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1.
Age composition and growth rates of the squid Loligo vulgaris(Lamark, 1797) were studied by examination of growth incrementswithin statohths of 419 specimens (mantle length, ML, rangingfrom 32 to 400 mm). The squid were obtained by monthly samplingfrom the catches of commercial trawls off southern Portugalbetween March and September, 1993 The total number of growthincrements in the mounted and ground statohths was counted usinga semi-automatic image analysis system. ML was significantlycorrelated with both the statolith length, TSL and the numberof increments, NI. The female statolith was slightly largerthan the male statolith for the same mantle size. Growth ratesof individuals showed high variability with an average estimatedat 34.6 mm month1 for males and 33.5 mm month1for females. Growth in length between 70 and 280 days was bestdescribed by a power function for both sexes. The growth indexof the statolith (TSL/NI) decreased with individual growth.This result may be related with the onset of sexual maturation.L. vulgaris hatched throughout the year with two distinct peaks,in spring which is the mam breeding period, and in autumn. Thelife cycle of the L. vulgaris population on the south Portugueseshelf was completed in one year
*Present address for correspondence: Instituto de InvestigacionMariflas. Eduardo Cabello. 6 - 36208 VIGO. Spain (Received 28 November 1995; accepted 7 February 1996) 相似文献
2.
Statolith microstructure was studied in two abundant planktoniccranchiids, Cranchia scabra (56 specimens, 38127 mm mantlelength, ML) and Liocranchia reinhardti (34 specimens, 99205mm ML) sampled in epipelagic waters of the western part of theGulf of Guinea (tropical Atlantic). Growth increments were revealedin ground statoliths of both species. It was possible to distinguishtwo growth zones in statolith microstructure by their colourin reflected light of the microscope: the translucent postnuclearzone and pale white opaque zone. Assuming that growth incrementsin statoliths were produced daily, ages of the largest immatureC.scabra and L.reinhardti were 166 and 146 days, respectively.Both cranchiids are fast-growing squids with growth rates inlength resembling those of juveniles of tropical ommastrephidsand Thysanoteuthis rhombus. Liocranchia reinhardti grows faster:its growth rate in ML is approximately twice that of same-agedC.scabra. The life cycle of both cranchiids consists of twophases. During their epipelagic phase, C.scabra and L.reinhardtifeed and grow rapidly from paralarvae to immature young in theepipelagic waters, attaining 120130 and 170200mm ML by ages of 45 months, respectively. Then they changetheir life style to a deepwater phase. 相似文献
3.
The microstructure, morphology and ontogenetic development ofstatoliths and age and growth of 405 planktonic paralarvae and117 juveniles belonging to 10 species of gonatid squids (Cephalopoda,Oegopsida) were studied in the region of the continental slopein the western part of the Bering Sea (57°00'61°30'N,163°00'E179°20'W). The statolith microstructureof all species was characterized by the presence of a largedroplet-shaped nucleus and bipartite postnuclear zone dividedinto two by the first stress check, except for Berryteuthismagister which had only one stress check and an undivided postnuclearzone. In Gonatus spp., completion of development of the postnuclearzone coincided with full development of the central hook onthe tentacular club. Daily periodicity of statolith growth incrementswas validated by maintaining 13 paralarvae of the four mostabundant species in captivity. All species might be subdividedinto two groups based on statolith microstructure, i.e. specieswith a central position of the nucleus within the first statolithcheck (Gonatopsis spp., Egonatus tinro and B.magister) and specieswith the nucleus shifted to the inner side of the first statolithcheck (Gonatus spp.). Comparative analysis of statolith morphologyshowed that paralarval statoliths have species-specific charactersthat allowed the construction of keys to identify species ofgonatid paralarvae based on their statoliths. Analysis of paralarvalgrowth using statoliths revealed that these cold-water planktonicgonatid paralarvae have fast growth rates, attaining a mantlelength of 710 mm at 1520 days and 2025mm at 3570 days. 相似文献
4.
