Nitrogen deficiency system is helpful in characterizing regulation mechanisms of ectopic triacylglycerol accumulation in Arabidopsis seedlings

Triacylglycerol (TAG) is the major storage component accumulated in seed. However the regulatory mechanism of TAG synthesis and accumulation in non-seed tissues remains unknown. Recently, we found that nitrogen (N) deficiency (0.1mM N) caused an inducement of TAG biosynthesis in Arabidopsis seedlings. ABSCISIC ACID INSENSITIVE 4 (ABI4) was essential for the activation of Acyl-CoA:diacylglycerol acyltransferase1(DGAT1) expression during N deficiency in Arabidopsis seedlings. In this addendum, we further discussed the approaches to provide a net increase in total oil production in higher plants by using the low N platform. First, the N-deficient seedlings can be used to determine the key factors that regulate the ectopic expression of key genes in TAG metabolism. Second, the research on the relationship between TAG homeostasis and cell division will be helpful to find the key factors that specifically regulate TAG accumulation under the nutrient-limited condition.     

Metabolism of nitric oxide and nitrous oxide during nitrification and denitrification in soil at different incubation conditions

Abstract NO production and consumption rates as well as N₂O accumulation rates were measured in a loamy cambisol which was incubated under different conditions (i.e. soil moisture content, addition of nitrogen fertilizer and/or glucose, aerobic or anaerobic gas phase). Inhibition of nitrification with acetylene allowed us to distinguish between nitrification and denitrification as sources of NO and N₂O. Under aerobic conditions untreated soil showed very low release of NO and N₂O but high consumption of NO. Fertilization with NH₄⁺ or urea stimulated both NO and N₂O production by nitrification. Addition of glucose at high soil moisture contents led to increased N₂ and N₂O production by denitrification, but not to increased NO production rates. Anaerobic conditions, however, stimulated both NO and N₂O production by denitrification. The production of NO and N₂O was further stimulated at low moisture contents and after addition of glucose or NO₃⁻. Anaerobic consumption of NO by denitrification followed Michaelis-Menten kinetics and was stimulated by addition of glucose and NO₃⁻. Aerobic consumption of NO followed first-order kinetics up to mixing ratios of at least 14 ppmv NO, was inhibited by autoclaving but not by acetylene, and decreased with increasing soil moisture content. The high NO-consumption activity and the effects of soil moisture on the apparent rates of anaerobic and aerobic production and consumption of NO suggest that diffusional constraints have an important influence on the release of NO, and may be a reason for the different behaviour of NO release vs N₂O release.     

Operation of an aerobic granular pilot scale SBR plant to treat swine slurry

A pilot-scale Sequencing Batch Reactor was operated during 307 days in order to treat swine slurry characterized by its high variable composition: organic and nitrogen applied loading rates and C/N ratio were 1.4–6.3 kg COD_s/(m³ d), 0.5–2.5 kg N/(m³ d) and 1.9–9.4 g COD_s/(g N), respectively. Aerobic granules successfully developed in the reactor and their physical properties remained rather stable despite the feeding composition variability. Organic and ammonia removal efficiency reached 61–73% and 56–77%, respectively, however ammonia was mainly oxidized to nitrite. The reactor had a good biomass retention capacity to select for granular biomass. However, its efficiency to retain the solids present in the feeding was low. Aerobic granulation in SBR systems appears as an interesting alternative to treat slurry in small livestock facilities where the implementation of anaerobic digestion systems is not a feasible option or the removal of nitrogenous compounds is required.     

The Influences of A Nitrogen Atom Position in Dinucleoside 2-,3-,4-Pyridylphosphonates on Fragmentation Patterns in Electrospray Ionization Multistage Tandem Mass Spectra

2-,3-,4-Pyridylphosphonates and their phosphonothioate congeners were analyzed by electrospray ionization multistage tandem mass spectrometry (ESI-MSⁿ). It was found that the fragmentation pathways of these compounds were not influenced to any detectable extent by the stereochemistry at the phosphorus centers but were sensitive to the position of a nitrogen atom in the pyridine ring of these compounds. Possible mechanisms for fragmentations of the investigated compounds are discussed in detail.

     

Grimmia homodictyon Dixon

Abstract

We examined photosynthetic responses of two dominant pleurocarpous mosses, Actinothuidium hookeri (Mitt.) Broth. and Hylocomium splendens (Hedw.) Schimp. to low-level nitrogen (N) addition. The study was conducted in an old-growth fir forest on the eastern Tibetan Plateau. The added N, 1 g N/m², was mainly absorbed by the new-growth. The concentrations of chlorophyll a and b both increased 8 days after N addition. The quantum yield of Photosystem II (Φ_PSII) also increased. However, no significant changes were found in terms of gas exchange parameters. The mass-based CO₂ assimilation rate, chlorophyll a content, and chlorophyll a/b ratio (which is related to antenna size of the photosystem), of H. splendens were all higher than those of A. hookeri. Shoot mass per area (SMA) of H. splendens was lower than that of A. hookeri. We conclude that the photosynthetic rate was less sensitive to low-level N addition than chlorophyll contents and chlorophyll fluorescence parameters, suggesting other limiting factors in the photosynthetic process. Additionally, the faster growing H. splendens has a higher photosynthetic capacity than A. hookeri, allocating fewer resources to structural tissue.     

