Salivary peroxidase (SAPX): Genetic modification and relationship to the proline-rich (Pr) and acidic (Pa) proteins

There is genetic polymorphism of the peroxidase of human saliva, but not of leukocytes. The phenotypes are determined by autosomal inheritance, the phenotype of fast mobility (SAPX 1) being determined by homozygosity for a recessive gene (SAPX ¹) and the phenotypes of slow mobility (SAPX 2 and SAPX 3) being determined by two different genes, SAPX ² and SAPX ³, with completely dominant expression at the same locus. The phenotypes are modified by varying degrees of endogenous proteolysis. The SAPX 2 and SAPX 3 types appear to be genetically controlled modifications of SAPX 1 rather than different primary gene products, because of their completely dominant inheritance, their larger molecular size compared to SAPX 1, and their dissociation with 2-mercaptoethanol to give SAPX 1. The acidic protein type Pa 1 is always found in association with SAPX 2, and an uncommon variant type Pa 2 is associated with SAPX 3. The most likely hypothesis is that the genes Pa ¹ and Pa ² produce products which modify the SAPX 1 type. When the Pa type is Pa 0, the SAPX phenotype is SAPX 1. Since 2-mercaptoethanol can dissociate the Pa 1 protein into a probable monomeric form, and can dissociate SAPX 2 and SAPX 3 to give SAPX 1, it is probable that Pa 1 and Pa 2 monomers complex with SAPX 1 through disulfide bonds to give SAPX 2 or SAPX 3 types. The frequencies of the genes determining the SAPX types are the same as those for Pa: SAPX ¹ and Pa ⁰=0.787, SAPX ² and Pa ¹=0.208, SAPX ³ and Pa ²=0.005.This study was supported by a grant from the National Institutes of Dental Research (2-RO1-DE-03658-11).     

Effect of soil matric potential on leaf water potential,diffusive resistance,growth and development ofGmelina arborea L. seedlings

Gmelina arborea L. seedling growth and diurnal stomatal opening (as measured by stomatal resistance) were studied at soil matric potential 0, -0.1 and -0.72 × 10^?5 Pa. Leaf area, leaf number, plant height and dry weights of the vegetative parts were significantly reduced as soil matric potential decreased from 0 to -0.72 × 10^?5 Pa. The growth responses followed the same trend as net assimilation rate and relative growth rate. The highest moisture stress induced leaf senescence and leaf fall. Leaf water potential decreased from - 2 × 10^?5 Pa to - 20 × 10^?5 Pa with increasing soil moisture stress. Results indicate that the diurnal stomatal opening is controlled by photon flux density when this species is grown at soil matrio potential 0 Pa. However, with decreasing soil matrio potential (- 0.10 and -0.72 × 10^?5 Pa) the internal plant water deficit appears to oontrol the stomatal opening.     

Epidermal diffusive conductance as related to leaf water potential and photon flux density

Response of epidermal diffusive conductance to simultaneous changes in leaf water potential and photon flux density was studied in primary bean leaves. Values of epidermal conductance corresponding to every photon flux density decreased with decreasing leaf water potential below - 6.9 x 10⁵Pa; slight deorease was followed by a rapid one at water potential ranging from - 8.0 to -10.5 x 10⁵ Pa. In the leaves with water potential lower than -10.5 x 10⁵ Pa neither the saturated photon flux density (1200 [xeinstein m^-2s^-1) induced photoactive stomatal opening. Negative influence of one factor could be partially compensated by positive influence of the other. These results were in good agreement with the considered mechanism of action of leaf water potential and photon flux density on epidermal conductance.     

The onset of photosynthetic acclimation to elevated CO2 partial pressure in field-grown Pinus radiata D. Don. after 4 years

