The Influence of Temperature on Root Hair Infection of Trifolium parviflorum and T. glomeratum by Root Nodule Bacteria: I. THE EFFECTS OF CONSTANT ROOT TEMPERATURE ON INFECTION AND RELATED ASPECTS OF PLANT DEVELOPMENT

The onset and rate of infection in root hairs of T. parviflorumand T. glomeratum inoculated with Rhizobium trifolli strain5 varied much with root temperature. At moderate root temperature(18, 24, and 30 °C) infections were initiated earlier andin larger numbers than at low (6 and 12 °C) or moderatelyhigh (36 °C) temperatures. Both species showed a broad temperatureoptimum between 18 and 30 °C. The site of thread initiation(apically or laterally in a hair) was independent of temperature,as was also the proportion of successful threads penetratingthe root cortex, which increased with seedling age. Threadsgrew more slowly at low temperatures. The size of hair nucleinear infection threads remained unaffected by temperature, butnuclei associated with laterally originating threads were largerthan those associated with apical threads. Infection was non-randomly distributed along the main root atall temperatures. More zones of infection were found at moderatetemperatures than at temperature extremes (6–12 or 36°C). Probit plots of numbers of infections for individualplants were steplike, the linear sloping parts correspondingto normal distributions of infection within zones. Between 18 and 30 °C numbers of infections increased exponentiallyin two phases, the first more rapid phase ending at about thetime nodules appeared. A model devised for the infection processand fitted to the data suggested the existence of two kindsof infections: primary ones occuring randomly at a slow rateand probably not affected by temperature and secondary infectionsthat appeared to increase with rising temperatures in the range12 to 30 °C. Nodule numbers were relatively more sensitive to high and lowtemperatures than infection. The numbers of infections and nodulesand the root lengths of T. parviflorum were twice those of T.glomeratum except at the temperature extremes. Numbers of infectionswere otherwise unrelated to root length or cotyledon or leafareas. The development of lateral organs (primordia, lateralroots, and nodules) was reduced at temperatures below 18 °Cand above 30 °C.     

Studies on the Physiology of Nodule Formation: IX. The Influence of Combined Nitrogen, Glucose, Light Intensity and Day Length on Root-hair Infection in Clover

Small amounts of nitrate or nitrite salts (10 µg N/plant)in the root medium of Trifolium glomeratum or T. repens delayednodulation, prolonged the initial rapid phase of root infectionand slightly stimulated lateral root formation, whereas equivalentquantities of ammonium sulphate or urea did not. Growth of rootsand root hairs was unaffected by any of these substances at10 µg N/plant. Altering the carbohydrate status of the clover seedlings byadding glucose to the root medium, or by changing day lengthor light intensity, influenced neither the stimulation of root-hairinfection nor the delay in nodulation induced by nitrate at10 fig N/plant, except that plants grown in total darkness hadfewer hairs infected when the root medium contained small amountsof nitrate. The nitrogenous compounds at 100 µg to 1,000 µg N/plant generally delayed and decreased nodulation,increased lateral root formation, slowed hair infection, andincreased root growth.     

Microscopic characterization of early nodulation events in a non-nodulating soybean mutant (NN5) and lack of response to high inoculum dose

The microscopic events leading to nodulation in normally nodulatingsoybean [Glycine max (L.) Merr.] genotypes, and the effectsof Bradyrhizobium strain and inoculum dose on nodulation, wereexamined in the NN5 non-nodulating mutant derived from cv. Williams.The NN5 mutant possesses the recessive genes rj₅ and ,rj₆. BradyrhizoblumJaponicum strain USDA 110 cells attached normally to the rootsurface of NN5, many in a polar manner as in its wild-type parent,but failed to induce root hair curling and sub-epidermal celldivision in the root. Co-culturing NN5 and Williams did notmodify nodulation of either genotype. Hydroponically-grown NN5seedlings did not nodulate at a high inoculum dose (1 x 10¹⁰cells seedling^–1) of any B. japonicum strain tested (USDA110, USDA 26, USDA 136, and the tryptophan metabolic variantsB-14075 and ta 11 Nod⁺). A higher inoculum dose of 3 x 10 USDA136 cells seedling also failed to induce nodulation in NN5 andnod139 (a non-nodulating mutant of cv. Bragg). The lack of nodulationof NN5 at any inoculum dose is contrary to previous observationsof sparse nodulation of other non-nodulating mutants at highinoculum dose. Genetic control of non-nodulation in NN5 is probablysimilar to nodl39. Key words: Nodulation events, non-nodulating mutant, soybean     

