Lag period of 14CO2 evolution from dioctyl sulpho[2,3-14C]succinate in relation to adaptation of bacterium, Comamonas terrigena, to dialkyl esters of sulphosuccinate

Comamonas terrigena, strain N3H, which was isolated from soil polluted with crude oil products, degraded dioctyl sulphosuccinate, a synthetic commercial surfactant. The primary degradation of this compound, the cleavage of ester bonds between octyl groups and sulphosuccinate, lasted significantly shorter time than the subsequent breakdown of the sulphosuccinate moiety of dioctyl sulpho[2,3-(14)C]succinate. (14)CO(2) evolution had a significant shorter lag period with cells in Tris/phosphate medium, without inorganic sulphate and adapted to surfactant, than unadapted cells. The acceleration of the primary degradation by adapted cells also suggest that some enzymes involved in surfactant degradation are inducible. The bacterium may be useful for bioremediation.     

Separation and purification of penicillin acylase from Escherichia coli using AOT reverse micelles

Summary The extraction of penicillin acylase by reverse micellar solutions of a surfactant was studied. A 50 mM solution of dioctyl sodium sulphosuccinate in isooctane extracted 46% of the enzyme activity in a crude periplasmic extract of induced cells of E. coli ATCC 9637. The increase in the specific activity of the final enzyme preparation, after stripping of the organic phase at pH 7.5, in the presence of 1 M KCl, was 8 - fold.Abbreviations PA penicillin acylase (penicillin amidohydrolase EC 3.5.1.11) - AOT Aerosol OT (dioctyl sodium sulphosuccinate) - NIPAB 6-nitro-3-(phenylacetamido)-benzoic acid - NABA 6-nitro-3-aminobenzoic acid - BSA bovine serum albumin - SDS sodium dodecylsulphate     

Sorption isotherms and kinetics in the primary biodegradation of anionic surfactants by immobilized bacteria:: II. Comamonas terrigena N3H

Comamonas terrigena N3H was immobilized by covalent linking on silanized inorganic supports and by physical entrapment of cells within calcium alginate beads and reticulated polyurethane foam. Both entrapped cells were efficient for the primary biodegradation of the anionic surfactants dihexyl sulphosuccinate (DHSS) and dioctyl sulphosuccinate (DOSS), furthermore, exhibiting, in the case of polyurethane immobilized cells, a positive fractionating effect of the substrate by adsorption onto the polymer matrix. The overall kinetics for the surfactant removal from water were well-fitted to a biphasic process, a rapid passive sorption step of the surfactant onto the cell-loaded support and the intrinsic primary biodegradation slower step, both acting synergically.     

Production and structural characterization of surfactin (C14/Leu7) produced by Bacillus subtilis isolate LSFM-05 grown on raw glycerol from the biodiesel industry

The production of biosurfactant by Bacillus subtilis LSFM-05 was carried out using raw glycerol, obtained from a vegetable oil biodiesel plant in Brazil, as the sole carbon source. Production of the biosurfactant was carried out in a 15-L bench-top fermentor and the surfactant was obtained from the foam produced. The crude surfactant was purified by silica gel column chromatography with a yield of 230 mg of the purified biosurfactant per liter of foam. TLC, IR spectroscopy, ¹H and ¹³C NMR and Fourier transform ion cyclotron resonance mass spectrometry with electrospray ionization (ESI-FTMS) were used to characterize the purified surfactant. The isolated surfactant was identified as a surfactin lipopeptide. MS/MS data identified the amino acid sequence as GluOMe-Leu-Leu-Asp-Val-Leu-Leu and showed that the fatty acid moiety contained 14 carbons in iso, anteiso or normal configurations. The critical micelle concentration of the C₁₄/Leu₇ surfactin was 70 μM, with emulsification efficiency after 24 h (E₂₄) of 67.6% against crude oil. Raw glycerol represents an abundant and renewable carbon source and provides an opportunity for reducing the cost of biosurfactant production and may add value to biodiesel production by creating new commercial applications for this by-product.     

