress, we describe a high-yielding method to isolate intact tomato chloroplasts and stromal proteins for proteomic studies. The parameters that limit tomato chloroplast yields were identified and revised to increase yields. Compared to published data, our optimized method increased chloroplast yields by 6.7- and 4.3-fold relative to published spinach and Arabidopsis leaf protocols, respectively; furthermore, tomato stromal protein yields were up to 79-fold higher than Arabidopsis stromal proteins yields. We provide immunoblot evidence for the purity of the stromal proteome isolated using our enhanced methods. In addition, we leverage our nanoliquid chromatography tandem mass spectrometry (nanoLC–MS/MS) data to assess the quality of our stromal proteome. Using strict criteria, proteins detected by 1 peptide spectral match, by one peptide, or were sporadically detected were designated as low-level contaminating proteins. A set of 254 proteins that reproducibly co-isolated with the tomato chloroplast stroma were identified. The subcellular localization, frequency of detection, normalized spectral abundance, and functions of the co-isolating proteins are discussed.ConclusionsOur optimized method for chloroplast isolation increased the yields of tomato chloroplasts eightfold enabling the proteomics analysis of the chloroplast stromal proteome. The set of 254 proteins that co-isolate with the chloroplast stroma provides opportunities for developing a better understanding of the extensive and dynamic interactions of chloroplasts with other organelles. These co-isolating proteins also have the potential for expanding our knowledge of proteins that are co-localized in multiple subcellular organelles.

Neutral electrolyzed oxidizing water is effective for pre-harvest decontamination of fresh produce

Pre-harvest sanitization of irrigation water has potential for reducing pathogen contamination of fresh produce. We compared the sanitizing effects of irrigation water containing neutral electrolyzed oxidizing water (EOW) or sodium hypochlorite (NaClO) on pre-harvest lettuce and baby spinach leaves artificially contaminated with a mixture of Escherichia coli, Salmonella Enteritidis and Listeria innocua (~1 × 108 colony-forming units/mL each resuspended in water containing 100 mg/L dissolved organic carbon, simulating a splash-back scenario from contaminated soil/manure). The microbial load and leaf quality were assessed over 7 days, and post-harvest shelf life evaluated for 10 days. Irrigation with water containing EOW or NaClO at 50 mg/L free chlorine significantly reduced the inoculated bacterial load by ≥ 1.5 log10, whereas tap water irrigation reduced the inoculated bacterial load by an average of 0.5 log10, when compared with untreated leaves. There were no visual effects of EOW or tap water irrigation on baby spinach or lettuce leaf surfaces pre- or post-harvest, whereas there were obvious negative effects of NaClO irrigation on leaf appearance for both plants, including severe necrotic zones and yellowing/browning of leaves. Therefore, EOW could serve as a viable alternative to chemical-based sanitizers for pre-harvest disinfection of minimally processed vegetables.

Green synthesized CuxO@Cu nanocomposites on a Cu mesh with dual catalytic functions for dye degradation and hydrogen evaluation

Here we introduce an ecological facile method to grow heterogeneous copper oxide (CuxO) nanocomposites on a Cu mesh using spinach leaf extract. After annealing at different temperatures, morphological and structural characterizations revealed that samples annealed at 300 °C comprise the highest Cu+/Cu2+ ratio and reveal the most porous structure. Such samples exhibited dual catalytic functions as both photocatalysts for dye degradation, and electrocatalysts for hydrogen evolution. Their photocatalytic activity for degradation of methylene blue (MB) was investigated under sunlight irradiation of 7 mW/cm2. A complete degradation, with an average kinetic rate of 63.2 m min−1, was achieved after 60 min. Moreover, the samples revealed a good electrochemical catalytic property for hydrogen evolution reaction (HER) in acidic medium. They exhibited HER onset at 357 mV with a small charge transfer resistance of 8.2 Ω. Such promising outcomes could open a new path for mass-production applications in water-energy fields.

