Novel rhodium porphyrin derivatives

Hydrated rhodium trichloride reacts with porphyrins in dimethylformamide to give bis-dimethylamino (DMA) derivatives of general formula [RhP(DMA)₂- X]. Modifications of the spectral properties caused by anion exchange are discussed.     

A growing family: New structures of coordination polymers containing adamantane-shaped phosphorus-nitrogen cage ligands

Two new structurally characterized coordination polymers containing the P₄(NR)₆ ligand system are described. A convenient one-pot synthesis of P₄(NR)₆ (R = benzyl) via reaction of lithiated primary amine with phosphorus trichloride demonstrates an expanded scope for the preparation of this adamantane-type structure. Reactions of P₄(NR)₆ (R = Et, Bn) with cuprous iodide yield different products due to the differences in steric demands of the ligands.     

An Improved Method for the Preparation of Methyl dichlorophosphite. A Key Reagent In the Phosphite Method of Oligonucleotide Synthesis

Abstract

The reaction between phosphorus trichloride (PCl₃) and trimethyl phosphite (CH₃O)3^p, has been examined by ³¹Pnmr, in order to achieve a simple and efficient procedure for the formation of methyl dichlorophosphite (CH₃OPCl₂), which is a key intermediate in the synthesis of oligonucleotides. The yield of the reaction was also studied on a preparative scale and it was found that the optimal condition is obtained when the reactants molar ratio is 1:1.     

Effect of nitrogen starvation on ammonium-inhibition of nitrogenase activity in Azotobacter chroococcum

When Azotobacter chroococcum cells grown in batch culture under N₂-fixing conditions were transferred to a medium lacking a nitrogen source, the cellular C/N ratio, the amount of alginic acid released into the external medium and the rate of endogenous respiration increased appreciably after 6 h to the exclusion of dinitrogen, whereas nitrogenase activity did not undergo any significant change. Nitrogen deficiency caused a decrease in the ammonium inhibition of nitrogenase activity from 95% inhibition at zero time to 14% after 6 h incubation under dinitrogen starvation, with no difference in the rate of ammonium utilization by N₂-fixing and N₂-starved cells being observed. This suggests that a balance of nitrogen and carbon assimilation is necessary for the ammonium inhibition of nitrogenase activity in A. chroococcum to take place.     

Nitrogen and phosphorus concentrations and export for the upper Kuparuk River on the North Slope of Alaska in 1980

Nitrogen and phosphorus concentrations were measured from May to August 1980 in the upper Kuparuk River, a tundra stream on the North Slope of Alaska. Mean values for nitrogen were 10.8 μg N 1⁻¹ for ammonium, 21.4 μg N 1⁻¹ for nitrate plus nitrite and 248 μg N 1⁻¹ for dissolved organic nitrogen. Mean values for phosphorus were 8.1 μg P 1⁻¹ for total dissolved phosphorus and 4.7 μg P 1⁻¹ for fine particulate phosphorus. Nitrate concentrations were inversely correlated with flow whereas particulate phosphorus concentrations increased during high flows. Export of nitrogen and phosphorus from the watershed during 1980 was estimated to be 4.69, 3.25 and 91 kg km⁻² yr⁻¹ for NO₃-N, NH₄-N and DON-N, respectively, and 2.86 and 3.03 kg km⁻² yr⁻¹ for TDP-P and PP-P. Both the relative concentrations of N and P and the relative amounts exported suggest that phosphorus is in short supply but both nutrients are present in low concentrations comparable to those found previously in tundra ponds at Point Barrow, Alaska.     

Nitrogen fixation by the hydrogen-oxidizing bacterium Alcaligenes latus

The aerobic hydrogen-oxidizing bacterium Alcaligenes latus represented by three strains was found to be able to grow with dinitrogen as the sole nitrogen source: The doubling time of total (Kjeldahl) nitrogen during growth on glucose at 30°C under an atmosphere containing 2% (v/v) oxygen in dinitrogen amounted to 39 h, while that in the presence of ammonium was 3 h. Nitrogen fixation did apparently not occur under air. During diazotrophic growth the cells accumulated up to 75% (w/dry weight) poly--hydroxybutyric acid. The efficiency of nitrogen fixation varied between 10 and 15 mg N per g glucose utilized. The specific nitrogenase activity measured in the acetylene reduction assay amounted to 5–17 nmol C₂H₄ formed per min and mg protein.     

