Non-destructive measurement of stem water content by time domain reflectometry using short probes

Time Domain Reflectometry (TDR) has previously been used todetermine the water content of soils. Here, TDR is assessedas a method of tracking the seasonal change in water contentof the stems of mature trees (Pinus sylvestris L.). The longerprobes used for soil were replaced by 50 mm probes, insertedradially into the stems at 1 m above the ground. Tests on blocksof wood in the laboratory suggested that the probe is influencedby the water content several centimetres around it, and thesensitivity of the system enables volumetric water content (W)in the physiological range to be measured to a resolution greaterthan 0.01 m³ (H₂0) m^–3. The use of very short probes preventsthe development of a universal calibration between measureddielectric constant and W. Calibrations for both 50 mm and 20mm long probes are reported. The effect of temperature on thecalibration was negligible. The system was used successfullyon mature trees in 1995, and no evidence of wound reaction aroundthe permanently installed probes was apparent in the measurements. Key words: TDR, dielectnc constant, water content, Pinus sylvestris, xylem embolism     

Mucilage in Cacti: Its Apoplastic Capacitance, Associated Solutes, and Influence on Tissue 5

Mucilage content in the stems of four sympatric cactus speciesvaried from none for Ferocactus acanthodes, 19% by dry weightfor Opuntia basilaris, 26% for Opuntia acanthocarpa, and 35%for Echinocereus engelmannii. Although the mucilage differedchemically among the species (the arabinose content ranged from17% to 51% of the sugar monomers), its relative capacitance(change in relative water content per unit change in water potential)remained about 15 Mpa^–1. The relative capacitance of thewater-storage parenchyma averaged 1·04 Mpa^–1 andwas consistent with the mucilage content, being lowest for F.acanthodes and highest for E. engelmannii. Mucilage isolatedfrom hydrated tissue was accompanied by solutes with an osmoticpressure of about 0·2 MPa. Such associated solutes influencethe water-release characteristics of mucilage and hence itsrole as an apoplastic capacitor. In particular, extracellularsolutes can facilitate the release of appreciable mucilage-boundwater to the cells at tissue water potentials occurring duringthe initial phases of drought. Key words: Echinocereus engelmannii, Ferocactus acanthodes, Opuntia acanthocarpa, Opuntia basilaris, water potential isotherms     

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     

Water potentials for developing cladodes and fruits of a succulent plant, including xylem-versus-phloem implications for water movement

Developing cladodes had lower water potentials and developingfruits had higher water potentials than the underlying cladodesof the widely cultivated prickly pear cactus, Opuntia ficus-indica.The 0.06 MPa lower value in 4-week-old daughter cladodes indicateda typical water potential gradient from the underlying clad-odealong the xylem of –0.2 MPa m^–1; the 0.17 MPa highervalue in 4-week-old fruits, which decreased to 0.07 MPa by 10weeks, implicated the phloem as their supplier of water. Thephloem sap of the underlying cladodes had an osmotic pressureof only 0.90 to 0.98 MPa, so the phloem could supply a relativelydilute solution to the photosynthetically dependent fruits (daughtercladodes of O. ficus-indica are photosynthetically independentat 4 weeks). Although the water potentials were similar foradjacent tissues, the osmotic pressures were lower for the water-storagecompared with the photosynthetic tissue; the osmotic pressureswere higher for xylem sap from fruits, for which xylary flowapparently occurred toward the underlying cladodes, than fordaughter cladodes. The relative capacitance (change in relativewater content divided by change in tissue water potential) wasapproximately 0.71 MPa^–1 for the water-storage tissueand the photosynthetic tissue of both daughter cladodes andfruits at 4 weeks of age. When these organs approached maturityat 10 weeks, the relative capacitance increased about 40% fortheir water-storage tissue, but decreased 30% for their photosynthetictissue. As the plant water content decreases during drought,about twice as much water will thus be lost per unit volumeof the water-storage tissue compared with the photosynthetictissue of maturing fruits and cladodes. Key words: Opuntia ficus-indica, phloem, relative water content, water capacitance, water potential     

