Increase In Nitrate Reductase Activity Research Articles

Investigating the association between nitrate dosing and nitrite generation by the human oral microbiota in continuous culture.

The generation of nitrite by the oral microbiota is believed to contribute to healthy cardiovascular function, with oral nitrate reduction to nitrite associated with systemic blood pressure regulation. There is the potential to manipulate the composition or activities of the oral microbiota to a higher nitrate-reducing state through nitrate supplementation. The current study examined microbial community composition and enzymatic responses to nitrate supplementation in sessile oral microbiota grown in continuous culture. Nitrate reductase (NaR) activity and nitrite concentrations were not significantly different to tongue-derived inocula in model biofilms. These were generally dominated by Streptococcus spp., initially, and a single nitrate supplementation resulted in the increased relative abundance of the nitrate-reducing genera Veillonella, Neisseria, and Proteus spp. Nitrite concentrations increased concomitantly and continued to increase throughout oral microbiota development. Continuous nitrate supplementation, over a 7-day period, was similarly associated with an elevated abundance of nitrate-reducing taxa and increased nitrite concentration in the perfusate. In experiments in which the models were established in continuous low or high nitrate environments, there was an initial elevation in nitrate reductase, and nitrite concentrations reached a relatively constant concentration over time similar to the acute nitrate challenge with a similar expansion of Veillonella and Neisseria. In summary, we have investigated nitrate metabolism in continuous culture oral biofilms, showing that nitrate addition increases nitrate reductase activity and nitrite concentrations in oral microbiota with the expansion of putatively NaR-producing taxa.IMPORTANCEClinical evidence suggests that blood pressure regulation can be promoted by nitrite generated through the reduction of supplemental dietary nitrate by the oral microbiota. We have utilized oral microbiota models to investigate the mechanisms responsible, demonstrating that nitrate addition increases nitrate reductase activity and nitrite concentrations in oral microbiota with the expansion of nitrate-reducing taxa.

Contribuição do QuitoMax® no metabolismo hormonal e enzimático em tomate sob estresse salino

ABSTRACT Salinity stress severely restricts plant nutrition and hinders biochemical and physiological processes crucial for growth. In several crop systems bioactive products which confer growth promotion, are applied as a sustainable alternative for contributing to food security. The aim of this work was to evaluate the biochemical contribution of QuitoMax® to hormonal and enzymatic metabolism in tomato under saline stress. Three treatments were applied: saline without QuitoMax®, nonsaline + QuitoMax® and saline + QuitoMax®. A tolerant (Amalia) and a susceptible (Claudia) tomato variety were used as experimental models. The normalized difference vegetation index (NDVI) was measured as a morphological variable, and peroxidase (POD), glutamine synthetase (GS) and nitrate reductase (NR) enzyme activities were determined. Gibberellic (GA) and abscisic acid (ABA) concentrations were also determined. Due to the effects of QuitoMax®, the plants maintained high NDVI values even under saline conditions. A decrease in POD and GS activity and an increase in NR activity were also found. The GA concentration in the leaves was higher in the tolerant variety when QuitoMax® was applied than in the saline treatment but lower in the susceptible variety. The opposite behavior was found when the ABA concentration was quantified. This study demonstrates the protective action of QuitoMax® under salinity stress on tomato crops in both tolerant and susceptible varieties. In crux, QuitoMax® can be opted as a shotgun approach to tackle salinity in tomato.

Discovery of Benzothiazolylpyrazole-4-Carboxamides as Potent Succinate Dehydrogenase Inhibitors through Active Fragment Exchange and Link Approach.

