Effect of soil sodicity on the growth,yield and chemical composition of groundnut (Arachis hypogaea Linn.)

Summary A replicated field experiment was conducted to study the effect of exchangeable sodium percentage (ESP) on the yield, chemical composition, protein and oil content and uptake of nutrients by groundnut (Arachis hypogaea Linn.) variety M-13. ESP over 15 delayed germination and emergence of flowers. There was continuous decrease in dry matter yield at 30 and 60 days of growth, grain and straw yield after harvest and protein, oil and kernel percent with increase in soil ESP. A 50 per cent reduction in groundnut yield was observed at an ESP of 20. Increasing soil ESP, increased Na and decreased K, Ca and N contents, but had no effect on the Mg, P, S, Fe, Mn, Zn and Cu contents of the plant. Sodium content of the plant increased, while potassium and nitrogen decreased with age of the plant. The uptake of all the nutrients decreased with increase in soil ESP. The results showed that groundnut is a relatively sensitive crop to soil sodicity.     

Soaking seeds of Lens culinaris with 28-homobrassinolide increased nitrate reductase activity and grain yield in the field in India

Surface‐sterilised seeds of Lens culinaris cv. Pusa‐6 were soaked in 0 M, 10^?6 M, 10^?8 M or 10^?10 M aqueous solutions of 28‐homobrassinolide (HBR) for 4 h, 8 h or 12 h and planted in the field in a sandy loam soil. Plants were sampled 60, 90 and 120 days after sowing (DAS). Soaking with HBR decreased root length and nodule number per plant but increased nitrate reductase activity (E.C.1.6.6.1). Soaking with HBR also increased grain yield at the final harvest 140 DAS. The greatest increase was obtained with an HBR concentration of 10^?8 M.     

Anaerobic energy metabolism of the sulfur-reducing bacterium “Spirillum” 5175 during dissimilatory nitrate reduction to ammonia

In a batch culture experiment the microaerophilic Campylobacter-like bacterium “Spirillum” 5175 derived its energy for growth from the reduction of nitrate to nitrite and nitrite to ammonia. Hereby, formate served as electron donor, acetate as carbon source, and l-cysteine as sulfur source. Nitrite was quantitatively accumulated in the medium during the reduction of nitrate; reduction of nitrite began only after nitrate was exhausted from the medium. The molar growth yield per mol formate consumed, Y_m, was 2.4g/mol for the reduction of nitrate to nitrite and 2.0 g/mol for the conversion of nitrite to ammonia. The gain of ATP per mol of oxidized formate was 20% higher for the reduction of nitrate to nitrite, compared to the reduction of nitrite to ammonia. With succinate as carbon source and nitrite as electron acceptor, Y_m was 3.2g/mol formate, i.e. 60% higher than with acetate as carbon source. No significant amount of nitrous oxide or dinitrogen was produced during growth with nitrate or nitrite both in the presence or absence of acetylene. No growth on nitrous oxide was found. The hexaheme c nitrite reductase of “Spirillum” 5175 was an inducible enzyme. It was present in cells cultivated with nitrate or nitrite as electron acceptor. It was absent in cells grown with fumarate, but appeared in high concentration in “Spirillum” 5175 grown on elemental sulfur. Furthermore, the dissimilatory enzymes nitrate reductase and hexaheme c nitrite reductase were localized in the periplasmic part of the cytoplasmic membrane.     

Effect of 28-homobrassinolide treatment on nickel toxicity in <Emphasis Type="Italic">Brassica juncea</Emphasis>

Plants of Brassica juncea L. cv. T-59 were supplied with 50 or 100 μM nickel (Ni₅₀, Ni₁₀₀) at 10 d after sowing (DAS), and sprayed with 28-homobrassinolide (HBR) at 20 DAS. The plants treated with Ni alone exhibited reduced growth, net photosynthetic rate, content of chlorophyll, and the activities of nitrate reductase (E.C.1.6.6.1) and carbonic anhydrase (E.C. 4.2.1.1) at observed 40 DAS, whereas, the contents of peroxidase (PER), catalase (CAT), and proline were increased. However, the spray of HBR partially neutralized the toxic effect of Ni on most of the parameters. Moreover, the treatment of HBR in association with either of the Ni concentration boosted the contents of PER and CAT in leaves and that of proline both in leaves and roots.     

