Morphogenesis in Cultured Floral Parts of African Violet

Callus tissue was induced from floral parts of African violetcultured on MS medium containing NAA (2 mg I^–1) and BAP(0.2 mg I^–1). When maintained on this medium in the presenceof light, the callus produced many shoots and roots. Large numbersof adventitious shoot buds were formed apparently in the absenceof callusing when ovary, sepal, and petal tissue was culturedon MS medium supplemented with BAP (1 mg I^–1) and NAA(1 mg I^–1). In contrast, culturing the same floral partson MS medium augmented with kinetin (1 mg I^–1) and NAA(0.5 mg I^–1) and NAA (0.5 mg 1-¹) led to the profuse developmentof roots. Organs seemed to be initiated from the epidermis ofcultured floral parts and did not appear to be related to particularcells or loci. Transfer of shoots to MS medium deviod of growthsubstances resulted in the formation of plantlets, which ata height of 3 cm could be transferred to soil and grown to maturitywithout variation in morophology or cytology.     

Differential Responses of Buckwheat Leaf Cells to Growth Substances Stimulating Cell Division

Isolated buckwheat cotyledons form calli, roots or buds whencultured in an appropriate medium. A medium containing high2,4-D (5 mg 1^–1) and low KN (01 mg I^–1), which inducescallus formation, was found to stimulate cell division in thelayer between palisade and spongy parenchyma tissue after 72h. Low 2,4-D and low KN (01 mg I^–1 each), which stimulatesroot formation in buckwheat cotyledons, induces divisions primarilyin spongy parenchyma cells. In a high benzylaminopurine (10^–5M) and a low IAA (10^–6 M) medium, which favours bud induction,cell divisions were localized to the palisade layer. The differentialresponsiveness of leaf cells to various hormone treatments isdiscussed.     

Micropropagation of Pissardi Plum

An efficient medium for multiplication of Prunus cerasifera,J. F. Ehrh. cv. ‘Atropurpurea’, Pissardi plum, consistedof Linsmaier-Skoog basal medium (LS) supplemented with 3% sucrose,10mg 1^–1 N⁴-(²-isopentenyl) adenine (2iP), and 162 mg1^–1 phloroglucinol (Phl). Phl in the medium significantlyenhanced growth (P < 0.1 %) over cultures maintained on LSmedium with 10 mg 1^–1 2iP and no Phl. Plantlets were rootedon a half-strength Murashige-Skoog (MS) medium supplementedwith 0.2 mg 1^–1 indole-3-butyric acid (IBA). Prunus cerasifera, Pissardi plum, micropropagation, phloroglucinol, N⁶-(²-isopentenyl) adenine     

NAA-Induced Organogenesis and Embryogenesis in Hypocotyl Callus of Solarium melongena L.

Hypocotyl explants of S. melongena showed three types of regenerationthrough callus formation depending on the concentration of NAAin the medium. At 0.8 mg l^–1, only callus was produced.Lower concentrations resulted in callus, adventitious roots(optimum, 0.016 mg 1^–1 NAA), and adventitious shoots (noNAA). Roots and shoots developed during the early stages ofculture. Higher concentrations of NAA depressed callus growthand stimulated embryoid formation (optimum 8.0 mg 1^–1NAA), Embryoids were identifiable after about 6 weeks as greenspots on the surface of callus: Addition of 6-BA enhanced shootproduction but inhibited both root and embryoid production.Whole plants were obtained from embryogenic callus after transferto NAA free medium. Genotypic differences in response were observed. In general,the potential for embryogenesis was independent of or inverselyrelated to the potential for organogenesis.     

Production of Plantlets of Shorea roxburghii G. Don. from Embryonic Axes Cultured In Vitro

Development of axillary shoots was induced in embryonic axesof the dipterocarp Shorea roxburghii G. Don. cultured on a modifiedMS medium containing 6-benzyl-aminopurine (BAP) at an optimumconcentration of 5 mg I^–1. Excised axillary shoots wereused in multiplication and rooting experiments. Vigorous rootdevelopment occurred in shoots supported on filter paper bridgesin liquid medium containing naphthaleneacetic acid (NAA) andindolebutyric acid (IBA) (0.1 mg I^–1 each). Shorea roxburghii, Dipterocarpaceae, tissue culture, plantlet formation     

Effects of Growth Regulators and Glutamine on In Vitro Development of Zygotic Embryos of Taro (Colocasia esculenta var. antiquorum)