The patterns of growth, assimilation of 14CO2 and distribution of 14C-assimilate within vegetative plants of Loliumperenne at low and high density

The patterns of growth, assimilation of ¹⁴CO₂ and distribution of ¹⁴C-labelled assimilate were followed for 12 wk from sowing in individual plants of Lolium perenne grown in miniswards at either low (500 plants m^-2) or high (5000 plants m^-2) density. At the latter density, plants were characterised by a 50% reduction in RGR, by the production of fewer tillers, especially second- and third-order tillers, and by a reduction in mean tiller weight. All the green and senescing leaves of each tiller assimilated ¹⁴CO₂ and the overall assimilatory capacity of a tiller was directly related to its dry weight. At both densities the plant consisted of a main shoot and established tillers with comparable assimilatory activities and a range of developing tillers that assimilated relatively small amounts of ¹⁴CO₂. As each successive primary tiller developed it was supplied with assimilate from the main shoot and the degree of support was inversely proportional to the dry weight of the tiller. At both densities it was concluded that the first primary tiller could be regarded as an independent assimilatory unit when it reached a dry weight of about 25 mg even though some import of main shoot assimilate continued until the tiller was double this weight. The supply of assimilate to the root system was greatly reduced at both densities compared with previous observations on plants grown singly.     

DECARBOXYLATION STUDIES OF GLUTAMATE, GLUTAMINE, AND ASPARTATE FROM BRAIN LABELLED WITH [1-14C] ACETATE, l-[U-14C]-ASPARTATE, AND l-[U-14C]GLUTAMATE

Studies in vivo and in vitro of the distribution of label in C-1 of glutamate and glutamine and C-4 of aspartate in the free amino acids of brain were carried out. [1-¹⁴C]-Acetate was used both in vivo and in vitro and l -[U-¹⁴C]aspartate and l -[U-¹⁴C]glutamate were used in vitro.

• 1 The results obtained with labelled acetate and aspartate suggest that CO₂ and a 3-carbon acid may exchange at different rates on a CO_a-fixing enzyme.
• 2 The apparent cycling times of both glutamate and glutamine show fast components measured in minutes and slow components measured in hours.
• 3 With [1-¹⁴C]acetate in vitro glutamine is more rapidly labelled in C-1 than is glutamate at early time points; the curves cross over at about 7 min.
• 4 The results support and extend the concept of metabolic compartmentation of amino acid metabolism in brain.

     

Sorption isotherms and kinetics in the primary biodegradation of anionic surfactants by immobilized bacteria: I. Pseudomonas C12B

The surfactant-degrading biocatalyst Pseudomonas C12B was immobilized by covalent linking on silanized inorganic supports and by physical entrapment of cells within reticulated polyurethane foam. Both immobilized biocatalysts have been shown to be appropriate for the effective primary biodegradation of the anionic surfactants sodium dodecyl sulphate (SDS), dodecylbenzene sulphonic acid (DBS), dioctyl sulphosuccinate (DOSS) and dihexyl sulphosuccinate (DHSS). The overall surfactant removal from water by cells entrapped in reticulated polyurethane foam exhibits a biphasic process, a rapid sorption step of the surfactant onto the cell-loaded support and the intrinsic primary biodegradation slower step, both acting cooperatively. The optimization of variables for the adsorption and the biodegradation processes (flow rate, particle size, substrate concentration) have been studied. Sorption isotherms for the surfactants on reticulated polyurethane foam have been established as type II of the Brunauer, Deming, Deming and Teller (BDDT) classification. The kinetics of the primary biodegradation of SDS by cells covalent linked on sepiolite treated with 3-aminopropyl triethoxysilane (APTS) were found to be first-order. In this case, surfactant adsorption does not exist.     