The effects of CO₂ enrichment on photosynthesis and ribulose‐1,5‐bisphosphate carboxylase/oxygenase (rubisco) were studied in current year and 1‐year‐old needles of the same branch of field‐grown Pinus radiata D. Don trees. All measurements were made in the fourth year of growth in large, open‐top chambers continuously maintained at ambient (36 Pa) or elevated (65 Pa) CO₂ partial pressures. Photosynthetic rates of the 1‐year‐old needles made at the growth CO₂ partial pressure averaged 10·5 ± 0·5 μmol m^?2 s^?1 in the 36 Pa grown trees and 11·8 ± 0·4 μmol m^?2 s^?1 in the 65 Pa grown trees, and were not significantly different from each other. The photosynthetic capacity of 1‐year‐old needles was reduced by 25% from 23·0 ± 1·8 μmol m^?2 s^?1 in the 36 Pa CO₂ grown trees to 17·3 ± 0·7 μmol m^?2 s^?1 in the 65 Pa grown trees. Growth in elevated CO₂ also resulted in a 25% reduction in V_cmax (maximum carboxylation rate), a 23% reduction in J_max (RuBP regeneration capacity mediated by maximum electron transport rate) and a 30% reduction in Rubisco activity and content. Total non‐structural carbohydrates (TNC) as a fraction of total dry mass increased from 12·8 ± 0·4% in 1‐year‐old needles from the 36 Pa grown trees to 14·2 ± 0·7% in 1‐year‐old needles from the 65 Pa grown trees and leaf nitrogen content decreased from 1·30 ± 0·02 to 1·09 ± 0·10 g m^?2. The current‐year needles were not of sufficient size for gas exchange measurements, but none of the biochemical parameters measured (Rubisco, leaf chlorophyll, TNC and N), were effected by growth in elevated CO₂. These results demonstrate that photosynthetic acclimation, which was not found in the first 2 years of this experiment, can develop over time in field‐grown trees and may be regulated by source‐sink balance, sugar feedback mechanisms and nitrogen allocation.     

Bacterial siderophores : structure and NMR assignment of pyoverdins Pa,siderophores ofPseudomonas aeruginosa ATCC 15692

Summary In iron-deficient conditions,Pseudomonas aeruginosa ATCC 15692 synthesizes two major siderophores, pyoverdins Pa and pyoverdin Pa B. Two other compounds, pyoverdin Pa A (occurring from hydrolysis of pyoverdin Pa during the culture) and pyoverdin Pa C (occurring artifactually during the purification procedure) were also isolated. All these compounds possess the same partly cyclic peptide chain wherel-Orn(OH · HCO) isN -formyl,N -hydroxy-l-ornithine. The chain is bound to a chromophore derived from 2,3-diamino-6,7-dihydroxyquinoline and having the (S) configuration. The four pyoverdins differ only in the acyl substituent bound to the nitrogen atom bound to carbon C3 of the chromophore. This is succinamide (pyoverdin Pa), succinic acid (pyoverdin Pa A), methyl succinate (pyoverdin Pa C) and 2-oxoglutaric acid (pyoverdin Pa B). The complete¹H- and¹³CNMR assignments, using two-dimensional total correlation NMR spectroscopy (TOCSY) and rotating-frame Overhauser enhancement spectroscopy (ROESY) procedures, as well as¹H-¹³C correlations, are reported. The complete sequence of the peptide using CH-NH correlations was achieved by NMR and confirmed the partly cyclic structure earlier reported using fast-atom-bombardment mass spectrometry (FAB-MS) on the siderophores and their dansylated fragments [Briskot G, Taraz K, Budzikiewicz H (1989)Liebigs Ann Chem: 375–384]. The use of these NMR procedures appears to be a tool of choice and a complementary approach to FAB-MS in the structure determination of some complex pyoverdins.Abbreviations Ser serine - Arg arginine - Thr ethreonine - Lys lysine - OHOrn N -hydroxyornithine - Chr chromophore     

A Comparative Study of the Non-acidic Chemically Mediated Antifoulant Properties of Three Sympatric Species of Ascidians Associated with Seagrass Habitats

In this study, the mechanical properties of biofilms formed at the surface of nano-filtration (NF) membranes from a drinking water plant were analysed. Confocal laser scanning microscopy observations revealed that the NF biofilms formed a dense and heterogeneous structure at the membrane surface, with a mean thickness of 32.5 ± 17.7 μm. The biofilms were scraped from the membrane surface and analysed in rotation and oscillation experiments with a RheoStress 150 rotating disk rheometer. During rotation analyses, a viscosity decrease with speed of shearing characteristic of rheofluidification was observed (η = 300 Pa s for ý = 0.3 s^?1). In the oscillation analyses with a sweeping of frequency (1–100 Hz), elasticity (G′) ranged from 3000 to 3500 Pa and viscosity (G″) from 800 to 1200 Pa. Creep curves obtained with an application of a shear stress of 30 Pa were viscoelastic in nature. The G ₀ and η values were, respectively, 1.4 ± 0.3 × 10³ Pa and 3.3 ± 0.65 × 10⁶ Pa s. The relationship between the characteristics of NF biofilms and the flow conditions encountered during NF is discussed.     