Soyabean Stem In Vivo Nitrate Reductase Activity

Stem from three- and four-week-old Soyabean [Glycine max (L.)Merr. cv. Tracy] plants reduced from 0.3 to 0.7 µmol nitrateh^–l g^–l f. wt. Leaf activity was 4.7–7.6 µmolnitrate h^–l g^–l f. wt. Outer stem was two to fourtimes more active at reducing nitrate than was inner stem. Plantnitrate nutrition had a strong effect upon the ratio of activitypresent in stem and leaf. More nitrate increased the proportionpresent in leaves. Glycine max L., soyabean, nitrate assimilation, nitrogen metabolism, Rhizobium japonicum     

Ionic Currents across the Plasmalemma of Chara inflata Cells: III. WATER-RELATIONS PARAMETERS AND THEIR CORRELATION WITH MEMBRANE ELECTRICAL PROPERTIES

The water-relations parameters of Chara inflata cells were determineddirectly using the micro pressure probe technique. The turgorpressure of cells in artificial pond water (₀ = 0.06 MPa) wasabout 0.65 MPa and the half-time (T_1/2) for water exchange wasabout 6.5 s. The calculated values of the hydraulic conductivity(L_P) were in the range 1–2 ? 10^–6m s^–1 (MPa)^–1.The volumetric elastic modulus () was 32.8 MPa for turgor rangingfrom 0.77 to 0.82 MPa. Large changes in the water-relations parameters and the electricalproperties of the membrane occurred when the turgor was decreasedto low values. These changes included: (i) a decrease in theT_1/2 for water exchange, (ii) an increase in L_P and (iii) depolarizationof the membrane potential difference (V_m). The micro pressure probe, which enabled the turgor pressureof the cell to be altered, was used in combination with thevoltage-clamp technique to determine the relationship betweenK⁺ and Cl^– conductances of the plasmalemma and the cellturgor. The K⁺ conductance increased reversibly as the turgorwas reduced in the range 0 to 0.6 MPa and the Cl^– -conductanceincreased as the turgor was reduced in the range 0.1 to 0.5MPa. It is suggested that these pressure-dependent K⁺ and Cl^–conductances may have a dual role in electrical events and thenon-electrical responses such as changes in the cell volume. Key words: Chara inflata, membrane conductances, ion channels, water-relations parameters     

The Water Relations of Young Olive Trees in a Mediterranean Winter: Measurements of Evaporation from Leaves and Water Conduction in Wood

We report measurements of evaporation rate, leaf resistanceto evaporation and water conduction in the stems of young olivetrees (Olea europea L.) growing in Messina, Italy, during thewinter and early spring. We have measured what Zimmermann calls‘leaf specific conductivity’ (LSC) of stem segmentsexcised from olive trees. The LSC is a measure of the specifichydraulic conductivity of stem segments normalized per unitarea of leaves supplied by the stem segment rather than perunit area of sapwood cross-sectional area. We find that theLSC's of primary stems were the largest followed in magnitudeby the LSC's of secondary stems and tertiary stems. Under winterand early spring conditions the maximum evaporative flux fromCoratina and Nocellara varieties of olive trees is about 2.6x 10^–5 kg 8^–1 m^–2. From this and the LSC measurementswe calculate that the pressure gradients needed to maintainthis rate of evaporation in the steady state is 65 kPa m^–1in primary stems, 170 kPa m^–1 in secondary stems and 560kPa m^–1 in tertiary stems. Olive, Olea europea L, evaporation, leaf specific conductivity, hydraulic conductivity, leaf resistance     

Variability and predictability of the empirical conversion factor for converting 3H-thymidine uptake into bacterial carbon production for a eutrophic lake