Leaf Surface Topography Contributes to the Ability of Escherichia coli on Leafy Greens to Resist Removal by Washing, Escape Disinfection With Chlorine, and Disperse Through Splash.

The attachment of foodborne pathogens to leaf surfaces is a complex process that involves multiple physical, chemical, and biological factors. Here, we report the results from a study designed to specifically determine the contribution of spinach leaf surface topography as it relates to leaf axis (abaxial and adaxial) and leaf age (15, 45, and 75 days old) to the ability of Escherichia coli to resist removal by surface wash, to avoid inactivation by chlorine, and to disperse through splash impact. We used fresh spinach leaves, as well as so-called “replicasts” of spinach leaf surfaces in the elastomer polydimethylsiloxane to show that leaf vein density correlated positively with the failure to recover E. coli from surfaces, not only using a simple water wash and rinse, but also a more stringent wash protocol involving a detergent. Such failure was more pronounced when E. coli was surface-incubated at 24°C compared to 4°C, and in the presence, rather than absence, of nutrients. Leaf venation also contributed to the ability of E. coli to survive a 50 ppm available chlorine wash and to laterally disperse by splash impact. Our findings suggest that the topographical properties of the leafy green surface, which vary by leaf age and axis, may need to be taken into consideration when developing prevention or intervention strategies to enhance the microbial safety of leafy greens.

Arsenic in leafy vegetable plants grown on mine water-contaminated soils: Uptake, human health risk and remedial effects of biochar

Field investigation and microcosm experiment were conducted to examine the uptake of arsenic by vegetable plants grown on the soils contaminated by acidic mine water and evaluate the human health risk from consuming the vegetables. Plant uptake of arsenic was related to the ratio of phosphorus to arsenic in soil solution for the same vegetable species. Bioaccumulation coefficient (BAC) of arsenic was highly variable amongst the different vegetable species with water spinach (white stem) and sweet potato leaf being identified as major vegetable species with high BAC. There was a reasonably good relationship between the gastric phase-bioaccessible arsenic and the gastrointestinal phase-bioaccessible arsenic. Consumption of the vegetables grown in the investigated area poses a significantly potential human health risk with a hazard quotient (HQ) of 2.7. Application of biochar significantly inhibited the uptake of arsenic by the vegetable plant due to protonation of biochar surfaces under acidic conditions, which favoured adsorption of arsenic. The bioaccessibity of arsenic in the edible part of vegetable was also reduced due to biochar application. The HQ of the test vegetable plant (Gynura cusimbua) after soil amendment by biochar was reduced to 2 from 6 for the unamended soil.

Efficient mineralization and osteogenic gene overexpression of mesenchymal stem cells on decellularized spinach leaf scaffold.

Until now, various methods have been introduced to fabricate 3D scaffolds to provide a suitable substrate for cell growth and proliferation and subsequent use in tissue engineering to repair damaged tissues. The 3D scaffolds can simulate the natural cellular microenvironment well. Herein, the decellularized leaf spinach has been used which not only have no problems associated with artificial scaffolds, but they also do not cost significantly. Decellularized scaffolds surface properties were characterized by the investigation of scaffolds surface roughness, hydrophilicity, mechanical properties, size and shape of porosities and specific surface area. In the next step, osteogenic differentiation potential of bone marrow derived mesenchymal stem cells cultured on the scaffold and culture plate (as a control) was evaluated using alizarin staining and calcium content, alkaline phosphatase activity and bone related genes expression assays. The results indicated that the surface properties and shape of scaffold pores were effective in the stem cells binding, growth and proliferation. This higher biocompatibility due to the ideal surface hydrophilicity as well as high specific surface area due to the presence of a rough grid surface ultimately increased the efficiency of stem cell's bone differentiation. Taken together, it can be concluded that the decellularized spinach leaf scaffold, due to its easy availability, low prices and high efficiency, can be considered as a promising potential candidate for use as a proper substrate for stem cell growth and differentiation in bone tissue engineering.

