Screening of turfgrass species and cultivars for NaCl tolerance

Summary Information regarding the relative levels of salt tolerance between cultivars of Kentucky bluegrass (Poa pratensis L.) is lacking. The objectives of this study were to 1) develop a simple, quick and sensitive method of screening turfgrass species for NaCl tolerance and 2) to compare the relative salt tolerance of five cultivars of Kentucky bluegrass (Ram I, Adelphi, Baron, Bensun, and Nassau) to other known salt tolerant turfgrass species such as alkalaigrass (Puccinellia distans (L.) Parl. cv. Fults) and two cultivars of red fescue (Festuca rubra L. Dawson, and Checker).Alkalaigrass and both cultivars of red fescue retained a high level of salt tolerance compared to the Kentucky bluegrass cultivars. Significant variability in salt tolerance was apparent among the Kentucky bluegrass cultivars with Adelphi and Ram I exhibiting the best overall tolerance.     

Pioneer and late stage tropical rainforest tree species (French Guiana) growing under common conditions differ in leaf gas exchange regulation,carbon isotope discrimination and leaf water potential

Leaf gas exchange rates, predawn _wp and daily minimum _wm leaf water potentials were measured during a wet-to-dry season transition in pioneer (Jacaranda copaia, Goupia glabra andCarapa guianensis) and late stage rainforest tree species (Dicorynia guianensis andEperua falcata) growing in common conditions in artificial stands in French Guiana. Carbon isotope discrimination () was assessed by measuring the stable carbon isotope composition of the cellulose fraction of wood cores. The values were 2.7 higher in the pioneer species than in the late stage species. The calculated time integratedC _i values derived from the values averaged 281 mol mol^–1 in the pioneers and 240 mol mol^–1 in the late stage species. The corresponding time-integrated values of intrinsinc water-use efficiency [ratio CO₂ assimilation rate (A)/leaf conductance (g)] ranged from 37 to 47 mmol mol^–1 in the pioneers and the values were 64 and 74 mmol mol^–1 for the two late stage species. The high values were associated—at least inJ. copaia—with high maximumg values and with high plant intrinsinc specific hydraulic conductance [Cg/(_wm–_wp], which could reflect a high competitive ability for water and nutrient uptake in the absence of soil drought in the pioneers. A further clear discriminating trait of the pioneer species was the very sensitive stomatal response to drought in the soil, which might be associated with a high vulnerability to cavitation in these species. From a methodological point of view, the results show the relevance of for distinguishing ecophysiological functional types among rainforest trees.     

The reliability of parasitic water-mites (Hydracarina) as indicators of physiological age in mosquitoes (Diptera: Culicidae)

The reliability of parasitic water-mites as criteria of a nulliparous condition has been investigated in ten species of mosquito in Uganda. Larvae of two kinds of hygrobatid-type mites, when alive, were found only on nulliparous mosquitoes; but living larvae of two other hygrobatids occurred on a small proportion of pars also. Larvae of thyasid-type mites occurred at least as often on pars as on nullipars. Different types of scars caused by mites can provide information concerning the original infestation rate of a population and also the likelihood that an individual female is parous.In the species of mosquito studied, the infestation rate of nullipars sometimes exceeded 80%, but was usually less than 20%.

