Distinct roles of PMCA isoforms in Ca2+ homeostasis of bladder smooth muscle: evidence from PMCA gene-ablated mice

We previously showed that plasma membrane Ca²⁺-ATPase (PMCA) activity accounted for 25–30% of relaxation in bladder smooth muscle (8). Among the four PMCA isoforms only PMCA1 and PMCA4 are expressed in smooth muscle. To address the role of these isoforms, we measured cytosolic Ca²⁺ ([Ca²⁺]_i) using fura-PE3 and simultaneously measured contractility in bladder smooth muscle from wild-type (WT), Pmca1^+/–, Pmca4^+/–, Pmca4^–/–, and Pmca1^+/–Pmca4^–/– mice. There were no differences in basal [Ca²⁺]_i values between bladder preparations. KCl (80 mM) elicited both larger forces (150–190%) and increases in [Ca²⁺]_i (130–180%) in smooth muscle from Pmca1^+/– and Pmca1^+/–Pmca4^–/– bladders than those in WT or Pmca4^–/–. The responses to carbachol (CCh: 10 µM) were also greater in Pmca1^+/– (120–150%) than in WT bladders. In contrast, the responses in Pmca4^–/– and Pmca1^+/–Pmca4^–/– bladders to CCh were significantly smaller (40–50%) than WT. The rise in half-times of force and [Ca²⁺]_i increases in response to KCl and CCh, and the concomitant half-times of their decrease upon washout of agonist were prolonged in Pmca4^–/– (130–190%) and Pmca1^+/–Pmca4^–/– (120–250%) bladders, but not in Pmca1^+/– bladders with respect to WT. Our evidence indicates distinct isoform functions with the PMCA1 isoform involved in overall Ca²⁺ clearance, while PMCA4 is essential for the [Ca²⁺]_i increase and contractile response to the CCh receptor-mediated signal transduction pathway. PMCA; bladder smooth muscle; gene-altered mice     

Photosynthetic characteristics of Dinophysis norvegica Claparede & Lachmann, a red-tide dinoflagellate

The relationships between photosynthesis and photosyntheticphoton flux densities (PPFD, P-l) were studied during a red-tideof Dinophysis norvegica (July-August 1990) in Bedford Basin.Dinophysis norvegica, together with other dinoflagellates suchas Gonyaulax digitate, Ceratium tripos, contributed {small tilde}50%of the phytoplankton biomass that attained a maximum of 16.7µg Chla 1^– and 11.93 10⁶ total cells I^–1.The atomic ratios of carbon to nitrogen for D.norvegica rangedfrom 8.7 to 10.0. The photosynthetic characteristics of fractionatedphytoplankton (>30 µm) dominated by D.norvegica weresimilar to natural bloom assemblages: o (the initial slope ofthe P-l curves) ranged between 0.013 and 0.047 µg C [µgChla]^–1 h–1 [µmol m^– s^–1]^–1the maximum photosynthetic rate, p^B_m, between 0.66 and 1.85µg C [µghla]^–1 h^–1; l_k (the photoadaptationindex) from 14 to 69 µ,mol m^–2 s^–1. Carbonuptake rates of the isolated cells of D.norvegica (at 780 µmolm^–2 s^–1) ranged from 16 to 25 pg C cell^–1h^– and were lower than those for C.tripos, G.digitaleand some other dinoflagellates. The variation in carbon uptakerates of isolated cells of D.norvegica corresponded with P^B_mof the red-tide phytoplankton assemblages in the P-l experiments.Our study showed that D.norvegica, a toxigenic dinoflagellate,was the main contributor to the primary production in the bloom.     

Somatic Embryogenesis and Plant Regeneration from Inflorescence Culture of Java Citronella: (Cymbopogon winterianus)

Embryogenic callus was induced from immature inflorescence segmentsof Java citronella (Cymbopogon winterianus) and maintained for2 years on Murashige and Skoog's medium supplemented with 2,4-D(l mg l^–1). The callus cells retained the original chromosomenumber of 2n = 20. The somatic embryos germinated into plantletson MS basal medium or medium with IAA, NAA, BAP or KN individually(l mg l^–1). The regenerated plantlets developed a goodroot system on full strength solid MS inorganics medium withIAA (1 mg l^–1). The regenerated plants were similar tothe donor plant in morphology and had the same chromosome number,but showed some variation in the essential oil content. Java citronella, Cymbopogon winterianus, somatic embryogenesis, regeneration, inflorescence culture     

Collection and Chemical Composition of Pure Phloem Sap from Zea mays L.

