Effect of light on the initiation of pileus formation in a basidiomycete, Favolus arcularius

Pileus formation in Favolus arcularius is induced by light,but no photoinduction occurred in young epileate stipes. Thestipes usually had to attain a length of about 5 mm to be photosensitive.Synchronous pileus formation could be induced by exposure tolight using epileate stipes which had been preincubated in darknessfor 48 to 72 hr. The pileus primordium formed about 24 hr afterthe start of illumination, however, continuous illuminationwas not necessary to produce this effect. A dark period givenbetween 1 and 8 hr after the start of illumination did not retardpileus formation. The photoinduction of pileus formation involvedtwo light-requiring processes, one occurring during the firsthour (the first light process) and the other from the 8th tothe 24th hr (the second light process). The photoresponse inthe first light process was saturated with 5 lux of light, buta light intensity below 1 lux was essentially ineffective. Onthe other hand, the reaction in the second light process couldbe started by less than 2 lux, and was accelerated by increasingthe light intensities up to about 150 lux. Further increasesin light intensity did not improve any significant effect. (Received April 30, 1974; )     

Ethylene-Enhanced Transport of Uranine, a Fluorescent Dye, in Rice-Seedling Explants in Relation to Ethylene-Stimulated Coleoptile Growth

Ethylene enhanced the transport of uranine, a fluorescent dye,through the coleoptiles of rice (Oryza sativa L. cv. Sasanishiki)seedlings explants after a 2-h lag period. The uranine transportincreased with increasing concentration of ethylene, reachinga maximum at 1 µ1.liter^–1 ethylene. It decreasedwhen some metabolic inhibitors, 2,4-dinitrophenol, carbonylcyanide 3-chlorophenylhydrazone and N-ethylmaleimide, were appliedto the scutella. Mechanical rupture or heating at the vascular-bundlesides of the coleoptiles also interfered with the ethylene-enhancedtransport of uranine. The wounding and removal of the scutellasimilarly blocked uranine transport. Moreover, strong fluorescenceof uranine was observed on the phloem regions of two vascularbundles of a coleoptile under a fluorescence microscope. Itis suggested that the ethylene-enhanced transport of uraninein the coleoptile of rice-seedling explants occurs through thephloem. On the other hand, the removal of the endosperm or therupture of the vascular bundles inhibited the ethylene-stimulatedelongation of the rice coleoptiles. Moreover, ethylene increaseddry weight of the shoots. These results suggest that the ethylene-stimulatedelongation of rice coleoptiles was supported partly by the ethylene-enhancedtranslocation of materials from the endosperms to the coleoptiles. (Received September 6, 1984; Accepted November 15, 1984)     

Calibration of Pd-porphyrin phosphorescence for oxygen concentration measurements in vivo

Sinaasappel, M., and C. Ince. Calibration ofPd-porphyrin phosphorescence for oxygen concentration measurements in vivo. J. Appl. Physiol. 81(5):2297-2303, 1996.Quantitative measurement of oxygenconcentrations in the microvasculature is of prime importance in issuesrelated to oxygen transport to tissue. The introduction of thequenching of the Pd-porphyrin phosphorescence as oxygen sensor in vivoby Wilson et al. (J. Appl. Physiol.74: 580-589, 1993) has provided in this context a major advance inthis area of research. For in vivo application, the dye is coupled toalbumin to restrict the dye to the circulation and to measure oxygen in the physiological range. In this study a phosphorimeter with a gatedphotomultiplier is presented and validated. Furthermore, anonlinear-fit method using the Marquardt-Levenberg algorithm is used tocalculate the decay time. With this new phosphorimeter, calibrationmeasurements were performed to investigate the effects of pH,temperature, and diffusivity. The results present a preparation methodfor albumin coupling of the dye that eliminates the pH dependency ofthe quenching kinetics. Furthermore, the decreased oxygen diffusivityof serum was compared with that of water, and it was shown thatcalibration constants measured in water can be extrapolated to serum.