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Zusammenfassung An 10 Mückenarten von Uganda wurde untersucht, inwieweit schmarotzende Wassermilben zuverlässig sind zur Unterscheidung alter Mücken (d.h. solcher, die Eier gelegt haben) von jungen Mücken (d.h. solchen, die noch keine Eier gelegt haben). Untersuchung der Ovarien ermöglichte es, weibliche Mücken in alte und junge Individuen einzuteilen. Zu diesem Zweck wurden mehr als 20.000 Mücken seziert.Der Lebenszyklus der an Mücken schmarotzenden Wassermilben wird besprochen. Die Larven zweier Arten von hygrobatischen Wassermilben wurden lebend nur an jungen Mücken gefunden; lebende Larven von zwei anderen hygrobatischen Milbenarten kamen auch an einem kleinen Teil von alten Mücken vor. Larven von thyasischen Milben wurden mindestens ebenso oft an alten wie an jungen Mücken gefunden. Deshalb war es wichtig, den Milbentypus festzustellen und zu erkennen, ob die Milben lebendig oder tot waren.Die Infektion der Mücken durch fünf der gewöhnlichen Wassermilben-Species wird beschrieben. Es hängt von der Milben- und von der Wirts-Art ab, welche Stelle die Milben zum Anheften wählen. Verschiedene Typen der durch die Milben verursachten Narben informieren über die ursprüngliche Befallsrate einer Bevölkerung und auch über die Wahrscheinlichkeit, dass die Mücke alt ist. Die Stärke der Infektion ändert sich bei einer einzigen Mückenart von Monat zu Monat beträchtlich. Manchmal sind über 80% der jungen Mücken befallen, im allgemeinen aber weniger als 20%.Bei Culex annulioris, bei dem die hygrobatischen Larven sich auf die jungen Mücken beschränken, ist der Stechzyklus eines befallenen Weibchens derselbe wie dem aller jungen Weibchen. Deshalb kann der Stechzyklus der jungen Mücken, nicht aber der der alten, direkt von den untersuchten milbentragenden Weibchen abgeleitet werden.Es wird gefolgert, dass bestimmte Wassermilben des hygrobatischen Typus für eine schnelle Diagnose von jungen Mücken nützlich sind; vorher muss jedoch in ausgedehnten Versuchen der Grad ihrer Zuverlässigkeit für jede Wirtsart festgelegt werden.

     

Size fractionation of trace metal species in freshwaters: implications for understanding their behaviour and fate

Data on both the colloid size distributionpresent in freshwaters and the extent to whichtrace metal ions associate with the differentsize fractions within the so-called dissolved phasein these systems are examined. Several keyfeatures are identified: (i) division of totalmetal into particulate and dissolved fractions via a single ca. 450 nm filtrationprocedure provides no useful information, (ii)within the dissolved fraction, a continuum ofparticle sizes exists in the colloidal sizerange in freshwaters, (iii) for the tracemetals Cu, Cd, Zn, Cr, Co, and Ni, the greatestproportion of dissolved trace metals are in the low molecular mass fraction, together withthe largest proportion of DOC, (iv) in allrivers, and in lakes with a low DOC content,the predominant determiner of the sizedistribution of trace metals is the lowermolecular size, more strongly complexing,pedogenic organic matter fraction.     

Effect of alpha-isopropylmalate on the synthesis of RNA and protein in Neurospora

Summary The leu-3/-IPM (-isopropylmalate) regulatory system, previously shown to control several genes of leucine, isoleucine, valine, and histidine biosynthesis, appears likely to be involved also in the regulation of overall RNA and protein synthesis in Neurospora. Upon addition of -IPM the synthesis of all major species of stable RNA was found to be transiently inhibited by approximately 50%. A similar reduction was observed in overall protein synthesis. The inhibition was dependent in both cases on a functional leu-3 gene product, in conformance with previously established patterns of -IPM dependent gene regulation. The overt resemblance of the phenomenon described here to the stringent response of bacteria is noted but neither the mechanism of inhibition nor the precise role of -IPM in the process has been established.     

Evolution of the variable gene segments and recombination signal sequences of the human T-cell receptor α/δ locus

The T-cell receptor (TCR) and loci are particularly interesting because of their unique genomic structure, in that the gene segments for each locus are interspersed. The origin of this remarkable gene segment arrangement is obscure. In this report, we investigated the evolution of the TCR and variable loci and their respective recombination signal sequences (RSSs). Our phylogenetic analyses divided the and variable gene segments into two major groups each with distinguishing motifs in both the framework and complementarity determining regions (CDRs). Sequence analyses revealed that TCR variable segments share similar CDR2 sequences with immunoglobulin light chain variable segments, possibly revealing similar evolutionary histories. Maximum likelihood analysis of the region on Chromosome 14q11.2 containing the loci revealed two possible ancestral TCR / variable segments, TRDV2 and TRAV1-1/1-2, respectively. Maximum parsimony revealed different evolutionary patterns between the variable segment and RSS of the same variable gene arguing for dissimilar evolutionary origins. Two models could account for this difference: a V(D)J recombination activity involving embedded heptamer-like motifs in the germline genome, or, more plausibly, an unequal sister chromatid crossing-over. Either mechanism would have resulted in increased diversity for the adaptive immune system.     