Growth and nitrogen utilization in seedlings of mountain birch (Betula pubescens ssp. tortuosa ) as affected by ultraviolet radiation (UV-A and UV-B) under laboratory and outdoor conditions

 Growth patterns and nitrogen economy were studied in pot-grown seedlings of mountain birch subjected to different ultraviolet radiation under both laboratory and outdoor conditions at Abisko in northern Sweden. In the laboratory, nutrient supply, temperature, humidity, ultraviolet radiation-A (UV-A, 320–400 nm) and B (UV-B, 280–320 nm) were controlled, while photosynthetically active radiation (PAR, 400–700 nm) and photoperiod varied naturally. Under outdoor conditions nutrient supply was controlled, and the irradiation treatments were ambient and above-ambient UV-B using additional fluorescent lamps. Mountain birch nitrogen economy was affected by increased ultraviolet radiation, as reflected by a changed relationship between plant growth and plant nitrogen both in the laboratory and outdoors. In the laboratory enhanced UV-A decreased leaf area per unit plant biomass (leaf area ratio) but increased biomass productivity, both per unit leaf area (leaf area productivity) and per unit leaf nitrogen (leaf nitrogen productivity). Low levels of UV-B affected growth patterns and nitrogen economy in a similar way to enhanced UV-A. High levels of UV-B clearly decreased relative growth rate and nitrogen productivity, as leaf area ratio, leaf area productivity and leaf nitrogen productivity were all decreased. Under outdoor conditions above-ambient levels of UV-B did not alter growth or biomass allocation traits of the seedlings, whilst nitrogen productivity was increased. Mountain birch seedlings originating from different mother trees varied significantly in their responses to different ultraviolet radiation. Received: 10 April 1997 / Accepted: 19 September 1997     

几种豆科树木结瘤固氮的初步研究

 作者通过野外调查和盆栽试验,探讨了几种豆科树种的结瘤固氮特征,土壤条件的影响和植株生长。木豆、山毛豆、刺槐在南亚热带褐红土种植,山合欢、刺槐在中亚热带紫色土种植,对绿化荒山荒地、改良土壤和促进生态平衡具有重要意义。     

Novel autotrophic nitrogen removal system using gel entrapment technology

A pilot plant involving a nitritation-anammox process was operated for treating digester supernatant. In the preceding nitritation process, ammonium-oxidizing bacteria were immobilized in gel carriers, and the growth of nitrite-oxidizing bacteria was suppressed by heat-shock treatment. For the following anammox process, in order to maintain the anammox biomass in the reactor, a novel process using anammox bacteria entrapped in gel carriers was also developed. The nitritation performance was stable, and the average nitrogen loading and nitritation rates were 3.0 and 1.7 kg N m⁻³ d⁻¹, respectively. In the nitritation process, nitrate production was completely suppressed. For the anammox process, the startup time was about two months. Stable nitrogen removal was achieved, and an average nitrogen conversion rate of 5.0 kg N m⁻³ d⁻¹ was obtained. Since the anammox bacteria were entrapped in gel carriers, stable nitrogen removal performance was attained even at an influent suspended solids concentration of 1500 mg L⁻¹.     

Evidence for adenylylation/deadenylylation control of the glutamine synthetases of Rhodospirillum tenue and Rhodocyclus purpureus

The phylogenetically related phototrophic bacteria Rhodospirillum tenue and Rhodocyclus purpureus modulate activity of their glutamine synthetases by adenylylation/deadenylylation. Evidence for covalent modification includes the inhibitory effect of Mg²⁺ on the activity of glutamine synthetase extracted from cells of either species grown on excess ammonia, and the lack of Mg²⁺ inhibition of activity of the enzyme isolated from N₂-(R. tenue) or glutamine (R. purpureus)-grown cells. In addition, snake venom phosphodiesterase treatment of glutamine synthetase from either species grown on excess ammonia relieved Mg²⁺ inhibition of the enzyme (as measured via the -glutamyl transferase assay), and changed the cation specificity from Mn²⁺ to Mg²⁺ (in the biosynthetic assay).     

Effects of acid irrigation and liming on two clones of Norway spruce

Summary The effect of acid irrigation on the growth of rooted cuttings ofPicea abies (L.) Karst, was investigated in a pot experiment lasting 3 years. It involved two clones of Norway spruce, H 253 Bogstad I and H 254 Bogstad II. Irrigation water of pH 5.4, 4.0, 3.0 and 2.5 was used. Liming was included in the experiment.After the experimental period, the plants of all treatments were growing reasonably well. However, those plants irrigated at pH 2.5 were slightly discoloured. The plant mortality was only 3% throughout the experiment, and was not connected to acid irrigation. The limiting growth factor was N. All other nutrient elements measured in the plants were close to optimal concentration. Plants irrigated at pH 2.5, and to some extent at pH 3, contained excessively high concentrations of Al, t-S and SO₄. The total amount of Ca, Fe and Mn taken up by the plants decreased with increasing soil acidity. The increased growth of clone H 254 relative to H 253, produces a corresponding impression on soil characteristics. Soil acidity is governed by acid irrigation and CaCO₃ application, but the clonal effects are also of importance. Norway spruce appears to be tolerant to Al concentrations as high as 50 mmol/kg in the needles.