Statolith morphology and microstructure were studied in twocommon species of panktonic cranchiid squids, Belonella borealis[four juveniles with mantle length (ML) 375450 mm] andGaliteuthis phyllura (13 paralarvae and juveniles, ML 9235mm),caught near the bottom and in pelagic layers over the continentalslope of Siberia in the northwest Bering Sea. The total numberof growth increments within the statoliths ranged from 277 to294 in B.borealis and from 10 to 209 in G.phyllura. Assumingthat these increments were produced daily, both species growrapidly in length (daily growth rate = 1.13mm day1 duringthe first 810 months of their juvenile phase in the mesopelagiclayers, prior to migration into deeper waters for maturation. 相似文献
5.
Background and Aims Neotyphodium lolii is a fungal endophyteof perennial ryegrass (Lolium perenne), improving grass fitnessthrough production of bioactive alkaloids. Neotyphodium speciescan also affect growth and physiology of their host grasses(family Poaceae, sub-family Pooideae), but little is known aboutthe mechanisms. This study examined the effect of N. lolii onnet photosynthesis (Pn) and growth rates in ryegrass genotypesdiffering in endophyte concentration in all leaf tissues. Methods Plants from two ryegrass genotypes, Nui D andNui UIV, infected with N. lolii (E+) differing approx. 2-foldin endophyte concentration or uninfected clones thereof (E)were grown in a controlled environment. For each genotype xendophyte treatment, plant growth rates were assessed as tilleringand leaf extension rates, and the light response of Pn, darkrespiration and transpiration measured in leaves of young (3045d old) and old (>90 d old) plants with a single-chamber openinfrared gas-exchange system. Key Results Neotyphodium lolii affected CO2-limited ratesof Pn, which were approx. 17 % lower in E+ than E plants(P < 0·05) in the young plants. Apparent photon yieldand dark respiration were unaffected by the endophyte (P >0·05). Neotyphodium lolii also decreased transpiration(P < 0·05), but only in complete darkness. There wereno endophyte effects on Pn in the old plants (P > 0·05).E+ plants grew faster immediately after replanting (P < 0·05),but had approx. 10 % lower growth rates during mid-log growth(P < 0·05) than E plants, but there was noeffect on final plant biomass (P > 0·05). The endophyteeffects on Pn and growth tended to be more pronounced in NuiUIV, despite having a lower endophyte concentration than NuiD. Conclusions Neotyphodium lolii affects CO2 fixation,but not light interception and photochemistry of Pn. The impactof N. lolii on plant growth and photosynthesis is independentof endophyte concentration in the plant, suggesting that theendophyte mycelium is not simply an energy drain to the plant.However, the endophyte effects on Pn and plant growth are stronglydependent on the plant growth phase. 相似文献
6.
MATTSSON M.; LUNDBORG T.; LARSSON M.; LARSSON C.-M. 《Journal of experimental botany》1992,43(1):25-30
Barley (Hordeum vulgare L., cvs Golf, Mette, and Laevigatum)was grown under nitrogen limitation in solution culture untilnear maturity. Three different nitrogen addition regimes wereused: in the HN culture the relative rate of nitrate-Naddition (RA) was 0·08 d1 until day 48 and thendecreased stepwise to, finally, 0·005 d1 duringgrain-filling; the LN culture received 45% ofthe nitrogen added in HN; the CN culture was maintainedat RA 0·0375 d1 throughout. Kinetics of net nitrateuptake were measured during ontogeny at 30 to 150 mmol m3external nitrate. Vmax (which is argued to reflect the maximuminflux rate in these plants) declined with age in both HN andLN cultures. A pronounced transient drop was observed just beforeanthesis, which correlated in time with a peak in root nitrateconcentration. Similar, but less pronounced, trends were observedin CN. The relative Vmax (unit nitrogen taken up per unit nitrogenin plants and day) in all three cultures declined from 1·32·3d1 during vegetative growth to 0·10·7d1 during generative growth. These values are in HN andLN cultures 15- to more than 100-fold in excess of the demandset by growth rates throughout ontogeny. Predicted balancingnitrate concentrations (defined as the nitrate concentrationrequired to support the observed rate of growth) were below6·0 mmol m3 in HN and LN cultures before anthesisand then decreased during ontogeny. In CN cultures the balancingnitrate concentration increased during grain-filling. Apartfrom the transient decline during anthesis, most of the effectof ageing on relative Vmax can be explained in terms of reducedcontribution of roots to total biomass (R:T). The loss in uptakeper unit root weight is largely compensated for by the declinewith time in average tissue nitrogen concentrations. The quantitativerelationships between relative Vmax and R:T in ageing plantsare similar to those observed for vegetative plants culturedat different RAs. The data support the contention that the capacity for nitrateacquisition in N-limited plants is under general growth control,rather than controlled by specific regulation of the biochemicalpathway of nitrate assimilation. Key words: Barley, nitrogen concentration, root: total plant biomass ratio, Vmax 相似文献
7.