Pure phloem sap was collected from leaf sheaths of Zea maysL. by the insect laser technique, and its chemical compositionwas analyzed. Sucrose was the only sugar detected. The predominantinorganic ions were K⁺ and Cl^–. The adenylate energy chargeof phloem sap was between 0.72 and 0.86. (Received October 18, 1989; Accepted May 11, 1990)     

Effects of Seed Treatments on the Emergence of Oil Seed Rape Seedlings from Compacted Soil

Imbibition of seeds of oil seed rape (Brassica napus cv Jetneuf)in 10^–3 M aminoethoxyvinylglycine (AVG) or 10^–2silver thiosulphate (Ag⁺) had no effect on germination nor onthe emergence of seedlings from uncompacted or lightly compressedsoil, but significantly reduced emergence from moderately compressedsoil of 68.4 or 143.3 N cm^–2 impedance. Exertion of force by emerging control seedlings against a staticcantilever bar fitted with strain gauges reached a maximum (F_max)of 6 g over 10 h. Higher axial forces were achieved when theseedlings were emerging from compressed soil, without any changein the time required to reach F_max, so that the build-up offorce was considerably (1.8 fold) faster than in uncompressedsoil. This adaptive response to soil impedance was modified by theseed pretreatments employed. Seedlings from AVG or Ag⁺pretreatedseeds produced lower axial forces than controls, and neitherF_max nor the rate at which force developed showed any responseto soil compression. After pretreatment in 10^–3 ethephon or 10^–4 naphthaleneacetic acid (NAA) the seedlings achieved similar F_max to controlseedlings, but responded more rapidly to soil compression sothat the rate of build up of emergence force was 2.3 fold (NAA)or 2.8 fold (ethephon) faster in compressed than in uncompressedsoil. The results suggest that the exertion of force by a seedlingagainst a barrier involves a dynamic response to impedance onthe part of the seedling. This response can be either enhancedor suppressed by substances which affect ethylene productionor ethylene action. Such compounds may have promise for modifyingseedling emergence from impeding soils. Brassica napus, oil seed rape, seedling emergence, soil compaction, ethylene, Ethrel, silver, aminoethoxyvinylglycine, naphthalene acetic acid     

Some Experimental and Theoretical Observations Concerning Mass Flow in the Vascular Bundles of Heracleum

The theory and practice of applying the thermodynamics of irreversibleprocesses to mass-flow theories is presented. Onsager coefficientswere measured on cut and uncut phloem and cut xylem strandsof Heracleum muntegazzimum. In 0.3 N sucrose + 1 mN KC1 theyare as follows. In phloem, L_EE = 5 ? 10–⁴ mho cm^–1,L_pE = 9 ? 10^–6 cm³ s^–1 cm^–2 volt^–1 cm,and L_PP = 0.16 cm³ s^–1 cm^–2 (J cm^–3)^–1cm. In uncut phloem strands L_EE is about 1 ? 10^–3 mhocm^–1. In xylem in 2 x 10^–3 N KCI, L_pp = 50 to 225,L_PE = 2 ? 10^–4, and L^EE = 4 ? 10^–3. The measurementsare tentative since the blockage of the sieve plates is an interferingfactor, but if they are valid they lead to the conclusion thatneither a pressure-flow nor an electro-kinetic mechanism envisaginga ‘long distance’ current pathway can be the majormotive ‘force’ for transport in mature phloem. Measurementsof biopotentials along conducting but laterally detached phloembundles of Heracleum suggest, nevertheless, that there may bea small electro-osmotic component of at least 0.1 mV cm^–1endogenous in the phloem.     

Vibrating probe measurement of ionic currents around developing embryo of oil palm (Elaeis guineensis Jacq.)