To assess the variability and predictability of the empiricalconversion factor (CF) for converting the uptake of ³H-thymidine(TDR) to bacterial carbon production rates in eutrophic environments,we performed 11 dilution culture experiments and results wererelated to a set of important concomitantly recorded environmentalvariables. TDR incorporation data from a field study were thenconverted to carbon production with the established empiricalCF and a theoretical CF and compared to production estimatesderived from leucine incorporation. Mean empirical CF variedbetween 0.5 and 7.0 x 10⁶ cells (pmol TDR)^–1 over theyear and showed highly significant negative correlation withTDR incorporation rate and a highly significant positive correlationto temperature. Values of carbon production derived with thevariable empirical CF were lower than the values obtained bythe use of the theoretical CF of 1 x 10⁶ cells (pmol TDR)^–1.They showed less seasonal variation than values obtained byleucine incorporation, and periods of uncoupling were observed.However, when the empirical CF was calculated from the multipleregression equation including TDR incorporation and temperature,the resulting carbon production rates showed a high correspondencewith the leucine-derived production rates. Results of the analyseswere interpreted as an indication that under favourable conditions(resulting in high TDR incorporation) bacteria may be able tooptimize DNA duplication over protein synthesis as a possiblestrategy to persist and to maintain their potential to divideunder limiting conditions (e.g. decrease in temperature andsubstrate availability). In unfavourable conditions (resultingin low incorporation rates), bacteria may then use already producedDNA copies for rapid growth, when the environmental conditionsturn favourable again. Thus, an experimental set-up causingnutrient enrichment of the sampled water by autoclaving andfiltering, as generally used for dilution culture experiments,does not always reflect in situ situations, especially duringperiods of low nutrient concentrations.     

Root Hydraulic Conductivity of Two Cactus Species in Relation to Root Age, Temperature, and Soil Water Status

The effects of root age, temperature, and soil water statuson root hydraulic conductivity (L_P) were investigated for twocactus species, Ferocactus acanthodes and Opuntia ficus-indica.The volumetric flux density of water was measured for excisedroot segments, either using negative hydrostatic pressures appliedto the proximal end or using reverse flow of water from theroot to the soil. For both species, L_P at 20 ?C increased withroot age, average values reaching a maximum of 3.9 ? 10^–7m s^–1 MPa^–1 for F. acanthodes and 5.2 ? 10^–7m s^–1 MPa^–1 for O.ficus-indica at 11 to 17 weeksof age; L_P subsequently declined with increasing root age forboth species. L_P was maximal at a temperature of about 10 ?Cfor the youngest roots (1–3 weeks), this optimum shiftingto 40 ?C for 8-week-old roots of both species. For older roots(up to 1.5-years-old), L_P increased with temperature from 0?C to 50 ?C, with a Q₁₀ of 1.3 between 20 ?C and 30 ?C. At asoil water potential (_soil) of –0.016 MPa, root L_P wasindependent of the direction of water flow for both species.Depending on root age, L_P declined 45- to 500-fold for F. acanthodesand 90- to 800-fold for O.ficus-indica as _soil was reduced from–0.016 to –1.06 MPa, consistent with a rectifier-likebehaviour with respect to water movement between soil and roots.Incorporation of such responses into water uptake models shouldlead to a better understanding of root function. Key words: Ferocactus acanthodes, Opuntia ficus-indica, water potential, tension, reverse flow     

Discontinuite hydrobiologique dans le detroit du Pas-de-Calais

Hydrobiological studies in the Straits of Dover show a differencebetween the characteristics of the French coastal water andthe open sea water. A cruise between Boulogne-sur-mer and Dover(October 15, 1985) confirms the existence of a frontal area(4 miles off the French coast). This area is characterized byan increase of the salinity (1%) and decrease of the suspendedmatter content (from 27 to 20 mg l^–1), of primary production(from 15 to 3 mg C m^–3h^–1) and of chlorophyll aconcentration (from 4.5 to 1.5 mg m^–3). The presence ofdifferent zooplanktonic species in the two water masses alsocharacterizes this discontinuity. Oncaea sp., Corycaeus anglicus,Centropages typicus and Calanus helgolandicus are indicatorspecies of open sea water, while Cyciopina littoralis and ‘Saphirella’are only present in coastal water.     