Succinate dehydrogenase (SDH) is an attractive target for developing green fungicides to manage agricultural pathogens in modern agriculture research. Herein, in this work, we report the discovery of benzothiazolylpyrazole-4-carboxamides I-III as potent SDH inhibitors using active fragment exchange and link approach. The results of the fungicidal activity assays showed that some of the synthesized compounds exhibited excellent inhibition against the tested fungi. Systematic structure-activity relationship studies led to the discovery of compound Ip, N-(1-((4,6-difluorobenzo[d]thiazol-2-yl)thio)propan-2-yl)-3-(difluoromethyl)-N-methoxy-1-methyl-1H-pyrazole-4-carboxamide, which showed higher fungicidal activity against Fusarium graminearum Schw (EC50 = 0.93 μg/mL) than the commercial fungicides thifluzamide (EC50 > 50 μg/mL) and boscalid (EC50 > 50 μg/mL). The molecular simulation studies suggested that hydrophobic interactions were the primary driving forces between ligands and SDH. Promisingly, we found that Ip could stimulate the growth of wheat seedlings and Arabidopsis thaliana and increase the biomass of the treated plants. Preliminary studies on the plant growth promoter mechanism of Ip indicated that it could increase nitrate reductase activity in planta, that, in turn, stimulates the growth of plants.

Photosynthetic Rate and Root Growth Responses to Ascophyllum nodosum Extract–based Biostimulant in Creeping Bentgrass under Heat and Drought Stress

Creeping bentgrass (Agrostis stolonifera) experiences quality decline during summer in the United States transition zone and warmer regions. Various bioproducts have been used to improve creeping bentgrass performance and to mitigate effects of summer stress in the United States transition zone. This 2-year study was carried out to examine if foliar application of seaweed extract (SWE; Ascophyllum nodosum)-based biostimulant Utilize® could enhance creeping bentgrass nitrate reductase (NaR) activity, and root viability under heat and drought stress conditions. The Utilize® was sprayed biweekly on creeping bentgrass foliage at 0, 29, 58, 87, and 116 µL⋅m−2, with application volume of 815 L⋅ha−2. Two weeks after first application, plants were exposed to heat (35/25 °C, day/night) and drought stress (40% to 50% evapotranspiration replacement) conditions for 42 days in an environment-controlled growth chamber. In general, the abiotic stress caused turf quality reduction. Foliar application of Utilize® at 58, 87, and 116 µL⋅m−2 increased turf quality, leaf color ratings, leaf chlorophyll, carotenoid content, and net photosynthetic rate (Pn). Utilize® at 58, 87, and 116 µL⋅m−2 increased NaR activity by 26.5%, 16.3%, and 16.3%, respectively, when compared with the control. Utilize® at 58, 87, and 116 µL⋅m−2 increased root biomass, root length, surface area (SA), and root volume when compared with the control. Utilize® at 58 and 87 µL⋅m−2 improved root viability by 16.3% and 30.9%, respectively, when compared with the control. Our data indicate that the SWE-based biostimulant Utilize® improves nitrogen (N) metabolism and root viability. Utilize® treatment at 58 µL⋅m−2 biweekly can be considered an effective approach for improving creeping bentgrass performance during summer stress.

Pengukuran Aktivitas Nitrat Reduktase (ANR) Pada Tanaman Poaceae Secara In vivo

Corn, rice, and sugarcane are included in the Poaceae family which have high economic value as staple foods. Nitrate reductase plays a role in reducing nitrate to ammonia. The nitrate reductase activity testing can help biotechnology studies, in this case, fertilizer production or organic waste treatment, because the nitrate reductase enzyme can be used to convert nitrate into more useful nitrogen compounds. The purpose of this study was to analyze the activity of nitrate reductase (ANR) from the leaves of the Poaceae family, namely corn, rice, and sugarcane. In vivo ANR measurements were carried out using the spectrophotometric method with two types of spectrophotometers, namely the Vis/UV Spectrophotometer, Genesys10UV, and Visible Spectrophotometer, with a wavelength of 540 nm. This study concludes that rice had the highest ANR of 0.1503 µmol/gram leaf weight/hour of incubation. The increase in nitrate reductase activity indicates that the energy for nitrate reduction also increases and provides a large capacity for synthesizing amino acids, proteins, or total N assimilation.