Characteristics of [14C]Guanidinium Accumulation in NG 108-15 Cell Exposed to Serotonin 5-HT3 Receptor Ligands and Substance P

Abstract: In the presence of substance P (SP; 10 μM), serotonin (5-HT; 1 μM) triggered a cation permeability in cells of the hybridoma (mouse neuroblastoma X rat glioma) clone NG 108-15 that could be assessed by measuring the cell capacity to accumulate [¹⁴C]guanidinium for 10-15 min at 37°C. In addition to 5-HT (EC₅₀, 0.33 μM), the potent 5-HT₃ receptor agonists 2-methyl-serotonin, phenylbiguanide, and m-chlorophenylbiguanide, and quipazine, markedly increased [¹⁴C]guanidinium uptake in NG 108-15 cells exposed to 10 μM SP. In contrast, 5-HT₃ receptor antagonists prevented the effect of 5-HT. The correlation (r= 0.97) between the potencies of 16 different ligands to mimic or prevent the effects of 5-HT on [¹⁴C]guanidinium uptake, on the one hand, and to displace [³H]zacopride specifically bound to 5-HT₃ receptors on NG 108-15 cells, on the other hand, clearly demonstrated that [¹⁴C]guanidinium uptake was directly controlled by 5-HT₃ receptors. Various compounds such as inorganic cations (La³⁺, Mn²⁺, Ba²⁺, Ni²⁺, and Zn²⁺), D-tubocurarine, and memantine inhibited [¹⁴C]guanidinium uptake in NG 108-15 cells exposed to 5-HT and SP, as expected from their noncompetitive antagonistic properties at 5-HT₃ receptors. However, ethanol (100 mM), which has been reported to potentiate the electrophysiological response to 5-HT₃ receptor stimulation, prevented the effects of 5-HT plus SP on [¹⁴C]guanidinium uptake. The cooperative effect of SP on this 5-HT₃-evoked response resulted neither from an interaction of the peptide with the 5-HT₃ receptor binding site nor from a possible direct activation of G proteins in NG 108-15 cells. Among SP derivatives, [D-Pro⁹]SP, a compound inactive at the various neurokinin receptor classes, was the most potent to mimic the stimulatory effect of SP on [¹⁴C]guanidinium uptake in NG 108-15 cells exposed to 5-HT. Although the cellular mechanisms involved deserve further investigations, the 5-HT-evoked [¹⁴C]guanidinium uptake appears to be a rapid and reliable response for assessing the functional state of 5-HT₃ receptors in NG 108-15 cells.     

Alterations in the Production of 14CO2 and [14C]Acetylcholine from [U-14C]Glucose in Brain Subregions Following Transient Forebrain Ischemia in the Rat

Abstract: The production of ¹⁴CO₂ and [¹⁴C]acetylcholine from [U-¹⁴C]glucose was determined in vitro using tissue prisms prepared from the dorsolateral striatum (a region developing extensive neuronal loss following ischemia) and the paramedian neocortex (an ischemia-resistant region) following 30 min of forebrain ischemia and recirculation up to 24 h. Measurements were determined under basal conditions (5 mMK⁺) and following K⁺ depolarization (31 mM K⁺). The production of ¹⁴CO₂ by the dorsolateral striatum was significantly reduced following 30 min of ischemia for measurements in either 5 or 31 mM K⁺ but recovered toward preischemic control values during the first hour of recirculation. Further recirculation resulted in ¹⁴CO₂ production again being reduced relative to control values but with larger differences (20–27% reductions) detectable under depolarized conditions at recirculation times up to 6 h. Samples from the paramedian neocortex showed no significant changes from control values at all time points examined. [¹⁴C]Acetylcholine synthesis, a marker of cholinergic terminals that is sensitive to changes in glucose metabolism in these structures, was again significantly reduced only in the dorsolateral striatum. However, even in this tissue, only small (nonstatistically significant) differences were seen during the first 6 h of recirculation, a finding suggesting that changes in glucose oxidation during this period were not uniform within all tissue components. The results of this study provide evidence that in a region susceptible to ischemic damage there were specific changes during early recirculation in the metabolic response to depolarization. This apparent inability to respond appropriately to an increased need for energy production could contribute to the further deterioration of cell function in vivo and ultimately to the death of some cells.     

