Boron Nutrition of Cultured Tobacco BY-2 Cells: I. Requirement for and Intracellular Localization of Boron and Selection of Cells that Tolerate Low Levels of Boron

Cultured cells of tobacco (Nicotiana tabacum L. cv. Bright Yellow2) grown under the standard culture conditions (1 mg boron liter^–1medium as boric acid) contained boron at a concentration of2.26 mg boron kg^–1 oven-dried cells and the protoplastcontained 1.26% of the boron in the cells. The cells requiredboron for growth and the half-maximum growth rate was obtainedwith 0.056 mg of boron liter^–1 medium. Subculturing thecells in media with lower concentrations of boron allowed selectionof cells that can grow even in the presence of 1 µg boronliter^–1 medium. Cell walls of the selected cells seemedto be thicker than those of the control cells and Golgi bodieswere accompanied by more secretory vesicles than those in thecontrol cells. (Received May 25, 1992; Accepted September 10, 1992)     

Ethylene and Ethane Production in 2,4-D Treated and Salt Treated Tobacco Tissue Cultures

Gas chromatography was used to measure ethylene (ethene) andethane production by tobacco (Nicotiana tabacum cv. Wisconsinno. 38) callus tissues grown on media containing inorganic saltsaccording to Murashige and Skoog (1962), sucrose, myo-inositol,thiamine-HCl kinetic according to Linsmaier and Skoog (1965),and either 2,4-dichiorophenoxyacetic acid (2,4-D) in the range0–100 mgl^–1 or 2 mgl^–1 indoi-3-ylacetic acidplus NaCl in the range 0–200 Meq l^–1. Ethylene productionrates were high (> 500 nl h^–1 g^1– fresh weight)initially in all treatments. Subsequently, ethylene productiondeclined in rapidly growing cultures but remained high in moderatelyand severely 2,4-D (> 0·5 mgl^–1) stressed andin severely NaCl (150 Meql^–1) stressed cultures. Highinitial rates of ethane production (> 200 nl h^–1 g^–1fresh weight) were obtained under conditions of severe stresscaused by 2,4-D or NaCl but not in control or moderately inhibitedcultures. With further incubation ethane production declinedin the severely stressed cultures. It is concluded that ethyleneproduction can be used as an index of moderate 2,4-D stressand severe NaCl stress by virtue of the high persisting ratesof ethylene production in stressed cultures. Ethane productioncan be used as an early index of severe stress caused by either2,4-D or NaCl in vitro. Nicotiana tabacum L., tobacco, ethylene, ethenen, ethane, 2,4-dichlorophenoxyacetic acid, auxin, stress, callus tissue     

The Composition of Phloem Exudate and Xylem Sap from Tree Tobacco (Nicotiana glauca Grah.)

The composition of xylem sap and exudate from stem incisionsof Nicotiana glauca Grah. was compared in detail. Exudationfrom stem incisions occurred over a 5 min period in certainplants, enabling collection of 5–30 µl of sap. Therate of exudation showed an exponential decline. Exudate hada high dry matter content (170–196 mg ml^–1) andhigh sugar (sucrose) levels. Xylem sap had a low pH (5.8) andexudate a pH of 7.9. Glutamine dominated the amino compoundsin xylem sap and exudate, and K⁺ was the major cation. Totalamino compounds in stem exudate reached 10.8 mg ml^–1 whereasxylem sap contained much lower levels (0.28 mg ml^–1).All mineral elements and amino compounds with the exceptionof calcium were more concentrated in stem exudate than in xylemsap. Sucrose was labelled heavily in stem exudate following pulsingof an adjacent leaf with ¹⁴CO₂. A concentration gradient ofsugar (2.1 bar m^–1) was recorded for stems. Levels ofsucrose, amino compounds and K⁺ ions in stem exudate showeda diurnal periodicity. Each commodity reached maximum concentrationat or near noon and minimum concentration about dawn. The evidencesuggests that exudate from stem incisions of N. glauca is arepresentative sample of solutes translocated in the phloem. Nicotiana glauca Grah., phloem sap, xylem sap, sucrose, amino compounds, mineral ions     

GROWTH OF JUVENILE BITHYNIA TENTACULATA (PROSOBRANCHIA, BITHYNIIDAE) UNDER DIFFERENT FOOD REGIMES: A LONG-TERM LABORATORY STUDY

