Maximum Nitrate Reductase Activity Research Articles

Growth, Physiology and Nutritional Quality of C4 Halophyte Portulaca oleracea L. Grown Aeroponically in Different Percentages of Artificial Seawater under Different Light-Emitting Diode Spectral Qualities.

Edible halophyte Portulaca oleracea L., known as purslane, was grown in two percentages of artificial seawater (ASW) under two combined red (R) and blue (B) LED spectra. High salinity (40% ASW) negatively affected shoot productivity and leaf growth of purslane compared to those grown in 10% ASW. Photosynthetic pigment and total reduced nitrogen concentrations were significantly higher in purslane grown in 10% ASW than in 40% ASW. However, LED spectral quality did not markedly influence these parameters. Grown in 10% ASW under R/B 2.2, purslane had the highest maximum nitrate reductase activity, while those in 40% ASW under R/B 2.2 had the highest activation state. Under both light qualities, purslane had a sevenfold increase in proline concentration in 40% ASW than in 10% ASW. Total phenolic compounds' concentration was the highest in 10% ASW under R/B 0.9, while there were no significant differences in the accumulation of total soluble sugars and ascorbic acids among all plants. Antioxidant enzymes activities were lower in 40% ASW under R/B 2.2 compared to the other conditions. In conclusion, salinity affected the yield, physiology and nutritional quality of purslane. The impacts of LED spectral quality on purslane were only reflected by certain physiological and nutritional parameters.

Productivity, photosynthetic light-use efficiency, nitrogen metabolism and nutritional quality of C4 halophyte Portulaca oleracea L. grown indoors under different light intensities and durations.

Portulaca oleracea L. (known as purslane), is a nutritious facultative C4 halophyte. Recently, it has been successfully grown indoors under LED lightings by our team. However, basic understanding about the impacts of light on purslanes are lacking. This study aimed to investigate the effects of light intensity and duration on productivity, photosynthetic light use efficiency, nitrogen metabolism and nutritional quality of indoor grown purslanes. All plants were grown in 10% artificial seawater hydroponically under different photosynthetic photon flux densities (PPFDs) and durations and thus different daily light integrals (DLI). They are, L1 (240 µmol photon m-2 s-1, 12h, DLI = 10.368mol m-2 day-1); L2 (320 µmol photon m-2 s-1, 18h, DLI = 20.736mol m-2 day-1); L3 (240 µmol photon m-2 s-1, 24h, DLI = 20.736mol m-2 day-1); L4 (480 µmol photon m-2 s-1, 12h, DLI = 20.736mol m-2 day-1), respectively. Compared to L1, higher DLI promoted root and shoot growth and thus increased shoot productivity by 2.63-,1.96-, 3.83-folds, respectively for purslane grown under L2, L3, L4. However, under the same DLI, L3 plants (continuous light, CL) had significantly lower shoot and root productivities compared those with higher PPFDs but shorter durations (L2 and L4). While all plants had similar total chlorophyll and carotenoid concentrations, CL (L3) plants had significantly lower light use efficiency (Fv/Fm ratio), electron transport rate, effective quantum yield of PSII, photochemical- and non-photochemical quenching. Compared to L1, higher DLI with higher PPFDs (L2 and L4) increased leaf maximum nitrate reductase activity while longer durations increased leaf concentrations and total reduced nitrogen. There were no significant differences in leaf total soluble protein, total soluble sugar and total ascorbic acid concentrations in both leaf and stem regardless of light conditions. However, L2 plants had the highest leaf proline concentration but leaf total phenolic compounds concentration was higher in L3 plants instead. Generally, L2 plants had the highest dietary minerals such as K, Ca, Mg and Fe among the four different light conditions. Overall, L2 condition is the most suitable lighting strategy in enhancing productivity and nutritional quality of purslane.