Photoadaptation in Antarctic phytopfankton: variations in growth rate, chemical composition and P versus I curves 总被引:1,自引:0,他引:1
The response of phytoplankton to variations in the light regimewas studied during the VULCAN and ACDA cruises in the Antarctic.Unenriched batch cultures of 1219 days' duration reachedchl concentrations of 1050 µg1 and exhibitedexponential growth rates, with the maximal rate being 0.41 doubl,day1. Ice edge algae exhibited maximum growth rates atphoton flux densities (PFD) of 30100 µE m2S1and the growth rate was reduced by about 30% at 5001000µE m2S1 The chl/C ratio ranged between 0.004and 0.018, with the lowest ratios at PFDs above 500 µEm2S1 chl/C ratios were also below maximum at PFDsbelow 4050 µE m2S1 The C:N:P ratioswere close to the Redfield ratios; the Si/C ratio averaged 0.16(atoms), and the ATP/C ratio averaged from 0.0024 to 0.0050in different culture senes. When thawed after having been frozenfor 10 days, shade-adapted cultures were in a much better conditionthan sun-adapted ones. P versus I data showed that the maximumassimilation number varied from 0.75 to 4.4 µg C (µgchl)1h1. It varied inversely with the chl/C ratio;therefore the maximum carbon turnover rate varied little betweensamples (0.024/0.035 h1). Low biomass communities exhibitedrelatively high values for (the initial slope of P versus Icurves), low values for 1sat (160330 µE m2S1),and they were susceptible to photoinhibition. In contrast, communitiesdominated by Odontella weissflogii exhibited low values for, a high value for Isat (560 µE m2S1 andthey tolerated high PFDs. The photo-adaptational status of thephytoplankton in natural water samples is discussed relativeto the profile of water column stability and mixing processes. 相似文献
8.
In situ growth and development of Neocalanus flemingeri/plumchrusstage C1C4 copepodites were estimated by both the artificial-cohortand the single-stage incubation methods in March, April andMay of 20012005 at 56°C. Results from thesetwo methods were comparable and consistent. In the field, C1C4stage durations ranged from 7 to >100 days, dependent ontemperature and chlorophyll a (Chl a) concentration. Averagestage durations were 12.414.1 days, yielding an averageof 56 days to reach C5, but under optimal conditions stage durationswere closer to 10 days, shortening the time to reach C5 (fromC1) to 46 days. Generally, growth rates decreased with increasingstage, ranging from 0.28 day1 to close to zero but weretypically between 0.20 and 0.05 day1, averaging 0.110± 0.006 day1 (mean ± SE) for single-stageand 0.107 ± 0.005 day1 (mean ± SE) forartificial-cohort methods. Growth was well described by equationsof MichaelisMenten form, with maximum growth rates (Gmax)of 0.170.18 day1 and half saturation Chl a concentrations(Kchl) of 0.450.46 mg m3 for combined C13,while Gmax dropped to 0.080.09 day1 but Kchl remainedat 0.380.93 mg m3 for C4. In this study, in situgrowth of N. flemingeri/plumchrus was frequently food limitedto some degree, particularly during March. A comparison withglobal models of copepod growth rates suggests that these modelsstill require considerable refinement. We suggest that the artificial-cohortmethod is the most practical approach to generating the multispeciesdata required to address these deficiencies. 相似文献
9.