The growth of juvenile Bithynia tentaculata (Proso-branchia,Bithyniidae) was measured under controlled laboratory conditionsover 18 months. The animals were fed with different concentrationsof suspended food (Chlamydomonas reinhardii at 2, 000 cells.ml^–1and at 10, 000 cells.ml^–1), solid food (lettuce) and combinationsof both (lettuce with 2, 000 cells.ml^–1 and with 10, 000cells.ml^–1 Chlamydomonas). The growth of all animals wasmeasured weekly, and after 1 years final shell sizes, shelldry weights and ash-free dry weights, as well as soft body dryweights and ash-free dry weights were determined. Survival rateof the animals increased from 20% when fed with 2, 000 algalcells.ml^–1 to 75% with lettuce and 10, 000 cells.ml^–1as food. Final shell sizes and shell weights were not influencedby food, but soft body dry weights were significantly reducedwhen animals were fed on suspended food only. Reproduction (i.e.egg laying) was observed at the end of the second summer whenlettuce (with or without algal addition) was given as food.The ecological consequences of these results are discussed. (Received 7 April 1993; accepted 9 August 1994)     

Laboratory study of the spawning rate of the calanoid copepod Centropages typicus: effect of fluctuating food concentration

The spawning rate of laboratory-reared Centropages typicus fedHymenomonas elongala increases with food concentration, up toa value of {small tilde}2800 µg C (16 500 cells) ml^–1.An alternation of a low food (1000 cells ml^–1) and highfood concentration (16 500 cells ml^–1) is not favourableto egg release when its periodicity is 1 or 2 days, whereasit may be of advantage if it is longer (3–6 days). Inthe latter case, Centropages typicus will benefit best fromthe rich food diet if this coincides with (or just follows)the last moult.     

Development of Jobacco Carpel Primordia in vitro

The state of determination of the two emergent carpel primordiaof Nicotiana tabacum was tested. Carpel rudiments were excisedand cultured singly or in pairs. The basal medium was that ofLinsmaier and Skoog, supplemented with 1.0 mg 1^–1 kinetin.Over the ensuing 4 week period, whole differentiated pistilsformed from the pairs and half pistils grew from the singlecarpels. It is concluded that these emergent organs show a certaindegree of autonomy and that they may have been determined atthe time of isolation. Nicotiana tabacum L, tobacco, carpel, organ determination, tissue culture, morphogenesis     

Density and distribution of bacterioplankton and planktonic ciliates in the Bering Sea and North Pacific

The total number of planktonic bacteria in the upper mixed layerof the Bering Sea during the late spring-early summer periodranged between 1 and {small tilde}4 x 10⁶ ml^–1 (biomass10–40mg C m^–3). In the northern Pacific, along 47–52⁶N,the corresponding characteristics of the bacterioplankton densityin the upper mixed water layer were: total number 1–2x 10⁶ cells ml^–1 and biomass 15–46mg C m^–3Below the thermocline at 50–100 m, the density of bacterioplanktonrapidly decreased. At 300 m depth, it stabilized at 0.1–0.2x 106 cells ml^–1. The integrated biomass of bacterioplanktonin the open Bering Sea ranged between 1.2 and 3.6 g C m^–2(wet biomass 6–18 g m^–2) Its production per dayvaried from 2 to 23 mg C m^–3 days^–1 in the upper0–100 m. The numerical abundance of planktonic ciliatesin this layer was estimated to be from 3 to l0 x 10³ cells l^–1,and in the northern Pacific from 0.4 to 4.5 x 10³ l^–2.Their populations were dominated by naked forms of Strombidium,Strombilidium and Tontonia. In some shelf areas, up to 40% ofthe total ciliate population was represented by the symbioticciliate Mesodinium rubrum. The data on the integrated biomassof basic groups of planktonic microheterotrophs are also presented,and their importance in the trophic relationships in pelagiccommunities of subarctic seas is discussed.     

The seasonal abundance of the phototrophic ciliate Mesodinium rubrum in Southampton Water, England