Lignocellulose Mineralization by Arctic Lake Sediments in Response to Nutrient Manipulation

Mineralization of specifically labeled ¹⁴C-cellulose- and ¹⁴C-lignin-labeled lignocelluloses by Toolik Lake, Alaska, sediments was examined in response to manipulation of various environmental factors. Mineralization was measured by quantifying the amount of labeled CO₂ released from the specifically labeled substrates. Nitrogen (NH₄NO₃) and, to a greater degree, phosphorus (PO₄⁻³) additions enhanced the mineralization of white pine (Pinus strobus) cellulose during the summer of 1978. Nitrogen and phosphorus together had no cumulative effect. During the summer of 1979, nitrogen or phosphorus alone had only a slight stimulatory effect on the mineralization of a sedge (Carex aquatilis) cellulose; however, together, they had a dramatic effect. This variable response of mineralization to nutrient addition between 1978 and 1979 was probably attributable to year-to-year variation in nutrient availability within the lake. Cellobiose addition and oxygen depletion inhibited the amount of pine cellulose mineralized. Whereas addition of nitrogen to oxygen-depleted treatments had limited effect, addition of phosphorus resulted in mineralizations equal to or greater than that of the controls. Nitrogen had no effect on mineralization of pine or Carex lignins. Phosphorus, however, inhibited mineralization of both lignins. With Carex lignin, the phosphorus inhibition occurred at a concentration as low as 0.1 μM. The antagonistic role of phosphorus in cellulose and lignin mineralizations may be of significance in understanding the increased proportion of lignin relative to cellulose in decomposing litter.     

The utilization of phosphorus from muds by the phytoplankter,Scenedesmus dimorphus,and the significance of these findings to the practice of pond fertilization

Muds from 12 types of soils were used as the only source of phosphorus in cultures of Scenedesmus dimorphus. Some muds supported as much algal growth as was obtained with 0.075 to 0.5 mg/1 of phosphorus, while little or no growth occurred in cultures which contained other muds as a source of phosphorus. Algal growth was correlated with the fractions of soil phosphorus which were extracted with the following solutions; I — the phosphorus — free nutrient solution, II — 0.05N HCl plus 0.025N H₂SO₄, III — 0.002N H₂SO₄ plus 3 g/l of K₂SO₄, and IV — 0.1N HCl plus 0.03N/NH₄F. Additions of phosphorus to the soils prior to their use as muds increased the suitability of some as sources of phosphorus, but for others the added phosphorus was so tightly bound to the soil that little or none was available to S. dimorphus. The findings indicate that the type of soil in a pond will likely have a large influence on the efficiency of fertilization with phosphate fertilizers.

     

Influence of nitrogen source on growth and nitrogenase activity inAzotobacter vinelandii

Growth and nitrogenase activity were studied in cultures ofAzotobacter vinelandii growing with dinitrogen, ammonium sulfate, aspartic acid or yeast extract. Nitrogenase activity was measured by means of the C₂H₂ reduction test.In the presence of ammonium sulfate nitrogenase is completely repressed. After exhaustion of ammonia its activity is restored following a diauxic lag period of 30 min. With aspartic acid nitrogenase activity is partially repressed, and growth yield is higher than in the culture growing with N₂ only. This is due to simultaneous use of dinitrogen and aspartate. Fluctuations of nitrogenase activity occurring during exponential growth and the mechanism of their regulation are discussed.Abbreviations NA nitrogenase activity - BNF Burk's nitrogen free medium     

Effects of delayed soil and foliar N fertilization on yield and N2 fixation of soybean