Impact of Vermicompost Fertilizer on Spinach Yield and Nutritional Components

Alternative fertilization practices, such the use of vermicompost (VC), have shown great potential to improve both the physical and biological attributes of soils and supplement the nutrient status of soils to improve fertility for vegetable crop production. Modification of soils with coffee vermicompost (CVC) has the potential to improve soil organic content, structure, and microbial activity. Generally, organic fertilizers with slow release nutrient capabilities efficiently use nitrogen and reduce nitrate levels in leafy green vegetables and have been shown to increase ascorbic acid (AA) content. A greenhouse study was conducted over two growing seasons (2011 and 2012) to assess the influence of four CVC rates (0, 25%, 50%, and 75% v/v of soil mix) on Spinacia oleracea growth parameters including fresh leaf weight, leaf area, plant height, leaf number, fresh leaf ascorbic acid (AA) and dry leaf nitrate (DLN). Spinach leaf number and fresh leaf weight increased with CVC rate for both growing seasons and were best described by increasing linear relationships. Surprisingly, spinach AA content remained the same whether DLN content was high or low; and AA and nitrate content were both at highest levels with the 75% v/v CVC treatment in both years. These results indicated that applications of an alternative fertilizer such as CVC can improve spinach yield and that AA content does not always decrease with higher VC application rates, even as nitrate content increases.

Temperature Increase Research of Particles Formed by Ultrasonic Grinding of Spinach Leaves

The researchers chose spinach leaves as the research object for obtaining a natural dye based on chlorophyll because the vegetable is a food raw material rich in this pigment, and biologically active substances source with variety of its functional properties. To solve the problem of more complete chlorophyll extraction from crushed spinach leaves, they are to subject to a preliminary short-term soaking in a water/organic reagent emulsion under ultrasonic influence. Given that the water-based spinach suspension is thermolabile, a man must observe temperature restrictions, since when a certain critical temperature value is exceeded, the chlorophyll decomposition probability with its consumer properties loss is high. As it is practically impossible to determine the temperature inside a fine particle suspended in an aqueous emulsion experimentally, the authors considered to model internal and external heat transfer by solving the differential equation of heat energy transfer under appropriate boundary conditions using the numerical method of finite differences. The research determined structural-mechanical and thermophysical characteristics of crushed spinach leaves experimentally using the complex calculation method of thermophysical parameters based on the thermal inertia properties of a thermocouple. A man verified the solution adequacy by empirically determined suspension temperature after completion of the technological procedure. According to the developed algorithm, the authors compiled a program for the temperature fields evolution in the object of study considering the incident ultrasonic flow and an internal heat source with the new surface formation when grinding spinach particles in order to comply with thermal restrictions and maximize the quality parameters preservation. The article considers the rational duration of the ultrasonic grinding process without exceeding the recommended threshold temperatures.

Evaluation of recycle and reuse of nitric acid from sample digests by sub-boiling distillation

An analytical procedure was developed for recovering HNO3 from sample digests generated after microwave-assisted digestion procedures. Rice and bovine muscle digests were mixed with technical grade HNO3 in different proportions and submitted to distillation using a sub-boiling apparatus. Arsenic, Ca, Cu, Fe, Mg, Mn, Na, P, and Zn were determined before and after distillation of solutions, revealing that the procedure was efficient for removal of most contaminants. It was observed that the percentage of contaminant removal ranged from 98.1 to 99.8% for all evaluated procedures. Two certified reference materials, NIST 8414 (Bovine Muscle) and NIST 1570a (Spinach Leaves), were digested using recovered acid from rice digests by sub-boiling distillation and all analyte recoveries ranged from 73 to 106%. Digests obtained from NIST 8414 were also submitted to the same sub-boiling distillation procedure and As, Al, Ca, Cd, Co, Cu, Fe, Mg, Mn, Na, P, Pb, Se, Sr, V, and Zn were determined. Sub-boiling distillation of sample digests is a promising procedure for adopting green chemistry principles, such as minimizing the quantity of residues generated and recycling of reagents.