Zygotic embryos of taro, Colocasia esculenta var. antiquorumcultured on Linsmaier-Skoog (LS) medium without the additionof hormones develop into mature plants only in the presenceof endosperm tissue. Growth is usually evident within the firstweek of culture when embryos swell and become green. Embryosexcised from endosperm and cultured on LS containing 0-01 mg1^–1 naphthaleneacetic acid (NAA), and 0–01 mg 1^–16-dimethylaminopurine (6-DMAP) grow at a rate comparable withcontrols for the first week of culture. During the second week,growth rates are higher than controls primarily because embryosform elongated hypocotyl regions which often produce swollentissues and/or callus. In the presence of 200 mg 1^–1 glutamineand a range of concentrations of 6-dimethylaminopurine, benzyladenine,or NAA, elongation of the hypocotyl axis is inhibited, and acompact callus may develop. Embryos grown on LS containing 200mg 1^–1 glutamine and 2.0 mg 1^–1 2, 4, 5-trichlorophenoxyaceticacid form friable callus which was used to generate short-livedsuspension cultures. Growth Regulators, Glutamine, tygotic embryos, Colocasia esculenta, endosperm     

Trophodynamics of the scyphomedusae Aurelia aurita. Predation rate in relation to abundance, size and type of prey organism

Ephyra larvae and small medusae (1.7–95 mm diameter, 0.01–350mg ash-free dry wt, AFDW) of the scyphozoan jellyfish Aureliaaurita were used in predation experiments with phytoplankton(the flagellate Isochrysis galbana, 4 µm diameter, {smalltilde}6 x 10^–6 µg AFDW cell^–1), ciliates (theoligotrich Strombidium sulcatum, 28 µm diameter, {smalltilde}2 x 10^–3 µg AFDW), rotifers (Synchaeta sp.,0.5 µg AFDW individual^–1) and mixed zooplankton(mainly copepods and cladocerans, 2.1–3.1 µg AFDWindividual^–1). Phytoplankton in natural concentrations(50–200 µg C I^–1) were not utilized by largemedusae (44–95 mm diameter). Ciliates in concentrationsfrom 0.5 to 50 individuals ml^"1 were consumed by ephyra larvaeand small medusae (3–14 mm diameter) at a maximum predationrate of 171 prey day^–1, corresponding to a daily rationof 0.42%. The rotifer Synchaeta sp., offered in concentrationsof 100–600 prey I^–1, resulted in daily rations ofephyra larvae (2–5 mm diameter) between 1 and 13%. Mixedzooplankton allowed the highest daily rations, usually in therange 5–40%. Large medusae (>45 mm diameter) consumedbetween 2000 and 3500 prey organisms day^"1 in prey concentrationsexceeding 100 I^–1. Predation rate and daily ration werepositively correlated with prey abundance. Seen over a broadsize spectrum, the daily ration decreased with increased medusasize. The daily rations observed in high abundance of mixedzooplankton suggest a potential ‘scope for growth’that exceeds the growth rate observed in field populations,and this, in turn, suggests that the natural populations areusually food limited. The predicted predation rate at averageprey concentrations that are characteristic of neritic environmentscannot explain the maximum growth rates observed in field populations.It is therefore suggested that exploitation of patches of preyin high abundance is an important component in the trophodynamicsof this species. ¹Present address: University of Bergen, Department of MarineBiology, N-5065 Blomsterdalen, Norway     

Determinate Floral Buds of Plantain (Musa AAB) as a Site of Adventitious Shoot Formation

Floral buds of the ‘False Horn’ plantain clonesMusa (AAB) ‘Harton Verde’, ‘Harton Negra’,and ‘Currare’ terminate in a large single floralstructure. The apices of these floral buds are here designatedas determinate since they have lost the ability to produce additionalfloral initials or buds. Terminal peduncle segments can be culturedin a modified Murashige and Skoog (1962) medium supplementedwith N⁶-benzyl-aminopurine (5 mg I^–1). Under these conditions,this apparent inability to yield buds can be overcome as vegetativeshoot clusters form in the axils of the bracts. Rooted plantletsare obtainable by treating shoots with naphthaleneacetic acid(1 mg I^–1) and activated charcoal (0.025%). The adventitiousorigin of the shoots has been established. Musa cultivars, plantains, floral bud, adventitious buds, tissue culture     