Summary Field experiments were conducted to determine the effects of the amount, time and method of fertilizer N application on the efficiency of N uptake, N₂ fixatio and yield of soybean. Soil and foliar fertilizer N, applied during the pod-filling stage were absorbed by plants with equal and high efficiency, compared to an appreciably lower utilization efficiency for N applied before seedling emergence. These results reveal that the soybean roots were active in N uptake during these late stages of growth. Nitrogen fertilization during pod-filling resulted in significant yield increases over the control treatment which received an early application of 20 Kg N/ha. Seed yield increases were, however, more pronounced than total dry matter yield, and virtually all of the late-applied N was translocated into the pods. Nitrogen fixation in soybean was not influenced by the application of 40 kg N/ha to plants as soil or foliar N during the pod-filling stage. However, 80 kg N/ha supplied during pod-filling as 40 kg soil plus 40 kg foliar N/ha significantly reduced the amount of N₂ fixed. The results obtained in these studies suggest that inadequate N supply during pod-filling limited soybean yields, and that by the judicious application of fertilizer N during the late stages of growth, it was possible to enhance soybean yields without necessarily inhibiting N₂ fixation.     

Plant assimilation and nitrogen cycling

Nitrogen, an abundant and yet limiting nutrient for crop and food production, enters the plant as nitrate or ammonium, or as dinitrogen through biological fixation by procaryotes associated with the plant. Nitrogen incorporation into the soil-plant-animal system is ultimately restricted by rates of biological and industrial fixation. Biological fixation conserves fossil fuel, but fertilization is preferred in most present agriculture. Nitrogen-metabolism research has the practical objectives of allowing more efficient N-fertilizer utilization by plants, including those that fix N₂ but benefit from fertilizer_N supplements. Nitrogen accumulation by harvested crops results in changes in soil acidity, with the direction of change depending on the N-source. There is little information on long-term effects of crop N-nutrition on acidity, and acidity is a critical factor that affects agricultural productivity in many tropical soils. Thus, plant control of pH and the acid/base balance in the soil as a consequence of nitrogen uptake and assimilation are important areas of future research.     

Assess suitability of hydroaeroponic culture to establish tripartite symbiosis between different AMF species, beans, and rhizobia

Background  

Like other species of the Phaseoleae tribe, common bean (Phaseolus vulgaris L.) has the potential to establish symbiosis with rhizobia and to fix the atmospheric dinitrogen (N₂) for its N nutrition. Common bean has also the potential to establish symbiosis with arbuscular mycorrhizal fungi (AMF) that improves the uptake of low mobile nutrients such as phosphorus, from the soil. Both rhizobial and mycorrhizal symbioses can act synergistically in benefits on plant.     

Uptake of phosphorus by plants in relation to carbon dioxide production and organic phosphorus mineralization in soils

Summary In previous work, the yield of phosphorus in plants grown in the greenhouse on 36 alkaline soils was correlated significantly with the organic phosphorus mineralized during incubation of the soils in the laboratory, independently of the labile inorganic phosphorus. In this investigation, the same soils were used to test the hypothesis that the apparent organic-phosphorus effect observed previously was an indirect effect of CO₂ evolved from soil organic matter in increasing the susceptibility of the inorganic phosphorus to uptake by plants. The hypothesis was tested on the basis of measurements of CO₂ evolved and organic phosphorus mineralized concurrently during incubation of the soils in the laboratory. Statistical tests showed that the yield of phosphorus in the plants was correlated significantly with the organic phosphorus mineralized, independently of correlations with CO₂ evolved and labile inorganic phosphorus; the yield of phosphorus in plants, however, was not correlated significantly with CO₂ evolved, independently of correlations with organic phosphorus mineralized and labile inorganic phosphorus. The results thus provide no justification for discarding the organic-phosphorus theory and for substituting the CO₂ theory in its place.Journal Paper No. J-5691 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project No. 1183.Rockefeller Foundation Fellow and Professor of Soils.     

Complexes of binucleating ligands. XVI. Some diazotate-bridged palladium(II) complexes

The acetate-bridged complex, LPd₂(CH₃CO₂), in which L^3? is a binucleating ligand containing a bridging thiophenoxide unit, reacts with the syn-phenyldiazotate ion to yield the syn-diazotate-bridged complex LPd₂(syn-C₆H₅NNO) and with the anti-phenyldiazotate ion to yield LPd₂ (anti-C₆H₅NNO). The anti-complex isomerises to syn in boiling benzene, in contrast to the isomerisation of the free diazotate ions which proceeds spontaneously in the opposite direction. A para-nitro substituent has a pronounced labilising effect upon the isomerisation and LPd₂(CH₃CO₂) reacts with sodium anti-p-nitrophenyldiazotate at room temperature to yield the syn complex, LPd₂(syn-p-NO₂·C₆H₄·NNO). Nitrosourethane, C₂H₅OOC·NH·NO, reacts with LPd₂(CH₃CO₂) to generate LPd₂(C₂H₅OOC·NNO).     