Cloning and sequencing of a ligninase gene from a lignindegrading basidiomycete,Phanerochaete chrysosporium

Summary A ligninase gene has been cloned from a Phanerochaete chrysosporium genomic DNA library. Nucleotide sequencing of the gene has revealed that the ligninase structural gene contains 1116 bp of the protein-encoding sequence, of which 84 bp encode the signal peptide. The protein-encoding sequence is interrupted by eight introns which conform to the universal G-T/A-G splicing rule observed for the 3 and 5 intron boundaries. The putative eukaryotic regulatory sequences, i.e. CAAT and TATA box-like sequences, are present in the 5 flanking region.     

Microsatellite markers in the hexaploid Prunus domestica species and parentage lineage of three European plum cultivars using nuclear and chloroplast simple-sequence repeats

In a previous study, cDNA microsatellite markers were described in apricot (Prunus armeniaca L.). Specific PCR primers were designed to amplify the microsatellite-containing regions from genomic DNA in different Prunus species. In the present work, cDNA microsatellite markers were developed in the hexaploid Prunus domestica L. species and polymorphism was ascertained in a segregating plum population. Co-dominant mendelian segregation of alleles was demonstrated and microsatellite polymorphism displayed up to 6 alleles per SSR locus per individual. Parentage lineage of three full-sib European plum cultivars (cv. Cacanska najbolja, Cacanska rana and Cacanska lepotica) was reconstructed by the analysis of the above nuclear SSR markers, completed by four chloroplastic microsatellite loci. The six most informative nuclear loci enabled discrimination between the three Cacak cultivars and unrelated individuals as well as the previously proposed parents, Wangenheim and Pozegaca. Data obtained support previous evidence that these cultivars originated from the Stanley cultivar. However, SSR analysis finally excluded Wangenheim as the other possible parent. Based on the results obtained with nuclear and chloroplast SSR loci, we propose the origin of those three Cacak cultivars in a cross between Stanley as the mother plant and Ruth gerstetter as the pollinator. Furthermore, we demonstrate the utility of these apricot SSR markers for genotype fingerprinting of the hexaploid plum cultivars.     

Regulation of adenosine 5′-phosphosulfate sulfotransferase activity by H2S and cyst(e)ine in primary leaves of Phaseolus vulgaris L.

During chloroplast development in the primary leaves of Phaseolus vulgaris, the extractable activity of adenosine 5-phosphosulfate sulfotransferase increased ten-fold. When chloroplast development took place in air enriched with 3.5 l H₂S·l^-1 there was a decrease in adenosine 5-phosphosulfate sulfotransferase activity. Cyst(e)ine in concentrations up to 1 mM (in the external medium) did not affect the increase in adenosine 5-phosphosulfate sulfotransferase activity in intact plants. In plants with excised roots, 0.75 mM cyst(e)ine inhibited this increase. In green primary leaves, H₂S or cyst(e)ine treatment resulted in a decrease of extractable adenosine 5-phosphosulfate sulfotransferase activity. In intact plants, this effect of cyst(e)ine was observed at a concentration of 1 mM, and in plants with excised roots, 0.25 mM had a comparable effect.In developing plants, the extractable activities of O-acetyl-L-serine sulfhydrylase (EC 4.2.99.9) and ribulosebisphosphate carboxylase (EC 4.1.1.39.) were not affected by H₂S or cyst(e)ine.Abbreviations APS adenosine 5-phosphosulfate - APSSTase adenosine 5phosphosulfate sulfotransferase - BSA bovine serum albumin - DTE dithioerythritol - EDTA ethylenediaminetetra-acetic acid - OASSase O-acetyl-L-serine sulfhydrylase - PAPS adenosine 3-phosphate 5-phosphosulfate - POPOP 1,4 Di 2-(5-phenyloxazolyl)-benzene - PPO 2,5-diphenyloxazol - RubP ribulose-bisphosphate - RubPCase ribulosebiphosphate carboxylase This is no. 8 in the series Regulation of Sulfate Assimilation in Plants. The term cysteine is used when it is clear that cystine is not involved; cyst(e)ine is used for an undefined mixture of cysteine and cystine. The concentrations are expressed in all cases relative to cysteine     