Apple orchard tests on the efficacy of the granulosis virus of the codling moth,Laspeyresia pomonella [Lep.: Olethreutidae]

The protection of apples against damage by the codling moth,Laspeyresia pomonella (L.), by applications of the granulosis virus ofL. pomonella was assessed in apple orchard tests at 4 locations in Canada in 1974–1978. Sprays containing 3×10⁹ to 4×10¹⁰ granules/litre, applied 2 or 3 times per generation of codling moth larvae, reduced injury to apples by 44 to 85% compared to reductions of 72 to 98% by applications of azinphos-methyl or phosmet. Applications of the virus did not reduce numbers of arthropods predaceous on pest insects and mites.

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Résumé L'efficacité de la protection des pommes contre le carpocapse,Laspeyresia pomonella (L.), par des applications du virus de la granulose deL. pomonella a été évaluée par des assais dans 4 vergers du Canada entre 1974 et 1978. Des pulvérisations contenant de 3×10⁹ à 4×10¹⁰ granules/litre, appliquées 2 ou 3 fois par génération de larves du carpocapse des pommes, ont réduit les dommages aux pommes de 44 à 85% comparé à des réductions de 72 à 98% obtenues avec des pulvérisations d'azinphos-méthyl ou de phosmet. Les applications de virus n'ont pas réduit les populations d'arthropodes prédateurs d'insectes nuisibles et d'acariens.

     

Effects of nitrogen nutrition and root medium water potential on growth, nitrogen uptake and osmotic adjustment of rice

The effects of nitrogen (N) nutrition on growth, N uptake and leaf osmotic potential of rice plants (Oryza sativa L. ev. IR 36) during simulated water stress were determined. Twenty-one-day-old seedlings in high (28.6 × 10 ^?4M) and low (7.14 × 10 ⁴M) N levels were exposed to decreased nutrient solution water potentials by addition of polyethylene glycol 6000. The roots were separated from the solution by a semi-permeable membrane. Nutrient solution water potential was ?0.6 × 10⁵ Pa and was lowered stepwise to ?1 × 10⁵, ?2 × 10⁵, ?4 × 10⁵ and ?6 × 10⁵ Pa at 2-day intervals. Plant height, leaf area and shoot dry weight of high and low nitrogen plants were reduced by lower osmotic potentials of the root medium. Osmotic stress caused greater shoot growth reduction in high N than in low N plants. Stressed and unstressed plants in 7.14 × 10⁴M N had more root dry matter than the corresponding plants in 28.6 × 10⁴M N. Dawn leaf water potential of stressed plants was 1 × 10⁵ to 5.5 × 10⁵ Pa lower than nutrient solution water potential. Nitrogen-deficient water-stressed plants, however, maintained higher dawn leaf water potential than high nitrogen water-stressed plants. It is suggested that this was due to higher root-to-shoot ratios of N deficient plants. The osmotic potentials of leaves at full turgor for control plants were about 1.3 × 10⁵ Pa higher in 7.14 × 10^?4M than in 28.6 × 10^?4M N and osmotic adjustment of 2.6 × 10⁵ and 4.3 × 10⁵ Pa was obtained in low and high N plants, respectively. The nitrogen status of plants, therefore, affected the ability of the rice plant to adjust osmotically during water stress. Plant water stress decreased transpiration and total N content in shoots of both N treatments. Reduced shoot growth as a result of water stress caused the decrease in amount of water transpired. Transpiration and N uptake were significantly correlated. Our results show that nitrogen content is reduced in water-stressed plants by the integrated effects of plant water stress per se on accumulation of dry matter and transpiring leaf area as well as the often cited changes in soil physical properties of a drying root medium.     

Heterogeneity of twoBeauveria bassiana strains revealed by biochemical tests,protein profiles and bio-assays ofLeptinotarsa decemlineata (Col.: Chrysomelidae) andColeomegilla macultata lengi (Col.: Coccinellidae) larvae

Biochemical profiles on API Rapid CH^* strips and protein profiles on polyacrylamide gels in the presence of sodium dodecyl sulfate were used to distinguish two strains of the entomopathogenic fungusBeauveria bassiana (Balsamo) Vuillemin, ARSEF 2991 and ATCC 44860. Next, the toxicity of these two strains was determined at concentrations of 10², 10⁴, 10⁶ and 10⁸ blastospores/ml on larvae of the Colorado potato beetleLeptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) and of its predator, the spotted ladybird beetle,Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Both strains were highly toxic toL. decemlineata larvae. However, the two strains exhibited different levels of toxicity forC. maculata larvae: ARSEF 2991 was toxic, whereas ATCC 44860 caused little coccinellid larval mortality.