Variation in Leaf Nitrate Reductase Activity during Phenological Stages of Hyptis suaveolens (L.) Poit.: An Ethnomedicinal weed of Tripura, India

Leaf Nitrate Reductase activity was studied in Hyptis suaveolens (L.) Poit. at different phenological stages in relation to leaf position. Variability in nitrate reductase activity at different stages of growth coincident with seasonal changes was recorded. Least amount of nitrate reductase activity was observed in young vegetative stage during summer. This was followed by maximum nitrate reductase activity (4.90 ± 1.47μmole NO2 g−1f.wt.h−1) in mature vegetative stage during rainy season and subsequent decline at flowering stage. Increased activity of nitrate reductase was also observed during post flowering stage of fruit setting in winter. Irrespective of phenological stages, apical leaves exhibited moderately high NRA. High nitrate reductase activity in mature vegetative stage of H. suaveolens characterizes an enhanced potential for nitrate assimilation ascribing to invasive nature of the weed. Present finding highlights a possible impact of morphophysiological status of the plant coinciding with seasonal changes on leaf nitrate reductase activity.

Standardization of substrate and buffer concentrations for in-vivo nitrate reductase activity in Adenanthera microsperma leaves

The combination of different substrate concentrations (0.05M, 0.10M, 0.15M, 0.20M and 0.25M, KNO3) with different pH of phosphate buffer (0.10 M and 0.20 M, KH2PO4 of the pH 7.0, 7.5, 7.6, 7.7, and 7.8) solutions were tried for in-vivo nitrate reductase activity of Adenanthera microsperma leaves. Maximum nitrate reductase activity was observed in the combination of buffer solution (0.20M KH2PO4) having pH 7.7 and substrate solution 0.20 M concentration.

Effect of Nitrogen Starvation on the Responses of Two Rice Cultivars to Nitrate Uptake and Utilization

Ammonium (NH+4) is the main nitrogen (N) form for rice crops, while NH+4 near the root surface can be oxidized to nitrate (NO−3) by NH+4 oxidizing bacteria. Nitrate can be accumulated within rice tissues and reused when N supply is insufficient. We compared the remobilization of NO−3 stored in the tissue and vacuolar between two rice (Oryza sativa L.) cultivars, Yangdao 6 (YD6, indica) with a high N use efficiency (NUE) and Wuyujing 3 (WYJ3, japonica) with a low NUE and measured the uptake of NO−3, expression of nitrate reductase (NR), NO−3 transporter genes (NRTs), and NR activity after 4 d of N starvation following 7-d cultivation in a solution containing 2.86 mmol L−1 NO−3. The results showed that both tissue NO−3 concentration and vacuolar NO−3 activity were higher in YD6 than WYJ3 under N starvation. YD6 showed a 2- to 3-fold higher expression of OsNRT2.1 in roots on the 1st and 4th day of N starvation and had significantly higher values of NO−3 uptake (maximum uptake velocity, Vmax) than the cultivar WYJ3. Furthermore, YD6 had significantly higher leaf and root maximum NR activity (NRAmax) and actual NR activity (NRAact) as well as stronger root expression of the two NR genes after the 1st day of N starvation. There were no significant differences in NRAmax and NRAact between the two rice cultivars on the 4th day of N starvation. The results suggested that YD6 had stronger NRA under N starvation, which might result in better NO−3 re-utilization from the vacuole, and higher capacity for NO−3 uptake and use, potentially explaining the higher NUE of YD6 compared with WYJ3.