On the presence of Pseudo-nitzschia calliantha Lundholm, Moestrup et Hasle and Pseudo-nitzschia delicatissima (Cleve) Heiden in the Southern Adriatic Sea (Mediterranean Sea, Italy)

This investigation included a 2-year monitoring program aimedat assessing the abundance and distribution of harmful marinephytoplankton along the Southern Adriatic coast of Italy. Monthlysampling was conducted from April 1995 to March 1997 at foursampling stations along four transects, to determine the temporaland spatial presence/abundance of the potentially toxic Pseudo-nitzschiaspecies. The study focussed on the most abundant taxa Pseudo-nitzschiacalliantha and Pseudo-nitzschia delicatissima, the identitiesof which were confirmed by TEM on cleaned net material. Thedistribution patterns of these potential Amnesic Shellfish Poisoning(ASP) toxin producers were statistically analysed by GeneralisedLinear Model ANalysis Of VAriance, Principal Component Analysis(GLM ANOVA, PCA) and Spearman’s correlation analysis inorder to address relationships between environmental variableand population dynamics. Abundances displayed horizontal andvertical structure in the study area. Inter-annual variabilitywas also observed for both species that appeared to responddifferently to the environmental factors investigated. Distributionsof P. calliantha showed a stronger seasonality and was morecorrelated with winter water conditions than P. delicatissima,which in turn exhibited a broader temporal distribution andappeared independent from major environmental constraints. Thisis the first report of the occurrence and dynamics of P. callianthaand P. delicatissima populations in Southern Adriatic coastalwaters. First two authors equally contributed to this work.     

The Effect of Moisture Stress on Infection of Trifolium subterraneum L. by Rhizobium trifolii Dang

Moisture stress and method of inoculation greatly affected thenumber and distribution of infected root hairs and nodules ofyoung seedlings of Trifolium subterraneum. A reduction of soilmoisture from 5·5 to 3·5% (–0·36to –3·6 x 10⁵ Pa) significantly decreased the numberof infection threads and completely inhibited nodulation, althoughthe number of rhizobia in the rhizosphere was unaffected. Atlow soil moisture levels the root hairs were abnormally shortand swollen. Infection and nodulation were little affected between5·5 and 9·5% moisture (–0·36 to –0·089x 10⁵ Pa). Distribution of infected root hairs depended on the initialplacement of the inoculum; with the inoculum mixed evenly throughthe soil, infection threads occurred at discrete foci alongthe root. With seedlings inoculated at planting, infection threadswere restricted to the top 1–2 cm of root, even at thehighest soil moisture tested. Watering increased the number of infections in plants grownat 3·5% moisture; nodules were formed at a rate equivalentto non-stressed plants. Watering also enabled movement of theseedling-borne inocula; new infections were formed along theroot surface bearing mature root hairs.     

The effect of food availability on byssogenesis by the zebra mussel (Dreissena polymorpha Pallas)

The effect of varying algal availability on byssal thread productionby re–attaching zebra mussels (Dreissena polymorpha) wasquantified. The byssal apparatus was severed and mussels allowedto re–attach to a hard substratum for a 21 day periodduring which they were fed at algal concentrations of 0.0, 0.1,0.5, 1.0 or 2.0 mg C l^-1. Byssal thread production was quantifiedby counting the number of new attachment plaques present eachday. Results showed that starved mussels continued to partition organiccarbon towards thread production but the resultant byssal masswas compromised, containing fewer threads than those producedby fed mussels. The daily average byssal thread production bymussels fed at 2.0 mg C l^-1 was greater than that of starved musselsand the final mean dry soft tissue weight higher. At algal Cconcentrations below maintenance requirements byssal threadproduction was elevated compared to starved mussels, but therewas no concurrent increase in soft tissue. This suggests thatbelow maintenance levels assimilated carbon was solely partitionedtowards byssus production and stored reserves may have beenutilized. The ratio of organic carbon contained in the byssusto that in the soft tissues remained relatively constant acrossall feeding levels. This suggests that the carbon content ofthe byssus is a constant function of that of the soft tissuemass. These results may explain seasonal variation in attachmentstrength of numerous byssate species and seasonal vertical migrationsby D. polymorpha. Present Address-Queen Mary & Westfield College, Dept of Biology,University of London, Mile End Road, London E1 4NS, UK (Received 16 March 1998; accepted 30 September 1998)     