The current patterns around zygotic embryos of the oil palmembryo (Elaeis guineensis Jacq.) were investigated. Ionic currentsaround the embryo were measured at different stages in its developmentusing a two-dimensional vibrating probe system. The averagecurrent density was found to be in the order of 1–µAcm^–2. In the early developmental stage, the current wasfound entering the cotyledon and leaving the radicle. Both themagnitude and direction of this current changed when embryosat different developmental stages were observed. The currentswere found to enter the region in the process of differentiationor elongation, and in some cases this could be the reverse ofthe current direction in the preceding stage. Within one ofthe stages of the embryos, current density was correlated withthe rate of elongation. A very large inward current (up to 20µAcm^–2) was also detected at the point where the shoot wasbreaking through the surface. This was probably caused by theso-called ‘injury current’. Key words: Ionic currents, vibrating probe, oil palm embryo, E. guineensis, injury current     

Biochemical Limitations to Carbon Assimilation in C3 Plants--A Retrospective Analysis of the A/Ci Curves from 109 Species

Species-specific differences in the assimilation of atmosphericCO₂ depends upon differences in the capacities for the biochemicalreactions that regulate the gas-exchange process. Quantifyingthese differences for more than a few species, however, hasproven difficult. Therefore, to understand better how speciesdiffer in their capacity for CO₂ assimilation, a widely usedmodel, capable of partitioning limitations to the activity ofribulose-1,5-bisphosphate carboxylase-oxygenase, to the rateof ribulose 1,5-bisphosphate regeneration via electron transport,and to the rate of triose phosphate utilization was used toanalyse 164 previously published A/C_i, curves for 109 C₃ plantspecies. Based on this analysis, the maximum rate of carboxylation,Vc_max, ranged from 6µmol m^–2 s^–1 for the coniferousspecies Picea abies to 194µmol m^–2 s^–1 forthe agricultural species Beta vulgaris, and averaged 64µmolm^–2 s^–1 across all species. The maximum rate ofelectron transport, J_max, ranged from 17µmol m^–2s^–1 again for Picea abies to 372µmol m^–2 s^–1for the desert annual Malvastrum rotundifolium, and averaged134µmol m^–2 s^–1 across all species. A strongpositive correlation between Vc_max and J_max indicated that theassimilation of CO₂ was regulated in a co-ordinated manner bythese two component processes. Of the A/C_i curves analysed,23 showed either an insensitivity or reversed-sensitivity toincreasing CO₂ concentration, indicating that CO₂ assimilationwas limited by the utilization of triose phosphates. The rateof triose phosphate utilization ranged from 4·9 µmolm^–2 s^–1 for the tropical perennial Tabebuia roseato 20·1 µmol m^–2 s^–1 for the weedyannual Xanthium strumarium, and averaged 10·1 µmolm^–2 s^–1 across all species. Despite what at first glance would appear to be a wide rangeof estimates for the biochemical capacities that regulate CO₂assimilation, separating these species-specific results intothose of broad plant categories revealed that Vc_max and J_maxwere in general higher for herbaceous annuals than they werefor woody perennials. For annuals, Vc_max and J_max averaged 75and 154 µmol m^–2 s^–1, while for perennialsthese same two parameters averaged only 44 and 97 µmolm^–2 s^–1, respectively. Although these differencesbetween groups may be coincidental, such an observation pointsto differences between annuals and perennials in either theavailability or allocation of resources to the gas-exchangeprocess. Key words: A/C_i curve, CO₂ assimilation, internal CO₂ partial pressure, photosynthesis     

On the causes of interspecific differences in the growth-irradiance relationship for phytoplankton. Part I. A comparative study of the growth-irradiance relationship of three marine phytoplankton species: Skeletonema costatum, Olisthodiscus luteus and Gonyaulax tamarensis