Enhancing Rice Yield and Nitrogen Utilization Efficiency through Optimal Planting Density and Reduced Nitrogen Rates

Rice yields can only be achieved by selecting a high-quality population. Nitrogen rates and transplanting density play a significant role in determining population quality and yield. Field experiments were conducted in Heshan District, Hunan Province, China, to explore suitable nitrogen rates and appropriate transplanting densities for rice production in 2021 and 2022. In this study, three levels of nitrogen, e.g., N1, N2, and N3 (0, 150, and 210) kg ha−1, and three transplanting densities, e.g., B1, B2, and B3 (1, 2, and 3) seedlings per hill were used to study their individual or combined effects on rice (Taiyou 390) population quality, yield, and yield components, nitrogen-related enzyme activities, and nitrogen absorption and utilization efficiency. The results showed that N2B3 had the highest yield, with an average yield of 9.30 t ha−1 in two years, which was 3.7~49.6% higher than other treatments. This increase was attributed to higher dry matter accumulation (1538.22 g m−2) and effective panicle number (435.2 × 104 ha−1), influenced by increased nitrate reductase activity at the booting stage and glutamine synthase at the heading stage, along with maintenance of higher SPAD value and leaf area index. Nitrogen rates and transplanting densities significantly affected nitrogen use efficiency, with the contribution rate of nitrogen fertilizer to yield decreasing as nitrogen rates increased. However, N2B3 improved nitrogen use efficiency and stabilized rice yield by reducing nitrogen fertilizer application. This study suggested that N2B3 treatment could enhance rice yield by improving plant nitrogen use efficiency under low nitrogen supplementation.

Enhancing simultaneous nitrate and phosphate removal in sulfur‑iron (II) autotrophic denitrification biofilters by endogenous magnetic fields: Performance and mechanism

The sulfur‑iron (II) autotrophic denitrification (SIAD) technology can achieve simultaneous nitrogen and phosphorus removal from wastewater with a low C/N ratio without an organic carbon source. However, the low nutrient removal load limits its large-scale application. To enhance N removal load and decrease the effluent SO42− concentration, we propose a novel bioaugmentation technology by adding magnetite to a sulfur‑iron (II) biofilter to generate an endogenous magnetic field (EMF). The treatment characteristics of two biofilters with sulfur‑iron (II) (S1) and sulfur‑iron (II)-magnetite (S2) were comparatively studied in long-term experiments. The maximum nitrate removal load of the S2 system was 1.02 ± 0.04 kg N/(m3·d), 1.27 times higher than that of S1. The S2 system also showed a 40 % higher PO43− removal efficiency compared to S1. The production of SO42− was reduced by >12.34 % in S2 with 5.40 g SO42−/g N. The EMF significantly increased nitrate reductase activity by 3.50 times and enhanced the size of the attached microbial bacterial population by 30 %–50 %. Functional gene prediction indicated that amino acid metabolism, cell activity, N/S metabolism were improved under the EMF, and the genera Ferritrophicum and Thiobacillus were the predominant autotrophic bacteria, forming a symbiotic relationship. Our study demonstrates a novel solution to resolve the limits of high sulfate byproduct and low nutrient removal load in SIAD biofilters, which could promote large-scale application of SIAD process as a highly efficient and low-cost postdenitrification process.

Multi-walled carbon nanotubes promote the accumulation, distribution, and assimilation of 15N-KNO3 in Malus hupehensis by entering the roots.