     

Dispersion characteristics of two planktonic diatoms

Not all phyloplankton behave as ideal water tracers. Longitudinaldispersion experiments were conducted in a large flume withseawater of constant depth and velocity. The transport of thepassive, fluorescent tracer, Rhodamine B dye, was compared withunialgal cultures of a large, fast-sinking diatom (Odontellachinensis) and a small, slow-sinking diatom (Skeletonema costatum).Horizontal dispersion rates, proportional to variance per distance,were linear for the dye and Skeletonema but nonlinear for Odontella.Results are explained by the interaction of Odontella sinkingand advection. Longitudinal dispersion coefficients for thedye and Skeletonema were between 60–80 cm² s^–1 andas high as 280 cm² s^–1 for Odontella. This may have implicationsfor nutrient uptake in natural phytoplankton populations.     

The Influence of Factors of the Aeration Complex and Light upon Fruit-body Form in Pure Cultures of an Agaric and a Polypore

Methods involving controlled temperature and illumination, continuouslyrenewed sterile culture atmosphere of defined gaseous compositionand vapour pressure, and automatic replacement of water lossfrom the medium have been applied to the analysis of sporophoreform in Collybia velutipes and Polyporus brumalis. In P. brumalisprogressive suppression of the pileus but enhanced stipe elongationoccurs as light intensity (over a certain range) or transpirationalwater-loss are reduced. These factors act additively. Cap expansionin C. velutipes requires light and is, in addition, inhibitedby an atmospheric staling agent removable by KOH and replaceableby CO₂. Data and observations on conditions affecting timesof production, numbers and dimensions of fruit-bodies are given,especially for P. brumalis. Other aeration factors are consideredbut shown to have no morphological effect.     

The Change of Tropism in Polyporus brumalis Stipes and the Effect of Directional Stimuli on Pileus Differentiation

The directional influences of light and gravity upon the developmentof pileate and epileate sporophores of Polyporus brumalis, producedin pure culture, have been investigated. Growth in the dimiticfruit-body has a considerable subapical component which in thestipe is responsible for tropistic curvature. The stipe is competentto react negatively to unilateral gravitational and positivelyto unilateral photic stimulation throughout development, butwhen both stimulioperate phototropism masks geotropism. If illuminatedfrom one side the growing epileate stipe is strongly positivelyphototropic but as the pileus reaches a characteristic diameterthe stipe becomes negatively geotropic. Experiments with changingdirection of illumination and with artificial pilei of blackpaper suggest that the change of tropism is explicable by theshading action of the expanding pileus on the sub-pilcal photoperceptiveand photoreactive region of the stipe. Developing sporophores continuously rotated with reference tofixed directions of gravitational and light stimulation andothers with stipes inverted as a result of illumination frombelow during development have in common that the morphologicallyupper surface of the pileus always develops towards and approximatelyat right angles to the direction from which the maximum lightintensity is received. Normal but inverted stipes and dissepimentsshow no tendency to geotropic reorientation.     

Riboflavin transport by isolated perfused rabbit renal proximal tubules

Rabbit renal proximal tubular transport of riboflavin(RF) was examined by using the in vitro isolated tubule perfusiontechnique. We found that proximal tubules actively reabsorbed(J_lb) and secreted (J_bl)RF. At 0.1 µM RF concentration, J_bl wassignificantly higher than J_lb, resulting in anet secretion. This net secretion of RF was decreased at 0.01 µM RFconcentration and increased at 1 µM RF concentration. BothJ_lb and J_bl wereinhibited by lowering temperature or by adding iodoacetate, a metabolicinhibitor, and lumichrome, an RF analog, suggesting the involvement ofcarrier-mediated transport mechanisms. J_bl wasinhibited by probenecid, an anion transport inhibitor, and bypara-aminohippuric acid, an organic anion, suggesting therelevance of RF secretion to renal organic anion transport.J_bl was also inhibited by alkaline pH (8.0) and by the calmodulin inhibitor trifluoperazine, indicating the influence of pH and Ca²⁺/calmodulin-dependent pathway on RFsecretion. Finally, we found that addition of chlorpromazine, aphenothiazine derivative, inhibited both J_lb andJ_bl, raising the concern about the nutritionalstatus in patients receiving such a type of medication.