Three marine phytoplankton species (Skeletonema costatum, Olisthodiscusluteus andGonyaulax tamarensis) were grown in batch culturesat 15°C and a 14:10 L:D cycle at irradiance levels rangingfrom 5 to 450 µEinst m^–2 s^–1. At each irradiance,during exponential growth, concurrent measurements were madeof cell division, carbon-specific growth rate, photosyntheticperformance (both O₂ and POC production), dark respiration,and cellular composition in terms of C, N and chlorophyll a.The results indicate that the three species were similar withrespect to chemical composition, C:N (atomic) = 6.9 ±0.4, photo-synthetic quotient, 1.43 ± 0.09, and photosyntheticefficiency, 2.3 ±0.1 x 10^–3 µmol O₂ (µgChl a)^–1 h^–1 (µEinst m^–2 s^–1)^–1.Differences in maximum growth rate varied as the –0.24power of cell carbon. Differences in growth efficiency, werebest explained by a power function of Chl a:C at µ = 0.Compensation intensities, ranged from 1.1 µEinst m^–2s^–1 for S. costatum to 35 forG. tamarensis and were foundto be a linear function of the maintenance respiration rate.The results indicate that interspecific differences in the µ–Irelationship can be adequately explained in terms of just threeparameters: cell carbon at maximum growth rate, the C:Chl aratio (at the limit as growth approaches zero) and the respirationrate at zero growth rate. A light-limited algal growth modelbased on these results gave an excellent fit to the experimentalµ–I curves and explained 97% of the observed interspecificvariability. ¹Present address: Lamont-Doherty Geological Observatory Columbiaof University, Palisades, NY 10964, USA     

Measurement of Yield Threshold and Cell Wal Extensibility of Intact Wheat Roots under Different Ionic, Osmotic and Temperature Treatments

Yield stress threshold (Y) and volumetric extensibility () arethe rheological properties that appear to control root growth.In this study they were measured in wheat roots by means ofparallel measurement of the growth rate (r) of intact wheatroots and of the turgor pressures (P) of individual cells withinthe expansion zone. Growth and turgor pressure were manipulatedby immersion in graded osmoticum (mannitol) solutions. Turgorwas measured with a pressure probe and growth rate by visualobservation. The influence of various growth conditions on Yand was investigated; (a) At 27 °C.In 0.5 mol m^–3 CaCl₂ r, P, Y and were20.7±4.6 µm min^–1, 0.77±0.05 MPa,0.07±0.03 MPa and 26±1.9 µm min^–1MPa^–1 (expressed as increase in length), respectively.Following 24 h growth in 10 mol m^–3 KC1 these parametersbecame 12.3±3.5 µm min^–1, 0.72±0.04MPa, 0.13±0.01 MPa and 21±0.7 µm min^–1MPa^–1. After 24 h osmotic adjustment in 150 mol m^–3mannitol/0.5 mol m^–3 CaCl₂ r= 19.6±4.2 µmmin^–1, P = 0.68±0.05 MPa and Y and were 0.07±0.04MPa and 30±0.2 µm min^–1 MPa^–01, respectively.After 24 h growth in 350 mol m^–3 mannitol/0.5 mol m^–3CaCl₂ r= 13.3±4.1 µm min^–1, P= 0.58±0.07MPa, Y=0.12±0.01 MPa and ø 32±0.2 tim min^–1MPa^–1. During osmotic adjustment in 200 mol m^–3mannitol/0.5 mol m^–3 CaCl₂, with or without KCl, the recoveryof growth rate corresponded to turgor pressure recovery (t1/2approximately 3 h). (b) At 15 °C. Lowered temperature dramatically influencedthe growth parameters which became r= 8.3±2.8 um min^–1,P=0.78 MPa, r=<0.2 MPa and =15±0.1 µm min^–1MPa^–1. Therefore, Y and are influenced by 10 mol m^–3 K⁺ ionsand low temperature. In each case the effective pressure forgrowth (P-Y) was large indicating that small fluctuations ofsoil water potential will not stop root elongation. Key words: Yield threshold, cell wall extensibility, wheat root growth, temperature, turgor pressur     

Field Measurements of the Gas Exchange of Woody Plant Species in Simulated Sunflecks