Multi-walled nanotubes(MWCNTs)consistofmultiplerolled layersofgraphene. Nitrogen plays an important role in apple growth. The effect of MWCNTs on nitrogen utilization in apple needs to be further investigated. In this study, the woody plant Malus hupehensis seedlings were used as plant materials, the distribution of MWCNTs in the roots was observed, and the effects of MWCNTs on the accumulation, distribution, and assimilation of nitrate by the seedlings were explored. The results showed that MWCNTs could penetrate the roots of Malus hupehensis seedlings, and the 50, 100, and 200 µg·mL-1 MWCNTs significantly promoted the root growth of seedlings, increased root number, root activity, fresh weight, and nitrate content of seedlings, and also increased nitrate reductase activity, free amino acid, and soluble protein content of roots and leaves. 15N tracer experiments indicated that MWCNTs decreased the distribution ratio of 15N-KNO3 in Malus hupehensis roots but increased its distribution ratio in stems and leaves. MWCNTs improved the utilization ratio of 15N-KNO3 in Malus hupehensis seedlings, with the values being increased by 16.19%, 53.04%, and 86.44% following the 50, 100, and 200 µg·mL-1 MWCNTs, respectively. The RT-qPCR analysis showed that MWCNTs significantly affected the expression of genes (MhNRTs) related to nitrate uptake and transport in roots and leaves, and MhNRT1.4, MhNRT1.7, MhNRT1.8, MhNRT2.1, MhNRT2.5, and MhNRT2.7 were notably up-regulated in response to 200 µg·mL-1 MWCNTs. Raman analysis and transmission electron microscopy images indicated that MWCNTs could enter the root tissue of Malus hupehensis and were distributed between the cell wall and cytoplasmic membrane. Pearson correlation analysis showed that root tip number, root fractal dimension, and root activity were the main factors affecting root uptake and assimilation of nitrate. These findings suggest that MWCNTs promoted root growth by entering the root, stimulated the expression of MhNRTs, and increased NR activity, thereby enhancing the uptake, distribution, and assimilation of nitrate by root, and ultimately improved the utilization of 15N-KNO3 by Malus hupehensis seedlings.

Aktivitas Nitrat Reduktase (ANR) Tanaman Jagung pada Pola Tumpangsari yang Diberi Serasah Jagung-Kedelai serta Biochar di Lahan Suboptimal Sidondo Sulawesi Tengah

The aim of the study was to examine the relationship between nitrate reductase activity and N uptake, tissue N content, N uptake, and chlorophyll content of corn plants in intercropping patterns which are given corn-soybean litter and biochar. The use of plant litter and biochar derived from crop residues as a source of organic matter in different intercropping patterns affected nitrate reductase activity, tissue N content, N uptake, and chlorophyll content of maize. This experiment was carried out on sub-optimal Sidondo land, Central Sulawesi with the main limiting factors being the availability of water and alkaline soil pH (7.21) which were arranged in a divided plot design with five litter treatments as subplots and five cropping patterns as the main plot with three replicates. Parameters observed were N levels, plant tissue N uptake, chlorophyll, and nitrate reductase activity. Collected data were analyzed using Anova and Duncan's multiple random tests. The results showed that corn litter, soybean mixed corn + soybean litter and their biochar in different intercropping patterns affected nitrate reductase activity, nitrogen uptake, chlorophyll levels very significantly (P˂0.01), increased nitrate reductase activity by 9710.86 mol NO2- -1g-1hour-1 at the age of 55 DAP, while N uptake (2237 mg.kg-1), tissue N content (4.33%), and total chlorophyll content (10.61 mg.l-1) were the highest in the litter treatment, corn and soybeans as well as biochar in corn and soybean intercropping (1:2), and (2:4). Thus, the provision of corn and soybean litter and biochar in intercropping systems can increase nitrate reductase activity, N uptake, tissue N levels, and corn chlorophyll levels in the corn-soybean intercropping system.
 