     

Auxin-Promoted Transport of Metabolites in Stems of Phaseolus vulgaris L.: EFFECTS REMOTE FROM THE SITE OF HORMONE APPLICATION

Phloem transport in stems of Phaseolus vulgaris was found tobe sensitive to treatment with the auxin transport inhibitor,2,3,5-triidobenzoic acid (TIBA). The response was dependenton the concentration of TIBA applied. A concentration of TIBA(0?5% in lanolin) which did not interfere with normal phloemtransport proved inhibitory to both basipetal transport of IAAand the acropetal component of IAA-promoted metabolite transport.In contrast, both acropetal IAA transport and basipetal IAA-promotedmetabolite transport were unaffected by TIBA treatment. Theinhibitory effect of TIBA on acropetal IAA-promoted transportwas overcome by providing IAA below the point of TIBA application.Both acropetal and basipetal IAA-promoted transport in stemsegments were unaccompanied by any corresponding changes inthe accumulation of [¹⁴C]sucrose by the segments.     

Active uptake of inorganic carbon by Chlorella saccharophila is not repressed by growth in high CO2

Regulation of transport of dissolved inorganic carbon (DIC)in response to CO₂ concentration in the external medium hasbeen compared in two closely-related green algae, Chlorellaellipsoidea and Chlorella saccharophila. C. ellipsoidea, whengrown in high CO₂, had reduced activities of both CO₂ and transport and DIC transport activitieswere increased after the cells had acclimated to air. However,high CO₂-grown C. saccharophila had a comparable level of photosyntheticaffinity for DIC to that of air-grown C. ellipsoidea and thiswas accompanied by a capacity to accumulate high internal concentrationsof DIC. The high photosynthetic affinity and the high intracellularDIC accumulation did not change in cells grown in air exceptthat the occurrence of external carbonic anhydrase (CA) in air-grownC. saccharophila stimulated the intracellular DIC accumulationin the absence of added CA. These data indicate that activeDIC transport is constitutively expressed in C. saccharophila,presumably because this alga is insensitive to the repressiveeffect of high CO₂ on DIC transport. This strongly supportsthe existence of a direct sensing mechanism for external CO₂in Chlorella species, but also indicates that external CA isregulated independently of DIC transport in Chlorella species. Key words: Carbonic anhydrase, Chlorella, CO₂-insensitive, DIC transport, wild type     

Common mechanisms of monoacylglycerol and fatty acid uptake by human intestinal Caco-2 cells

Free fatty acids (FFA) andsn-2-monoacylglycerol (sn-2-MG), the twohydrolysis products of dietary triacylglycerol, are absorbed from thelumen into polarized enterocytes that line the small intestine.Intensive studies regarding FFA transport across the brush-bordermembrane of the enterocyte are available; however, little is knownabout sn-2-MG transport. We therefore studied the kineticsof sn-2-MG transport, compared with those of long-chain FFA(LCFA), by human intestinal Caco-2 cells. To mimic postprandial luminaland plasma environments, we examined the uptake of taurocholate-mixed lipids and albumin-bound lipids at the apical (AP) and basolateral (BL)surfaces of Caco-2 cells, respectively. The results demonstrate thatthe uptake of sn-2-monoolein at both the AP and BL membranes appears to be a saturable function of the monomer concentration ofsn-2-monoolein. Furthermore, trypsin preincubation inhibits sn-2-monoolein uptake at both AP and BL poles of cells.These results suggest that sn-2-monoolein uptake may be aprotein-mediated process. Competition studies also support aprotein-mediated mechanism and indicate that LCFA and LCMG may competethrough the same membrane protein(s) at the AP surface of Caco-2 cells.The plasma membrane fatty acid-binding protein (FABP_pm) isknown to be expressed in Caco-2, and here we demonstrate that fattyacid transport protein (FATP) is also expressed. These putative plasmamembrane LCFA transporters may be involved in the uptake ofsn-2-monoolein into Caco-2 cells.