The photosynthetic responses of eight tree and shrub speciesto simulated sunflecks was measured in the field. The net carbonexchange (NCE) of Corylus avellana and Ulmus glabra increasedwith irradiance up to the maximum irradiance of 230 µmolm^–2 s^–1. The NCE of Fraxinux excelsior, Hedera helixand the sun and shade forms of Rhododendron ponticum saturatedat about 120 µmol m^–2 s^–1 whereas the NCEof Ilex aquifolium, Daphne laureola and Fagus sylvatica hadeffectively saturated at 27 µmol m^–2 s^–1. In all cases the quantum efficiency of NCE could be predictedfrom measurements of chlorophyll fluorescence and the maximumvalue for NCE from measurements of stomatal conductance. Therelationships were combined into a model for predicting NCE/irradiancecharacteristics. Corylus avellana L., Daphne laureola L., Fagus sylvatica L., Fraxinus excelsior L., Hedera helix L., Ilex aquifolium L., Prunus laurocerasus L., Rhododendron ponticum L., Ulmus glabra Huds., gas exchange, stomatal resistance, water use efficiency, chlorophyll fluorescence, quantum efficiency     

Nitrate Effects on Growth of the First Four Main Stem Leaves of a Range of Temperate Cereals and Pasture Grasses

The effects of different applied NO₃^– concentrations onextension growth and final length and area of leaves 1–4of five cereals and six pasture grasses of temperate originwere examined. Increased applied NO₃^– in the range 0.1–0.5.0mol m^–3 caused decreased duration of growth but increasedgrowth rate and final length of leaves 2–4 of the cerealsAvena saliva, Hordeum vulgare, Secale cereale, x Triticosecaleand Triticum aestivum. For all cereals, increased NO₃^–resulted in increased area of leaves 1–4. Pasture grasseswere supplied either 0.5 or 50 mol m^–3 NO₃^–. Increasedapplied NO₃^– (0.5–5.0 mol m^–3) resulted indecreased duration of growth and increased growth rate and finalarea of leaves 1–4 of Bromus wiltdenowii, leaves 2–4ofFestuca arundinaceae and leaves 3 and 4 of Lolium muitiflorum.In addition, length of leaves 3 and 4 of B. witidenowii increasedwith increased NO₃^–. Increased NO₃^– resulted inincreased area of leaves 2–4 of Dactylis gtomerata andLolium perenne and leaves 3 and 4 of Phalaris aquaiica but hadno effect on extension growth of all three species. Avena sativa L, oat, Hordeum vulgare L, barley, Secale cereale L, rye, x Triticosecale Wittm, triticale, Triticum aestivum L, wheat, Bromus willdenowii Kunth, prairie grass, Dactylis gtomerata L, cocksfoot, Festuca arundinaceae Shreb, tall fescue, Lolium multijlorum Lam, Italian ryegrass, Lolium perenne L, perennial ryegrass, Phalaris aquatica L, nitrate, leaf extension, leaf expansion     

Separation of marine seston and density determination of marine diatoms by density gradient centrifugation

An attempt has been made to separate constituents of marineseston samples: inorganic material, detritus and the algal species,by density gradient centrifugation, without affecting the physiologicalstate of the algae. A relatively inert gradient material, consistingof Percoll, salt and sucrose, was composed. Since the densitiesof detritus and algae as well as those of different algal speciesoften overlapped, only 10 of the 100 samples processed in thecourse of the year showed a reasonable separation. However,an enrichment with respect to one or more species was oftenachieved. Densities of eleven species of marine diatoms andof one dinoflagellate have been determined at different timesof the year. For eight diatom species and for the dinoflagellatethe following specific density ranges were established: Bidduiphiaaurita: 1.18–1.23 g cm^–3, Biddulphia sinensis: 1.03–1.08g cm^–3, Cerataulina bergonii: 1.03–1.06 g cm^–3,Ditylum brightwellii: 1.07–1.13 g cm^–3, Rhizosoleniadelicatula: 1.04–1.09 g cm^–3, Skeletonema costatum:1.12–1.17 g cm^–3, Streptotheca thamensis: 1.04–1.10g cm^–3 , Thalassiosira rotula: 1.05–1.10 g cm^–3,Peridinium sp.: 1.08–1.12 g cm^–3. No seasonal variationin density was demonstrated. Gradients of different compositiondid not influence density measurements.     