Syntheses of 1-O-benzyl-α-glucoside and 1-O-benzyl-α-maltoside by transglycosylation of α- amylase from soluble starch in aqueous solution

Glycosides, 1-O-benzyl--glucoside (BG) and 1- O-benzyl--maltoside (BM), were synthesized from soluble starch and benzyl alcohol by transglycosylation with an -amylase in a water system. BG was mostly obtained in a reaction mixture of pH 5.0, while BM was synthesized in pH 8.0. The synthesized glycosides had -configuration linkage between sugar and benzyl alcohol. The BG was rapidly hydrolyzed to benzyl alcohol and glucose by -glucosidase. The BM was hydrolyzed to BG and glucose below pH 5.0 by the -amylase used for its synthesis but it was not hydrolyzed above pH 8.0.     

Acetylcholinesterase molecular forms from rat and human erythrocyte membrane

Summary Inhibition of growth of PY815 mouse mastocytoma cells in vitro by N⁶, O²-dibutyryladenosine 3,5 cyclic monophosphate (DB cyclic AMP) was accompanied by increases in intracellular cyclic AMP and histamine and minor changes in cytosolic cyclic AMP-dependent histone kinase activity. However, DEAE-cellulose chromatography revealed substantial changes in the relative proportions of the principal cyclic AMP-dependent protein kinases and in free cyclic AMP-binding protein after DB cyclic AMP treatment. The activity of cytosolic cyclic AMP-dependent protein kinase type I (PK_I) decreased relative to cyclic AMP-dependent protein kinase type II (PK_II) and there was an increase in a cytosol cyclic AMP-binding protein with little associated protein kinase activity. The relative changes in activity of PK_I, PK_II and cyclic AMP binding protein after DB cyclic AMP treatment may reflect events important in the regulation of growth and differentiation of mast cells.Abbreviations DB cyclic AMP N⁶,O²-dibutyryladenosine-3, 5-cyclic monophosphate - cyclic AMP adenosine 3,5-cyclic monophosphate - PK_I type I cyclic AMP-dependent protein kinase - PK_II type II cyclic AMP-dependent protein kinase     

Treatment of NOE constraints involving equivalent or nonstereoassigned protons in calculations of biomacromolecular structures

Summary Two modifications to the commonly used protocols for calculating NMR structures are developed, relating to the treatment of NOE constraints involving groups of equivalent protons or nonstereoassigned diastereotopic protons. Firstly, a modified method is investigated for correcting for multiplicity, which is applicable whenever all NOE intensities are calibrated as a single set and categorised in broad intensity ranges. Secondly, a new set of values for pseudoatom corrections is proposed for use with calculations employing centre-averaging. The effect of these protocols on structure calculations is demonstrated using two proteins, one of which is well defined by the NOE data, the other less so. It is shown that failure to correct for multiplicity when using r^-6 averaging results in overly precise structures, higher NOE energies and deviations from geometric ideality, while failure to correct for multiplicity when using r^-6 summation can cause an avoidable degradation of precision if the NOE data are sparse. Conversely, when multiplicities are treated correctly, r^-6 averaging, r^-6 summation and centre averaging all give closely comparable results when the structure is well defined by the data. When the NOE data contain less information, r^-6 averaging or r^-6 summation offer a significant advantage over centre averaging, both in terms of precision and in terms of the proportion of calculations that converge on a consisten result.Abbreviations HMG high mobility group - NOE nuclear Overhauser enhancement - NOESY nuclear Overhauser enhancement spectroscopy - rmsd root-mean-square deviation - YASAP yet another simulated-annealing protocol     

Nutrient transport between ryegrass plants differeing in nutrient status

Summary It is known that nitrogen and phosphorus can be transferred from one living plant to another, but it is not known whether the amounts transferred are large enough to influence the growth of the species in the field. Two Lolium perenne plants were grown per pot of unfertilized soil. During 25 weeks one plant (the donor) in each pot was fed nutrients through leaves; donors in control pots received only water. The receiver plants which shared a pot with the nutrient-fed donors increased significantly, compared with the controls, in leaf number and concentration of phosphorus, though not in concentration of nitrogen, potassium, calcium or magnesium. The rate of phosphorus transfer agreed well with previous results using ³²P. The results are compared with rates of phosphorus uptake in the field. It is concluded that nutrient transfer could have an influence on the balance between coexisting species in the field, but probably the influence will be small.     