Growth and Metabolism of Senna as Affected by Salt Stress

Pot culture experiments were conducted using different NaCl concentrations to assess their impact on the growth and metabolic changes in senna (Cassia angustifolia Vahl.). Five treatments (0, 40, 80, 120, and 160 mM NaCl) were given to the plants at three phenological stages, i.e. at pre-flowering, (45 days after sowing, DAS); flowering (75 DAS) and post-flowering (90 DAS) stages. A significant reduction in the biomass and length of the roots and shoots, photosynthetic rate, stomatal conductance, the total chlorophyll content, protein content, nitrate reductase activity, and reduced nitrogen content of the leaves was observed at each phenological stage with each salt concentration applied. Contrary to this, proline and nitrate contents of the leaves increased markedly. The post-flowering stage was most sensitive to NaCl treatment.     

Lithotrophic growth ofSulfurospirillum deleyianum with sulfide as electron donor coupled to respiratory reduction of nitrate to ammonia

Sulfurospirillum deleyianum grew in batch culture under anoxic conditions with sulfide (up to 5 mM) as electron donor, nitrate as electron acceptor, and acetate as carbon source. Nitrate was reduced to ammonia via nitrite, a quantitatively liberated intermediate. Four moles of sulfide were oxidized to elemental sulfur per mole nitrate converted to ammonia. The molar growth yield per mole sulfide consumed, Y_m, was 1.5 ± 0.2 g mol^–1 for the reduction of nitrate to ammonia. By this type of metabolism, S. deleyianum connected the biogeochemical cycles of sulfur and nitrogen. The sulfur reductase activity in S. deleyianum was inducible, as the activity depended on the presence of sulfide or elemental sulfur during cultivation with nitrate or fumarate as electron acceptor. Hydrogenase activity was always high, indicating that the enzyme is constitutively expressed. The ammonia-forming nitrite reductase was an inducible enzyme, expressed when cells were cultivated with nitrate, nitrite, or elemental sulfur, but repressed after cultivation with fumarate. Received: 13 March 1995 / Accepted: 29 May 1995     

Diverse effects of formate on the assimilatory metabolism of nitrate and nitrite inRhizobium

Two strains ofRhizobium, cowpeaRhizobium 32H1 andRhizobium japonicum CB 1809, showed a marked stimulation in growth on addition of formate to the minimal medium containing nitrate as the sole source of nitrogen. The amount of accumulated nitrite and specific nitrate reductase activity was much higher in cultures supplemented with formate than in the control medium. In contrast, growth, consumption of nitrite and specific nitrite reductase activity in minimal medium + nitrite was greatly reduced by the addition of formate. A chlorate resistant mutant (Chl-16) was isolated spontaneously which contained a nitrite reductase which was not inhibited by formate. The results suggest that formate serves as an electron donor for nitrate reductase and inhibits nitrite assimilation inRhizobium     

The effect of nitrogen refeeding on starved cells of Platymonas striata Butcher

A rapid uptake of nitrogen was observed in nitrogen-starved cells of Platymonas striata after refeeding with ammonium or nitrate ions. This was followed by a net loss of nitrogen per cell. Cells initially grown in and then starved in a regime of continuous light showed greater increases in average cell nitrogen on refeeding with ammonium or nitrate ions than did cells initially grown in and then starved in a regime of alternating light and darkness. A particulate subcellular location was observed for nitrate reductase (EC 1.6.6.1) in broken cell suspensions prepared by sonication. Nitrite reductase (EC 1.6.6.4) was located in the soluble fraction of these cell suspensions. Broken cell preparations displayed a lowered nitrate reductase activity as compared with the particulate component of these preparations. This was shown not to be due to heat-stable inhibitors present in the soluble phase of the cell. It appeared to be an artefact produced by the high nitrite reductase activity of the broken cell preparations, which removed much of the nitrite as it was formed. Nitrogen starvation of nitrate-grown cultures produced cellular increases in nitrate reductase and nitrite reductase activities which were further increased after the addition of nitrate. The results are discussed.Abbreviations ASP2 complete culture medium - ASP2 INF medium lacking in inorganic nitrogen - ASP2 NF medium lacking all nitrogen - NAR nitrate reductase - NIR nitrite reductase - EDTA Ethylenediaminetetracetic acid - PVP Polyvinylpyrollidone, M.W. 44,000     

Mutants of Azotobacter vinelandii altered in the regulation of nitrate assimilation

The two enzymes involved in the assimilatory pathway of nitrate in Azotobacter vinelandii are corregulated. Nitrate reductase and nitrite reductase are inducible by nitrate and nitrite. Ammonium represses induction by nitrate of both reductases. Repression by ammonium is higher in media containing 2-oxo-glutarate as carbon source than in media containing sucrose. Mutants in the gene ntrC lost nitrate and nitrite reductase simultaneously. Ten chlorate-resistant mutants with a new phenotype were isolated. In media without ammonium they had a normal phenotype, being sensitive to the toxic effect of chlorate. In media containing low ammonium concentrations they were resistant to chlorate. These mutants seem to be affected in the repression of nitrate and nitrite reductases by ammonium.     