Patterns of horizontal distribution of the larvae of southern bluefin (Thunnus maccoyii) and other tuna in the Indian Ocean

The fine- to coarse-scale distribution patterns of tuna larvaein the east Indian Ocean were investigated by a combinationof continuous transect sampling using surface tows and randomsampling using double oblique tows. Thunnus maccoyii was themost abundant species, reaching densities near patch centresof 22 m^–1 in surface tows, which is 25 times greater thanthe highest previous records for tuna larvae. Patches of T.maccoyiilarvae in areas of high abundance appeared to 5.2 for T.maccoyii.There was no change in the index when tow distance was doubledto 1200 m, older larvae. Lloyd's index of patchiness was consistentlyhigh for all tuna species, ranging from 3.0 to 5.2 for T.maccoyyii.There was no change in the index when tow distance was doubledto 1200 m, which suggests that the dominant patch size was somewhatlarger than the larger sampling interval. Sampling larvae atthe same site 4 days apart resulted in estimates of abundancethat differed by an order of magnitude. Abundance estimatedfrom a single station would depend largely on what day the stationwas occupied and where the sample was taken in relation to apatch. ¹Present address: Victoria Institute of Marine Sciences andDepartment of Zoology, University of Melbourne, Parkville, Victoria3052, Australia     

On the trophic fate of Phaeocystis pouchetii (Harlot). III. Functional responses in grazing demonstrated on juvenile stages of Calanus finmarchicus (Copepoda) fed diatoms and Phaeocystis

The objective of this study was to quantify the functional responsein feeding rate in the various developmental stages of Calanusfinmarchicus to different concentrations of the diatoms Thalassiosiranordenskioeldii and Porosira glacialis, and the haptophyseanPhaeocystis pouchetii. Grazing of copepodite stage I–VC.finmarchicus was measured using two different approaches.Feeding rates were obtained from either incubation experiments,estimating the rate of removal of particles from suspension,or by quantifying the turnover rate of the plant pigments inthe gut. Clearance as a function of algal concentration (1–30µg plant pigment 1^–1) was described in juvenilestages of C.finmarchicus fed the diatoms T.nordenskioeldii [20µm equivalent spherical diameter (ESD)], P.glacialis (40µm ESD), and two size categories (30–100 µmand >100 µm ESD) of the gelatinous alga P.pouchetii.When the copepodite stages were fed T.nordenskioeldii, the gutcontent of plant pigments was in general higher than when fedP.glacialis. Rates obtained were variable when the same copepoditestages were offered the two size categories of P.pouchetii,but within the same order of magnitude as those obtained forthe larger diatom. At unialgal diets, diatoms were more readilyconsumed than the larger size fraction among colonies of P.pouchetiiby copepodite stage I–III C.finmarchicus. But given anappropriate prey size, C.finmarchicus grazed both diatoms andcolonies of gelatinous algae at equal rates. A linear relationshipbetween gut content and food concentrations <10 µgchlorophyll 1^–1 was found. This indicates that the ingestionrate in C.finmarchicus is directly proportional to the ambientfood concentration during the most productive period in Mayand June in high latitudes irrespective of algal species present. ¹Present address: Marine Biological Laboratory, University ofCopenhagen, Strandpromenaden 5, DK-3000 Helsingør, Denmark ²Present address: Greater Copenhagen Council, Gl. KøgeLandevej 1–3, DK-2550 Valby, Denmark     

A comparison of meta-analysis methods for detecting differentially expressed genes in microarray experiments