Creation of a contractile biomaterial from a decellularized spinach leaf without ECM protein coating: An in vitro study.

Myocardial infarction (MI) results in the death of cardiac tissue, decreases regional contraction, and can lead to heart failure. Tissue engineered cardiac patches containing human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) can restore contractile function. However, cells within thick patches require vasculature for blood flow. Recently, we demonstrated fibronectin coated decellularized leaves provide a suitable scaffold for hiPS-CMs. Yet, the necessity of this additional coating step is unclear. Therefore, we compared hiPS-CM behavior on decellularized leaves coated with collagen IV or fibronectin extracellular matrix (ECM) proteins to noncoated leaves for up to 21 days. Successful coating was verified by immunofluorescence. Similar numbers of hiPS-CMs adhered to coated and noncoated decellularized leaves for 21 days. At Day 14, collagen IV coated leaves contracted more than noncoated leaves (3.25 ± 0.39% vs. 1.54 ± 0.60%; p < .05). However, no differences in contraction were found between coated leaves, coated tissue culture plastic (TCP), noncoated leaves, or noncoated TCP at other time points. No significant differences were observed in hiPS-CM spreading or sarcomere lengths on leaves with or without coating. This study demonstrates that cardiac scaffolds can be created from decellularized leaves without ECM coatings. Noncoated decellularized leaf surfaces facilitate robust cell attachment for an engineered tissue patch.

Sensitivity of spinach seed germination to moisture is driven by oxygen availability and influenced by seed size and pericarp

Uniform seedling emergence is crucial for economically viable spinach (Spinacia oleracea) leaf production. However, non-uniform seed germination occurs due to variation in moisture sensitivity between and within spinach seed lots. To test moisture sensitivity, we developed a floating germination system with fixed distances between germination papers and the water table, so that moisture levels could be standardised. We tested germination performance of different cultivar seed lots, with one seed lot fractioned in different seed sizes, and of seeds with an intact, open or removed pericarp. At a high moisture level, smaller seeds germinated better than larger seeds, and seeds without a pericarp or with an open pericarp germinated better than intact seeds. Further, the pericarp of smaller seeds was thinner than the pericarp of larger seeds. A lower temperature or increased oxygen level resulted in higher germination rates for differently-sized seeds at high moisture levels. In conclusion, the sensitivity of spinach seed germination to moisture is influenced by seed size, hence pericarp thickness and intactness, and is driven by the oxygen availability to the seed embryo. To determine the full germination potential of spinach seed lots, we recommend a standardised low moisture level in addition to a temperature of 15 or 20°C.

Effects of an Eco-Friendly Sanitizing Wash on Spinach Leaf Bacterial Community Structure and Diversity

Ready-to-eat (RTE) spinach is considered a high-risk food, susceptible to colonization by foodborne pathogens; however, other microbial populations present on the vegetable surface may interact with foodborne pathogens by inhibiting/inactivating their growth. In addition, sanitizers applied to minimally processed salad leaves should not disrupt this autochthonous barrier and should be maintained throughout the shelf life of the product. This investigation aimed at comparing the effects of a pH neutral electrochemically activated solution (ECAS), a peroxyacetic acid (PAA)-based commercial sanitizer (Ecolab Tsunami® 100), and tap water wash on the minimally processed spinach leaf microbiome profile for 10 days after washing. The bacterial microbiota composition on spinach samples was assessed by 16S rRNA pyrosequencing and downstream analyses. Predominant phyla observed in decreasing order of abundance were Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes corresponding with the dominant families Micrococcaceae, Clostridiales Family XII, Flavobacteriaceae, Pseudomonadaceae, and Burkholderiaceae. Bacterial species richness and evenness (alpha diversity) and bacterial community composition among all wash types were not significantly different. However, a significant difference was apparent between sampling days, corresponding to a loss of overall heterogeneity over time. Analysis of composition of microbiome (ANCOM) did not identify any amplicon sequence variants (ASVs) or families having significantly different abundance in wash types; however, differences (17 ASVs and five families) were found depending on sampling day. This was the first bacterial microbiome composition study focused on ECAS and PAA-based wash solutions. These wash alternatives do not significantly alter microbial community composition of RTE spinach leaves; however, storage at refrigerated temperature reduces bacterial species heterogeneity.