Effects of sodium on mineral nutrition in rose plants

The effects of sodium (Na⁺) ion concentration on shoot elongation, uptake of ammonium (NH₄⁺) and nitrate (NO₃^?) and the activities of nitrate reductase (NR) and glutamine synthetase (GS) were studied in rose plants (Rosa hybrida cv. “Lambada”). The results showed that shoot elongation was negatively correlated with sodium concentration, although no external symptoms of toxicity were observed. Nitrate uptake decreased at high sodium levels, specifically at 30 meq litre4 of sodium. As flower development was normal under high saline conditions, this could suggest that nitrogen was being mobilised from shoot and leaf reserves. Ammonium uptake was not affected by any of the salt treatments applied probably because it diffuses through the cell membrane at low concentrations. Nitrate reductase activity was reduced by 50% at 30 meq litre 1 compared with control treatment, probably due to a decrease in the free nitrate related to nitrate uptake pattern. None of the salt treatments used affected total leaf GS activity (both chloroplastic and cytosolic isoforms) or leaf NPK mineral contents. Nitrate reductase activity in leaves increased at 10 meq litre^?1 of sodium and GS activity in roots (cytosolic isoform only) followed the same pattern as NR. It is suggested that the activation of both enzymes at low salt level could be attributed to the beneficial effect of increased sulphur in the nutrient solutions.     

Synthesis of wheat leaf nitrite reductase de novo following induction with nitrate and light

Nitrite reductase has been purified almost 3000-fold, in 35% yield, to a specific activity of 77 units (mg protein)-1 from wheat leaves using a multi-step procedure with affinity chromatography on ferredoxin-Sepharose as the final step. The purified enzyme, although not homogeneous, exhibited absorption maxima at 278, 390, 568 and 687 nm. Minor contaminants were removed by gel filtration in the presence of sodium dodecyl sulphate to yield a single polypeptide of Mr 60 500 as judged by polyacrylamide gel electrophoresis. Antibodies raised against this polypeptide were shown to cross-react with native nitrite reductase and were used to study the synthesis of nitrite reductase in vivo and in vitro. The increase in nitrite reductase activity following exposure of dark-grown plants to nitrate and light was shown by immunodecoration of Western blots to be due to synthesis de novo. Poly(A)-rich RNA isolated from plants actively synthesising nitrite reductase was shown to direct the synthesis in a rabbit reticulocyte lysate of a polypeptide of Mr 64000 which was immunoprecipitated by antibodies to nitrite reductase.     

Effect of water deficit on photosynthetic and other physiological responses in grapevine (Vitis vinifera L. cv. Riesling) plants

The grapevine (Vitis vinifera L. cv. Riesling) plants subjected to water deficit were studied for changes in relative water content (RWC), leaf dry mass, contents of chlorophyll (Chl), total leaf proteins, free amino acids, and proline, and activities of ribulose-1,5-bisphosphate carboxylase (RuBPC), nitrate reductase (NR), and protease. In water-stressed plants RWC, leaf dry matter, Chl content, net photosynthetic rate (P _N), and RuBPC and NR activities were significantly decreased. The total leaf protein content also declined with increase in the accumulation of free amino acids. Concurrently, the protease activity in the tissues was also increased. A significant two-fold increase in proline content was recorded.     

Indirect determination of nitric oxide production by reduction of nitrate with a freeze-thawing-resistant nitrate reductase from Escherichia coli MC1061

Preparation of a nitrate reductase lysate of Escherichia coli MC1061 to measure nitrate and nitrite in biologic fluids is described. To obtain the crude bacterial lysate containing nitrate reductase activity, E. coli MC1061 was subjected to 16-20 freeze-thawing cycles, from -70 to 60 degrees C, until nitrite reductase activity was < or = 25%. Nitrate reductase activity was detected mainly in the crude preparation. To validate the nitrate reduction procedure, standard nitrate solutions (1.6-100 microM) were incubated with the nitrate reductase preparation for 3 h at 37 degrees C, and nitrite was estimated by the Griess reaction in a microassay. Nitrate solutions were reduced to nitrite in a range of 60-70%. Importantly, no cofactors were necessary to perform nitrate reduction. The biological samples were first reduced with the nitrate reductase preparation. After centrifugation, samples were deproteinized with either methanol/ether or zinc sulfate and nitrite was quantified. The utility of the nitrate reductase preparation was assessed by nitrate+nitrite determination in serum of animals infected with the protozoan Entamoeba histolytica or the bacteria E. coli and in the supernatant of cultured lipopolysaccharide-stimulated RAW 264.7 mouse macrophages. Our results indicate that the nitrate reductase-containing lysate provides a convenient tool for the reduction of nitrate to determine nitrate+nitrite in biological fluids by spectrophotometric methods.     