 Keywords: chlorophyll, N content of corn plant tissue, nitrate reductase activity, N uptake

Effects of different peanut-cotton intercropping modes on physiological characteristics and yield of peanut in late growth stage

Using peanut cultivar Huayu 25 and cotton cultivar Liaomian 19 as experimental material, we examined the effects of different intercropping patterns on physiological characteristics of peanut in later growth stage, yield and economic benefit, based on an experiment with five treatments, including intercropping modes of 4 rows peanut and 4 rows cotton (H4M4), 6 rows peanut and 4 rows cotton (H6M4), 4 rows peanut and 4 rows cotton (H4M2), sole peanut (DH) and sole cotton (DM). The results showed that intercropping mode increased the length of main stem and branches of peanut, but decreased green leaves number of main steam, leaf area index, and total dry matter accumulation. Among the intercropping modes, chlorophyll content, chlorophyll fluorescence parameters, root vigor, nitrate reductase activity under H6M4 and H4M2 were significantly higher than that under H4M4, as well as higher superoxide dismutase, peroxidase, catalase activity and decreased malondialdehyde content. Intercropping significantly reduced peanut and cotton yields, but enhanced the gross economic output value. The yield reduction of H6M4 was the lowest and the economic output was the highest among all the intercropping modes. In addition, the land equivalent ratio of H6M4 was greater than 1, indicating the obvious advantage of intercropping. Our results indicated that appropriate reduction of the ratio of cotton under the peanut-cotton intercropping systems could strengthen root vigor and increased nitrate reductase activity, promote nutrient absorption capacity, reduce senescence, and increase the economic output.

Selenium increases photosynthetic capacity, daidzein biosynthesis, nodulation and yield of peanuts plants (Arachis hypogaea L.)

This study aimed to investigate the roles of selenium (Se) application on the profile of photosynthetic pigments, oxidant metabolism, flavonoids biosynthesis, nodulation, and its relation to agronomic traits of peanut plants. Two independent experiments were carried out: one conducted in soil and the other in a nutrient solution. When the plants reached the V2 growth stage, five Se doses (0, 7.5, 15, 30, and 45 μg kg−1) and four Se concentrations (0, 5, 10, and 15 μmol L−1) were supplied as sodium selenate. The concentration of photosynthetic pigments, activity of antioxidant enzymes and the concentration of total sugars in peanut leaves increased in response to Se fertilization. In addition, Se improves nitrogen assimilation efficiency by increasing nitrate reductase activity which results in a higher concentration of ureides, amino acids and proteins. Se increases the synthesis of daidzein and genistein in the root, resulting in a greater number of nodules and concentration and transport of ureides to the leaves. Se-treated plants showed greater growth, biomass accumulation in shoots and roots, yield and Se concentration in leaves and grains. Our results contribute to food security and also to increase knowledge about the effects of Se on physiology, biochemistry and biological nitrogen fixation in legume plants.

Soil Conditioner Affects Tobacco Rhizosphere Soil Microecology.

Reasonable fertilization management can increase nutrient content and enzyme activity in rhizosphere soil, and even increase soil microbial richness. However, different fertilizers could raise distinct influences on the soil properties, including soil environmental factors (physicochemical properties and enzymatic activities) and microbial community. Here, the effects of two soil amendments (microbial fertilizer and woody peat) on environmental factors and microbial community structure in tobacco rhizosphere soil were evaluated, with the correlations between microbes and environmental factors explored. As the results, microbial fertilizer could effectively alleviate soil acidification, increase available potassium and organic matter contents in soil, and was also beneficial to increase nitrate reductase activity in rhizosphere soil. Fertilizers cause changes in the abundance of certain microbes in the soil. Besides, it was shown that the candidate phyla Gal15, Acidobacterota, Latescibacterota, Mortierellommycota, Basidiomycota, and Rozellomycota in tobacco rhizosphere soil had significant correlation with soil environmental factors. Through the functional analysis of these populations, it can be deduced that the changes in the abundance of certain microorganisms may be an important reason for the differences in environmental factors. All these indicated that the differences of environmental factors in different treatments are closely related to the abundance of some special soil microorganisms. Studying the life activities of these microbes would provide good guidance for exploring the interaction among crops, soil, and microorganisms and improving crop yields.