Alterations of β-adrenoceptor-G-protein-regulated adenylyl cyclase in heart failure

Alterations of receptor-G-protein-regulated adenylyl cyclase activity have been suggested to represent an important alteration leading to contractile dysfunction in the failing human heart. Recent experiments suggest that the ₁-adrenoceptor(₁AR) density and mRNA levels are reduced, while ₂-adrenoceptors and stimulatory G-proteins are unchanged (mRNA and protein level). Functional assays demonstrated that the catalyst of the adenylyl cyclase is not different between failing and nonfailing myocardium. Inhibitory G-proteins are increased (pertussis toxin substrates, protein and mRNA) and correlate to the reduced inotropic effects of -adrenoceptor agonists and of CAMP-PDE inhibitors. Gi-coupled m-cholinoceptors and A₁-adrenergic receptors are unchanged in density and affinity. Stimulation of these receptors resulted in an unchanged antiadrenergic effect on force of contraction. In conclusion, a downregulation of ₁-AR and an increase of Gi have been observed as signal transduction alteration in failing human myocardium. These alterations are due to alterations of gene expression in the failing heart and are related to a defective regulation of force of contraction in heart failure.     

Solid-phase peptide synthesis using Nα-trityl-amino acids

The preparation of N-trityl-amino acids is described. Several derivatives of trifunctional amino acidscarrying acid- and base-labile side-chain protecting groups and the trityl group at the N position are prepared for first time. The incorporation of N-trityl-amino acids into peptide sequences usingsolid-phase protocols was achieved. The use of the trityl groupfor the protection of the -amino group in conjunction with base-labile side-chain protecting groups constitutes a newmethod for the assembly of peptides in mild conditions.     

Some properties of 2-5A binding/nucleolytic activities in gel filtered rabbit reticulocyte lysates

Rabbit reticulocyte lysates, gel filtered on Sephadex G-25 with or without ATP (or its analogs), were preincubated at 37°C and their subsequent binding to p₃A₄,3-[³²P]pCp was studied. Lysates filtered without ATP or in the presence of 0.1 mM 8-bromo-ATP, 1,N⁶-etheno-ATP, or ITP showed a time-dependent decrease in binding activity. This decrease was completely prevented when lysates were filtered with 0.1 mM ATP, 2-deoxy-ATP, --methylene-ATP, or ATP--S. The stability of binding provided by ATP or 2-deoxy-ATP analogs corresponds to a more active 2–5A dependent endonucleolytic (RNAase L) activity based on studies using [³H] viral mRNA. Chromatography on heparin-agarose showed that ATP-supplemented gel-filtered reticulocyte lysates had a different p₃A₄,3-[³²P]pCp binding activity elution-profile than lysates gel-filtered in the absence of ATP. Covalent cross-linking of periodate-oxidized p₃A₄,3-[³²P]pC to gelfiltered lysates, preincubated at 0°C or 37°C for 30 min, showed the following results: (1) all lysates gave a major cross-linking of the radioactive ligand to an 80 000 dalton polypeptide, regardless of the temperature of preincubation, (2) Iysates gel-filtered without ATP, with 0.1 mM ITP, or --methylene-ATP, showed a significant reduction in the cross-linking of the 80 000 dalton protein, after preincubation at 37°C for 30 min. This decrease was accompanied by an increase in the labeling of two smaller polypeptides.Abbreviations used 2 5-oligoadenylates oligonucleotides consisting of 5-adenylic acid residues joined by a 2 5-phosphodiester linkage     