The abundance of the marine phototrophic planktonic ciliateMesodinium rubrum was monitored throughout an annual cycle attwo stations in the Southampton Water estuary. Seasonal changesin the concentration of nitrate, ammonia and phosphate weremonitored both at the inner estuary station (NW Netley) andouter estuary station (Calshot). Nutrient levels in the winterwere similar at both stations, and were diminished during sequentialdiatom blooms dominated initially by Sketetonema costatum andthen by Rhizosolenia dclicatula. Nitrate was reduced to a seasonalminimum in the outer estuary following these spring diatom blooms,but in the inner estuary was sustained >500 µg I^–1until the onset of the M.rubrum bloom. During the developmentof a visible red tide of M.rubrum in June/July at NW Netley,nutrient concentrations were considerably reduced. Cell numbersof M.rubrum varied between 2 and 3 cells ml^– during winterto >400 cells ml^–1 during the bloom at NW Netley, whereasat Calshot cell abundance did not increase above 25 cells ml^–1at any time of the year. At NW Netley, dense accumulations ofthe ciliate occurred over restricted depth intervals duringthe bloom and possible factors influencing the observed verticaldistribution of cells are considered. ¹Present address: Biology Department, Faculty of Science, AddisAbaba University, PO Box 1176, Addis Ababa, Ethiopia     

A study of feeding in predacious ciliates using prey ciliates labeled with fluorescent microspheres

Feeding in predacious estuarine ciliates was investigated ina series of laboratory experiments using a new method of preylabeling which facilitates microscopic indentification of ingestedprey items. Ingestion rates of Mesodinium pulex, Euplotes vannusand E.woodruffi were estimated using the appearance, insidethe predator, of bacteriovorous ciliates (Metanophrys sp., Cyclidiumsp.and Pleuronema sp ) labeled with fluorescent microspheres. Preyremain motile and have presumably unaltered surface characteristics.Ingestion rates of log-growth phase predators increased withprey density. Mesodinium pulex ingested 0 15–0.32 cellsh^–1 over a prey concentration of 60–2300 ml^–1.Maximum ingestion rates of E. woodruffi and E. vannus were 4.5and 3.4 cells h^–1 respectively, estimated at prey abundancesof 75 and 172 cells ml^–1 respectively. Comparisons offeeding rates on prey of different sizes, and the effects ofstarvation, indicated that ingestion is likely limited by differentfactors in ‘raptorial’ (M pulex) and ‘filterfeeding’ (Euplotes spp.) predators.     

Infection of Coscinodiscus granii by the parasitoid nanoflagellate Pirsonia diadema: III. Effects of turbulence on the incidence of infection

The influence of turbulence on the incidence of infection ofthe diatom Coscinodiscus granii by the parasitoid nanoflagellatePirsonia diadema was investigated experimentally with two initialhost densities. Independently of the initial diatom densitiesof 7 and 44 cells ml^–1, under calm conditions both diatomsand parasitoids became extinct within 6–9 days. Turbulence,however, led to the survival of diatoms at a reduced densityof 0.1–2 cells ml^–1 for >30 days. A population-dynamicmodel is formulated that takes into account the non-homogeneousdistribution of infecting flagellates among host diatoms. Applicationof the results to parasitoid–diatom interactions in naturalwaters suggests that, under turbulent conditions, endemic infectionsmay effectively prevent the mass development of host diatoms.     

Identification of Antheridic Acid as an Antheridiogen in Anemia rotundifolia and Anemia flexuosa

Antheridic acid was identified by retention time and full massspectra from GCMS analysis as an antheridiogen in Anemia rotundifoliaand A. flexuosa. In the dark spore germination assay, antheridicacid was active down to 10^–10 and 5 ? 10^–12g.ml^–1in A. rotundifolia and A.flexuosa, respectively. In the antheridiumformation assay, antheridic acid was active down to 10^–10g.ml^–1 in both A. rotundifolia and A.flexuosa (Received April 14, 1987; Accepted July 8, 1987)     

Effects of Olisthodiscus luteus on the feeding and reproduction of the marine rotifer Synchaeta cecilia

The chrysophyte Olisthodiscus luteus is not ingested by Synchaetacecilia. It inhibits the feeding on other, acceptable food atO. luteus densities as low as 50 cells ml^–1 and reducessurvival and reproduction at O. luteus densities > 10³ cellsml^–1. The possible mechanisms and implications of thisphenomenon for the distribution and abundance of S. ceciliaare discussed.     

Abundance and productivity of heterotrophic nanoplankton in Georgia coastal waters

The population abundances and rates of biomass production ofheterotrophic nanoplankton (HNAN) in Georgia coastal waterswere evaluated by epifluorescence microscopy. HNAN populations(mostly non-pigmented microflagellates <10 µm in diameter)ranged from 0.3 x 10³ cells ml^–1 in shelf waters 15 kmoffshore to 6.3 x 10³ cells ml^–1 in waters 0.25 km fromthe coast. There was a strong correlation (r = 0.83) betweenHNAN and free bacterioplankton population abundances, but noapparent relation (r = 0.38) between HNAN and phototrophic nanopLankton(PNAN) abundances. HNAN biomass production in estuarine andnearshore shelf waters, as estimated from increases in HNANpopulations during laboratory incubations of natural water samples,ranged from 0.10 to 0.79 mg C m^–3 h^–3, with populationgeneration times of 9.7 to 26.5 h. There was a significant linearrelation (r = 0.95) between HNAN biomass and HNAN productivity.We calculated that HNAN may graze at least 30% to 50% of dailybacterioplankton production in Georgia coastal waters.     