Synthesis of Silver Nanoparticles and Incorporation with Certain Antibiotic Using Gamma Irradiation

Aims: The study was explaining that silver nanoparticles (AgNPs) were synthesized biologically by Bacillus megaterium culture supernatant (as reducing and stabilizing agents) by the optimization of medium components for nitrate reductase production to enhance the synthesis of AgNPs. And use of gamma irradiation for the synthesis and incorporation of AgNPs with selected antibiotics at distinct dose.Place and Duration of Study: The study was carried out in 2012 in the Department of Drug Radiation Research, Egyptian Atomic Energy Authority.Methodology: The optimized conditions for AgNPs formation by B. megaterium culture supernatant were as follows; media containing: (%) yeast extract: 0.15, peptone: 0.25, KNO3:0.1 temp: 30ºC and incubation period 24 h with maximum nitrate reductase activity of (680.89U/ml). Physical synthesis of AgNPs and incorporation with antibiotics such as (Sodium Cefotaxime, Gentamycin sulphate and Amoxicillin) by γ-rays doses such as (0.5, 1, 1.5, 2, 2.5 and 3 kGy) were studded. AgNPs were characterized by (UV-Vis.), (DLS), (FT-IR) and (TEM) analysis. Combined and individual antibacterial activities of Amoxicillin and AgNPs were investigated against different pathogenic bacterial species by measuring the (ZOI) and by determining the (MIC).Results: This method shows that Aqueous Ag+ ions were reduced to AgNPs when added to the cell-free supernatant of B. megaterium this is indicated by the color change from whitish yellow to brown and the control showed no color change. In physical method Amoxicillin was incorporated with AgNPs perfectly at 2.5kGy. The decreasing order of the average antibacterial activity against bacterial group was observed to be AgNPs > Amoxicillin > Amoxicillin + AgNPs.Conclusion: The radiation-induced AgNPs synthesis is a simple, clean which involves radiolysis of aqueous solution that provides an efficient method to reduce metal ions. B. megaterium was found to be an effective biological tool for the extracellular biosynthesis of AgNPs. The bactericidal activity have proved that AgNPs in combination with amoxicillin kill bacteria at such low concentrations (units of ppm), which do not reveal acute toxic effects on human cell, in addition to overcoming resistance, and lowering cost when compared to conventional antibiotics.

Potassium Fertilization - An Effective Mitigator of Unused Nitrogen in Forage Sorghum

Forages tend to accumulate elevated levels of nitrate when fields are heavily fertilized with nitrogenous fertilizers or are environmentally stressed due to drought, cold, frost, hail, etc. Elevated levels of nitrate have detrimental effects on animal health and are regarded as a causative factor for several mass cattle-death incidents. It was observed that nitrate concentration in Sorghum bicolor L. obtained from local fields of Uttar Pradesh (Ghaziabad and Meerut) and Haryana (Gurgaon and Faridabad) exceeded the safe limit (2500 mg of nitrate kg-1 of fresh wt.) in a significant number of samples (31.7%) studied. Given this, the investigation was conducted in earthen pots to determine nitrate contents in 16 genotypes of S. bicolor L. A significant difference in nitrate content was observed among genotypes, many of which accumulated nitrate to toxic levels. POP-52 (V9), a high nitrate reductase (HNR) genotype and EB-15 (V7), a low nitrate reductase (LNR) genotype of sorghum were selected to study the effect of potassium (K) application on nitrate accumulation in specially designed PVC-drums. The minimum nitrate concentration (V9= 816.6 mg/kg fresh wt. and V7= 2691.8 mg/kg fresh wt.), coupled with maximum NR activity (V9= 9.916 μmol NO2 –1 h–1 g–1 fresh wt. and V7= 5.018 μmol NO2 –1 h–1 g–1 fresh wt.) were observed in 60 day old K60 treated plants. K application reduced the nitrate concentration by 35.24% in V9 and by 25.54% in V7 genotypes by increasing nitrate reductase (NR) activity by 86.23 % in V9 and lesser increase of 32.07% in V7 genotype of sorghum at 30 days. A two- fold (approx.) decrease in nitrate concentration was observed at K60 in both genotypes from 30 to 60-days-after-sowing. K application also reduced considerably the nitrate in the leachate indicating that K is effective in mitigating nitrate pollution in plants and soil. The data emphasizes the importance of K in increasing the nitrogen use efficiency and of balanced fertilization in combating the nitrate-related implications on human beings, animals and environment.