Motivation: The proliferation of public data repositories createsa need for meta-analysis methods to efficiently evaluate, integrateand validate related datasets produced by independent groups.A t-based approach has been proposed to integrate effect sizefrom multiple studies by modeling both intra- and between-studyvariation. Recently, a non-parametric ‘rank product’method, which is derived based on biological reasoning of fold-changecriteria, has been applied to directly combine multiple datasetsinto one meta study. Fisher's Inverse ² method, which only dependson P-values from individual analyses of each dataset, has beenused in a couple of medical studies. While these methods addressthe question from different angles, it is not clear how theycompare with each other. Results: We comparatively evaluate the three methods; t-basedhierarchical modeling, rank products and Fisher's Inverse ²test with P-values from either the t-based or the rank productmethod. A simulation study shows that the rank product method,in general, has higher sensitivity and selectivity than thet-based method in both individual and meta-analysis, especiallyin the setting of small sample size and/or large between-studyvariation. Not surprisingly, Fisher's ² method highly dependson the method used in the individual analysis. Application toreal datasets demonstrates that meta-analysis achieves morereliable identification than an individual analysis, and rankproducts are more robust in gene ranking, which leads to a muchhigher reproducibility among independent studies. Though t-basedmeta-analysis greatly improves over the individual analysis,it suffers from a potentially large amount of false positiveswhen P-values serve as threshold. We conclude that careful meta-analysisis a powerful tool for integrating multiple array studies. Contact: fxhong{at}jimmy.harvard.edu Supplementary information: Supplementary data are availableat Bioinformatics online. Associate Editor: David Rocke Present address: Department of Biostatistics and ComputationalBiology, Dana-Farber Cancer Institute, Harvard School of PublicHealth, 44 Binney Street, Boston, MA 02115, USA.     

LARVAL GROWTH AND THE INDUCTION OF METAMORPHOSIS OF A TROPICAL SPONGE-EATING NUDIBRANCH

The Hawaiian dorid nudibranch Hypselodoris infucata (Rppell& Leuckart, 1828) was reared to metamorphosis in the laboratory.Egg diameter averaged 88 µm and veligers hatched, afterabout 5 days at 25°C, with a coiled shell averaging 149µm in length. Larvae fed on phytoplankton grew to a maximumshell length of 306 µm in about 15 days. Larval growthwas affected by both quality and quantity of the algal diet.Some larvae were competent to metamorphose 16 days post-hatchingat 26°C, and competence could be retained for at least oneweek. Metamorphosis is complete within 24 hours of exposureto an inducer. At least three species of sponge, Halichondriacoerulea, Sig-modocia sp., and Tedania macrodactyla, in additionto the nudibranch's adult prey species, Dysidea sp., inducedmetamorphosis of competent larvae. Primary films grown on glassslides also induced metamorphosis in some larvae, as did 20µM excess potassium ions in seawater. These data suggestthat nonspecific induction of metamorphosis occurs in this specieseven though the adult nudibranchs are highly prey specific.This implies that in the field, H. infucata find Dysidea sp.after settlement and metamorphosis Present address: Dept of Genetics and Development, College ofPhysicians and Surgeons of Columbia Univeisity, 701 West 168thStreet, NewYork, 10032, USA (Received 22 June 1987; accepted 3 March 1988)     

In vitro Regeneration from Excised Leaf Discs of Three Brassica Species

Excised leaf discs of three Brassica species, B. oleracea, B.napus, and B. campestris were induced to produce adventitiousbuds and subsequently entire plants by culture on media withspecific combinations of 6-benzylaminopurine (BAP) and -naphthylaceticacid (NAA). Each species required a particular hormone concentrationfor optimum growth and differentiation: B. oleracea, BAP 10mg^–1 and NAA 1 mg 1^–1; B. napus, BAP 10 mg 1^–1and NAA 10 mg 1^–1; B. campestris, BAP 1 mg 1^–1 andNAA 10 mg 1^–1. In a more detailed study on one of these species, namely B.oleracea, the relative influence of other media components suchas amino acids and other organic additives was examined. Itwas also found that the source and size of the explant greatlyaffected the growth response, as did the size of the culturevessel. The regenerated plants dislayed a range of ploidy as well asphenotypic abnormalities. Findings are discussed in relation to results from other tissueculture systems.     