The Biological Properties of Cyclopenin and Cyclopenol

Cyclopenin (C₁₇H₁₄O₃N₂) and cyclopenol (C₁₇H₁₄O₄N₂), isolatedfrom an abberent strain of Penicillium cyclopium (NRRL 6233),significantly inhibited the growth of etiolated wheat (Triticumaestivum) coleoptile segments. The former inhibited at 10^–3and 10^–4 M, the latter at 10^–3 M. Cyclopenin producedmalformation of the first set of trifoliate leaves in bean (Phaseolusvulgaris) at 10^–2 M and necrosis and stunting in corn(Zea mays) at 10^–2 M. Cyclopenol induced no apparent effectsin bean or corn plants. Neither compound changed the growthor morphology of tobacco (Nicotiana tabacum) plants. Cyclopenininduced intoxication, prostration and ataxia in day-old chicksat 500 mg/kg, but they recovered within 18 hours. Cyclopenolwas inactive against chicks when dosed at levels up to 500 mg/kg. (Received October 11, 1983; Accepted December 15, 1983)     

Isolation, Culture, and Plant Regeneration of Protoplasts of Two Shrubby Oxalis Species from South America

Protoplasts were successfully isolated from internodal callustissues of both Oxalis glaucifolia and O. rhombeo-ovata whenthey were digested in a solution containing 0.1% (w/v) MacerozymeR-10, 0.5% (w/v) cellulase Onozuka R-10 and 0.3 mmol m^–3sucrose. Protoplasts proliferated to give cell colonies on Gamborget al.'s B5 medium supplemented with 0.3 mmol m^–3 mannitol,0.5 mg dm^–32, 4-D, and 2.0 mg dm^–3 kinetin. Calluswas produced upon transfer of cell colonies to Murashige andSkoog medium containing 2.0 mg dm^–3 l-naphthaleneaceticacid (NAA) and 0.1 mg dm^–3 kinetin for O. glaucifolia,or with 5.0 mg dm^–3 NAA and 0.5 mg dm^–3 6-benzylaminopurine,for O. rhombeo-ovata. Plants were regenerated from O. glaucifoliaprotoplasts on a medium containing 0.1 mg dm–3 NAA, 1.0mg dm^–3 kinetin and 1.0 mg dm^–3 gibberellic acid,but only vascular nodules were differentiated by O. rhombeo-ovataprotoplast-derived calli. Key words: Tissue culture, protoplasts, plant regeneration, Oxalis spp     

Auxin Transport in Secondary Tissues1

Auxin transport was investigated in excised stem segments ofNicotiana tabacum L. by the agar block technique using [1-¹⁴C]indol-3yl-acetic acid (IAA). The ability of the stems to transportauxin basipetally increased as secondary development proceeded;by contrast the ability of the pith to transport auxin declinedwith age. By separation of the stem tissues it was shown thatthe great majority of auxin transport took place in cells associatedwith the internal phloem and in cells close to the cambium;in both cases similar velocities of transport were found (c.5.0 mm h^–1 at 22°C). The effects of osmotic gradientson auxin transport through the internal phloem were investigated.IAA was found by chromatography to account for practically allthe radioactivity in receiver blocks and other extracts of stemsegments. The significance of these results is discussed.     