Standardization of In-Vivo Nitrate Reductase activity in the leaves of Albizia Procera (Roxb.) Benth.

The combination of different concentration of substrate (0.025M, 0.05M, 0.10M, 0.15M, 0.20M and 0.25M, KNO3) with different pH of buffer (0.10 M and 0.20 M, KH2PO4 of the pH 6.5, 7.0, 7.2, 7.4, 7.5, 7.6, 7.7 and 7.8) solution were tried for the nitrate reductase activity of Albizia procera. Maximum nitrate reductase activity was observed in the combination of buffer solution of 0.10M KH2PO4 having pH 7.5 and substrate solution of the concentration 0.20M.

Assessment of Nitrate Reductase Activity in the Leaves of Erythrina Blakei R. Parker

Combinations of different concentrations of substrate (0.025M, 0.05M, 0.1M, 0.15M, 0.20M and 0.25M KNO3) with different pH of buffer (0.1M, KH2PO4 of the pH 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.5, 7.6, 7.7, 7.8) solutions were tried for the nitrate reductase activity of Erythrina blakei leaves. Maximum nitrate reductase activity was observed in the combination of buffer solution of 0.1M having pH 6.8 and substrate solution of the concentration 0.15M. NR activity and moisture content in single leaf blades of Erythrina blakei leaves of different branches from different levels of tree have different concentration of activity and Moisture percentage. In single leaf blades maximum NR activity was recorded in leaf number 10, Branch number 3. And maximum moisture percentage observed in leaf number 12, Branch number 3.

Enhanced silver nanoparticle synthesis by optimization of nitrate reductase activity

Nanostructure materials are attracting a great deal of attention because of their potential for achieving specific processes and selectivity, especially in biological and pharmaceutical applications. The generation of silver nanoparticles using optimized nitrate reductase for the reduction of Ag + with the retention of enzymatic activity in the complex is being reported. This report involves the optimization of enzyme activity to bring about enhanced nanoparticle synthesis. Response surface methodology and central composite rotary design (CCRD) were employed to optimize a fermentation medium for the production of nitrate reductase by Bacillus licheniformis at pH 8. The four variables involved in the study of nitrate reductase were Glucose, Peptone, Yeast extract and KNO 3. Glucose had a significant effect on nitrate reductase production. The optimized medium containing (%) Glucose: 1.5, Peptone: 1, Yeast extract: 0.35 and KNO 3: 0.35 resulted in a nitrate reductase activity of 452.206 U/ml which is same as that of the central level. The medium A (showing least nitrate reductase activity) and the medium B (showing maximum nitrate reductase activity) were compared for the synthesis. Spectrophotometric analysis revealed that the particles exhibited a peak at 431 nm and the A 431 for the medium B was 2-fold greater than that of the medium A. The particles were also characterized using TEM. The particles synthesized using the optimized enzyme activity ranged from 10 to 80 nm and therefore can be extended to various medicinal applications.

Standardization of in-vivo nitrate reductase activity in Mimosa hamata Willd. Leaves

The combination of different concentration of substrate (0.10M, 0.15M, 0.20 and 0.25M; KNO3) with different pH of buffer (0.2M KH2PO4 of the pH 6.5, 7.0, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.5 and 9.0) solution were tried for the nitrate reductase activity of Mimosa hamata Willd. leaves. Maximum nitrate reductase activity was observed in the combination of buffer solution of 0.20 M having pH 7.7 and substrate solution of the concentration 0.20 M.