Seed Water Relations and the Regulation of the Duration of Seed Growth in Soybean

Soybean [Glycine max (L.) Merrill] seeds and cotyledons weregrown in an in vitro culture system to investigate the relationshipsbetween cell expansion (net water uptake by the seed) and drymatter accumulation. Seeds or cotyledons grown in a completenutrient medium containing 200 mol m^–3 sucrose continueddry matter accumulation for up to 16 d after in planta seedsreached physiological maturity (maximum seed dry weight). Seedor cotyledon water content increased throughout the cultureperiod and the water concentration remained above 600 g kg^–1fresh weight. These data indicate that the cessation of seeddry matter accumulation is controlled by the physiological environmentof the seed and is not a pre-determined seed characteristic.Adding 600 mol m^–3 mannitol to the medium caused a decreasein seed water content and concentration. Seeds in this mediumstopped accumulating dry matter at a water concentration ofapproximately 550 g kg^–1. The data suggest that dry matteraccumulation by soybean seeds can continue only as long as thereis a net uptake of water to drive cell expansion. In the absenceof a net water uptake, continued dry matter accumulation causesdesiccation which triggers maturation. Key words: Glycine max (L.) Merrill, solution culture, duration of seed growth, water content, dry matter accumulation     

Soil Water Extraction, Measured by Computer-Assisted Tomography, in Seedling Lupinus angustifolius cv. Yandee when Healthy and Infected with Phytophthora cinnamomi

The water-mould fungus Phytophthora cinnamomi Rands causes drought-likesymptoms on many hosts, and yet the mechanisms by which infectionleads to wilting are not fully understood. This is the firststudy to describe in detail changes in soil water around theroot with infection. Computer-assisted tomography (CAT) wasused with Lupinus angustifolius L. cv. Yandee to examine drawdowns(removal of soil water) around a central root infected by P.cinnamomi in a white sand. No growth differences in roots or shoots were found betweenhealthy and diseased plants during the 8 d of the experiment.However,drawdowns failed at high levels of inoculum (8–16 /Pc-infectedmillet seeds/plant) by 8 d. Water contents in pots with uninfectedplants were in the range 0·09–0·12 cm³ watercm^–3 soil in the centre of the pot, while water contentsin pots with infected plants at 16 millet seeds applied werein the range of 0·16–0·19 cm³ water cm^–3soil in the centre of the pot. A higher transpirational demand produced lower soil water contentsnear the root but this effect was confounded with infection:disease was more pronounced with higher transpirational demand,and disease led to an increase in water content. Key words: Root disease, Phytophthora cinnamomi, water uptake, soil-root interface, computer-assisted tomography     

Studies on the Movement of Water Through Apple Trees

Resistances to the flow of water through young potted appletrees were estimated by measuring the transpiration rate oftrees with and without root systems. Root system resistanceswere obtained by difference. Whole-plant resistances were ofthe order 10 x 10¹³ Pa s m^–3 and there was some evidencethat root resistances (R_r) varied with transpiration rate; theratio R_r:R_x (where R_x is resistance to water flow in the stemsystem) altered from 2:1 at relatively high transpiration ratesto 1:1 at lower rates. The trunk of a 9-year-old orchard tree (trunk diameter {smalltilde}7 cm, height {small tilde}2.5 m) was cut under water andestimates of the flow resistances in this tree were obtained.These were much lower than the resistances to flow in the pottedtrees. Capacitance (defined as the change in stored water content perunit change in plant water potential) values were calculatedfor the small trees and the large tree from measurements ofweight and water potential changes after the trees were removedfrom water. They were very similar on a weight basis (approx.2.0 x 10^–8 kg kg^–1 Pa^–1). Leaf capacitancevalues ({small tilde}1 x 10^–8 kg Pa^–1 m^–2)were also obtained. Stomatal conductances decreased with water potential and increasedwith short-wave radiation, but the relationships were not definitive.Estimates of boundary layer conductance in a greenhouse (verylow wind speeds) were of the same order ({small tilde}5 mm s^–1)as values obtained previously.     