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Résumé Les profils biochimiques sur galeries API Rapid CH^* et les profils protéiques sur gels de polyacrylamide ont été utilisés pour distinguer deux souches du champignon entomopathogèneBeauveria bassiana (Balsamo) Vuillemin. La toxicité de ces deux souches a été déterminée à des concentrations de 10², 10⁴, 10⁶ et 10⁸ blastospores/ml sur des larves du doryphore,Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) et de la coccinelle maculéeColeomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Les deux souches deB. bassiana se sont avérées actives à l'égard des larves deL. decemlineata. Toutefois la souche ARSEF 2991 s'est avérée pathogène pour les larves deC. maculata, alors que la souche ATCC 44860 a provoqué une faible mortalité des larves.

     

The responses of stomata and leaf gas exchange to vapour pressure deficits and soil water content

The responses of leaf conductance, leaf water potential and rates of transpiration and net photosynthesis at different vapour pressure deficits ranging from 10 to 30 Pa kPa^-1 were followed in the sclerophyllous woody shrub Nerium oleander L. as the extractable soil water content decreased. When the vapour pressure deficit around a plant was kept constant at 25 Pa kPa^-1 as the soil water content decreased, the leaf conductance and transpiration rate showed a marked closing response to leaf water potential at-1.1 to-1.2 MPa, whereas when the vapour pressure deficit around the plant was kept constant at 10 Pa kPa^-1, leaf conductance decreased almost linearly from-0.4 to-1.1 MPa. Increasing the vapour pressure deficit from 10 to 30 Pa kPa^-1 in 5 Pa kPa^-1 steps, decreased leaf conductance at all exchangeable soil water contents. Changing the leaf water potential in a single leaf by exposing the remainder of the plant to a high rate of transpiration decreased the water potential of that leaf, but did not influence leaf conductance when the soil water content was high. As the soil water content was decreased, leaf conductances and photosynthetic rates were higher at equal levels of water potential when the decrease in potential was caused by short-term increases in transpiration than when the potential was decreased by soil drying.As the soil dried and the stomata closed, the rate of photosynthesis decreased with a decrease in the internal carbon dioxide partial pressure, but neither the net photosynthetic rate nor the internal CO₂ partial pressure were affected by low water potentials resulting from short-term increases in the rate of transpiration. Leaf conductance, transpiration rate and net photosynthetic rate showed no unique relationship to leaf water potential, but in all experiments the leaf gas exchange decreased when about one half of the extractable soil water had been utilized. We conclude that soil water status rather than leaf water status controls leaf gas exchange in N. oleander.     

Nosema whitei,a microsporidan pathogen of some species ofTribolium

The pathogenicity ofNosema whitei was studied using a dose-mortality technique; larvae ofTribolium castaneum were reared for the duration of each experiment in flour mixed with known numbers of spores. The susceptibility of each of the first 5 larval instars was compared. The LD₅₀ (for mortality after 20 days) increased consistently from the first instar (1.8×10⁶ spores/g) to the fifth instar (1.0×10¹⁰ spores/g). The slopes of the probit lines increased consistently as age increased (from b=1.1 to b=3.9). Two factors which reduce the development time ofT. castaneum, high temperature and high humidity, both reduced the pathogenicity ofN. whitei. Thus pathogenicity decreased as the temperature was increased fram 25°C (LD₅₀=4.2×10⁶) through 30°C (LD₅₀=1.3×10⁷) to 35°C (LD₅₀=3.2×10⁶), also pathogenicity decreased consistently as humidity was increased fram 10%, through 30, 50, 70% to 90% R.H. Adults, emerging fromNosema free larvae, became infected only when exposed to a very high dose (2×10¹⁰ spores/g for 14 days from the day of emergence). Infected larvae were treated for 1 hr. at 45°C in an attempt to cure the infection. The infected larvae were not cured, rather the treatment had an adverse alfect on their survival.

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Résumé La pathogénicité deNosema whitei a été étudiée en élevant des larves deT. castaneum dans de la farine mélangée à des quantités connues de spores. La sensibilité des larves diminue uniformément en fonction de l'age; La DL₅₀ varie de 1,8×10⁶/g (1^er stade) à 1,0×10¹⁰ spores/g (5^e stade). Deux facteurs, qui accélèrent le développement deT. castaneum, des températures et des humidités élevées, réduisent tous les deux la pathogénicité deN. whitei. Les adultes ne peuvent être infectés qu'en les exposant à la dose extrêmement élevée de 2×10¹⁰ spores/g. Un traitement par la chaleur (45°C pendant une heure) n'a pas réussi à guérir les larves.