Increased proline loading to phloem and its effects on nitrogen uptake and assimilation in water‐stressed white clover (Trifolium repens)

The aim of this study was to investigate the physiological significance of increased proline loading to phloem caused by water-deficit stress in relation to nitrogen (N) uptake and assimilation. N uptake and N assimilation were quantified by 15N tracing in well-watered (control) and water deficit-stressed white clover (Trifolium repens). De novo proline synthesis and proline loading to the phloem were also compared between treatments. The relationships among proline concentrations in phloem exudates, N uptake, and assimilation of newly absorbed N were assessed. The newly synthesized proline in the phloem exudates increased rapidly after 3 d of water deficit. The water-deficit treatment significantly reduced the maximum nitrate reductase activity (NRA), and also attenuated de novo synthesis of amino acids and proteins in the roots. The increase in proline concentrations in phloem exudates was closely related to reductions in NRA in the roots, N uptake, and the assimilation of newly absorbed N. The accumulation of proline induced in roots by exogenous proline and NH4Cl treatments was closely associated with the decrease in NRA. These results indicate that increased proline transport to roots via phloem caused by water deficit has a significant influence on the down-regulation of N uptake and the assimilation of newly absorbed N.

Distinct patterns of nitrate reductase activity in brown algae: light and ammonium sensitivity in Laminaria digitata is absent in Fucus species1

Fucus and Laminaria species, dominant seaweeds in the intertidal and subtidal zones of the temperate North Atlantic, experience tidal cycles that are not synchronized with light:dark (L:D) cycles. To investigate how nutrient assimilation is affected by light cycles, the activity of nitrate reductase (NR) was examined in thalli incubated in outdoor tanks with flowing seawater and natural L:D cycles. NR activity in Laminaria digitata (Huds.) Lamour. showed strong diel patterns with low activities in darkness and peak activities near midday. This diel pattern was controlled by light but not by a circadian rhythm. In contrast, there was no diel variation in NR activity in Fucus serratus L., F. vesiculosus (L.) Lamour., and F. spiralis L. either collected directly from the shore or maintained in the outdoor tanks. In laboratory cultures, transfer to continuous darkness suppressed NR activity in L. digitata, but not in F. vesiculosus; continuous light increased NR activity in L. digitata but decreased activity in F. vesiculosus. Furthermore, 4 d enrichment with ammonium (50 μmol · L−1 pulses), resulted in NR activity declining by >80% in L. digitata, but no significant changes in F. serratus. Seasonal differences in maximum NR activity were present in both genera with activities highest in late winter and lowest in summer. This is the first report of NR activity in any alga that is not strongly regulated by light and ammonium. Because light and tidal emersion do not always coincide, Fucus species may have lost the regulation of NR by light that has been observed in other algae and higher plants.

Atividade da redutase de nitrato em mudas de pupunheira (Bactris gasipaes)

A enzima redutase de nitrato (EC 1.6.6.1) é a principal enzima responsável pela assimilação de nitrogênio pelas plantas e tem a atividade fortemente afetada pela disponibilidade de água no solo, por isso é usada como variável na avaliação das plantas em diferentes condições ambientais. Assim, este estudo teve como objetivo a padronização de metodologia para avaliação in vivo da atividade da redutase de nitrato em folhas e raízes de pupunheira com nove meses e um ano. As mudas foram cultivadas em casa de vegetação, e os ensaios realizados de acordo com método clássico de análise in vivo. O delineamento experimental foi inteiramente casualizado, com seis repetições. A atividade máxima da enzima em folhas foi obtida com tempo de incubação ao redor de 60 minutos, pH do meio de reação em torno de 7, temperatura de 35 a 37°C e concentração de nitrato entre 28 a 30mmolL-1. A atividade desta enzima foi maior em plantas com nove meses de idade. As folhas mostraram maior atividade da enzima quando comparadas com as raízes. A atividade da enzima redutase de nitrato variou ao longo do dia, com máxima obtida às 10:00 horas, mostrando a influência do período luminoso e do estado hídrico da planta.