Purine and pyrimidine metabolism in cultured white spruce (Picea glauca) cells: Metabolic fate of 14C-labeled precursors and activity of key enzymes

In order to examine the biosynthesis, interconversion, and degradation of purine and pyrimidine nucleotides in white spruce cells, radiolabeled adenine, adenosine, inosine, uracil, uridine, and orotic acid were supplied exogenously to the cells and the overall metabolism of these compounds was monitored. [8‐¹⁴C]adenine and [8‐¹⁴C]adenosine were metabolized to adenylates and part of the adenylates were converted to guanylates and incorporated into both adenine and guanine bases of nucleic acids. A small amount of [8‐¹⁴C]inosine was converted into nucleotides and incorporated into both adenine and guanine bases of nucleic acids. High adenosine kinase and adenine phosphoribosyltransferase activities in the extract suggested that adenosine and adenine were converted to AMP by these enzymes. No adenosine nucleosidase activity was detected. Inosine was apparently converted to AMP by inosine kinase and/or a non‐specific nucleoside phosphotransferase. The radioactivity of [8‐¹⁴C]adenosine, [8‐¹⁴C]adenine, and [8‐¹⁴C]inosine was also detected in ureide, especially allantoic acid, and CO₂. Among these 3 precursors, the radioactivity from [8‐¹⁴C]inosine was predominantly incorporated into CO₂. These results suggest the operation of a conventional degradation pathway. Both [2‐¹⁴C]uracil and [2‐¹⁴C]uridine were converted to uridine nucleotides and incorporated into uracil and cytosine bases of nucleic acids. The salvage enzymes, uridine kinase and uracil phosphoribosyltransferase, were detected in white spruce extracts. [6‐¹⁴C]orotic acid, an intermediate of the de novo pyrimidine biosynthesis, was efficiently converted into uridine nucleotides and also incorporated into uracil and cytosine bases of nucleic acids. High activity of orotate phosphoribosyltransferase was observed in the extracts. A large proportion of radioactivity from [2‐¹⁴C]uracil was recovered as CO₂ and β‐ureidopropionate. Thus, a reductive pathway of uracil degradation is functional in these cells. Therefore, white spruce cells in culture demonstrate both the de novo and salvage pathways of purine and pyrimidine metabolism, as well as some degradation of the substrates into CO₂.     

Comparative Basipetal Transport of 6-Benzylaminopurine-8-14C, Gibberellin A3-3H, IAA-2-14C, and Sucrose-14C in the Root of Intact Citrus aurantium Seedlings

The transport and distribution of IAA-2-¹⁴C, gibberellin A₃-³H, 6-benzylaminopurine-8-¹⁴C and sucrose-¹⁴C (U) were studied in whole seedlings of Citrus aurantium L. after “replacing” the root tip with the solution of radiochemicals. All four substances were transported basipetally in the root and were distributed to the stem and leaves. The pattern of distribution of the label from 6-benzylaminopurine was similar to that of sucrose, while a considerably larger amount of gibberellin A₃ was transported to basal regions of the root, away from the tip, and into the shoot. Contrary to these three substances, the basipetal transport of IAA in the root was very low, and the majority of the label was retained in the terminal sections of the root. It is suggested that the different efficiencies at which various hormones move in the transpiration stream in the root may be an important factor in the attainment of a certain balance of hormones in the shoot.     