DCEBIO stimulates Cl- secretion in the mouse jejunum

We investigated the effects of 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one(DCEBIO) on the Cl^– secretory response of the mouse jejunum using the Ussing short-circuit current (I_sc) technique. DCEBIO stimulated a concentration-dependent, sustained increase in I_sc (EC₅₀ 41 ± 1 µM). Pretreating tissues with 0.25 µM forskolin reduced the concentration-dependent increase in I_sc by DCEBIO and increased the EC₅₀ (53 ± 5 µM). Bumetanide blocked (82 ± 5%) the DCEBIO-stimulated I_sc consistent with Cl^– secretion. DCEBIO was a more potent stimulator of Cl^– secretion than its parent molecule, 1-ethyl-2-benzimidazolinone. Glibenclamide or NPPB reduced the DCEBIO-stimulated I_sc by >80% indicating the participation of CFTR in the DCEBIO-stimulated I_sc response. Clotrimazole reduced DCEBIO-stimulated I_sc by 67 ± 15%, suggesting the participation of the intermediate conductance Ca²⁺-activated K⁺ channel (IK_Ca) in the DCEBIO-activated I_sc response. In the presence of maximum forskolin (10 µM), the DCEBIO response was reduced and biphasic, reaching a peak response of the change in I_sc of 43 ± 5 µA/cm² and then falling to a steady-state response of 17 ± 10 µA/cm² compared with DCEBIO control tissues (61 ± 6 µA/cm²). The forskolin-stimulated I_sc in the presence of DCEBIO was reduced compared with forskolin control tissues. Similar results were observed with DCEBIO and 8-BrcAMP where adenylate cyclase was bypassed. H89, a PKA inhibitor, reduced the DCEBIO-activated I_sc, providing evidence that DCEBIO increased Cl^– secretion via a cAMP/PKA-dependent manner. These data suggest that DCEBIO stimulates Cl^– secretion of the mouse jejunum and that DCEBIO targets components of the Cl^– secretory mechanism. 1-ethyl-2-benzimidazolinone; forskolin; glibenclamide; clotrimazole; H89     

Rate of Uptake of Potassium by Three Crop Species in Relation to Growth

Barley, ryegrass, and fodder radish were grown in flowing nutrientsolutions at four potassium concentrations, [K_e⁺], from 0.05to 4 mg I^–1. During the first 2 weeks after germinationthe response to [K_e⁺] (fodder radish > barley > ryegrass)depended on the potential relative growth rate, the ratio ofroot surface area to plant weight, and on the K⁺ flux into theroots. Subsequently, there was no effect of [K_e⁺] on growthrate within the range tested. The K⁺ flux decreased from 4–23? 10^–12 mol cm^–2 s^–1 in the first 2 weeksafter germination, when it was concentration-dependent, to 2–5? 10^–12 mol cm^–2 s^–1 after 4–5 weeks,when it became independent of [K_e⁺] down to 0.05 mg 1^–1.The results explain the importance of high [K_e⁺] and rapid rootgrowth during the first 2 weeks after seed germination.     

Annual Variation of Environmental Variables, Phytoplankton Species Composition and Photosynthetic Parameters in a Coastal Lagoon

Physical–chemical variables, phytoplankton biomass, speciescomposition and photosynthesis–irradiance (P-I) parameterswere analysed during 1 year in the Santo André Lagoon,SouthwestPortugal – a land-locked coastal ecosystem withtemporary connections with the sea. When the lagoon stayed closedthe observed phytoplankton blooms were mainly caused by Prorocentrumminimum, a potentially toxic dinoflagellate. It was dominantduring most of the year but the seawater inflow to the lagoontriggered a decrease in phytoplankton biomass and an abruptshift in species composition. The maximum photosynthetic rate(P_max) ranged from 2.0 to 22.5 mg C (mg chlorophyll a)^–1h^–1 and the light saturation index (I_k), ranged from 5.2to 335.0 µE m^–2 s^–1, with winter minima andsummer maxima. P_max and I_k were both positively correlated totemperature. Abundance ofP. minimum was associated with highnitrate concentrations whereas diatoms appear when ammonium,salinity and wind velocity are high. A mathematical model todescribe photosynthetic rate as a function of irradiance andtemperature [P (I, t)] was applied to the samples in which P.minimum was the dominant species     

Phytoplankton and nutrients in the waters north-west of Spitsbergen in the autumn of 1979

Phytoplankton biomass, primary production rates and inorganicnutrients were measured in the uppermost layer of the ice-edgeregion and in open water and compared with environmental factorsduring a three-week cruise in September – October 1979.Biomass and production values were low (maximum 2.2 µgchl a l^–1, 2.5 mg C m^–3 h^–1). A post-bloomcommunity of diatoms, consisting mainly of representatives ofChaetoceros, Leptocylindrus, Nitzschia and Thalassiosira, waspredominant. Concentrations of phosphate were quite low (maximum0.55 µM I^–1). Nitrate and silicate ranged from nomeasurable quantities to 5.7 µM l^–1 and 3.8 µMl^–1, respectively. The possibility of light and nutrientlimitation on phytoplankton growth is discussed.     