Enhancement of denitrification in biofilters by immobilized biochar under low-temperature stress

Efficient removal of nitrate under low temperature is challenging because of the reduction of the microbial activity. This study successfully explored the promotion on the performance of denitrification utilizing the immobilized biochar in biofilters under low temperature (6 ± 2 °C). The results showed that the immobilized biochar increased the denitrification rate by 76.8% and decreased the nitrous oxide emissions by 82.5%. Mechanistic studies revealed that the immobilized biochar increased the activities of the denitrifying enzymes and three enzymes involved in glycolysis. Furthermore, the immobilized biochar elevated the activity of the electron transport system by 31.8%. Finally, structural equation model explained that the increase of nitrate reductase activity was a crucial factor to enhance the total nitrogen removal efficiency in biofilters with immobilized biochar. Overall, the use of immobilized biochar can be a novel strategy to enhance nitrogen removal and reduce greenhouse gas emissions in biofilters under low temperature.

Actinonin resistance of pathogenic Vibrio anguillarum in aquaculture

Drug-resistant bacteria are an increasingly serious threat to the aquaculture industry. In order to develop new methods to combat these bacteria, it is necessary to first understand their mechanisms of drug resistance. We previously isolated a potential probiotic strain, Streptomyces sp. NHF165, which produced cytotoxic actinonin against the aquaculture pathogen Vibrio anguillarum. In this study, a spontaneous V. anguillarum mutant with an eight-fold increased MIC for actinonin was characterized for elucidation of actinonin resistance mechanisms. Transcriptomic analysis revealed significant up-regulation of genes related to anaerobic respiratory (nap and tor) and down-regulation of genes involved in anaerobic respiration (nqr, sdh and frd) in mutant strains. Meanwhile, no mutations in bacterial respiration genes or translation initiation genes (the proposed actinonin targeted pathway) were detected by whole genome resequencing analysis. A series of experiments confirmed that actinonin-resistance in the mutant strain was associated with respiration. When aerobic respiration was chemically disrupted by CCCP, the growth of wild-type V. anguillarum changed significantly, with a 11.74-fold increase in cell density under actinonin treatment. For anaerobic respiration, an increased nitrate reductase activity was detected in mutant cells by addition of an exogenous electron donor. Noteworthy was the finding that nitrate inhibited the growth of the wild-type strain but promoted the growth of the mutant. Futhermore, the product of nitrate-dependent anaerobic respiration, nitrite, did not arrest the growth of mutant V. anguillarum, which was contrary to previous reports and might exacerbate the formation of vibriosis. Finally, we showed that chemical inhibition of nitrate reductase could restore the susceptibility of mutant V. anguillarum to actinonin. Together these data demonstrate that the combined use of an anaerobic-respiratory inhibitor and an antibiotic might be a promising approach for the treatment of drug-resistant bacteria in aquaculture.

Growth response nitrogen metabolism of grafted cucumber fertilized with different ratios of nitrate: ammonium fertilizer

The use of an endemic plant as rootstock has many merits but its application for cucurbits production has not been extensively investigated. The present study determined the growth responses of grafted cucumber using two endemic rootstocks from Cucurbita pepo L. fertilized with different ratios of nitrate (NO3-): ammonium (NH4+) fertilizer. A greenhouse study was carried out using cucumber (C. sativus ‘Dominos’) grafted on two accessions of Cucurbita pepo L. collected from Babol and Isfahan with the control being ungrafted C. sativus ‘Dominos’. Different ratios of NO3-/NH4+ as follows: 100:0 (NO3− alone), 25/75, 50/50, 75/25 and 0/100 (NH4+ alone) were applied. It was found that different rootstock has the same physiology but different growth attributes. The growth of the ungrafted cucumber was lower than the grafted ones, and Babol showed better or equal growth compared to the Isfahan rootstock. The NO3-/NH4+ effect on growth of the cucumber shoot and root fresh and dry weights, root and shoot lengths, nodes, and number of leaves were increased in the 75/25 ratio compared to the other treatments. Grafting on the Isfahan and Babol showed the same effect of N metabolism i.e., grafting increased nitrate reductase activity and NO3- concentration in the 75/25 and the 100/0. Protein content and amino acids content of leaves increased in the grafted cucumber treated with 50/50 NO3-/NH4+. The same response of photosynthesis parameters was observed in the different rootstocks. In conclusion, the result suggested that the grafted ‘Dominos’ on Babol endemic rootstock at 50/50 NO3-/NH4+ ratio gave the high growth.