     

The Role of Basipetal Auxin Transport in the Positional Control of Abscission Sites Induced in Impatiens sultani Stem Explants

If segments of Impatiens sultani stem are explanted and incubated,separation layers often form across them and lead to abscission.To test the suggested role of auxin concentration in controllingthe position of abscission sites, explants were labelled byapplying [¹⁴C]IAA to the shoot tip 4 h prior to explanting;transport of auxin applied in this way seems to resemble thatof endogenous auxin. During subsequent incubation of explantsfor 20 h, basipetal transport resulted in ¹⁴C accumulating justabove the base of the explants (nearly 80 % in the bottom 4mm of 24 mm explants). In internodal explants that had beenwounded at explanting by incising one side so as to sever avascular bundle, and in nodal explants with the leaf removed,the ¹⁴C also accumulated just above the wound or node to abouttwice the concentration otherwise expected; this accumulationwas probably due to basipetal transport being impeded by vasculardiscontinuity at the wound or node. Accumulation just abovethe base, or above a wound or node, resulted in gradients of¹⁴C concentration (presumably reflecting endogenous auxin concentration)decreasing in the morphologically upward direction at each ofthese three positions where abscission sites tend to occur. Impatiens sultani, abscission, auxin, IAA, node, polarized transport, positional control, separation layer, wounding     

Phytoplanktonic carbon isotope fractionation: equations accounting for CO2-concentrating mechanisms

A model of carbon isotope discrimination by phytoplankton wasdeveloped which took into account the occurrence of a carbon-concentratingmechanism (CCM). A simple equation was obtained for the modelinvolving CO₂ active transport. In the case of HCO₃^– activetransport, another equation was developed based on a seriesof approximations. The former equation was used to analyse reportedand newly obtained data from culture experiments and field observationsin both freshwater and marine environments. In most cases, alinear relationship between a combined parameter, (1–f)Ci,which was made up of the relative contribution of active CO₂uptake to total carbon uptake (f) and the intracellular CO₂concentration (Ci), and CO₂ concentration in bulk solution (Ce)was obtained as (1–f)Ci = ace–b, with a high correlationcmfficient (r²>0.9). The slope a is suggested as a measureof the ratio of diffusive to total (diffusive+active) CO₂ transport,while bla represents CO₂ demand.     

Uptake and Compartmentation of Fluorescent Probes by Plant Cells

Several fluorescent compounds are now being used as probes forstudying plant transport processes. This review considers thepotential mechanisms of uptake of such probes with particularemphasis on their subsequent compartmentation within the cell.Physico-chemical parameters, such as the dissociation constant(pK_a) and polarity (log k^ow) of the dye molecule provide importantguides as to the likely permeability of the plasmalemma to differentfluorochromes and an ion-trap mechanism may explain the accumulationof many fluorescent probes by plant cells. However, physico-chemicalparameters alone do not always explain the subsequent compartmentationof fluorescent probes within the cell. Evidence is accumulatingthat many anionic fluorescent probes may cross the plasmalemmain the undissociated state, followed by carrier-mediated transportof the anion across the tonoplast. In the specialized case ofthe highly dissociated dye, Lucifer Yellow CH (LYCH), the physico-chemicalproperties of the molecule would predict that it should be unableto cross membranes. Despite this, there have been several reportsof the movement of LYCH from the apoplast to the vacuole ofplant cells. Fluid-phase endocytosis has been implicated inthe vacuolar accumulation of LYCH and also a range of high-molecularweight, purified fluorescent conjugates. This evidence is discussedin the light of some reports that membrane-impermeant dyes,including LYCH, may cross the tonoplast following their microinjectioninto the cytoplasm.     

Influences of environmental factors on fruiting body induction,development and maturation in mushroom-forming fungi