The Relationship Between the Rates of Carbon Transport and of Photosynthesis in Tomato Leaves

The rate of carbon transport based on the carbon balance overa 6-h period from a mature tomato leaf was measured overa rangeof net photosynthetic rates from 0.1 to 4.9 mg C dm^–2h^–1 under light flux densities from 4 to 140 W m^–2.A proportional relationship was demonstrated between the rateof carbon transport and carbon fixation when the carbon fixationrate was higher than 2 mg C dm^–2 h^–1.Below a carbonfixation rate of 1 mg C dm^–2 h^–1, the rate of carbonexport was maintained at 1 mg C dm^–2 h^–1 at theexpense of the breakdown of starch. A highly significant correlationwas observed between sucrose concentration and the rate of carbontransport. The sucrose concentration in the leaf appears tobe the factor controlling carbon export.     

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 Uptake of Nitrate by Lolium perenne from Flowing Nutrient Solution: II. EFFECT OF LIGHT, DEFOLIATION, AND RELATIONSHIP TO CO2 FLUX

Experiments with simulated swards of perennial ryegrass (Loliumperenne L.) grown in flowing nutrient solution with NO₃- heldat 0.1 mg N I^–1 show that the rate of NO₃- uptake wasrelated to diurnal, day-to-day, and seasonal changes in radiation.In summer the diurnal variation in NO₃-uptake ranged from 25to 50 mg N m^–2 h^–1 and the day-to-day variationranged from 500 to 1500 mg N m^–2 d^–1. Mean dailyrates of uptake over 12 d periods in summer and in winter averaged908 and 44 mg N m^–2, respectively. The pattern of NO₃-uptake followed that of CO₂ flux with the maximum rate of theformer occurring 5 or 6 h after the maximum CO₂ influx. Afterdefoliation, NO₃- uptake was severely curtailed for 2 d concomitantwith a very small influx of CO₂. Analysis of the changes thatoccurred in the rate of NO₃- uptake immediately after the switchingon or off of artificial light suggests that two reversible processesmay be involved in the relation between NO₃-uptake and radiation,one with a longer and the other with a shorter time constant.     

Cl- secretory effects of EBIO in the rabbit conjunctival epithelium

Experiments were conducted to determine whether the Cl^– secretagogue, 1-ethyl-2-benzimidazolinone (EBIO), stimulates Cl^– transport in the rabbit conjunctival epithelium. For this study, epithelia were isolated in an Ussing-type chamber under short-circuit conditions. The effects of EBIO on the short-circuit current (I_sc) and transepithelial resistance (R_t) were measured under physiological conditions, as well as in experiments with altered electrolyte concentrations. Addition of 0.5 mM EBIO to the apical bath stimulated the control I_sc by 64% and reduced R_t by 21% (P < 0.05; paired data). Under Cl^–-free conditions, I_sc stimulation using EBIO was markedly attenuated. In the presence of an apical-to-basolateral K⁺ gradient and permeabilization of the apical membrane, the majority of the I_sc reflected the transcellular movement of K⁺ via basolateral K⁺ channels. Under these conditions, EBIO in combination with A23187 elicited nearly instantaneous 60–90% increases in I_sc that were sensitive to the calmodulin antagonist calmidazolium and the K⁺ channel blocker tetraethyl ammonium. In the presence of an apical-to-basolateral Cl^– gradient and nystatin permeabilization of the basolateral aspect, EBIO increased the Cl^–-dependent I_sc, an effect prevented by the channel blocker glibenclamide (0.3 mM). The latter compound also was used to determine the proportion of EBIO-evoked unidirectional ³⁶Cl^– fluxes in the presence of the Cl^– gradient that traversed the epithelium transcellularly. Overall, EBIO activated apical Cl^– channels and basolateral K⁺ channels (presumably those that are Ca²⁺ dependent), thereby suggesting that this compound, or related derivatives, may be suitable as topical agents to stimulate fluid transport across the tissue in individuals with lacrimal gland deficiencies. Ussing chamber; short-circuit current; electrolyte transport; chloride secretagogue; potassium conductance; 1-ethyl-2-benzimidazolinone; 1,10-phenanthroline     

The Effect of Triacontanol on Peroxidase, IAA, and Plant Growth in Pisum sativum var.'Alaska' and 'Little Marvel'

