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1.
The calanoid copepod, Eudiaplomus graciloides, was reared fromegg to adult on uni-algal diets (0.1. 0.5 and 2.5 mg dry wt11) 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 11). 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 day1in the early to mid juvenile stage (N1 - C4) and 0.11 day1in the late juvenile to early adult stage (C4-A). At 14.5°Cthe corresponding growth rate constants were 0.10 and 0.08 day1.Similar growth rates were found at uni-algal concentrationsof 0.5 and 2.5 mg dry wt I1, and it was argued that thethreshold concentration for growth in Eudiaptomus was closeto 0.1 mg dry wt I1. The clearance (C, ml h1)of copepodites was measured on the uni-algal diets. The constantsof the regression (C = aWb) were: a = 0.125, b = 0.858 (2000C. reinhardtii ml1), 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 h1)was measured in individuals reared on the mixed diet. The constantsof the regression (R = aWb) 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. 相似文献
2.
Population structure and production of Eudiaptomus gracilis(G.O. Sars) have been calculated from daily measurements inLake Balaton for one month during each summer in 1975 and 1977.Fecundity was different in the two years 6.98 ? 1.16 and 10.68? 1.42 in 1975 and 1977, respectively. A total of 80% and 64%of the population were made up of larvae in 1975 and 1977, respectively.The ratio of males to females was 1:1.63 and 1:1.1, respectively.In 1975 it was possible to follow the development of cohorts,19 20 days in the former year, 17 20 days in thelatter. In both years of examination 80 83% of naupliiand 1215% of copepodites were eliminated. Daily net biomassproduction was 6.88 mg (dry wt.)/m3 in 1975 and 1.94 mg (drywt.)/m3 in 1977. Ratios of eggs, nauplii and copepodites indaily production was 1:2.4:1.4 in 1975 and 1:1.0:1.0 in 1977.The daily potential biomass production were 34.40 mg (dry wt.)/m3 and 10.28 mg (dry wt.)/m3 and the elimination were 80 and81 wt.%, respectively. P/B ratio allowing for net productionvalues was nearly the same in both periods of investigation(0.12 and 0.099 respectively). 相似文献
3.
Ammonium release by juveniles and adult females of the subtropical marine copepod Eucalanus pileatus
Release rates of ammonium by nauplii, copepodid stages (CIIand CIV) and adult females of the marine copepod Eucalanus pileatusat 0.1 and 3.0 mm3 11 of the diatom Thalassiosira weissflogiiwere determined at 20°C. When food was abundant, animalsof all stages released ammonium at similar rates per unit ash-freedry weight [2435 nmol NH4(mg AFDW)1 h1on average]. At low food levels, CIVs and adult females releasedammonium significantly more slowly than did the naupliior CIIs[28 and 24 versus 51 and 50 nmoles(mg AFDW)1h1].Because they weighed less (50%), low-food nauplii and CIIs hadhigher calculated weight-specific excretion rates, than high-foodones of the same stage but release rates per copepod were similarin the two food regimens. In contrast to the early life stages,the CIVs and adult females released less ammonium per copepodin the low-food than in the high-food environment.
1GLERL - Contribution No. 380 相似文献
4.
Juvenile growth and development rates for Metridia pacifica,one of the dominant larger copepods in the subarctic Pacific,were investigated from March through October of 20012004in the northern Gulf of Alaska. The relationship between prosomelength (PL, µm) and dry weight (DW, µg) was determined:log10 DW = 3.29 x log10 PL 8.75. The stage durationsof copepodites ranged from 3 to 52.5 days but were 815days under optimal condition. Seasonally, growth rates increasedfrom March to October and typically ranged between 0.004 and0.285 day1, averaging 0.114 ± 0.007 day1(mean ± SE). After standardization to 5°C (Q10 of2.7), growth rates averaged 0.083 ± 0.005 day1and were significantly correlated to chlorophyll a, with saturatedgrowth rates of 0.149 day1 for C1C3, 0.102 day1for C4C5 and 0.136 day1 for all stages combined.Measured juvenile growth rates were comparable with specificegg production rates in this species. The comparisons of ourrates in this study with those predicted by the global modelsof copepod growth rates suggested that further refinement ofthese models is required. 相似文献
5.