Eye movements in Daphnia magna

Summary Three types of behavior of the compound eye of Daphnia magna are characterized: flick, a transient rotation elicited by a brief flash of light; fixation, a maintained eye orientation in response to a stationary light stimulus of long-duration; tracking, the smooth pursuit of a moving stimulus. The magnitudes of the flick and fixation responses vary with stimulus position and are generally proportional to stimulus intensity, although at high intensities there is an attenuation of both behaviors. When the stimulus is placed at a position 80° dorsal to the eye axis, there is no response; this area is called the null region. For stationary stimuli in other positions, the direction of the response is such as to bring the stimulus closer to the null region. During tracking, the relative positions of the eye and stimulus change; the eye velocity is approximately half that of the moving stimulus. The regions of the eye in which these behaviors may be induced are different, being largest for flick and smallest for tracking. It is proposed that flick and fixation responses are a means for rotating the eye so that the stimulus is within the area surrounding the null region which is used for tracking.     

Zur Feinstruktur von Cuticula und Epidermis beim Flußkrebs Orconectes limosus während eines Häutungszyklus

Zusammenfassung Die Cuticula an der Innen- und Außenseite der Branchiostegite des Flußkrebses besteht wie für Arthropoden üblich aus Epi- und Procuticula. Sowohl die Epicuticula als auch die Procuticula von Innen- und Außenseite unterscheiden sich im Feinbau wesentlich voneinander. An der Innenseite ist die Epicuticula einfach gebaut; Die Procuticula ist lamelliert und zeigt meist die bogenförmigen Muster von Mikrofibrillen. Die Epicuticula an der Außenseite weist in den in dieser Arbeit untersuchten Entwicklungsstadien einen sehr viel komplizierteren Feinbau auf, der in der Entwicklung gewissen Änderungen unterliegt. In der wiederum lamellierten Procuticula an der Außenseite sind die Mikrofibrillen zu Balken gebündelt. Die Ausrichtung der Mikrofibrillen dreht sich innerhalb einer Lamelle um 180°. Durch die Procuticula ziehen Fortsätze der Epidermiszellen, außerdem Stäbe der sog. Verbindungsstrukturen.Die Bildung der Cuticula an der Innenseite konnte weitgehend vollständig verfolgt werden; sie ist gut mit der Bildung der Cuticula bei verschiedenen Insekten vergleichbar.Die Bildung der Cuticula an der Außenseite konnte dagegen nur von Beginn der Abscheidung der Proouticula bis zur Häutung verfolgt werden. Kurz vor Beginn der Cuticulaabscheidung kommt es in den Epidermiszellen zu einer stärkeren Entwicklung des rauhen ER. Während der gesamten von uns verfolgten Bildungsstadien sieht man Vesikel mit dichtem Inhalt besonders in der Nähe des Zellapex. Sie geben anscheinend hier ihren Inhalt, Cuticulamaterial, nach außen ab. Sie stammen wohl aus Golgibereichen. Auch Stachelsaumbläschen (coated vesicles) kommen regelmäßig vor, deren genetischer Zusammenhang mit multivesikulären Körpern diskutiert wird. Bei der Abscheidung der fibrillären Cuticulasubstanzen spielen besondere Differenzierungen der Zell oberfläche, — kappenartige Verdichtungen der Zelloberfläche, meist an der Spitze kleiner Mikrovilli — eine wesentliche Rolle.

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The ultrastructure of cuticle and epidermis in the crayfish Crconectes limosus during a moulting cycle

Summary The cuticle of the inside and outside of the branchiostegites of the crayfish consists of an epicuticle and a procuticle — as common in arthropods. Concerning their ultrastructure epicuticle and procuticle differ essentially from each other on both the inside as well as the outside. On the inside the epicuticle is built plainly; the procuticle is laminated, and, mostly it shows the arched patterns of microfibrils. In those developmental stages investigated in this project the epicuticle of the outside shows a much more intricated ultrastructure, since during formation it is subject to certain changes. On the outside the procuticle is also laminated; the microfibrils are bundled up to bars. The alignment of those microfibrils within one lamella is twisted for 180°. The procuticle is penetrated by processes of epidermal cells and by rods of the so-called connecting structures.The formation of the cuticle on the inside was observed completely; it is comparable to the forming of the cuticle in several insects. However, the formation of the cuticle on the outside was only observed from the beginning of the procuticular development up to the moulting.Shortly before formation of the cuticle the development of rough ER in the epidermal cells seems to be intensified. In all of developmental stages observed there appear vesicles with dense contents mainly situated nearby the cell apex. At this site they evidently deliver their contents — cuticular materials — to the outside of the cell; they probably originate in the Golgi areas. There occur coated vesicles regularity, too; their genetic relation to multivesicular bodies is discussed. Special differentiation on the cell surface i.e. dome-like consolidations of the cell surface mainly placed at the tip of small microvilli are of great importance for the secretion of the cuticle substances.