Effect of surfactants and fungicides on clubroot (Plasmodiophora brassicae) of brassicas

Two formulations of the surfactant sodium dioctyl sulphosuccinate (Aerosol OT, Monawet MO70), one of alkyl phenyl ethylene oxide (Agral) and three fungicides (PP192, dichlorophen and a thiabendazole/iodophor complex -Byatran) were tested in field trials for control of clubroot (Plasmodiophora brassicae) on cabbage in 1988 and 1989. A standard mercurous chloride treatment (pre-sowing compost incorporation) was included in all experiments. Plants were raised in 64 cm³ blocks (1988) or 15 cm³ free-fill cells (1989). Mercurous chloride reduced disease severity and increased yield in both years. Byatran was ineffective. The surfactants and dichlorophen, applied as pre-planting soaks to the plant-raising compost, restricted disease development and increased yield in 1988 but not in 1989. A similar treatment with PP192 restricted disease severity and enhanced yield in both years. Pouring the surfactants and dichlorophen into the planting hole was more effective than using them to soak the compost. In 1989 pour treatments with Agral and a combined soak/pour treatment with dichlorophen reduced disease severity and increased yields by 250% and 97% respectively; compost treatment with PP192 gave a 150% increase.     

Cytokinin Function: Increase in [Methyl−14C] Metabolism to Phosphatidylcholine and a Decrease in Oxidation to Carbon Dioxide−14C

Axillary buds of Nicotiana tabacum L. cv. Maryland Catterton normally suppressed by apical dominance are released from dormancy with 6-benzylaminopurine. This work was done to determine the change in the [methyl^?14C] metabolism from methionine during bud stimulation with cytokinin. Dormant buds metabolize [methyl^?14C] -methionine to ¹⁴CO₂ more effectively than buds released from dormancy. This oxidation of the methyl group is inhibited with benzylaminopurine. On the other hand, the methylation of polar membrane components, including phosphatidylcholine, is enhanced by the cytokinin during the period preceding the increase in bud weight. The interpretation is presented that the enhanced synthesis of membrane components, as well as the preservation of the methyl groups, are mechanisms for the cytokinin release of bud dormancy with 6-benzylaminopurine.     

Incorporation of 14CO2, 14C-phenylalanine and 14C-cinnamate into soluble and insoluble cinnamic derivatives in Mentha arvensis

With the successful development of methods for the isolation and purification of ethanol-insoluble cinnamic acid esters in mint it became possible to initiate kinetic, isotopic studies on purified, ‘insoluble’ derivatives of caffeic acid, ferulic acid and p-coumaric acid. Pulse-feeding experiments were conducted with ¹⁴CO₂, phenylalanine-U-¹⁴C and cinnamic acid-3-¹⁴C. The ferulic acid derivative exhibited a significant turnover as compared to the other insoluble derivatives which were relatively stable. Time-course tracer studies were performed to compare the turnover of soluble caffeic acid derivatives with ‘insoluble’ forms of caffeic acid. Caffeic acid associated with a macromolecular fraction consistently showed a higher specific activity than either soluble caffeic acid or the caffeic acid associated with a second insoluble derivative.     

Transport and Distribution of 14CO2 Assimilate in Lolium perenne in Response to Varying Nitrogen Supply to Halves of a Divided Root System

The movement of ¹⁴C assimilate from shoots to roots and its subsequent metabolism in the root of Lolium perenne L. was studied using variable N nutrition supplied to halves of a divided root system. Half of the N-deficient root system was supplied with either high NO₃-N or high NH₄-N for 16 hours or 6 days before ¹⁴CO₂ labeling of the shoots. The distribution of ¹⁴C in sugars, ethanol-soluble nitrogen and organic acids in roots appeared to be related to the N content of the tissue. Supply of high NO₃-N for 6 days resulted in significant internal translocation of N into the low N supplied root half. Both root halves also had similar patterns of ¹⁴C distribution among soluble and insoluble metabolites. However, NH₄-N supply for 6 days did not result in a significant increase of N in the low N supplied roots, thus only the high NH₄-N supplied roots displayed stimulated sugar metabolism, similar to that in both root halves in the high NO₃-N supply treatment. Percent transport of ₁₄C assimilates from shoot to root was influenced by form and level of N supplied to root halves. Root halves supplied with either high N source for 6 days accumulated greater amounts of ¹⁴C assimilate than the corresponding low N root half. However NH₄-N supply appeared to make roots stronger sinks since NH₄ supply resulted in significantly greater ¹⁴C accumulation in both the high NH₄ supplied and the low N root halves than did NO₃-N supply in corresponding root halves. The data suggest that factors other than root metabolism, such as N mediated metabolism in the shoot, may also influence the percent transport of assimilates to the root. Internal distribution of the incoming assimilate within the root system could be regulated by the metabolic activity or assimilate demand of the roots.     