Some Bag Experiments on Tibbs Run Lake,W.V., A Eutrophic Acidified Lake

Tibbs Run Lake was sampled from December 1979 to December 1980, monthly during the winter and biweekly during the spring, summer, and autumn. Primary production was measured from March 1980 to February 1981, either monthly or biweekly, as indicated above. The mean annual hydrogen ion concentration was equivalent to pH 4.33. This pH was 46% lower (based on H⁺ concentrations) than the 1977–1978 mean. The low pH of the lake is due to inputs of acid precipitation and the low buffering capacity of the watershed. Predictions of further reductions in the lake pH, based on mean annual hydrogen ion concentrations and hydrogen ion retention coefficients (RH) from Shellito (1979) and this study, indicate that the lake pH should reach an equilibrium with the precipitation pH between 1982 and 1985, assuming the precipitation pH continues to average 4.10. The stratified period mean chlorophyll a and total phosphorus concentrations were 22.1 mg/m³ and 19.3 μg/1, respectively. Total phosphorus loading to the lake was 0.233 gP/m²/yr. To examine the effects of neutralization and fertilization with phosphorus an in situ bag enclosure experiment, lasting 16 days, was performed during the summer of 1980. In the bags, phosphorus (20 μg/1 on days 0,4,8,12 as KH₂PO₄) was added alone and in combination with a base addition (IN KOH). The base additions raised the pH to approximately 7.8. Other treatments included base addition alone and a control. The maximum chlorophyll a concentration was found in the phosphorus treatment (∼30 mg/m³) on day 6. The phosphorus plus base treatment exhibited a 10 day lag before reaching a maximum chlorophyll a concentration (∼27 mg/m³) on day 16. The highest production rate was found in the phosphorus plus base treatment on day 12 (∼27 mgC/m³/hr.). A similar bag experiment, lasting 46 days, was performed during the late summer and early autumn of 1980. The treatments were the same as in the first experiment, however, the nitrate-nitrogen depletion in the lake and treatments necessitated the addition of nitrogen (2 mg/1 as NaNO₃) to one of each replicate treatment on day 5. On day 34, the maximum chlorophyll a concentrations were found in the phosphorus plus base nitrogen treatment (∼120 mg/m³) and the phosphorus plus nitrogen treatment (∼38.8 mg/m³). The control plus nitrogen treatment was submerged and possibly contaminated on day 5. All treatments not receiving nitrogen, except for the phosphorus plus base treatment, decreased in the chlorophyll a concentration throughout the experiment. The phosphorus plus base treatment peaked in the chlorophyll a concentration on day 45 (∼28 mg/m³) despite non-detectable levels of nitrate-nitrogen. The maximum primary production rate was found in the phosphorus plus base plus nitrogen treatment (∼32 mgC/m³/hr.) on day 11.     

Separation of the apoprotein and reconstitution of the holoprotein from the long-lived intermediate in bacterial bioluminescence

A long-lived intermediate in bacterial bioluminescence, which has been suggested to be an FMN flavoprotein, has been separated as an apoprotein plus free FMN and the holoprotein reconstituted by addition of FMN (K_a = 7 × 10⁵ M^?1). The apoprotein preparation reacts with long-chain aldehyde to give the full quantum yield observed for the complete system. Only after removal of all remaining FMN in the apoprotein preparation by prior dialysis of luciferase against KBr and inclusion of apoflavodoxin in the reaction mixture, can a dependence of the light output on FMN be observed. Bacterial bioluminescence therefore appears to be in the class of sensitized chemiluminescence with FMN acting as the specific sensitizing agent.     