Ontogeny of growth, respiration and feeding rate of the freshwater calanoid copepod Eudiaptomus graciloides

The calanoid copepod, Eudiaplomus graciloides, was reared fromegg to adult on uni-algal diets (0.1. 0.5 and 2.5 mg dry wt1^–1) using the green alga, Chlamydomonas reinhardtii,as food, or on a mixed diet consisting of Lake Esrom water filteredthrough a plankton net with pore size 45 µm and supplementedwith C. reinhardtii (2.5 mg dry wt 1^–1). On the mixeddiet at 21.0°C growth in body dry wt (W, µg dry wt)was exponential, and the growth constants were 0.21 day^–1in the early to mid juvenile stage (N1 - C4) and 0.11 day^–1in the late juvenile to early adult stage (C4-A). At 14.5°Cthe corresponding growth rate constants were 0.10 and 0.08 day^–1.Similar growth rates were found at uni-algal concentrationsof 0.5 and 2.5 mg dry wt I^–1, and it was argued that thethreshold concentration for growth in Eudiaptomus was closeto 0.1 mg dry wt I^–1. The clearance (C, ml h^–1)of copepodites was measured on the uni-algal diets. The constantsof the regression (C = aW^b) were: a = 0.125, b = 0.858 (2000C. reinhardtii ml^–1), a = 0.068, b = 0.849 (10 000), a= 0.028, b = 0.875 (50 000). Ingestion rates were calculatedfrom the clearances and the average algal concentrations. Atthe three food levels the average daily rations were 30, 67and 125% of body dry wt. The respiration rate (R, nl O₂ h^–1)was measured in individuals reared on the mixed diet. The constantsof the regression (R = aW^b) were: a = 4.82, b = 1.07 (nauplii,14.5°C), a = 4.17, b = 0.904 (copepodites and adults, 14.5°C),a = 6.87, b = 0.757 (copepodites and adults, 21.0°C). Nosignificant difference in the respiration rate of copepoditesreared on uni-algal diets and the mixed diet could be demonstrated.Energy budgets were calculated. The assimilation efficiencyand the gross growth efficiency of copepodites decreased markedlywith increasing food concentration, the net growth efficiencyvaried from an average of 0.44 at the lowest algal concentrationto 0.60 on the mixed diet. The results are discussed in relationto previous findings with both freshwater and marine copepods.     

Structure and Function of Oak Forests in Central Himalaya. I. Dry Matter Dynamics

The present study deals with structure and functioning of threeareas of Himalayan oak forest. Low- and mid-altitude oaks, namelyQuercus leucotrichophora, and Quercus floribunda, form predominantevergreen forests in Central and Western Himalaya. The totaltree basal cover ranged between 33·89 m² ha^–1 (Q.floribunda site) to 36·83 m² ha^–1 (Q. leucotrichophorasite). The density ranged between 570 and 760 individuals ha^–1.Allometric equations relating biomass of different tree componentsto GBH (girth at breast height) were significant with the exceptionof leaf biomass in Q. leucotrichophora and Rhododendron arboreum.Total vegetation biomass (29·40–467·0 tha^–1) was distributed as 377·1 t ha^–1 intrees, 5·40 t ha^–1 in shrubs and 1·23 tha^–1 in herbs. Total forest floor biomass ranged between4·6 and 6·2 t ha^–1. Of the total annuallitter fall (4·7–4·8 t ha^–1), 77·5% was contributed by leaf litter, 17·8 % by wood litterand 4·7 % by miscellaneous litter. Turnover rate of treelitter varied from 0·66 to 0·70. Net primary productionof total vegetation ranged between 15·9 and 20·6t ha^–1 yr^–1, of which the contribution of trees,shrubs and herbs was 81·2 %, 8·6 % and 10·2%, respectively. A compartment model of dry matter on the basisof mean data across sites was developed to show dry matter storageand flow of dry matter within the system. Quercus leucotrichophora forest, Q. floribunda forest, Q. lanuginosa forest, biomass, litter fall, net primary production, compartmental transfer     