Chemolithotrophic growth ofDesulfovibrio desulfuricans with hydrogen coupled to ammonification of nitrate or nitrite

Two of nine sulfate reducing bacteria tested,Desulfobulbus propionicus andDesulfovibrio desulfuricans (strain Essex 6), were able to grow with nitrate as terminal electron acceptor, which was reduced to ammonia. Desulfovibrio desulfuricans was grown in chemostat culture with hydrogen plus limiting concentrations of nitrate, nitrite or sulfate as sole energy source. Growth yields up to 13.1, 8.8 or 9.7 g cell dry mass were obtained per mol nitrate, nitrite or sulfate reduced, respectively. The apparent half saturation constants (K _s) were below the detection limits of 200, 3 or 100 mol/l for nitrate, nitrite of sulfate, respectively. The maximum growth rates {ie63-1} raised from 0.124 h^-1 with sulfate and 0.150 h^-1 with nitrate to 0.193 h^-1 with nitrite as electron acceptor. Regardless of the electron acceptor in the culture medium, cell extracts exhibited absorption maxima corresponding to cytochromec and desulfoviridin. Nitrate reductase was found to be inducible by nitrate or nitrite, whereas nitrite reductase was synthesized constitutively. The activities of nitrate and nitrite reductases with hydrogen as electron donor were 0.2 and 0.3 mol/min·mg protein, respectively. If limiting amounts of hydrogen were added to culture bottles with nitrate as electron acceptor, part of the nitrate was only reduced to the level of nitrite. In media containing nitrate plus sulfate or nitrite plus sulfate, sulfate reduction was suppressed.The results demonstrate that the ammonification of nitrate or nitrite can function as sole energy conserving process in some sulfate-reducing bacteria.     

Cloning and expression of distinct nitrite reductases in tobacco leaves and roots

Summary Three tobacco nitrite reductase (NiR) cDNA clones were isolated using spinach NiR cDNA as a probe. Sequence analysis and Southern blot hybridization revealed four genes in tobacco. Two of these genes presumably derived from the ancestral species Nicotiana tomentosiformis, the other two from the ancestor N. sylvestris. Northern blot analysis showed that one gene from each ancestral genome was expressed predominantly in leaves, whilst RNA from the other was detected mostly in roots. The accumulation of both leaf and root NiR mRNAs was induced by nitrate and repressed by nitrate- or ammonium-derived metabolites. In addition, the expression of the root NiR gene was detectable in leaves of a tobacco nitrate reductase (NR)-deficient mutant. Thus, the regulation of expression of tobacco NiR genes is comparable to the regulation of expression of barley NR genes.     

An assessment of the relative effects of adverse physical and chemical properties of sodic soil on the growth and yield of wheat (Triticum aestivum L.)

Two wheat varieties were grown in artificially created sodic soils in pots at a range of sodicity levels (exchangeable sodium percentage (ESP) 15–52), with and without an anionic polyacrylamide soil conditioner (PAM) to stabilise soil aggregates. Increasing sodicity decreased the % water stable aggregates (% WSA) in soil and survival, grain and straw yield of wheat. Plants grown at high sodicity also had higher Na⁺, lower K⁺ and Ca²⁺ concentrations and lower K⁺/Na⁺ ratio in flag leaf sap than plants grown in control (non-sodic) soil. Sodicity had no effect on the concentrations of Cu²⁺, Fe²⁺, Mn²⁺ and Zn²⁺ in grains and straw, but total uptake of these micronutrients was deceased due to lower dry weight of these tissues per plant. At all sodicity levels treatment of sodic soil with PAM increased the % WSA to values greater than in the non-sodic control soil, and slightly lowered ESP. Over the range ESP 15–44 the effects of PAM on wheat grain yield increased as sodicity increased, so that at ESP 44 grain yield in the treatment with PAM was only 25% lower than in the non-sodic control. However at ESP 52 the effects of PAM were smaller, and grain yield was 86% lower than in the control. At this sodicity level the decreases in grain yield due to sodicity and the increases in reponse to treatment of sodic soil with PAM were similar in the two varieties tested. At high sodicity levels (ESP 44 and 52) treatment of sodic soil with PAM decreased the concentration of Na⁺ and increased K⁺ and K⁺/Na⁺ ratio in flag leaf sap. However, at the highest sodicity level (ESP 52), flag leaf Na⁺ concentration remained above the level (100 mol m^-3) at which it has been found to be toxic. Concentrations of Cu²⁺, Fe²⁺, Mn²⁺ and Zn²⁺ in grain and straw were unaffected by PAM. These results suggest that at ESP up to 40–50 adverse physical characteristics are the major cause of low wheat yield in sodic soils, either due to their direct effects in decreasing growth, or their indirect effects in increasing uptake of Na⁺ and decreasing uptake of K⁺. Above ESP 50, roots are less able to exclude Na⁺, even in the presence of improved soil physical conditions, so that at these sodicity levels, both adverse physical and adverse chemical properties contribute to the decreased yield. This revised version was published online in June 2006 with corrections to the Cover Date.     