Temperature and GA3 on ROS and cytogenetic stability during in vitro cultivation of strelitzia zygotic embryos

ABSTRACT Tropical species may require higher temperatures as well as higher growth regulator concentrations for in vitro development. Since these conditions may affect plant metabolism, the objective of this study was to identify how different temperatures and gibberellin concentrations may affect the in vitro development of strelitzia embryos, analyzing the effect on ROS and cytogenetic stability. Zygotic embryos were cultivated on MS medium supplemented with 5, 10 and 20 µM GA3 under temperatures of 25 °C, 30/25 °C and 30 °C. After 60 days, higher embryonic germination rate (72%) and shoot length of plantlets (3.14 cm) were observed on medium containing 20 µM gibberellic acid (GA3). At this concentration, there was an increase in nitrate reductase activity with no change in the cytogenetic stability. The temperature influenced only shoot and root lengths, which were highest at 25 °C. At 30 °C, superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities increased compared with those at 25 °C. Thus, the addition of 20 µM GA3 to the culture medium and a temperature of 25 °C in the growth room should be used for zygotic embryo culture of strelitzia.

Differential modulation of S-nitrosoglutathione reductase and reactive nitrogen species in wild and cultivated tomato genotypes during development and powdery mildew infection

Nitric oxide plays an important role in the pathogenesis of Pseudoidium neolycopersici, the causative agent of tomato powdery mildew. S-nitrosoglutathione reductase, the key enzyme of S-nitrosothiol homeostasis, was investigated during plant development and following infection in three genotypes of Solanum spp. differing in their resistance to P. neolycopersici. Levels and localization of reactive nitrogen species (RNS) including NO, S-nitrosoglutathione (GSNO) and peroxynitrite were studied together with protein nitration and the activity of nitrate reductase (NR). GSNOR expression profiles and enzyme activities were modulated during plant development and important differences among Solanum spp. genotypes were observed, accompanied by modulation of NO, GSNO, peroxynitrite and nitrated proteins levels. GSNOR was down-regulated in infected plants, with exception of resistant S. habrochaites early after inoculation. Modulations of GSNOR activities in response to pathogen infection were found also on the systemic level in leaves above and below the inoculation site. Infection strongly increased NR activity and gene expression in resistant S. habrochaites in contrast to susceptible S. lycopersicum. Obtained data confirm the key role of GSNOR and modulations of RNS during plant development under normal conditions and point to their involvement in molecular mechanisms of tomato responses to biotrophic pathogens on local and systemic levels.

Functional Interaction of ROS and Nitric Oxide during Induction of Heat Resistance of Wheat Seedlings by Hydrogen Sulfide Donor