Feeding and metabolism of the siphonophore Sphaeronectes gracilis

The in situ predation rate of the siphonophore Sphaeronectesgracilis was estimated from gut content analysis of hand-collectedsiphonophores and from laboratory data on digestion rates ofprey organisms. At daytime prey densities of 0.25 copepods 1^–1,S. gracilis was estimated to consume 8.1 – 15.4 prey day^–1siphonophore^–1. From data on abundances of siphonophoresand copepods, S. gracilis was estimated to consume 2–4%of the copepods daily. In laboratory experiments, ingestionrates averaged 13.8 prey day^–1 siphonophore^–1 atprey densities of 5 copepods 1^–1 and 36.9 at 20 copeods1^–1. This was equivalent to a specific ingestion rate(for both carbon and nitrogen) of –17% day^–1 and45% day^–1, respectively, while specific ingestion in situwas only 2% day^–1. Ammonium excretion averaged 0.095 µg-atsiphonophore^–1 day^–1 at 5 prey 1^–1, and 0.162at 20 prey 1^–1. The specific respiration (carbon) andspecific excretion (nitrogen as ammonium) were calculated tobe 3% day^–1 at the lower experimental food level, and5% day^–1 at the higher food level. ¹Contribution from the Catalina Marine Science Center No. 66. ²Present address: Dept. of Biology, University of Victoria,Victoria, B.C., Canada V8W 2Y2.     

DENSITY FLUCTUATIONS, GROWTH AND DRY TISSUE PRODUCTION OF HYDROCOCCUS BRAZIERI (TENISON WOODS, 1876) AND ARTHRITICA SEMEN (MENKE, 1843) IN PEEL INLET, WESTERN AUSTRALIA

Hydrococcus brazieri and Arthritica semen on a sandflat at Coodanup,Peel Inlet, Western Australia, accounted for 89.5% of totalmollusc numbers. The mean density of H. brazieri was 9487 m^–2and A. semen averaged 8105 m^–2. H. brazieri grew at 0.5mm month^–1 and reached maturity in 4 months; A. semengrew at 0.3 mm month^–1 and reached maturity in 6 months.Somatic production in the Peel-Harvey estuarine system was estimatedto be 0.5 g m^–2yr^–1for H. brazieri and 4.1 g m^–2yr^–1for A. semen. The positions of these two species in the estuarinefoodweb is discussed. (Received 26 June 1981;     

Quantal Response of Seed Germination in Seven Genera of Cruciferae to White Light of Varying Photon Flux Density and Photoperiod

The response of the germination of seeds of Barbarea vema (Mill.)Aschers, Brassica chinensis L., Brassica juncea (L.) Czern.& Coss., Brassica oleracea L. var. gongylodes L., Camelinasaliva (L.) Crantz, Eruca saliva Mill., Lepidium sativum L.,Nasturtium officinale R. Br., and Rorippa palustris (L.) Besserto white fluorescent light of different photon flux densitiesapplied for different daily durations in a diurnal alternatingtemperature regime of 20 °C/30 °C (16 h/8 h) was quantifiedby linear relations between probit percentage germination andthe logarithm of photon dose, the product of photon flux densityand duration. The low energy reaction, in which increasing dosepromotes germination, was detected in all the seed populationsbut in Barbarea vema and Brassica Juncea the lowest photon doseapplied (10^–5–2 and 10^{–5 7} mol m^–2 d^–1,respectively) was sufficient to saturate the response. Comparisons,where possible, between photoperiods demonstrated reciprocity,i.e. germination was proportional to photon dose irrespectiveof photoperiod, for the low energy reaction in Brassica oleracea(1 min d^–1 to 1 h d^–1), Camelina saliva (1 min d^–1to 8 h d^–1), Eruca saliva (1 min d^–1 to 24 h d^–1),Lepidium sativum (I min d^–1 to 8 h d^–1) and Rorippapalustris (1 min d^–1 to 8 h d^–1), but not in Brassicachinensis and Nasturtium officinale. The high irradiance reaction,in which increasing dose inhibits germination, was detectedin Barbarea vema, Brassica chinensis, Brassica juncea, Brassicaoleracea, and Camelina saliva. The minimum dose at which inhibitionwas detected was lO^–0–3 mol m^–2 d^–1.These results are discussed in the context of devising optimallight regimes for laboratory tests intended to maximize germination The response of germination to photon dose was also quantifiedwith 3 x 10^–4 M GA₂, co-applied (Brassica chinensis, Camelinasaliva, and Lepidium sativum) and with 2 x 10^–2 M potassiumnitrate co-applied (Brassica chinensis). In the latter casepotassium nitrate had no effect in the dark and inhibited germinationin the light, but GA₂, promoted germination substantially inall three species. Variation amongst seeds in the minimum photondose required to stimulate germination was not affected by co-applicationof GA₂, in Brassica chinensis and Camelina saliva, whereas seedsof Lepidium salivum showed a narrower distribution of sensitivitiesto the low energy reaction in the presence of GA₂ Barbarea vema (Mill.) Aschers, Brassica chinensis L., Brassica juncea (L.) Czern. & Coss., Brassica oleracea L. var. gongylodes L., Camelina saliva (L.) Crantz, Eruca saliva Mill., Lepidium satiaum L., Nasturtium officinale R. Br., Rorippa palustris (L.) Besser, Cruciferae, light, gibberellic acid, seed germination, seed dormancy     