The influence of phosphorus and nitrogen on millet and clover growing in soils affected by salinity

Summary The growth of foxtail millet and clover in soils of varying degrees of salinity (0.5 to 13 mmhos/cm), treated with nitrogen and phosphorus, was studied. Salinity levels were achieved by addition of sodium chloride. Nitrogen (10 to 60 ppm N) and phosphorus (6.4 to 44.8 ppm P) were added as NH₄NO₃ and H₃PO₄, respectively. The growth of millet decreased sharply with increase in soil salinity, when N-P treatments were not applied. The development of this plant altered under saline conditions, however, when nitrogen and phosphorus were added; various N-P combinations affected plant growth in saline soil differently. Phosphorus, when applied at relatively high rates, significantly improved plant growth. Increased rates of nitrogen in the N-P treatments generally had no significant effect on growth; it was reduced when the N/P ration was highest. Clover ceased to grow when the salinity of the soil exceeded 7 mmhos/cm and no N-P was added. Phosphorus enhanced the growth of clover, and at high rates of its application in the N-P combinations, clover grew even at the highest salinity level tested (13 mmhos/cm). Nitrogen increase had no marked effect on plant development. Comparing enhancement of growth at high salinity levels, clover was somewhat less affected by the N-P treatment than millet. The top/root ratio of clover generally increased with increase of phosphorus in the N-P combinations. This research (Parts I and II) was supported in part by a grant from the U.S. Department of Agriculture under P. L. 480.     

Facets of diazotrophy in the oxygen minimum zone waters off Peru

Nitrogen fixation, the biological reduction of dinitrogen gas (N₂) to ammonium (NH₄⁺), is quantitatively the most important external source of new nitrogen (N) to the open ocean. Classically, the ecological niche of oceanic N₂ fixers (diazotrophs) is ascribed to tropical oligotrophic surface waters, often depleted in fixed N, with a diazotrophic community dominated by cyanobacteria. Although this applies for large areas of the ocean, biogeochemical models and phylogenetic studies suggest that the oceanic diazotrophic niche may be much broader than previously considered, resulting in major implications for the global N-budget. Here, we report on the composition, distribution and abundance of nifH, the functional gene marker for N₂ fixation. Our results show the presence of eight clades of diazotrophs in the oxygen minimum zone (OMZ) off Peru. Although proteobacterial clades dominated overall, two clusters affiliated to spirochaeta and archaea were identified. N₂ fixation was detected within OMZ waters and was stimulated by the addition of organic carbon sources supporting the view that non-phototrophic diazotrophs were actively fixing dinitrogen. The observed co-occurrence of key functional genes for N₂ fixation, nitrification, anammox and denitrification suggests that a close spatial coupling of N-input and N-loss processes exists in the OMZ off Peru. The wide distribution of diazotrophs throughout the water column adds to the emerging view that the habitat of marine diazotrophs can be extended to low oxygen/high nitrate areas. Furthermore, our statistical analysis suggests that NO₂⁻ and PO₄³⁻ are the major factors affecting diazotrophic distribution throughout the OMZ. In view of the predicted increase in ocean deoxygenation resulting from global warming, our findings indicate that the importance of OMZs as niches for N₂ fixation may increase in the future.     

Reactions of the carbon tetrachloride-related peroxy free radical (CCl3O2.) with amino acids : Pulse radiolysis evidence

Pulse radiolysis studies indicate that the free radical CCl₃O₂. but not the radical CCl₃ reacts rapidly with tryptophan, tyrosine, phenol or promethazine to yield transient products with strong visible absorption spectra.     

Response of grain sorghum to enhanced-ammonium supply

Two greenhouse experiments were conducted to examine the effects of increased levels of soil NH ₄ ⁺ on the growth and yield of grain sorghum (Sorghum bicolor (L.) Moench). Nitrogen was supplied as urea plus the nitrification inhibitor nitrapyrin (enhanced-NH ₄ ⁺ supply) or as a 41 molar ratio of CA(NO₃)₂ and Mg(NO₃)₂ at rates of 0 to 450 mg N kg^–1 soil in 37.5 mg N increments. Enhanced-NH ₄ ⁺ supply, in comparison to the NO₃ treatment, increased grain yield 15 and 18% in the two experiments. In one experiment this yield increase occurred through increased number of kernels and in a second experiment, through increased weight of kernels. During the first 28 days after plant emergence, the number of leaves, stalk width, plant weight, and plant N content were greater with enhanced-NH ₄ ⁺ supply than with NO ₃ ^– . However, at harvest total plant weight and plant N content were minimally affected by enhanced-NH ₄ ⁺ supply.