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This work financed by a Science Research Council (U.K.) studentship is based on a thesis submitted for a degree of Ph. D. at the University of Newcastle-upon-Tyne.     

Sensibilité des larves deSpodoptera littoralis [Lep.: Noctuidae] aux hyphomycètes entomopathogènesNomuraea rileyi etPaecilomyces fumoso-roseus

Résumé L'étude de la sensibilité des chenilles deSpodoptera littoralis Boisd. à des doses croissantes de spores deNomuraea rileyi (F.)Samson, montre que le 6^e et dernier stade est plus résistant que le 1^er et surtout les 4^e et 5^e stades larvaires. La virulence du pathotypeN. rileyi n^o 5 à l'égard des larves de cette noctuelle est élevée puisque le temps léthal 50 % (TL 50) est de 6 j en moyenne. Pendant l'incubation de la maladie les chenilles continuent de s'alimenter mais l'infection peut réduire jusqu'à 60 % la prise alimentaire par rapport à la consommation des larves des lots témoins. Toutes conditions égales par ailleurs, la mortalité provoquée parN. rileyi n^o 5 après traitement des larves nouvelles-nées est supérieure lorsque les insectes sont maintenus à 25°C par rapport à celle constatée à 20°C. Cependant pour une dose d'inoculum élevée, les conditions thermiques (20°, 25° ou 28°C), ne modifient pas sensiblement la réponse à l'infection parN. rileyi n^o 5 alors qu'elles limitent l'efficacité d'un pathotype moins virulent:Paecilomyces fumoso-roseus Wize no^o 39.

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Summary Laboratory studies were conducted to determine the susceptibility of various larval instars of the cotton leafworm,Spodoptera littoralis Boisd. to different spore doses ofNomuraea rileyi (F.)Samson to investigate the influence of temperature on the infection by this fungus and byPaecilomyces fumosoroseus Wize. Contaminations were obtained by direct spraying on larvae in tower apparatus or by feeding of larvae on treated pieces of leaf during 48 h or 72 h. The influence of cryptogamic infection on food consumption was studied by measuring surfaces of standard cabbage leaf disces submitted to treated and control larvae. Angular values mortality rates were submitted to the 2- or 3-way analysis of variance and comparisons of means were made by theDuncan's test. In some cases we have also considered the time-mortality and the dose-mortality curves. The 6th instar was more resistant than all other tested instars. TL50 were found to be 6 days in most cases. During incubation of the disease, larvae continued to feed, but food consumption could be reduced at 40 % of controls. Larval mortality due toN. rileyi N^o 5, recorded after 8 days of incubation, was higher at 25°C than at 20°C. Nevertheless, at high dosage, efficiency ofN. rileyi N^o 5 was not affected by temperature at 20°, 25° and 28°C. The other pathotype,P. fumoso-roseus N^o 39 was more effective at 20°C than at 25° and 28°. At 32°C, the temperature, unfavourable to fungal growth, limited mortality at non significant rates.

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Avec la collaboration technique deH. Vermeil de Conchard.     

Essai en culture de choux-fleurs du virus de la polyédrose nucléaire deMamestra brassicae [Lep.: Noctuidae]

Résumé Une préparation expérimentale de virus de la polyédrose nucléaire (VNP) deMamestra brassicae L. a été appliquée dans les conditions de la pratique dans un champ de choux-fleurs pour lutter contre cette noctuelle. La préparation, appelée virusine M.B., est fabriquée à partir de chenilles mortes, après infection en élevage de larves du 5^e stade. La période de traitement a été déterminée selon le vol des papillons, suivi par piégeage sexuel. Six traitements par virus ont été effectués tous les 5 à 8 jours. Les 3 doses expérimentées (resp. 0,6 10¹²/3.10¹² et 1,5 10¹³ polyèdres par ha) ont proportionnellement diminué aussi bien l'effectif de la population larvaire que les dégats à la culture de choux-fleurs.