Development and fate of Eutreptiella gymnastica bloom in nutrient-enriched enclosures in the coastal Baltic Sea 总被引:1,自引:0,他引:1
Response of the phytoplankton community to bottom-up (nutrients,organic carbon source) and top-down (fish) manipulations, bothsingly and together, were studied daily during a 3 week periodin July 1993 by using eight 50 m3 mesocosms in the coastal northernBaltic Sea. Nutrient additions (once per week) invoked a seriesof blooms of Eutreptiella gymnastica Throndsen (Euglenophyceae)(up to 13 x 103 cells ml1) which formed the major part(6090%) of the total autotrophic biomass. After rapiddepletion of nutrients (23 days) from the surface layer(06 m) downwards migration and a subsequent peak of E.gymnasticain the lower part of the water columns (612 m) followed.Settled material collected from the bottom of the enclosurescontained a considerable amount of E.gymnastica cells and restingcysts. Nevertheless, sinking loss rates of E.gymnastica wereestimated to be less than 1% day1 of the suspended cellnumbers. The fate of E.gymnastica blooms was estimated to begrazing through mesozooplankton. However, provided the nutrientsare plentiful in the water column, the growth potential of E.gymnasticaappears to exceed the ambient grazing pressure. If the nutrientsbecome depleted, it seems to be effectively controlled by mesozooplanktongrazing, which is probably limiting the likelihood of massiveE.gymnastica blooms in the coastal Baltic Sea. Our study suggeststhat E.gymnastica appears to be a fast-growing fugitive (bloom)species with flexible behavioural (vertical migration) and lifehistory (cyst formation) adaptations which is able to exertdominant role and direct trophic relations similar to otherbloom species adapted for decaying turbulence and high nutrientenvironments. 相似文献
10.
A study of feeding in predacious ciliates using prey ciliates labeled with fluorescent microspheres 总被引:1,自引:0,他引:1
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 0 150.32 cellsh1 over a prey concentration of 602300 ml1.Maximum ingestion rates of E. woodruffi and E. vannus were 4.5and 3.4 cells h1 respectively, estimated at prey abundancesof 75 and 172 cells ml1 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. 相似文献
11.
MACDUFF J. H.; JARVIS S. C.; LARSSON C-M.; OSCARSON P. 《Journal of experimental botany》1993,44(9):1475-1484
Two approaches to quantifying relationships between nutrientsupply and plant growth were compared with respect to growth,partitioning, uptake and assimilation of NO3 by non-nodulatedpea (Pisum sativum L. cv. Marma). Plants grown in flowing solutionculture were supplied with NO3 at relative addition rates(RAR) of 0·03, 0·06, 0·12, and 0·18d1, or constant external concentrations ([NO3)of 3, 10, 20, and 100 mmol m3 over 19 d. Following acclimation,relative growth rates (RGR)approached the corresponding RARbetween 0·030.12 d-1, although growth was notlimited by N supply at RAR =0.18 d-1. Growth rates showed littlechange with [NO3] between 10100 mmol m3(RGR=0·15 0·16 d-1). The absence of growthlimitation over this range was suggested by high unit absorptionrates of NO3, accumulation of NO3 in tissues andprogressive increases in shoot: root ratio. Rates of net uptakeof NO3 from 1 mol m3 solutions were assessed relativeto the growth-related requirement for NO3, showing thatthe relative uptake capacity increased with RGR between 0·030·06d1 , but decreased thereafter to a theoretical minimumvalue at RGR 相似文献
12.