Biological and Cultural Characteristics of the Effective Frankia Strain HFPCcl3 (Actinomycetales) from Casuarina cunninghamiana (Casuarinaceae)

From homogenates prepared from surface-sterilized nodules ofseedlings of Casuarina cunninghamiana grown aeroponically, astrain of Frankia designated HFPCc13 was isolated and has beengrown in pure filamentous culture in a defined synthetic nutrientmedium. Vesicle and sporangium formation can be induced by removalof combined nitrogen from the medium.Frankia strain HFPCc13nodulates young seedlings of C. cunninghamiana and C. equisetifoliawithin three weeks of inoculation with an optimum root mediumpH of 6–7 for nodulation and optimum temperature of 30–35^°C. The presence of combined nitrogen in the root mediuminhibits nodulation with NH₄⁺ more inhibitory than NO₃^–.Frankia HFPCc13 does not nodulate Allocasuarina species withinthe same family nor several other possible actinorhizal plantstested. Thus this strain is quite precise in its host specificity.The rate of acetylene reduction was greater in C. cunninghamianathan the closely related species C. equisetifolia. In neitherof these host species were vesicles observed to occur withinthe infected root nodules which had been demonstrated to beactively fixing dinitrogen. Root nodules were shown to be activein acetylene reduction over a range of O₂ concentration in thegaseous environment with an optimum at about 20 per cent O₂,the ambient P_O2 of the air. The mechanism(s) for oxygen protectionof nitrogenase within the filamentous form of Frankia withinthese nodules remains to be explained. Casuarina, Frankia, nodulation, nitrogen fixation     

Estrogen increases the permeability of the cultured human cervical epithelium by modulating cell deformability

Estrogens increase secretion of cervical mucusin females. The objective of this research was to study the mechanismsof estrogen action. The experimental models were human CaSki(endocervical) and hECE (ectocervical) epithelial cells cultured onfilters. Incubation in steroid-free medium increased transepithelialelectrical resistance(R_TE) anddecreased epithelial permeability to the cell-impermeant acid pyranine.Estrogen treatment reversed the effects, indicating estrogen decreasesepithelial paracellular resistance. The estrogen effect was time anddose related (EC₅₀ ~1 nM) andspecific (estradiol = diethylstilbestrol > estrone, estriol; noeffect by progesterone, testosterone, or cortisol) and was blocked byprogesterone, tamoxifen, and ICI-182780 (an estrogen receptorantagonist). Estrogen treatment did not modulate dilution potential orchanges in R_TE inresponse to diC8 or to low extracellularCa²⁺ (modulators of tightjunctional resistance). In contrast, estrogen augmented decreases inR_TE in responseto hydrostatic and hypertonic gradients [modulators of resistanceof lateral intercellular space (R_LIS)],suggesting estrogen decreasesR_LIS. Estrogendecreased cervical cell size, shortened response time relative tochanges in cell size after hypertonic challenge, and augmented thedecrease in cell size in response to hypertonic and hydrostaticgradients. Lowering luminal NaCl had no significant effect onR_TE, and the Cl channel blockerdiphenylamine-2-carboxylate attenuated the hypertonicity-induced decrease in cell size to the same degree in control andestrogen-treated cells, suggesting estrogen effects on permeability andcell size are not mediated by modulatingNa⁺ orCl transport. In contrast,estrogen increased cellular G-actin levels, suggesting estrogens shiftactin steady-state toward G-actin and the cervical cell cytoskeletontoward a more flexible structure. We suggest that the mechanism bywhich estrogens decreaseR_LIS and increasepermeability is by fragmenting the cytoskeleton and facilitatingdeformability and decreases in cervical cell size.