The Theory and Practice of Measuring Transport Coefficients and Sap Flow in the Xylem of Red Maple Stems (Acer rubrum)

In this paper we report measurements concerning the conductivityof water and ions and the interaction between the two in excisedpieces of xylem of red maple stems under various conditions.We have also demonstrated that it is possible to detect theflow of solutions through the stems of maple by measuring thedegree of interaction between the flow of water and ions. Inthis technique we apply voltage pulses of ±V volts acrossa length of stem and detect the unequal current pulses resultingfrom the greater frictional drag when current (which is carriedprimarily by cations) is flowing against the water stream thanwhen flowing with the water stream. The hydraulic conductivityof recent maple sapwood ranges from 30 to 90 cm³ s^–1 cm^–2(J cm^–3)^–1 cm; in 2 mM KCl the electrical conductivityis roughly 3 x 10^–4 mho cm^–1 and the electro-kineticcross coefficient is roughly 4x10^–5 A cm^–2 (J cm^–3)^–1cm.     

The influence of temperature and light on the upper limit of Microcystis aeruginosa production in a hypertrophic reservoir

Primary production was measured for 7 years, using the in situ¹⁴C-method in hypertrophic Hartbeespoort Dam, South Africa,to examine the influence of light and water temperature on theupper limit of Microcystis aeruginosa production. Water temperaturesvaried from 11 to >25°C and chlorophyll concentrationsreached 6500 mg m^–3. The maximum volumetric rate of production(A_max) was 12->8800 mg C m^–3 h^–1 with areal productions(A) of 69->3300 mg C m^–2 h^–1 for euphotic zonedepths of <0.5–8.4 m. The intrinsic parameters of phytoplanktonproduction (, A_max/B, I_k) indicated that the phytoplankton populationwas adapted to high light levels. Both A_max/B and I_k were correlatedwith temperature. Under optimal conditions, , the theoreticalupper limit of A, was calculated to be 2.8 g Cm^–2 h^–1,while the measured rate was 2.5 g Cm^–2 h^–1. Measuredareal rates exceeding were overestimated due to methodologicalproblems when working with Microcystis scums. Light and watertemperature interacted to yield high production rates: watertemperature through its direct effect on photosynthetic ratesand indirectly in the formation of diurnal mixed layers; lightindirectly through water temperature and directly through itsattenuation and induction of light-adapted physiology in Microcystis.     

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     

Salt Tolerance in the Halophyte, Suaeda maritima (L.) Dum.: The Influence of the Salinity of the Culture Solution on the Content of Various Organic Compounds

Plants of the halophyte Suaeda maritima were grown in tap wateror in a culture solution in the presence or absence of sodiumchloride and the levels of sugars, amino acids, organic acidsand quaternary ammonium compounds determined in relation tothe balance between cytoplasmic and vacuolar water potentials.The sugar content (some 7 µmol. g f. wt^–1) was unaffectedby the salinity of the growth medium as was the overall contentof amino acids (about 4 µmol. g f. wt^–1). The organicacid content was maximal in plants kept in tap water alone wherethe dominant acid was malic. Plants grown in culture solutioncontained the same acids, although addition of sodium chlorideto the medium brought about the apparent loss of glycolic acidand the appearance of oxalic acid. Only a single quaternaryammonium compound, glycinebetaine, was apparently present inthe tissues: the content of betaine doubled (to 37·5µrmol. g f. wt^–) when sodium chloride was addedto the culture solution. The content of these various compoundsis discussed in relation to the relative values of the cytoplasmicand vacuolar components of the overall tissue water potential Suaeda maritima, halophyte, salt tolerance, betaine, organic compounds, water potential     