Mushroom-forming fungi (restricted to basidiomycetous fungi in this review) differentiate by sensing several environmental factors for fruiting body formation. For fruiting body induction, nutrient, temperature and light conditions are critical environmental factors. Higher nitrogen and carbon sources in the media will suppress fruiting body induction in many mushroom-forming fungi, with induction being triggered by lower nitrogen and carbon concentrations. Low temperature or temperature downshift is another critical influencing factor for fruiting body induction in many cultivated mushrooms, such as Flammulina velutipes, Lentinula edodes, and Volvariella volvacea. Fungal response toward starvation and cold involves the production of sexual spores as the next generation. Species like F. velutipes and Coprinopsis cinerea can form fruiting bodies in the dark; however, light accelerates fruiting body induction in some mushroom-forming fungi. Remarkably, fruiting bodies formed in the dark have tiny or no pileus on heads (called dark stipe, pinhead fruiting body, or etiolated stipe). Light is essential for pileus differentiation in many, but not all mushroom species; one exception is Agaricus bisporus. Mushrooms have positive phototropism and negative gravitropism for effective dispersal of spores. Carbon dioxide concentrations also affect fruiting body development; pileus differentiation is suppressed at a high concentration of carbon dioxide. Thus, the pileus differentiation system of mushrooms may allow the most effective diffusion of spores. Full expansion of the pileus is followed by pileus autolysis or senescence. In C. cinerea, pileus autolysis occurs during spore diffusion. Fruiting body senescence, browning of gill, and softening occur after harvesting in several mushroom species. Fruiting body induction, development, and maturation in mushroom-forming fungi are discussed in this review.     

Characteristics of Sugar, Amino Acid and Phosphate Release from the Seed Coat of Developing Seeds of Vicia faba and Pisum sativum

After removal of the embryo from developing seeds of Vicia fabaL. and Pisum sativum L., the ‘empty’ ovules werefilled with a standard solution (pH 5.5). Seed coat exudatesof both species were collected during relatively long experiments(up to about 12 h) and the concentration of sugar (mainly sucrose),amino acids and phosphate in the exudate measured. A discussionis presented on the amino acid/sugar ratio and the phosphate/sugarratio in the seed coat exudate. A pretreatment (15 min) withp-chloromercuribenzenesulphonic acid (PCMBS) reduced the releaseof sugar, amino acids and phosphate from broad bean seed coats.After excision of ‘empty’ ovules of Vicia faba andPisum sativum from the maternal plant, 2–4 h after thistreatment a strong difference became visible between sucroserelease from excised seed coats and sucrose release from attachedseed coats. Similarly, when the rate of phloem transport ofsucrose into an ‘empty’ ovule of Vicia faba or Pisumsativum was reduced by a sub-optimal mannitol concentrationin the solution, a reduced rate of sugar release from the seedcoat could be observed. Excision and treatment with a sub-optimalmannitol concentration reduced the release of amino acids toa lesser extent than for sucrose. These treatments did not reducethe rate of phosphate release from the seed coat. Key words: Seed development, Seed coat exudate, Phloem transport     

Effect of the Osmotic Environment on Assimilate Transport in Isolated Developing Embryos of Maize (Zea mays)

Embryos obtained from developing kernels of maize (Zea maysL.) were incubated in a bathing medium, to measure the effectof the osmotic environment on the balance between uptake andrelease of assimilates by the embryo. Net efflux of sucroseand amino acids from the embryo decreased with increasing mannitolconcentration in the bathing medium and net uptake of [¹⁴C]valine increased with increasing mannitol concentration. Therole of a high osmolality of the seed apoplast in seed developmentis discussed Zea mays, maize, embryo, seed development, assimilate transport, turgor-sensitive transport     

Tidal transport of planktonic copepods across the sill of a British Columbia fjord

Estimates of plankton transport into and out of semi-enclosedbodies of water could be of value in long-term ecological monitoring.The study reported here examined the problems associated withthe estimates of tidal transport of four species of planktoniccopepods across the sill of a British Columbia fjord. Transportwas estimated by applying calculated tidal volume exchange toplankton field data collected over a 13-month period. Hydrographicdata during the period indicated that tidal exchange was thedominant mechanism for the transport of water Differences indepth distribution and behaviour resulted in a species-specificeffect of tidal exchange. The diel vertical migration of Metridialucens and the ontogenetic migration of Eucalanus bungi resultedin transport only during those periods when organisms were presentin water near or above sill depth. Corycaeus anglicus was presentabove sill depth at all times and transport occurred throughoutthe study period. Euchaeta japonica, although present in waterabove sill depth throughout the year, was transported acrossthe sill only during the winter months. Transport estimatescould be related to estimates of fjord concentrations for C.anglicus and E. bungii. For M. lucens and E. japonica, it issuggested that natality and mortality within the inlet was sufficientto mask the effect of tidal transport on the species concentration.     