The Response of Bean Plants to UV-B Radiation Under Different Irradiances of Background Visible Light 总被引:14,自引:1,他引:13
Plants of Phaseolus vulgaris L. (cv. Stella) were grown in controlledconditions under three different irradiances of visible lightwith or without UV-B (280320nm) radiation. The biologicallyeffective UV-B radiation (UV-BBE) was 6.17 kJ m2 d1,and simulated a c. 5% decrease in stratospheric ozone at 55.7?N,13.4?E. The photon flux densities of the photosyntheticallyactive radiation (PAR, 400700 nm) were either 700 µmolm21 (HL), 500, µmol m2 s1(ML) or 230 µmol m2 s1 PAR (LL). Under highlight (HL) conditions plus UV-B radiation, bean plants appearedmost resistant to the enhanced levels of UV-B radiation, andresponded only by increasing leaf thickness by c. 18%. A smallincrease in UV screening pigments was also observed. Both thelower irradiances (ML and LL) increased the sensitivity of theplants to UV-B radiation. Changes in leaf structure were alsoobserved. Photosystem II was inhibited under ML and LL togetherwith UV-B radiation, as determined by Chi fluorescence inductionand calculation of the fluorescence half-rise times. Leaf reflectivitymeasurements showed that the amount of PAR able to penetrateleaves of UV-B treated plants was reduced, and that a possiblecorrelation may exist between the reduced PAR levels, loss ofChi and lowered photosynthetic activity, especially for LL +UV-Bgrown plants, where surface reflection from leaves was highest.Changes in leaf chlorophyll content were mostly confined toplants grown under LL + UV-B, where a decrease of c. 20% wasfound. With regard to protective pigments (the carotenoids andUV screening pigments) plants subjected to different visiblelight conditions responded differently. Among the growth parametersmeasured, there was a substantial decrease in leaf area, particularlyunder LL + UV-B (c. 47% relative to controls), where leaf dryweight was also reduced by c. 25%. Key words: Chlorophyll fluorescence induction, bean, flavonoids, Phaseolus vulgaris, reflectance, UV-B radiation 相似文献
13.
The Growth and Development of the Wheat Apex: The Effects of Photoperiod on Spikelet Production and Sucrose Concentration in the Apex 总被引:2,自引:0,他引:2
Spring wheat (Triticum aestivum cv. Warimba) plants were grownin a controlled environment (20°C) in two photoperiods (8or 16 h). In the first instance, plants were maintained in eachof the photoperiods from germination onwards at the same irradiance(375 µE m2 s1). In the second case, allplants were grown in a long photoperiod until 4 days after double-ridgeinitiation when half the plants were transferred to a shortphotoperiod with double the irradiance (16 h photoperiod at225 or 8 h at 475 µE 2 s1). The rates of growth and development of the apices were promotedby the longer photoperiod in both experiments. Shoot dry weightgain was proportional to the total light energy received perday whereas the dry weight of the shoot apex increased withincreasing photoperiod even when the total daily irradiancewas constant. The principal soluble carbohydrate present in the shoot apexwas sucrose, although low concentrations of glucose and fructosewere found in the apices of long photoperiod plants late indevelopment. Sucrose concentration was invariably greater inthe slow-growing apices of short photoperiod plants, but roseto approach this level in the long photoperiod plants when theterminal spikelet had been initiated. Triticum aestivum, wheat, apex, spikelet initiation, photoperiod, flower initiation 相似文献
14.
The effects of population density on the growth of H. aspersaMÜller var. maxima under controlled environmental conditionswere examined. Inhibitory effects on snail growth and maturityresulting from increased population density, between 100800snails m2 of floor area, were observed for a range ofcontainer cleaning frequencies. At all population densities,enhanced snail growth was observed when the frequency of containercleaning was increased to a two-day interval. No significantdifferences were recorded, following 19 weeks growth, betweenfinal mean weights of snails from containers cleaned less frequently.The lowest snail mortality was consistently recorded at thelowest population density in the most frequently cleaned containers.At all snail population densities three phases of growth wereobserved: (a) lag (05 weeks), (b) rapid (615 weeks)and (c) stable (16 weeks and over). During the first three weeksof growth, high population density had a positive effect ondiet consumption, food conversion efficiency and snail growth.Adverse population density effects increased progressively duringphase (b), typically following 9 weeks growth. Juvenile snailstransferred from high to low population densities during phase(b) continued to exhibit slower growth rates associated withhigh population densities. Food conversion efficiency of snailsin all treatments decreased throughout the experimental periodbut with no overall effect of container cleaning frequency apparent.Inherent growth variability of sibling snails was unaffectedby population density or container cleaning frequency. The importanceof the results for intensive snail culture is discussed. (Received 23 June 1994; accepted 1 December 1994) 相似文献
15.