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Summary An experimental preparation of nuclear polyhedrosis virus (NPV) ofMamestra brassicae L. (named “virusine M.B.”, was applied under routine conditions to a field of cauliflower for control of this noctuid. The preparation was made from a filtrate of dead larvae, after infection of stock culture of 5 th instar larvae. This filtrate, with the addition of inert materials, was made into a powder in an industrial spray-drier. The resulting powder had the following composition: 50% vegetable charcoal, 35% skim milk powder, and 15% dried larval filtrate. It contained 6×10⁹ polyhedra/g. The biological activity of the preparation was evaluated by bioassay against the crude material prepared by acetone precipitation of a sample of the same filtrate. The objective of the field experiment was to determine the dosage of the preparation necessary to use under field conditions on cauliflower in the Rhone valley. The infection of newly hatched larvae was attempted, to take advantage of their susceptibility compared with later instars. The application period was determined by the flight of males into traps baited with virgin females reared in the laboratory. Six applications of virus were made, August 11, 18, and 24 and September 1, 6, and 13, 1977 (every 5 to 8 days). Between August 23 and September 2 a complementary release of 65 pairs ofMamestra was made to ensure a high population density of larvae in the crop. This action was unnecessary because it was demonstrated that the natural infestation was dense enough. Each dosage was applied to 4 plots of 180 m² with an average of 400 plants each. In addition, 2 spraying with Bactospeine (aBacillus thuringiensis preparation) was applied againstPieris brassicae L. on all 4 plots. The results of the treatment with virusine M.B. againstM. brassicae were quite satisfactory with regard to insect mortality and crop protection.

     

Carbon Monoxide, Hydrogen, and Formate Metabolism during Methanogenesis from Acetate by Thermophilic Cultures of Methanosarcina and Methanothrix Strains

CO and H₂ have been implicated in methanogenesis from acetate, but it is unclear whether they are directly involved in methanogenesis or electron transfer in acetotrophic methanogens. We compared metabolism of H₂, CO, and formate by cultures of the thermophilic acetotrophic methanogens Methanosarcina thermophila TM-1 and Methanothrix sp. strain CALS-1. M. thermophila accumulated H₂ to partial pressures of 40 to 70 Pa (1 Pa = 0.987 × 10^-5 atm), as has been previously reported for this and other Methanosarcina cultures. In contrast, Methanothrix sp. strain CALS-1 accumulated H₂ to maximum partial pressures near 1 Pa. Growing cultures of Methanothrix sp. strain CALS-1 initially accumulated CO, which reached partial pressures near 0.6 Pa (some CO came from the rubber stopper) during the middle of methanogenesis; this was followed by a decrease in CO partial pressures to less than 0.01 Pa by the end of methanogenesis. Accumulation or consumption of CO by cultures of M. thermophila growing on acetate was not detected. Late-exponential-phase cultures of Methanothrix sp. strain CALS-1, in which the CO partial pressure was decreased by flushing with N₂-CO₂, accumulated CO to 0.16 Pa, whereas cultures to which ca. 0.5 Pa of CO was added consumed CO until it reached this partial pressure. Cyanide (1 mM) blocked CO consumption but not production. High partial pressures of H₂ (40 kPa) inhibited methanogenesis from acetate by M. thermophila but not by Methanothrix sp. strain CALS-1, and 2 kPa of CO was not inhibitory to M. thermophila but was inhibitory to Methanothrix sp. strain CALS-1. Levels of CO dehydrogenase, hydrogenase, and formate dehydrogenase in Methanothrix sp. strain CALS-1 were 9.1, 0.045, and 5.8 μmol of viologen reduced min^-1 mg of protein^-1. These results suggest that CO plays a role in Methanothrix sp. strain CALS-1 similar to that of H₂ in M. thermophila and are consistent with the conclusion that CO is an intermediate in a catabolic or anabolic pathway in Methanothrix sp. strain CALS-1; however, they could also be explained by passive equilibration of CO with a metabolic intermediate.     

Laboratory evaluation of a carabid larva,Chlaenius bioculatus [Col.: Carabidae] as a predator of lepidopterous pests

Food preference as well as feeding efficiency studies of the carabid predator revealed that the grub of theChlaenius bioculatus Chaud preferred mostPolytella gloriosae F. larvae in both 2nd and 3rd instar.Tarache tropica Guénée was preferred least by the grub predator in both instar.T. tropica was found toxic and grubs of the predator died after consumption.

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Résumé Les préférences alimentaires, de même que l'efficacité prédatrice deChlaenius bioculatus Chaud, montrent que ce carabide prédateur préfère le plus les larves dePolytella gloriosae F. du 2^e et 3^e stade.Tarache tropica Guénée est le moins attaqué aux deux stades.T. tropica est toxique et les larves du prédateur meurent après sa consommation.