Callus Culture of Sainfoin (Onobrychis viciifolia) and Plant Regeneration through Somatic Embryogenesis

Callus of sainfoin (Onobrychis viciifolia Scop.) was initiatedfrom stem and root explants which were obtained from seedlingsgrowing in vitro, on Linsmaier Skoog (LS) medium supplementedwith 1 mg l^–1 2, 4-D and 1 mg l^–1 BA or only 1 mgl^–1 BA, and the Vacin and Went medium without hormones.Somatic embryos were formed on LS medium containing 1 m l^–1BA. Embryos developed into complete plants on filter paper saturatedwith hormone-free LS medium. Onobrychis viciifolia, somatic embryogenesis, callus culture, plant regeneration     

The Interaction of Genotype, Explant and Media on the Regeneration of Shoots from Complex Explants of Brassica napus L.

The relative importance of explant type, genotype and growthregulator regime in the determination of shoot regenerationfrequencies from complex explants of Brassica napus L. has beenevaluated. Cotyledon, hypocotyl and stem sections taken fromone spring (Westar) and three winter (Ariana, Cobra, Libravo)varieties of B. napus were cultured on three different growthregulator regimes, 0.5 mg dm^–3 NAA + 2.0mg dm^–3BAP, 0.5 mg dm^–3 NAA + 4.0mg dm^–3 BAP and 1.0mgdm^–3 NAA + 4.0mg dm^–3 BAP. The most significanteffects on shoot regeneration were due to explant type and variety.The regeneration from stem segments was not only two to threetimes higher than from hypocotyls or cotyledons, in all varieties,but the response was also more uniform across the varieties.The explant effect accounted for 44–95% of the regenerationresponse. In contrast, the contribution of growth regulatorregime was negligible. Although the growth regulator regimeas an independent effect was unimportant, regeneration fromboth Ariana and Libravo was significantly affected by the interactionof genotype with growth regulator regime. The importance ofboth the high shoot regeneration frequency from stem segmentsand the relative uniformity of response across the four testedgenotypes is discussed with respect to the potential benefitsof using this explant source in Agrobacterium-based transformationexperiments. Key words: Brassica napus, regeneration, genotype, tissue culture, complex explant     

Carbon and nitrogen content of Noctiluca scintillans in the Seto Inland Sea, Japan

The carbon and nitrogen content of Noctiluca scintillans cellsfrom the Seto Inland Sea, Japan was investigated in order toestimate its biomass in natural samples. The carbon contentof N.scintillans ranged from 123 to 627 ng C cell^–1 witha mean value of 353 ng C cell^–1, or 1.12 to 2.67 fg Cµm^–3 with a mean value of 1.98 fg C µm^–3.The nitrogen content ranged from 36.0 to 232 ng N cell^–1with a mean value of 131 ng N cell^–1, or 0.499 to 0.910fg N µm^–3 with a mean value of 0.694 fg N µm^–3.Total cell carbon and nitrogen increased but the carbon andnitrogen per cell volume decreased with increasing cell volume.The C/N ratio of the cells ranged from 2.3 to 4.4, which wasrelatively low compared with the Redfield ratio. The carbonand nitrogen content was extremely low (91.2 ng C cell^–1,41.8 ng N cell^–1) for starved cells, whereas it was extremelyhigh (528 ng C cell^–1, 205 ng N cell^–1) for cellswhich had ingested the large diatom, Coscinodiscus wailesii.Our results suggest that the carbon and nitrogen content ofN.scintillans varies depending on its physiological conditionand the type of food that it has recently consumed.