Oxalate synthesis from [14C1]glycollate and [14C1]glycoxylate in the hepatectomized rat

Hepatectomy significantly altered the metabolism of [1-¹⁴C]glyoxylate and [1-¹⁴C]glycollate in the rat. The production of ¹⁴CO₂ was reduced by 47% and 77%–86%, respectively, indicating the involvement of the liver in the oxidation of both substrates. Unidentified intermediates, assumed to be primary glycine, serine and ethanolamine, were also reduced by over 50%, was would be expected from the removal of the aminotransferase enzymes through the hepatectomy. The biosynthesis of [¹⁴C]oxalate from [1-¹⁴C]glycollate was reduced by more than 80% in the hepatectomized rat. This suggests that this oxidation is primarily catalyzed by the liver enzymes, glycolic acid oxidase and glycolic acid dehydrogenase, in the intact rat. The limited formation of [¹⁴C]oxalate from [¹⁴₁]glycollate observed in the hepatectomized rat is probably catalyzed by lactate dehydrogenase or extrahepatic glycolic acid oxidase. Hepatectomy did not significantly alter the rate of formation of [¹⁴C]oxalate from [¹⁴₁]glyoxylate. However, since saturating concentrations of glyoxylate could not be used because of the toxicity of this substrate, the involvement of glycollic acid oxidase in this oxidation reaction in the intact rat can not be ruled out. In the hepatectomized rat, lactate dehydrogenase appears to be the enzyme making the major contribution, although other as yet not identified enzymes may be contributing. The increased deposition of oxalate in the tissues, oxalosis, may result from the shift in oxalate synthesis from the liver to the extrahepatic tissues.     

A SOLUBLE PREPARATION FROM RAT BRAIN THAT INCORPORATES INTO ITS OWN PROTEINS [14C]ARGININE BY A RIBONUCLEASE-SENSITIVE SYSTEM AND [14C]TYROSINE BY A RIBONUCLEASE-INSENSITIVE SYSTEM

Abstract— A 100,000 g supernatant fraction from rat brain that was passed through a column of Sephadex G-25-40 was able, after addition of some factors, to incorporate [^I4C]arginine (apparent K_m= 5 μM) and [¹⁴C]tyrosine (apparent K_m= 20 μM) into its own proteins. The factors required for the incorporation of [¹⁴C]arginine were: ATP (optimal concentration = 0-25-2 μM) and Mg²⁺ (optimal concentration 5 mM). For the incorporation of [^I4C]tyrosine the required factors were: ATP (apparent K_m= 0-75 μM), Mg²⁺ (optimalconcentration 8-16 mM) and K⁺ (apparent K_m= 16 mM). Addition of 19 amino acids did not enhance these incorporations. Optimal pHs were: for [¹⁴C]arginine and [¹⁴C]tyrosine, respectively, 7-4 and 7-0 in phosphate buffer and 7–9 and 7-3-8-1 in tris-HCl buffer. Pancreatic ribonuclease abolished the incorporation of [¹⁴C]arginine but had practically no effect in the incorporation of [¹⁴C]tyrosine. Furthermore, [¹⁴C]arginyl-tRNA was a more effective donor of arginyl groups than [¹⁴C]arginine, whereas [¹⁴C]tyrosyl-tRNA was considerably less effective than [¹⁴C]tyrosine. The incorporations of [¹⁴C]arginine and [¹⁴C]tyrosine into brain proteins were from 25- to 2000-fold higher than for any other amino acid tested (12 in total). In brain [¹⁴C]arginine incorporation was higher than in liver and thyroid but somewhat lower than in kidney. In comparison to brain, the incorporation of [¹⁴C]tyrosine was negligible in liver, thyroid or kidney. Kinetic studies showed that the macromolecular factor in the brain preparation was complex. The protein nature of the products was inferred from their insolubilities in hot TCA and from the action of pronase that rendered them soluble. [¹⁴C]Arginine was bound so that its a-amino group remained free. Maximal incorporation of [¹⁴C]tyrosine in brain of 30-day-old rats was about one-third of that in the 5-day-old rat. The changes with postnatal age in the incorporation of [¹⁴C]arginine were not statistically significant.     