     

Interspecific variability and environmental influence on particulate organic carbon {delta}13C in cultured marine phytoplankton

The stable carbon isotope composition of particulate organicmatter expressed as ¹³C was measured in cultures of 13 speciesof marine microalgae in different phylogenetic groups. The effectsof salinity variations and changes in photoperiod were alsoassayed for three of them (i.e. Skeletonema costatum, Amphidiniumopercularum and Isochrysis galbana); the effect of nature ofnitrogen supply (nitrate. ammonium) was studied for one (S.costatum).These environmental parameters were chosen because of theirvariability in the ocean and their possible effects on ¹³C valuesof phytoplankton organic carbon. Batch culture conditions andsampling time after inoculum were strongly controlled in orderto provide cells in good physiological state which were comparablefrom one culture to the other. In the same way, sampling waslimited to the first 2 days of exponential growth, in orderto avoid a possible dissolved inorganic carbon (DIC) limitation.Carboxylase activities [of the enzyme ribulose 1,5-bisphosphatecarboxylase oxygenase (Rubisco), and the three ß carboxylases:phosphoenolpyruvate carboxylase (PEPC), phosphoenolpyruvatecarboxykinase (PEPCK) and pyruvate carboxylase (PC)] and totalchlorophyll a concentrations were assayed simultaneously. The¹³C values observed were between –30.2 and –12.7i.e. comparable to those observed in the world's oceans. Theisotopic composition of phytoplankton organic carbon was shownto be under the influence of the parameters tested but ¹³C variationsare specific to the species considered. The nature of ßcarboxylase found in each species, or systematic position, couldnot be linked to the isotopic composition of organic carbon.No linear or single correlation between ¹³C variations and environmentalmodifications were observed and there is no evidence for a simpleand universal relation between ¹³C of phytoplankters and theirenvironment. In monospecific cultures as in the field, ¹³C fractionationby Rubisco (and eventually by PEPCK) may be counterbalancedby other mechanisms.     

Functional Significance of Acid Phosphatase Distribution During Embryo Development in Pisum sativum L

The distribution of P₁, ester P and acid-insoluble nucleic acidP has been studied in relation to acid phosphatase activity(EC 3. 1. 3. 2) in the component parts of developing pea seeds(Pisum sativum L.). Despite the favourable pH of the liquidcontents of the embryo sac (pH 5.5), only very low acid phosphataseactivity was detected in this fluid (c. 0.01 units per seed).Potential substrates for phosphatase action were in fact absentfrom the secretion, the only form of P present being P_i, inconcentrations up to 8 mM. The data support the hypothesis thatthe high acid phosphatase activities which develop in the seed-coatsare involved in regulating the supply of P as P₁ to the developingembryo. Pisum sativum L., pea, embryo development, acid phosphatase, phosphorus, seed-coats, seed development     

The effects of lime-pelleting and lime-superphosphate fertilizer on the growth of three annual legumes in an acid sandy soil

Summary Three pioneer pasture legume species,Trifolium subterraneum, Trifolium glomeratum andOrnithopus compressus, were grown in a sandy soil of pH 5.0. The growth and nodulation of each species was examined in the presence and absence of lime pelleting and with superphosphate and lime-superphosphate fertilizer. In each species tested, plant yield, nodule number and nitrogen recovery as maximal where lime pelleting and lime-super were applied together. Plant calcium indicated that the response to lime was due to changes in soil pH rather than to a calcium response. T. glomeratum was the species most responsive to lime application but its growth was at best only half that ofT. subterraneum andO. compressus, which produced equally under both favourable (pH 5.9) and unfavourable (pH 4.4) conditions created by fertilizer applications.     

A new Trillium (Liliaceae) from the northwestern United States

A new species,Trillium parviflorum, is described inTrillium subgen.Phyllantherum Raf.Trillium parviflorum is easily distinguished fromT. albidum Freeman, which it superficially resembles, by its overall smaller size, much smaller linear-lanceolate petals, clove-like fragrance, and dark maroon fruit.     

Physiological Studies on Nodule Formation. The Characteristics and Inheritance of Abnormal Nodulation of Trifolium pratense by Rhizobium leguminosarum

Five to 7 per cent of plants of Trifolium repens L. and T.pratenseL. and 100 per cent of plants of T. subterraneum L. were nodulatedby Rhizobium leguminosarum but none of T. hybridum L., T. glomeratumL. or T parvifirum Ehrh. The frequency of nodulation of T. pratenseby R. leguminosarum was much increased by breeding from susceptibleplants. Such plants were not nodulated by bacteria isolatedfrom any other cross-inoculation group, but remained fully susceptibleto R. trifolii. The nodules formed by R. leguminosarum are generallyassociated with lateral roots and are ineffective.