Hexose Transport in Isolated Immature Barley Embryos

The pathways of monosaccharide assimilation in developing barleyembryos have been investigated in an in vitro assay system,and the results are discussed in relation to the primary carbohydratenutrients of the developing and germinating embryo. Glucoseand fructose are both rapidly taken up by immature embryos,and at a substrate concentration of 100 mM their assimilationrate exceeds by threefold that of sucrose. The kinetics of hexoseuptake are complex, reflecting a combination of passive diffusionand metabolically mediated uptake mechanisms. The hexose transportenergetics were further studied with the glucose analogue 3-O-methyl-D-glucose,shown to be a non-metabolite in the barley embryo. The kineticsof 3-O-methyl-D-glucose influx and efflux indicated that passivediffusion accounts for a major part of hexose assimilation inbarley embryos. However, an active transport component was revealedby the sensitivity of 3-O-methyl-D-glucose uptake to uncouplingagents and the demonstration of competitive inhibition of uptakebetween glucose analogues. These observations supported theview that part of the observed energy-dependence of hexose uptakemight be asociated with a direct coupling of energy to transport.A high-affinity active group translocation mechanism for glucoseassimilation could be important in embryo metabolism duringthe first hours of germination prior to hydrolysis of endospermstarch reserves. Analysis of the fate of assimilated hexosesshowed that the rapid consumption of the hexose pool in thesynthesis of sucrose must contribute to the influx of hexosesby the maintenance of a hexose concentration gradient betweenthe embryo and its environment. Hordeum distichum(L.) Lam, barley, embryo, hexose transport     

Modelling Shoot[ratio]Root Relations: the Only Way Forward?

The basic transport-resistance (TR) model of shoot[ratio]rootcarbon[ratio]nitrogen allocation is described. This approachassumes that the two processes of substrate transport and chemicalconversion determine allocation. It is suggested thatallallocationmodels, whether built for the purposes of theoretical investigationor practical application, should start with this irreducibleframework. Here it is assumed that the processes operate accordingto: (a) for substrate sources, dependence on shoot and rootsizes with possible product inhibition; (b) for transport, movementdown a substrate concentration gradient; and (c) for substratesinks or utilization, linear bisubstrate kinetics. Some dynamicproperties of the model are explored. Failure of this approachto allocation flags the need for additional mechanisms to controlthe processes. Details of the failure will indicate the modificationsneeded, which may involve hormones or reflect teleonomy (apparentlygoal-seeking behaviour), and which are added to the irreducibleframework. However, these additions should not replace the irreducibleframework of transport and chemical conversions, because theydo not in reality. Modifications to the basic model to representpossibilities such as ontogenesis with the transition from exponentialgrowth towards a steady state or with the scaling of within-planttransport resistances with plant size, the influence of hormones,and active transport, are described.Copyright 1998 Annals ofBotany Company Partitioning; allocation; model; shoot[ratio]root relations; plant growth.     

Isolation of new nonconditional Saccharomyces cerevisiae mutants defective in asparagine-linked glycosylation

We describe the isolation and partial characterization of Saccharomycescerevisiae nonconditional mutants that show defects in N-glycosylationof proteins. The selection method is based on the reductionof affinity for the ion exchanger QAE-Sephadex as a consequenceof the decrease in the negative charge of the cell surface.This characteristic reflects a decrease in the incorporationof mannosyl-phosphate units into the N-linked oligosaccharidesof the mannoproteins. The mutants exhibit low affinity for thebasic dye alcian blue and for that reason we have called themldb (low dye binding) mutants. Eight of the complementationgroups seem to be new as shown by complementation studies withpreviously isolated mutants of similar phenotype. Four of thegroups showed a significant reduction in the number and/or sizeof the N-linked oligosaccharides attached to secreted invertase.We have analyzed the N-linked oligosaccharides of ldb1 and ldb2,the mutants that show the most drastic reduction in the affinityfor the alcian blue dye. In both cases, the purified endo H-releasedoligosaccharides from the mannoproteins lacked detectable amountsof phosphate groups as shown by ion exchange chromatographyand the ¹H NMR spectra. In addition, ldb1 synthesizes a truncatedand unbranched outer chain lacking any