The effect of light quality on the induction of efficient photosynthesis under low CO2 conditions in Chlamydomonas reinhardtii and Chlorella pyrenoidosa

The effect of blue and red light on the adaptation to low CO₂ conditions was studied in high-CO₂ grown cultures of Chlorella Pyrenoidosa (82T) and Chlamydomonas reinhardtii(137⁺) by measuring O₂ exchange under various inorganic carbon (Cⁱ) concentrations. At equal photosynthetic photon flux density (PPFD), blue light was more favourable for adaptation in both species, compared to red light. The difference in photosynthetic oxygen evolution between cells adapted to low C_iunder blue and red light was more pronounced when oxygen evolution was measured under low C_i compared to high C_i conditions. The effect of light quality on adaptation remained for several hours. The different effects caused by blue and red light was observed in C. pyrenoidosa over a wide range of PPFD with increasing differences at increasing PPFD. The maximal difference was obtained at a PPFD above 1 500 μmol m^?2s^?1. We found no difference in the extracellular carbonic anhydrase activity between blue- and red light adapted cells. The light quality effect recorded under C_i-limiting conditions in C. reinhardtii cells adapted to air, was only 37% less when instead of pure blue light red light containing 12.5% of blue light (similar PPFD as blue light) was used during adaptation to low carbon. This indicates that in addition to affecting photosynthesis, blue light affected a sensory system involved in algal adaptation to low C_i conditions. Since the affinity for C_i of C. Pyrenoidosa and C. reinhardtii cells adapted to air under blue light was higher than that of cells adapted under red light, we suggest that induction of some component(s) of the C_i accumulating mechanism is regulated by the light quality.     

Determination of the isotope distribution in malate-14C with fumarase-negative lactic acid bacteria

No fumarase activity could be found in whole cells or in cell-free crude extracts from Leuconostoc mesenteroides or Lactobacillus curvatus. The degradation of l-malate-4-¹⁴C by these organisms yielded more than 95% of the label as ¹⁴CO₂. It is therefore recommended that these organisms, rather than Lactobacillus plantarum, should be used in the determination of isotope distribution in l-malate-¹⁴C, since L. plantarum exhibits a significant fumarase activity and thus randomizes malate prior to the decarboxylation of this substance by the malolactic enzyme.     

An appraisal of ear, leaf and stem 14CO2 assimilation, 14C-assimilate distribution and growth in a reproductive seed crop of amenity Lolium perenne

In seed crops of Lolium perenne, yield may be reduced by competition for a limited assimilate supply from sinks other than the ear. This study was undertaken to evaluate the priorities for allocation of assimilate within the crop from all photosynthetic sites on the main reproductive tiller after anthesis. Ear, stem and leaves were fed with ¹⁴CO₂ on two occasions; the assimilatory efficiency of these sources and the magnitude and pattern of ¹⁴C-assimilate export from each was determined. The growth of each part of the main tiller and subtending tillers was also measured. Stem elongation apparently dominated the current assimilate resource and the ear did not become a net importer of assimilate until this process had ceased. Assimilate allocation to the tillers was high throughout. The nature of any competition between these sinks is discussed. When crop growth was contrasted with that in a previous year, environmental factors were implicated as determinants of priority for assimilate allocation to each sink. Sources of carbon for seed filling are also discussed as is the relevance of these findings to seed crop management.