The participation of reactive oxygen species (ROS) and nitric oxide (NO), and also enzymatic systems generating them, in the development of heat resistance of wheat (Triticumaestivum L.) seedlings, induced by the hydrogen sulfide (H2S) donor sodium hydrosulfide (NaHS), has been studied. It was found that 24-h pretreatment of seedlings with 0.1–1 mM NaHS increased their survival after the subsequent 10-min damaging heating at 45°C. The content of hydrogen peroxide and nitric oxide increased together with the nitrate reductase (NR) activity in the seedling roots within the first 4 h of their treatment with the H2S donor. The rise in the NO level significantly suppressed by the inhibitor of NR sodium tungstate but not the inhibitor of NO synthase (NG-nitro-L-arginine methyl ester, L-NAME). The hydrogen peroxide scavenger dimethylthiourea (DMTU) and the NADPH oxidase inhibitor imidazole abolished the increase in NR activity and NO content in the roots. However, the nitric oxide scavenger (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, PTIO) and the inhibitors of the NO-producing enzymes only weakly influenced the increase in H2O2 content caused by the root treatment with sodium hydrosulfide. The NaHS-induced rise in the seedling heat resistance was eliminated by both ROS antagonists (DMTU and imidazole) and NO antagonists (PTIO and tungstate). It is concluded that the boost in the wheat seedling heat resistance, which is caused by exogenous hydrogen sulfide, is mediated by the increased ROS generation, followed by NR activation, and resultant rise in the level of nitric oxide produced by this enzyme.

Red Light Is Effective in Reducing Nitrate Concentration in Rocket by Increasing Nitrate Reductase Activity, and Contributes to Increased Total Glucosinolates Content.

Rocket cultivation is increasing to supply the expanding ready-to-eat market because of its unique taste, but crops are often over fertilized to avoid nitrogen deficiencies. This leads to nitrate accumulation in leaves, and the products of their degradation (nitrites and nitrosamines) have been related to several health problems. Nitrate concentrations in rocket and other leafy vegetables are subject to limits by the EU legislation, yet rocket holds a great nutritional value. Degradation products of glucosinolates (isothiocyanates) have been consistently linked with benefits to human health. We investigated the influence of nitrogen application (1 and 8 mM), species [Eruca sativa (L.) Cav. and Diplotaxis tenuifolia (L.) DC.] and light spectrum (full spectrum, red, blue and red + blue) on the nitrate concentration, nitrate reductase activity and glucosinolate content of rocket grown in a soil-less system. Red light decreased the nitrate concentration with respect to the blue spectrum (4,270 vs. 7,100 mg⋅kg–1 of fresh weight, respectively), but such reduction was influenced by the species and the nitrogen level (significantly higher in D. tenuifolia and with the higher concentration of N). The nitrate reductase activity increased under red light in D. tenuifolia, with the lower N concentration. Rocket is known to contain several health-promoting compounds mainly antioxidants and glucosinolates, as secondary metabolites that act as part of plant defense mechanisms. The total content of glucosinolates was mainly affected by the species (D. tenuifolia showed the highest concentrations). Our results will help growers to tailor light spectra with the aim of reducing nitrate concentration and to remain within EU legislative limits, without any detrimental influence on other qualitative parameters in rocket.

Biochemical Response of Hybrid Maize (Zea mays L.) to NPK Fertilization Based on Spent Bleaching Earth in Field Scale

Indonesia is one of the largest crude palm oil (CPO) producing countries in the world. To improve oil quality, CPO purification is carried out including bleaching earth. The process produced spent bleaching earth (SBE) and deoiled spent bleaching earth (DSBE) classified as hazardous and toxic materials waste. SBE and DSBE have the potential as an adhesive material in the manufacture of NPK fertilizers. This study aimed to compare the effects of SBE and DSBE on replacing clay minerals in terms of biochemical response. The study was arranged in randomized completly block design with three treatments and blocks. The treatment consisted of NPK fertilizer containing 10% brown clay (control), NPK fertilizer containing 5% pure clay minerals + 5% SBE, and NPK fertilizer containing 5% pure clay minerals + 5% DSBE. Data were analyzed using ANOVA and tested using LSD test at a 95% confidence level. The results showed that NPK containing DSBE was able to increase nitrate reductase activity (NRA) (41.9%), chlorophyll b content (4.7%), glycine betaine (GB) (2.5%), decreasing electrolite leakage (19%), malondialdehyde (MDA) (23%) compared NPK containing brown clay. Thus the use of NPK containing DSBE and NPK containing SBE to be able to replace NPK containing brown clay.