Salt Tolerance in the Triticeae: Growth and Solute Accumulation in Leaves of Thinopyrum bessarabicum 总被引:7,自引:0,他引:7
GORHAM J.; MCDONNELL E.; BUDREWICZ E.; JONES R. G. WYN 《Journal of experimental botany》1985,36(7):1021-1031
Gorham, J., McDonnell, E., Budrewicz, E. and Wyn Jones, R. G.1985. Salt tolerance in the Triticeae: growth and solute accumulationin leaves of Thinopyrum bessarabicum.J. exp. Bot. 36:10211031. The diploid wheatgrass Thinopyrum bessarabicum was found towithstand prolonged exposure to 350 mol m3 NaCl in hydroponicculture. During the gradual addition of salt to the externalmedium, osmotic adjustment was rapidly achieved by the accumulationof Na and Cl. Following osmotic adjustment constant leaf Naand Cl concentrations were maintained, and K was retained ata high level. Thinopyrum bessarabicum may be described as anosmoconformer, adjusting its internal osmotic pressure to 400500mOsmol kg1 above that of the external medium in hydroponicculture. Both slower shoot initiation and reduced leaf lengthcontributed to the reduced growth rates at higher salinities.Leaf width was not affected. Increasing salinity resulted inincreases in leaf concentrations of phosphate, glycinebetaine,sucrose and proline, and in decreases in the concentrationsof nitrate, sulphate, magnesium, calcium, total amino acidsand organic acids. Thinopyrum bessarabicum exhibits salt tolerancecharacters which may be useful in wheat breeding. Key words: Salt stress, solute accumulation, osmotic adjustment, Thinopyrum 相似文献
16.
Larval age, growth and mortality in the oceanic squid Sthenoteuthis pteropus (Cephalopoda, Ommastrephidae) from the eastern tropical Atlantic 总被引:2,自引:0,他引:2
Laptikhovsky Vladimir V.; Arkhipkin Alexander I.; Golub Alexander A. 《Journal of plankton research》1993,15(4):375-384
An investigation was carried out on larvae of the oceanic tropicalsquid Sthenoteuthis pteropus in the equatorial Atlantic (230'N7S;12W830'E) The age of the larvae was calculated from thestatolith microstructure of 20 larvae; mortality was estimatedfrom the size structure of 1128 larvae. The larval stage lasts3238 days. At ages ranging from 14 to 38 days. the dailyrelative growth rates of mantle length decrease from 7.5 to2.8% day1 and from 1416 to 5.8% of body weightday1 At age 1224 days, mortality rates were estimatedusing both raw catch data and corrected data accounting fornet avoidance. The mean value of raw mortality rates was 0.189,the corrected value was 0.158. During the proboscis division(transformation of the larva into juvenile) at age 2535days, a sharp decrease in larval growth rates and a simultaneousincrease in mortality rates (raw 0.443, corrected 0.379) wereobserved. 相似文献
17.
The cell cycle in Silene coeli-rosa shoot apices was measuredto test whether or not early components of the floral stimulus,produced during the 2nd and 3rd long days (LD) of an inductiveLD treatment, resulted in an increase in the duration of G2phase in constant 2024 h cell cycles. Plants were grownat 20°C in short days (SD) of 8 h light and 16 h darknessfor 28 d (day 0). Starting on day 0, plants were given SD or3 LD each comprising an identical 8 h day and 16 h photo-extension,or 3 dark-interrupted (d.i.) non-inductive LD, interrupted at1700 h of each day with 1 h of darkness. The cell cycle (percentagelabelled mitoses method) and changes in cell number were determinedin the shoot apical meristem. During days 12 of the SDtreatment, the cell cycle and mean cell generation time (MCGT)was 18 and 32 h, respectively, giving a growth fraction of 56%.During days 23, the cell cycle and MCGT shortened to15 and 23 h, respectively (growth fraction = 65%). During days12 of the LD and d.i. LD treatments, cell cycles andMCGTs were 910 and 2729 h, respectively, resultingin smaller growth fractions (about 33%). Thus, shortened cellcycles and altered growth fractions occurred regardless of whetheror not the treatment was inductive. The LD treatment resultedin a marked shortening of G1 and, to a lesser extent, S-phase,whilst G2 remained constant. These changes were consistent withincreases in the proportion of cells in G2 during the photoextensionof each LD which were suppressed during the comparable periodsof the d.i. LD treatment. The latter treatment resulted in eachphase occupying virtually identical proportions of the cellcycle as in the SD treatment. Thus, the unique cell cycle responsesto the initial part of the inductive LD treatment were increasesin the proportion of cells in G2 coupled with G1 and G2 beingof similar duration. Cell cycle, mean cell generation time, shoot apex, Silene coeli-rosa 相似文献
18.