     

Effet des racines vivantes sur la decomposition d’une litiere racinaire marquee au14C

Resume Du blé est marqué au¹⁴C sur sol dans des pots de culture depuis la germination jusqu’à la maturité dans une enceinte à teneur de CO₂ et¹⁴CO₂. La répartition du¹⁴C entre les parties aériennes, les racines et le sol est homogène pour l’ensemble des cultures (Tableau 1). Les parties aériennes sont coupées et les pots sont séchés sans perturber ni le sol, ni les racines. Les pots sont ensuite incubés à température et humidité contr?lées durant 62 jours. La moitié d’entre eux est soumise à une deuxième culture de blé en atmosphère normale sans¹⁴CO₂.. Le but du travail est d’étudier l’effet du système racinaire vivant sur la décompositon de la litière racinaire marquée préexistante. Le CO₂ et¹⁴CO₂ se dégageant du sol est mesuré en continu aux jours 0,8, 33 et 62 de l’incubation et la radioactivité restante est recherchée dans la litière racinaire et dans les différentes fractions du sol obtenues par hydrolyse croissante (Fig. 1). La litière racinaire dispara?t plus rapidement en présence de racines vivantes qu’en absence de plantes (Fig. 2). Le rythme d’apparition et de disparition du matériel humifié dans le sol sous culture s’effectue suivant deux phases (Fig. 3). Durant la période de croissance des racines (jusqu’à l’épiaison), on constate une accumulation plus importante de matériel, hydrolysable en milieu fortement acide, que dans le sol nu. Après l’épiaison et durant la période de moindre activité racinaire, le matériel accumulé précédemment est partiellement minéralisé et on constate alors un dégagement plus important de¹⁴CO₂ en présence de plantes qu’en leur absence (Fig. 4). Les variations de l’humification et de la minéralisation des composés de la litère racinaire sont en relation avec le stade phénologique de la plante vivante.

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Living roots effect on¹⁴C-labelled root litter decomposition

Summary Wheat was¹⁴C-labelled by cultivation on soil in pots, from seedling to maturity, in a chamber with constant CO₂ and¹⁴CO₂ levels. The¹⁴C-distribution was constant amongst the aerial parts, the roots and the soil in the whole pots (Tabl. I). After cutting the plant tops, the pots were dried without disturbing the soil and root system. The pots were then incubated under controlled humidity and temperature conditions for 62 days. In the same time a second wheat cultivation was grown on one half of the pots in normal atmosphere without plant cultivation. The purpose of the work is to study the effect of living roots on decomposition of the former¹⁴C labelled roots litter. The CO₂ and the¹⁴CO₂ released from the soil were continuously measured. On incubation days 0, 18, 33 and 62, the remaining litter was separated from soil, and the organic matter was fractionated by repeated hydrolysis and NaOH extraction (Fig. 1). Root litter disappeared faster when living roots were present than in bare soil (Fig. 2). The accumulation and mineralization rates of humified components in soil followed two stages (Fig. 3). While the roots of second wheat cultivation grew actively (until earing), the strong acid hydrolysable components accumulated in larger amount than in the case of bare soil. After earing, while roots activity was depressed, theses components were partly mineralized and the¹⁴CO₂ release was then higher with plants than with bare soil (Fig. 4). The humification and mineralization rate were related with living plant phenology stages.

     

The effect ofMetarhizium anisopliae (DAT F-001) concentration and exposure time on the survival of the subterranean pasture pest,Adoryphorus couloni (Col.: Scarabaeidae)

The virulence of the DAT F-001 isolate ofMetarhizium anisopliae forAdoryphorus couloni was tested by exposing final instar larvae (L3) to concentrations of 10¹ to 10⁷ spores/g in a sand-peat mix for up to 112 days at 20°±2°C. All concentrations were pathogenic to L3 larvae and survival was dependent on concentration and correlated with exposure time. The time to kill 50% of the treated larvae (LT₅₀) ranged from 18.9 days (10⁷ spores/g) to 82.7 days (10¹ spores/g). The effect of DAT F-001 on feeding by L3 larvae was determined by comparing the production and weight of frass pellets/larva/day of untreated control larvae with larvae rolled in sporulating cultures ofM. anisopliae DAT F-001 and DAT F-054 (low virulence). Exposure to, and infection byM. anisopliae DAT F-001 had minimal impact on larval feeding. L3 larvae continued to feed at the same rate as both untreated and DAT F-054 treated larvae virtually until they died.