The present study investigates the effects of triacontanol (CH₃(CH₂)₂₈CH₂OH),on plant growth (root and stem), peroxidase activity (apicalmeristem tissue), and auxin destruction (apical meristem tissue)in ‘Little Marvel’ dwarf (LM) and ‘Alaska’peas (AP). Triacontanol inhibited root growth in LM comparedto untreated controls. However, root growth in AP tissue wasenhanced by 1.0 mg I^–1 triacontanol and inhibited by allother treatments, in comparison to untreated controls. Wateruptake in triacontanol-treated AP plants was greater than inuntreated controls, with the converse being the case for LM.Triacontanol treatment caused an increase in peroxidase activityin both LM and AP plants compared to untreated controls. Interms of (1–¹⁴C)IAA destruction, GA₃ + 0.01 mg 1^–1triacontanol caused appreciable auxin breakdown (40%) in LMtissue, with GA₃ + 0.1 mg 1^–1 triacontanol giving a 43%decrease compared to untreated controls. In AP tissue, 10 µMGA3 increased auxin destruction by 188% whereas 0.1 mg I^–1triacontanol caused a 20% decrease compared to untreated controls.The effects of triacontanol on root and stem growth, peroxidaseactivity, and auxin destruction appear to be cultivar-specific,with respect to LM and AP varieties of peas.     

In Vitro Micropropagation of Delphinium malabaricum (Huth) Munz.--a Rare Species

A micropropagation technique was developed for Delphinium malabaricumusing nodes from inflorescence stalks Maximum shoot proliferationwas obtained on Murashige and Skoog's medium supplemented with2-1P (10 mg l^–1) and inositol (100 mg l^–1) Fromthe sixth passage onwards, shoots could be multiplied by omissionof inositol and reduction of 2-1P (0.5 mg l^–1) concentrationBest rooting response was obtained with a 24-h pulse treatmentof shoots with 0.5 mg I^–1 IBA in the dark, transfer oftreated shoots to hormone-free half-strength MS medium and incubationunder 24-h light. Regenerated plants were established successfullyin the field Cytological examination of root tips of in vitroand control plants showed identical chromosome number (2n =16) Delphinium malabaricum (Huth) Munz, micropropagation, tissue culture, rare plant     

Summer nutrient dynamics in the Middle Atlantic Bight: primary production and utilization of phytoplankton carbon

In late summer, production and utilization of carbon in thestratified water of the Middle Atlantic Bight appears to approachsteady-state conditions. In the euphotic zone there is a paniculateorganic carbon (POC) pool of {small tilde}6000 mg Cm^–2.Primary production adds {small tilde}350 mg C m^–2 d^–1,while zooplankton ingestion removes {small tilde}450 mg C m^–2d^–1, of which {small tilde}135 mg C m^–2 d^–1are returned to the POC pool as feces. Sinking of POC averages{small tilde}240 mg C m ^–2 d^–1. Thus, there is anet loss from the euphotic zone of {small tilde}200 mg C m^–2d^–1, which represents a removal rate from the POC poolof {small tilde}3%d^–1. However, sinking losses of phytoplanktoncarbon from the POC pool were small ({small tilde}12 mg C m^–2d^–1), which suggests that most of the primary productionenters the pelagic food chain. This is in sharp contrast tothe conditions in early spring, when the POC pool increasessubstantially, and the main loss is sinking rather than heterotrophicconsumption. ^*This research was supported by the U.S. Department of Energyunder Contract No. DE-AC02-76CH000I6.     

Morphogenic Potential of Cultured Explants of Crocus chrysanthus Herbert. cv. E. P. Bowles

Explants of leaves, basal plates, petals, anthers and ovariesof young growing corms of Crocus chrysanthus var. E. P. Bowleswere cultured on MS basal media with 20 different combinationsof either kinetin and NAA or BAP and 2, 4-D in the dark. Nomajor change was observed except on ovary explants. The ovaryexplants produced callus at 5.0 mg 1^–1 and 10 mg^–1BAP and subsequently stigma-like structures formed on the surfaceof the callus. Transfer to light resulted in the stigma-likestructures developing a yellow pigmentation whereupon they cameto resemble the naturally-grown stigmas. Corm formation andshoot regeneration was obtained from the callus when the ovaryexplants were cultured on media containing 5.0 and 10 mg I^–1BAP with 0.5 mg 1^–1 2, 4-D. Increasing the level of 2,4-D markedly reduced the number of shoots produced per explant. Key words: Crocus chrysanthus, callus, ovary explants