Biomass, feeding and production of Noctiluca scintillans in the Seto Inland Sea, Japan

The abundance and biomass of the large heterotrophic dinoflagellateNoctiluca scintillans, together with the changes in its potentialprey items, were monitored in the Seto Inland Sea, Japan, duringsummer 1997 (17 July-11 August). Growth and grazing rates ofNscintillans fed natural plankton populations were also measuredeight and seven times, respectively, during the survey period.The abundance and biomass of N scintillans averaged over thewater column (19 m) were in the range 1–345 cells 1^–1(temporalaverage = 93 cell1^–1) and 0.1–49.6 µg C l^–1(temporalaverage = 13.8 µg C l^–1; three times higher thanthat of calanoid copepods during the same period). Noctilucascintillans populations followed the changes in phytoplankton:N.scintillans biomass was increasing during the period of diatomblooms and was at a plateau or decreasing during periods oflow chlorophyll a. The growth rates of N.scintillans (µ)were also consistent with the wax and wane of the N.scintillanspopulation: N.scintillans showed highest growth rates duringdiatom blooms. A simple relationship between µ and chlorophylla concentration was established, and the production of N.scintillanswas estimated using this relationship and the measured biomass.The estimated production averaged over the water column wasin the range >0.1–5.2 µg C l^–1 day^–1(temporalaverage = 1.4 µg C l^–1 day^–1; 64% of the productionof calanoid copepods during the same period). Diatom clearancerates by N.scintillans were in the range 0.10–0.35 mlcell^–1 day^–1, and the phytoplankton population clearanceby N.scintillans was >12% day^–1. Thus, although thefeeding pressure of N.scintillans on phytoplankton standingstock was low, N.scintillans was an important member of themesozooplank-ton in terms of biomass and production in the SetoInland Sea during summer.     

Mechanism of Photoregulated Carotenogenesis in Rhodotorula minuta I. Photocontrol of Carotenoid Production

Rhodotorula minuta cells, which have only traces of carotenoidswhen grown in the dark, started carotenoid production with theonset of illumination and the amount increased almost linearlyuntil 70 hr then remained constant thereafter when incubationwas continued under illumination, with the number of cells continuingto increase. The rate of carotenoid production [Vc (µgg^–1 hr^–1)] depended on the intensity of light [I(ergcm^–2 sec^–1)], with the relationship of Vc=0.74 logI–1.46. The final carotenoid content [C(µg g^–1)]of cells incubated under continuous light was also controlledby the light intensity [I], with the relationship of C=52 logI–81. Control of carotenoid production by light occursas a two-phase process consisting of a temperatureindependentphotochemical reaction and light-independent biochemical reactions. (Received September 12, 1981; Accepted February 20, 1982)