Effect of Light Quality on Nitrogen Metabolism of Radish Plants

The long-term action of blue or red light on nitrogen metabolism was studied in radish (Raphanus sativus L.) plants. The potential activity of nitrate reductase (NR) in vivo and its maximum activity in vitro, the content of soluble protein and free amino acids were determined in the course of the growth of a third leaf of radish plants. The effect of light quality on NR activity was found to depend significantly on the stage of leaf development. Blue light (BL) stimulated NR activity in leaves, when their areas were about 11–13% of the fully developed leaves. The efficiency of red light (RL) was significantly lower, because the maximum NR activity was observed in the leaves developed to the stage, when their areas were 38–40% of the final one. The comparative analysis of the pool of free amino acids in expanding leaves of BL- or RL-grown plants revealed significant changes in the contents of individual amino acids. Despite a higher accumulation of two amino acids in the leaves of BL-grown plants, namely, Asp (27% as compared to 13–16% in the RL-grown leaves) and Gly (5% against 2.5% in RL-grown leaves), the BL-grown leaves also demonstrated a significant decrease in Ala (10% as compared to 23% in the RL-grown leaves) and some decrease in the amounts of Ser and Gly. The content of soluble protein in a juvenile BL-grown leaf was observed to decrease gradually during leaf development. However, the protein content in the BL-grown leaf was always higher than in the RL-grown leaf of the same age. We concluded that the photoregulatory action of BL on NR activity determined the different rates of nitrogen assimilation in BL- and RL-grown plants.

Modulation of nitrate reductase activity in rice seedlings under aluminium toxicity and water stress: role of osmolytes as enzyme protectant

Nitrate reductase (NR) activity in the presence of Mg2+ (NR act) representing the non-phosphorylated NR state and the activity in the presence of EDTA (NR max) representing maximum NR activity was measured in roots and shoots of 15 d grown aluminium and water stressed rice seedlings to examine changes in NR activation state due to these stresses. Seedlings subjected to a moderate water stress level of -0.5 MPa for 24 h or grown in presence of 80 microM Al3+showed decreased level of NR max but resulted in higher NR act and NR activation state. However, seedlings grown in presence of a higher level of 160 microM Al3+ showed a decline in NR act as well as NR max. With a higher water stress Level of -2.0MPa a marked decline in the levels of both NR act and NR max was observed, whereas NR activation state remained almost unaltered with severe water stress. NR activity appeared to be sensitive to H2O2, PEG-6000, NaCl and various metal salts. Incorporation of these components in the enzyme assay medium led to decreased affinity of enzyme towards its substrate with increase in Km and decrease in Vmax values. Addition of each of the osmolytes i.e. 1 mol/L proline, 1 mol/L glycine betaine or 1 mol/L sucrose in the enzyme assay medium caused a considerable protection to the enzyme against the damaging effects of stressful components. An enhanced level of proline and glycine betaine was observed in Al-stressed seedlings and sucrose in Al as well as water stressed seedlings. Results suggest that Al toxicity and water stress decrease total amount of functional NR in rice seedlings and the osmolytes proline, glycine betaine and sucrose appear to have a direct protective action on enzyme NR under stressful conditions

Nitrate reductase activity and its diurnal variation rhythm forCamptotheca acuminata seedlings

Nitrate reductase activity (NRA) in different plant organs and leaves in different positions ofCamptotheca acuminata seedlings was determined by anIn vivo assay, the diurnal variation rhythm of NRA in leaves of different positions was observed, and the correlations between leaf NRA, leaf area and lamina mass per unit area (LMA) were also examined. The results showed that NRA in the leaf was significantly highest, compared with that in other organs such as roots, stems and leaves. In this experiment, the 10 leaves were selected from the apex to the base of the seedlings in order. The different NRA occurred obviously in leaves of different positions ofC. acuminata seedlings from the apex to the base, and NRA was higher in the 4th–6th leaves. The diurnal change rhythm of leaf NRA showed a one peak curve, and maximum NRA value appeared at about midday (at 12∶30 or so). No obvious correlations between NRA and leaf area or lamina mass per unit area were observed. This study offered scientific foundation for the further research on nitrogen metabolism ofC. acuminata.