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Résumé La virulence deM. anisopliae DAT F-001 pourA. couloni a été analysée en exposant des larves L3 à des concentrations de 10¹ à 10⁷ spores/g dans un mélange de sable et de tourbe pendant un maximum de 112 jours à une température de 20°±2°C. Toutes les concentrations sont pathogènes pour les larves L3; la survie dépendait de la concentration et est en corrélation avec le temps d'exposition. Les LT₅₀ sont compris entre 18,9 jours (10⁷ spores/g) et 82,7 jours (10¹ spores/g). L'effet de DAT F-001 sur l'alimentation des larves L3 a été évalué en comparant la production et le poids des fèces/larve/jour des larves non-traitées avec des larves roulées dans des cultures sporulées deM. anisopliae DAT F-001 et DAT F-054 (faible virulence). L'exposition àM. anisopliae DAT F-001 suivie de l'infection a peu d'effet sur l'alimentation des larves. Les larves L3 continuent à s'alimenter au même rythme que les larves non-traitées de DAT F-054, quasiment jusqu'à leur mort.

     

Control experiments usingAgrotis segetum granulosis virus againstAgrotis ipsilon [Lep.: Noctuidae] on tobacco seedlings in Northern Pakistan

Agrotis segetum Schiff. granulosis virus propagated in Denmark was applied against released 2nd instar larvae ofAgrotis ipsilon (Hfn.) in tobacco plots in nurseries at Peshawar and Bhurbun (Murree), Northern Pakistan. Nursery bed plots were isolated from the surroundings by net roof and plastic sheets. Granulosis virus concentrations used were 5×10⁷ and 10⁹ capsules per ml water, and 250 ml water per plot (1–4 m²). Reductions of cutworms as well as cutworm damages varied between 72 and 100% as compared to plots only treated with water. Addition of active coal to the GV did not increase reduction percentages. A possible effect of the GV could be traced one year after treatment.

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Résumé Le virus de la granulose d'Agrotis segetum Schiff. multiplié au Danemark a été appliqué contre le 2^e stade des chenilles deAgrotis ipsilon (Hfn.) dans des parcelles expérimentales à Peshawar et Bhurbun (Murree), Pakistan du nord. Les parcelles isolées avec des filets et des feuilles plastiques furent infestées artificiellement en chenilles. Les concentrations de GV utilisées furent de 5×10⁷ et 10⁹ granules par ml d'eau, 250 ml de la suspension préparée étant distribués par parcelle de 1 à 4 m². La réduction du nombre de chenilles et celui des plantes endommagées varie de 72 à 100% par rapport aux notations effectuées dans les parcelles traitées avec de l'eau pure. L'addition du charbon actif au GV n'augmente pas son effet. Une action du traitement a été retrouvée un an après l'application.

     

Utilisation du15N2 pour estimer la fixation d'azote et sa repartition chez les legumineuses

Resumé Les auteurs proposent une méthode d'utilisation du¹⁵N₂ pour l'étude de la fixation d'azote dans les associations complexes légumineuses-Rhizobium cultivées sur sol. La procédure consiste, à marquer l'atmosphère du sol à l'aide de¹⁵N₂ et à calculer la quantité d'azote total fixé pendant cette période. Les premiers résultats obtenus sur des haricots et des trèfles démontrent qu'après seulement 7 h d'incubation, des quantités significatives de¹⁵N sont mesurées dans les plantes permettant ainsi de déterminer précisément la valeur du rapport C₂H₄/N₂ qui a été établi entre 2,6 et 3,1 dans les conditions de l'expérience. Sur de longues périodes, ces mêmes quantités se sont avérées suffisantes pour suivre la dynamique de l'azote des nodules vers les organes reproducteurs de plants de haricots.

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Use of¹⁵N to estimate dinitrogen fixation and distribution in legumes

Summary A method for use of¹⁵N₂ in the study of dinitrogen fixation by complex legumes-Rhizobium associations grown on soil is proposed. The procedure consists in labelling the soil atmosphere with¹⁵N₂ during short periods of time, measuring¹⁵N enrichment in the plants and calculating the total nitrogen fixed during this period. The first results obtained with bean and clover plants demonstrate that after only 7 h of incubation, significative amounts of¹⁵N are measured in the plants to allow precise determination of C₂H₄/N₂ ratio which ranged between 2.6 and 3.1 in this experiment. Over longer periods of time, such amounts are meaningfull to follow the pattern of N dynamic from the nodules to the reproductive organs of bean plants.