ISOLATION AND PARTIAL CHARACTERIZATION OF NITRATE ASSIMILATION MUTANTS OF DUNALIELLA TERTIOLECTA (CHLOROPHYCEAE)1

Fifteen nitrate assimilation-deficient mutants of the euryhaline green alga, Dunaliella tertiolecta Butcher were selected by their chlorate resistance. Ten mutants, unable to grow on NO₃^? but able to grow on NO₂^?, had no detectable nitrate reductase activity. Five mutants, unable to grow on either NO₃^? or NO₂^?, had depressed levels of both nitrate and nitrite reductase. A method for assaying methyl viologen-nitrate reductase in the presence of nitrite reductase is described.     

Membrane-bound nitrite oxidoreductase of Nitrobacter: evidence for a nitrate reductase system

Nitrite oxidoreductase, the essential enzyme complex of nitrite oxidizing membranes, was isolated from cells of the nitrifying bacterium Nitrobacter hamburgensis. The enzyme system was solubilized and purified in the presence of 0.25% sodium deoxycholate. Nitrite oxidoreductase oxidized nitrite to nitrate in the presence of ferricyanide. The pH optimum was 8.0, and the apparent K _m value for nitrite amounted to 3.6 mM. With reduced methyl-and benzylviologen nitrite oxidoreductase exhibited nitrate reductase activity with an apparent K _m value of 0.9 mM for nitrate. NADH was also a suitable electron donor for nitrate reduction. The pH optimum was 7.0.Treatment with SDS resulted in the dissociation into 3 subunits of 116,000, 65,000 and 32,000. The enzyme complex contained iron, molydbenum, sulfur and copper. A c-type cytochrome was present. Isolated nitrite oxidoreductase is a particle of 95±30 Å in diameter.Abbreviation DOC sodium deoxycholate     

Effects of electron donors on nitrate removal by nitrate and nitrite reductases

Effects of artificial electron donors to deliver reducing power on enzymic denitrification were investigated using nitrate reductase and nitrite reductase obtained fromOchrobactrum antropi. The activity of nitrite reductase in the soluble portion was almost the same as that in the precipitated portion of the cell extract. Nitrate removal efficiency was higher with benzyl viologen than with methyl viologen or NADH as an artificial electron donor. The turn-over numbers of nitrate and nitrite reductase were 14.1 and 1.9 μmol of nitrogen reduced/min·mg cell extracts, respectively when benzyl viologen was used as an electron donor.     

Aerobic nitrate and nitrite reduction in continuous cultures of Escherichia coli E4

Nitrate and nitrite was reduced by Escherichia coli E4 in a l-lactate (5 mM) limited culture in a chemostat operated at dissolved oxygen concentrations corresponding to 90–100% air saturation. Nitrate reductase and nitrite reductase activity was regulated by the growth rate, and oxygen and nitrate concentrations. At a low growth rate (0.11 h^–1) nitrate and nitrite reductase activities of 200 nmol · mg^–1 protein · min^–1 and 250 nmol · mg^–1 protein · min^–1 were measured, respectively. At a high growth rate (0.55 h^–1) both enzyme activities were considerably lower (25 and 12 nmol mg^–1 · protein · min^–1). The steady state nitrite concentration in the chemostat was controlled by the combined action of the nitrate and nitrite reductase. Both nitrate and nitrite reductase activity were inversely proportional to the growth rate. The nitrite reductase activity decreased faster with growth rate than the nitrate reductase. The chemostat biomass concentration of E. coli E4, with ammonium either solely or combined with nitrate as a source of nitrogen, remained constant throughout all growth rates and was not affected by nitrite concentrations. Contrary to batch, E. coli E4 was able to grow in continuous cultures on nitrate as the sole source of nitrogen. When cultivated with nitrate as the sole source of nitrogen the chemostat biomass concentration is related to the activity of nitrate and nitrite reductase and hence, inversely proportional to growth rate.