     

The contribution of phytoplankton productivity in turbid freshwaters to their trophic status

Certain factors influencing phytoplankton productivity are accentuated in turbid waters. They include mixing, spectral quality shifts, scattering, light fluctuations, and overall light attenuation. Measurements of productivity is influenced by the presence of inorganic turbidity. Together with the above factors high turbidity causes difficulties to assess and model phytoplankton productivity. Estimations of ^B, P_m ^B, I_k and _m only reflect on the physiological condition of the phytoplankton, which differs little between water types of temperate regions. Measurement of integral vertical productivity, efficiency and fractional absorption by the phytoplankton of light energy conversion, however, are greatly influenced by inorganic turbidity. Because of high ratios of mixing to euphotic depth, the critical mixing depth is one of the most important factors influencing overall productivity in turbid waters.     

Adoptions expérimentales de larves entre des fourmis de genres différents:Leptothorax nylanderi Förster etSolenopsis fugax Latreille

Résumé En l'absence de son propre couvain,Solenopsis fugax a élevé des larves deLeptothorax nylanderi, à la température de 22°C. Les ouvrières deSolenopsis détruisirent une partie de ces larves mais nourrirent celles qu'elles épargnèrent; ces dernières grossirent lentement pendant cinq à six mois, sans atteindre le stade prénymphe. Lorsque les ouvrières deS. fugax et les larves deL. nylanderi furent soumises ensemble à un hivernage préalable, elles donnèrent les mêmes résultats que sans hivernage. La présence d'une jeune reine deSolenopsis fut défavorable aux larves deLeptothorax.Inversement,L. nylanderi fut capable d'élever, à la température de 22°C, des larves deS. fugax et de les amener jusqu'au stade adulte. En présence de leurs propres larves, les ouvrières deL. nylanderi détruisirent tapidement toutes les larves deS. fugax introduites dans leur nid. D'autre part, un jeune couvain deLeptothorax remplaçait plus ou moins rapidement les larves deLeptothorax enlevées au préalable; sa présence était alors défavorable au développement des larves deSolenopsis. Un hivernage en début d'expérience fut plutôt favorable auxS. fugax, de même que la présence d'une reine féconde deLeptothorax. LesSolenopsis ainsi obtenus n'ont pas vécu plus de sept semaines. Ils étaient tous de caste ouvrière et de taille très petite.

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Summary When its own eggs and larvae missed,Solenopsis fugax bred larvae ofLeptothorax nylanderi, at a temperature of 22°C. TheSolenopsis workers killed some of this larvae and fed the others; these slowly grew bigger during five or six months but never reached the pre-pupa stage. The result was the same if the workers ofS. fugax and the larvae ofL. nylanderi overwintered together or not at all. A youngSolenopsis queen being there was noxious to the larvae ofLeptothorax.On the contrary,L. nylanderi has been able to breed larvae ofS. fugax up to the imago stage, at a temperature of 22°C. When its own larvae were in the nest, together with larvae ofS. fugax, the workers ofL. nylanderi killed the larvae ofS. fugax. On the other hand, new eggs and young larvae ofLeptothorax had to replace, more or less quickly, the larvae which had been taken away, and that was noxious to the growth ofSolenopsis larvae. An overwintering at the beginning of the experiment was rather favourable toS. fugax as was the presence of a fecundLeptothorax queen. TheSolenopsis thus obtained lived no longer than seven weeks. They all were workers and very small.

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S. Fugax L. Nylanderi 22° . Leptothorax , , , , . . S. Fugax Leptothorax.,L. Nylanderi 22° S. Fugax . L. Nylanderi ( )Leptothorax ; S. Fugax Solenopsis, Leptothorax. S. Fugax . .