Bacterivory in seawater samples estimated by a dual radioactive-labelling technique

A dual radioactive-labelled bacteria technique using Vibrio(DRLV), developed for laboratory studies on bacterivory, hasbeen refined for use at the concentrations of prey and predatorstypcially found at sea. Experiments with estuarine water collectedin spring and in autumn showed that bacterivorous nanoflagellates(HNF) (concentration 1.38±0.35x10³ HNF ml^–1) ingested2.7±0.96 DRLV flagellate1^–1 h^–1 at concentrationsof 0.8–2.2x10⁶ DRLV ml^–1 in the presence of 2.04±0.68x10⁶natural bacteria ml^–1. The method was also applied tosamples collected in October in the Celtic Sea, when on average1 ml of water from the surface layer contained 1.41±0.16x10⁶natural bacteria, 14.6x10³ cyanobacteria, 530±170 HNF,7.3±3.0x103 phototrophic nanoflagellates (1.5–4µm), 49.0±26.5 phototrophic dinoflagellates, 36.3±12.6heterotrophic dinoflagellates and 21.3±9.5 Leucocryptosmarina. Under these conditions the grazing rate in most samplesdid not exceed the coefficient of variation of the method (2%),although we estimate the grazing rate was -1.6 DRLV HNF^–1h^–1 and on one occasion a rate of 2.45 was recorded. Thegross growth efficiency for protein of -30% displayed by naturalHNF means that they could release about     

Effects of rotifers and ciliates on the growth and survival of Daphnia

Daphnia can suppress ciliates and rotifers through predationand interference competition, but it is not known whether thisproduces any direct benefit to Daphnia. We conducted survivorshipand cohort lifetable experiments to determine whether Daphniacan utilize ciliates and rotifers as food. Three species ofoligotrich ciliates (Halteria grandinella, Strobilidium gyransand Strobilidiumvelox) and one rotifer (Keratella cochlearis)were used. Lifetable experiments were conducted with a basallevel of algae (Cryptomonas sp.), plus either ciliates or rotifers,while survivorship experiments had only the rotifers or ciliates.Densities of 30 H.grandinella ml^–1, 50 S.gyrans ml^–1and 15 S.velox ml^–1 enhanced Daphnia pulex's populationgrowth rate 35–50% over controls with only algae. TenS.gyrans ml^–1 did not produce a significant change inDaphnia's growth rate. Densities of 100 and 300 K.cochlearis^–1 increased Daphnia population growth rates by II and10%, respectively. Both 10 and 50 S.gyrans ml^–1 enhancedDaphnia's survivorship compared to starved controls, but neither100 nor 300 K.cochlearis l^–1 enhanced its survivorship.The amount of enhancement of Daphnia growth rates by rotifersand ciliates is roughly proportional to the death rates imposedby Daphnia. The death rate imposed by Daphnia on rotifers isa function of both algal density and Daphnia size. Per unitbiomass, neither ciliates nor Keratella appear to be as nutritiousfor Daphnia as is Cryptomonas.     

Community structures of heterotrophic bacteria of copepod fecal pellets

The total and heterotrophic bacterial microflora of gut andfecal pellets of the copepod Temora stylifera was studied inthe coastal zone of the northwestern Mediterranean basin. Digestivetracts and feces were always found to contain bacteria. Withmean values close to 10¹¹ cells ml^–1and 10¹⁰ colony-formingunits (CFU) ml^–1, both total and heterotrophic communitiesfound in fecal pellets largely exceeded the corresponding bacterialmicroflora observed in surrounding seawater (10⁵ cells ml¹ and10³ CFU ml^–). In the same way, the frequency of dividingcells and mean cell volumes increased, respectively, from 3%and 0.12µm³ in seawater to >6% and 0.24 µm³ infecal pellets. The bacterial community structure was investigatedby carrying out 29 morphological and biochemical tests on 147isolated strains. Although Pseudomonas was always the most frequentlyencountered genus, the bacterial communities found in copepodfecal pellets clearly differ from those inhabiting seawater.Vibrio species, which were not detected in seawater microflora,were always present in fecal pellet communities. The close correspondenceobserved between the potential metabolic characteristics ofthe fecal bacterial communities isolated from a subantarcticdeposit feeder (Mytilus edulis) and from zooplankton in thisMediterranean study suggests that the fecal community differentiationis an even more general feature.     

Growth Stimulation by Conditioned Medium and Spermidine in Low-Density Suspension Cultures of Rice

Suspension cultures of Oryza sativa L. var IR 20 grew in Murashigeand Skoog medium (MS) supplemented with 2,4-D and kinetin ina density-dependant manner with a critical minimum inoculation-densityof 10,000 cells ml^–1. Conditioned medium obtained fromthese cultures and added to MS+2,4-D+kinetin induced the growthof cultures at 1,000 cells ml^–1. Growth stimulation byconditioned medium was mimicked by spermidine but not by otherpolyamines viz. putrescine and spermine. This is the first reportof a polyamine substituting for conditioned medium in cultures. ² Present address: Vice-Chancellor, Pondicherry University,Pondicherry 605 014, India.