Spinach leaf and chloroplast lipid: A natural rheology modifier for chocolate?

In this study the possibility of replacing current surfactants in chocolate formulations with natural lipids extracted from spinach leaf (SPLIP) or spinach chloroplast (CH.SPLIP) was evaluated. SPLIP and CH.SPLIP were extracted with chloroform/methanol following enzyme deactivation with hot isopropanol. Results showed a higher extraction yield for SPLIP while glycolipids were more concentrated in CH.SPLIP. Sugar/oil suspensions with dispersed volume fractions of 0.28, 0.33 and 0.37 containing 0.1% to 0.7% (w/w) surfactant (SPLIP, CH.SPLIP, lecithin and PGPR as commercial references) based on oil phase were prepared and analyzed in shear rheology. Apparent viscosity at 40 s−1 was significantly lower for the natural surfactants compared to lecithin at 0.5–0.7% (w/w) addition. With regard to yield stress, taken as the shear stress at 5 s−1, both natural surfactants showed comparable performance to PGPR at 0.3% to 0.7% addition. As SPLIP and CH.SPLIP behaved similar (p > 0.05), SPLIP, due to higher extraction yield, would be the preferred choice for application in chocolate matrices.

Elemental Compositions of Tropical Vegetables and Soils in Edo State, Nigeria Using X-ray Fluorescence Technique

Aim: This research work investigated the bioaccumulation of metals in selected edible vegetables from the soils on which they were grown.&#x0D; Place of Study: Two (2) different study locations were chosen from Etsako-West Local Government Areas of Edo State of the Federal Republic of Nigeria. Etsako-West Local Government Area has an area of 660 km² on Latitude 7.0878ºN and Longitude 6.5010ºE with the headquarters in Auchi.&#x0D; Methodology: Leaves of fluted pumpkin (Telfairia occidentalis), African spinach (Amaranthus hybridus) and water leaf (Talinum triangulare) and soil samples were randomly collected from Water Board and Iyerekhu farms in Etsako-West Local Government Area, Edo State, Nigeria and were analysed for their elemental compositions, using X-ray fluorescence (XRF) technique.&#x0D; Results: In both soil and plant samples, silicon (Si) were most abundant, ranging between 18.85 and 38.91%. The decreasing order of abundance of elements in the plant samples was Si&gt;K&gt;Ca&gt;Al&gt;Cl&gt;S&gt;P&gt;Mg&gt;Fe&gt;Ti&gt;Mn&gt;Zn&gt;Sr&gt;Cr. Toxic heavy metals such as As, Pb, Co, Cd and Cu were not detected in both soil and vegetable samples. The concentrations of the elements in the samples were higher than the permissible limits of WHO/FAO and EU for soils and plants, except Zn in the soil samples and Talinum triangulare from Iyerekhu farm. The peak transfer factor, 238.43 was obtained for K in Talinum triangulare from Iyerekhu farm while the least is 0.00 for Zn in all the plant samples. The overall mean ability of plant to absorb elements from the soil was most with Talinum triangulare, followed by Amaranthus hybridus.&#x0D; Conclusion: The vegetables studied had high tendency to bioaccumulate the bioavailable metals in soils. However, all the vegetables studied, especially T. triangulare could be used in phytoremediation of polluted soils.