One specimen of the sand-burrowing nudibranch Armina tigrinaRafinesque was collected from South Carolina in June. The specimendeposited a single egg mass of approximately 6500 white eggswhich developed into lecithotrophic veligers in 8 days at 23°C.Of the veligers which metamorphosed, 9 lived 45.5 months(i.e. the life cycle was subannual). Eight individuals reachedsexual maturity in about 80 days. Copulation began at a bodylength of 24 mm and oviposition at 28 mm. During the 1.5 monthegg-laying period, each individual laid 24 wavy egg masseswith 20007000 eggs per mass. Death followed oviposition.Average growth rate of fed and starved pre-ovipositional nudibranchswas 3.4% and 0.9% per day respectively. Growth rate of ovipositingspecimens was 0.6% or less per day. Based on average feedingrates, each nudibranch consumed approximately 1.6 g damp weightof Renilla reniformis (one small colony) between metamorphosisand egg laying and 6.1 g damp weight (about two average colonies)from egg laying to death. Feeding efficiency is presumably increasedby interlocking and abutting radular teeth. Egg diameters reportedfor Armina tigrina from South Carolina and Florida were 199µm and 82 µm respectively. This difference suggeststhe existence of two species of Armina or ne species with twogeographically separated developmental types.
Current address: Marine Science Institute, Northeastern University,Nahant, Massachusetts 01908. U.S.A. (Received 10 April 1980; 相似文献
19.
Ammonium release rates by individual marine copepods (Eucalanuspileatus) were examined kinetically over successive 10-min intervalsafter the animals were exposed to three concentrations of thediatom Thalassiosira fluviatilis as food. Food concentrationsspanned those expected in the natural environment. "Well-fed"(3 mm3 T. fluviatilis l1) copepods released ammoniumsignificantly (p<0.05) faster than those fed zero or lowconcentrations of food, but differences were not dramatic. Meanexcretion rates (± SE) for animals removed from foodfor 18 22 h [30 ± 6 nmol NH4(mg ash free dry weight)1h 1] were 60% of those for "well-fed" animals [49 ±8 nmol NH4 (mg ash free dry weight)1 h1]. Continuedhigh release rates after extended periods without food suggestthat E. pileatus must feed frequently in nature to maintainan adequate nitrogen balance. Depending on food concentration,animals released ammonium at rates ranging from 40 to > 100%of their N ingestion rates over the previous 1822 h.Long-term (46 h) kinetic excretion experiments with "well-fed"animals indicated that, on average, release rates decreasedwith time after food removal, but patterns varied among individualcopepods. In addition to ammonium release, o-phthalaldehydereactive amino acid nitrogen was occasionally released by E.pileatus in large "spurt events" lasting from 20 to 60 min.
1GLERL Contribution No. 283 相似文献
20.
Under short-day conditions the growth or the production of fronds in Lemna gibba G3 was stimulated by KIN (105 M);the longer the nyctoperiod, the greater the stimulation was.Under long-day conditions KIN was slightly inhibitory for thefirst 2 days, but promotive thereafter. IAA (105 M) reversedthe growth inhibition by KIN in long-days, and DCA (104to 106 M) and also CA (104 to 106 M), althoughless effectively, cancelled the growth promotion by KIN in short-days.DCA (105 M) little altered the KIN inhibition in thefirst 2 days of light culture, nevertheless it alleviated strikinglythe KIN promotion in the subsequent illuminated days. These and relevant findings explained the above-described promotionand inhibition by KIN of the duckweed growth in terms of invivo level of a cofactor (probably auxin) which may be underthe regulative influence of photoperiodic conditions given.Moreover, some bearing of the above conclusion on floweringmechanism in this long-day duck-weed was suggested. (Received September 12, 1966; ) 相似文献