The maximum nitrate reductase activity of the seagrass Zostera noltii (Hornem.) varies along its vertical distribution

Maximum nitrate reductase (NR) activity was measured in two intertidal morphotypes of Zostera noltii (Hornem.) in Ria Formosa tidal lagoon, southern Portugal. The two morphotypes develop in the upper and lower limits of the intertidal meadows. The NR activity was measured using an in vivo method, without cell disruption. NR activity was 30–40 fold higher in leaves than in roots, which indicates that nitrate reduction is essentially made through the aerial part of the plant. The effects of assay temperature (5 °C steps, from 5 to 45 °C), pH (7, 8 and 9) and elevation (upper and lower intertidal) on leaf NR activity were tested in a factorial design ( n=5). Both elevation and assay temperature had a significant effect on NR activity, but not pH. NR activity was always higher in the upper intertidal plants, at all temperatures. Activity peaks for upper and lower plants were, respectively, 6.12 μmol NO 2 − g −1 DW 0.5 h −1 at 25 °C, and 3.30 μmol NO 2 − g −1 DW 0.5h −1 at 35 °C. Further investigation on environmental factors concerning the intertidal environment must be developed, as they are probably responsible for the significant differences found between the values of NR activity in the upper and lower morphotype.

Comparative effectiveness of cattle manure, poultry manure, phosphocompost and fertilizer-NPK on three cropping systems in vertisols of semi-arid tropics. II. Dry matter yield, nodulation, chlorophyll content and enzyme activity

A field experiment was conducted on a deep Vertisol of Bhopal, India to compare root and shoot biomass, chlorophyll content, enzyme activity and nodulation in three cropping systems at three combinations of organic manure and inorganic-fertilizer: 75%NPK + 5 t farmyard manure (FYM), 75%NPK + 1.5 t poultry manure (PM), and 75%NPK + 5 t phosphocompost (PC) vis-a-vis 0%, 75% and 100% of fertilizer-NPK. In general, nodule number and its mass were lower in intercrop soybean than sole soybean. Also there was decrease in the nodule number with higher NPK dose. The FYM treated plots recorded 22.0% and 7.6% higher nodule mass than poultry manure and phosphocompost plots, respectively. Also, the total chlorophyll content was higher in organically treated plots than that in 100% NPK particularly at 30 days after sowing (DAS, pre-flowering). In sorghum the peak nitrate reductase (NR) activity was recorded at 60 DAS while in soybean it was at 30 DAS. The NR activity was higher in intercrop sorghum than that in sole sorghum. Maximum NR activity was observed in 100% NPK. Soybean/sorghum intercropping system recorded significantly higher root and shoot biomass than sole soybean and sorghum. The crop growth rates were relatively rapid during 30–60 DAS and followed the order; intercropping > sole sorghum > sole soybean. With the increase in NPK dose from 0% to 100% there was significant improvement in the dry matter (DM) production in sole sorghum and soybean/sorghum intercropping system. Soybean as preceding crop recorded the highest DM, chlorophyll content, NR activity in wheat while these values were the lowest in sorghum–wheat system.

Nitrate reduction in tendrils of semi-leafless pea.

The recessive gene af produces a modification of Pisum sativum L. leaf morphology, where leaflets are replaced by tendrils. Previous reports have suggested that tendrils may contribute to plant growth in a similar way to flat leaf structures, but these reports have been restricted to carbon metabolism. In this work, we investigate the nitrate reduction (nitrate reductase activity) capacity of tendrils of a semi-leafless variety, Solara, in relation to other leaf structures. Maximum nitrate reductase activity (EC 1.6.6.1), expressed on a protein basis, was significantly lower in tendrils compared to flat structures. However, the activation state of nitrate reductase was significantly higher in tendrils, reaching 70%, compared to flat leaf structures. According to these results, tendrils contributed up to 25% of the overall plant nitrate reduction in the semi-leafless variety. This figure was even higher when nitrate reduction was calculated from in vivo measurements. The results are discussed in relation to nitrate, magnesium, carbohydrates, amino acids and adenylate levels of tendrils.