Green spinach leather as a Fe source to increase nutritional intake

The basic health research data which has been released in 2013 shows that the anemia incidence number is still high, 21.7%. This is caused by the lack of micronutrition (fiber, folic acid, vitamin A or B12) as the result of the lack of green vegetable consumption. This research aims to reform the green spinach (Amaranthus spp.) into green spinach leather in a form of vegetable leather, to increase the perception of the vegetable reception and minimized the lost Fe content during processing to increase nutritional intake. This research uses experimental research design with the formulation of 85% green spinach leaf and 15% agar-agar as the binder. The Fe content measurement was conducted using Absorption Spectrometer (AAS). The measurement of the green spinach vegetable leather product sensory acceptance is conducted using rating hedonic test. The sensory test result from 53 panelists states that the vegetable leather has a significantly better perception compared with the original spinach for the flavor attribute, aroma, and texture. The Fe content test results in the Vegetable Leather product is 3.3 mg/100 g. This result still has enough Fe content as the daily intake.

Biochar counteracts nitrification inhibitor DMPP-mediated negative effect on spinach (Spinacia oleracea L.) growth.

The use of nitrification inhibitors (NIs) such as 3,4-dimethylpyrazole phosphate (DMPP) has been suggested to diminish agricultural soil nitrate (NO3-) loss and increase nitrogen (N) use efficiency (NUE). However, the yield of ammonium (NH4+)-sensitive plants such as spinach (Spinacia oleracea L.) may be adversely affected by the application of NIs at high N levels and, on the other hand, the efficiency of the NIs may also be affected by soil amendments such as biochar. These two issues are still not adequately addressed. The aim of this study was to evaluate the effect of different N levels including DMPP or not in a calcareous soil with and without amendment of wheat straw biochar on spinach yield, NUE, nitrate concentration of spinach leaf, activity of enzymes nitrate reductase (NR) and nitrite reductase (NiR), and soil ammonium (NH4+) and NO3- concentration under greenhouse conditions. This experiment was carried out with different N rates factor at seven levels (un-fertilized, N0; fertilized with 50mgN kg-1 soil, N50; fertilized with 75mgN kg-1 soil, N75; fertilized with 100mgN kg-1 soil, N100; fertilized with N50+DMPP; fertilized with N75+DMPP; and fertilized with N100+DMPP) and biochar (BC) factor at two levels (0, 0%BC; and 2% (w/w), 2%BC) with six replications over a 56-day cultivation period of spinach. Results showed that the application of DMPP had no significant effect on the yield of spinach plant at low and medium levels of N (50 and 75mgN kg-1 soil), but decreased the yield of this plant at the higher level of N (100mgN kg-1 soil). However, application of BC decreased the negative effect of DMPP on spinach yield as the yield in spinach plants fertilized with N75+DMPP and N100+DMPP significantly increased. Both application of DMPP and addition of BC to soil decreased leaf NO3- concentration by 29.2% and 16.3% compared to control, respectively. Biochar compared to control decreased NR activity by 46.3%. With increasing N rate, NR and NiR activities increased, but DMPP decreased the activities of both enzymes. Biochar reduced the efficiency of DMPP as soil NH4+ concentration was higher in the treatments containing DMPP without BC at 56 days after planting. Biochar and DMPP could increase the quality of spinach plant through decreasing the leaf NO3- concentration. In general, wheat straw biochar counteracted DMPP-mediated negative effect on growth of spinach plant at high level of N by decreasing the efficiency of this inhibitor. These results provide the useful information for managing the application rate of N fertilizers including DMPP in biochar-amended soil.

Rapid organic solvent extraction coupled with surface enhanced Raman spectroscopic mapping for ultrasensitive quantification of foliarly applied silver nanoparticles in plant leaves

An organic solvent-based extraction approach coupled with surface enhanced Raman spectroscopic mapping technique to quantify silver nanoparticles in spinach leaf.