Experimental and Field Studies of Mesocyclops notius (Copepoda: Cyclopoida) from a Subtropical Chinese Lake, Lake Donghu 总被引:2,自引:0,他引:2
This paper reports experimental and field studies on the cyclopoidMesocyclops notius from subtropical Lake Donghu close to theYangtze river. Mesocyclops notius, a dominant crustacean zooplankterthroughout tropical Australia, was previously considered tobe endemic to Australia, but recently, Mesocyclops leuckartiin Lake Donghu was re-identified as M. notius. Laboratory cultureexperiments were conducted to reveal the effect of temperature(15, 20, 25 and 30°C) on the development, growth and reproductionof M. notius. Temperature was inversely related to developmenttimes of eggs, nauplii and copepodites, body length and physiologicallongevity of adults, and brood size. Body length and physiologicallongevity of females were greater than those of males at thesame temperature. No reproduction took place at 15°C. Productionand seasonal cycles of M. notius during 19801982 werestudied at two sampling stations of Lake Donghu. At the mid-lakestation, the annual production and production/biomass (P/B)ratio of M. notius varied between 6.0 and18.0 g dry wt m2year1 and 74.6 and 95.5, respectively. Mesocyclops notiusreached their highest density peaks in the warm months (JulyOctober),with a maximum density of 1256 individuals l1 at a littoralsite. No reproduction and recruitment by M. notius took placeduring the cold months (DecemberMarch) when the temperatureof the lake water was <15°C. Mesocyclops notius weremore abundant at a littoral station than at a pelagic station,possibly due to different food availability. The higher male:femalesex ratio of M. notius at the littoral station was most likelycaused by size-selective fish predation on larger females. 相似文献
6.
The geographical distribution, seasonal life cycle, biomassand production of a copepod Calanus sinicus were investigatedin and around Kii Channel of the Inland Sea of Japan. The distributioncenter of the population was located in Kii Channel. The patternof the seasonal variation in abundance of copepodites and adultsdiffered geographically within the study area. In Kii Channel,for example, they were most abundant in June-July and leastabundant in October. Over the study area, the reproduction ofC.sinicus took place throughout the year, indicating the absenceof diapause phase. In adults, females usually outnumbered males.The prosome length of late copepodites and adults was inverselycorrelated with water temperature. The annual mean biomass washighest (4.87 mg C m3 or 231 mg C m2) in Kii Channel.The potential production rate of the population exhibited aseasonal variation more or less similar to that of the biomassand the annual potential production rate was 358 mg C m3year1 (14.1 g C m2 year1) in Kii Channel.Daily production and biomass (P/B) ratios in Kii Channel increasedfrom 0.11 at 11.8°C to 0.26 at 20°C. 相似文献
7.
Biomass and production of the major dominant crustacean zooplankton in a tropical Rift Valley lake, Awasa, Ethiopia 总被引:1,自引:0,他引:1
Seasonal variation of the biomass (B), production (P) and P/Bratio of the numerically dominant crustaceans in Lake Awasa(Mesocydops aequatonalis stmilts, Thermocyclops consunilis andDiaphanosoma exisum) were studied during 1986 and 1987. Quantitativenet samples (64 (xm mesh) were taken at three stations on 10day intervals throughout 1986, and the dry weights and developmenttimes for each life stage were obtained from laboratory measurementsand cultures Total biomass of most of the dominant crustaceans,determined from 390 samples during 1986, was 44.85 mg m3(dry weight, DW) with adult females of Mesocyclops making >43.5%.Alona diaphana, another common crustacean, is dealt with ina separate paper, as are the Rotifera. Production of the dominantcrustaceans during 1986 was estimated by the growth incrementsummation (Winberg) and instantaneous growth (Ricker) methodsThe annual integrated production of the two dominant cyclopoidsis 535.2 mg (DW) m3 (Winberg) while annual crustaceanproduction totals 2.5 g (DW) m3 (Ricker) The mean annualP/B ratio for individual species and stages varied from 221.0for Diaphanosoma, to 121.7-143.0 for nauplii and 9.8187 for copepodites of the cyclopoids It was 55 8 for the dominantzooplankton species Low or high zooplankton production and biomassturnover rates (P/B) cannot be used to characterize all tropicallakes consistently However, production per unit biomass is likelyto be higher in tropical lakes. 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.
Determining the mass density of marine copepods and their eggs with a critical focus on some of the previously used methods 总被引:3,自引:0,他引:3
We collected Calanus finmarchicus copepodites CIV, CV and CVIfemales in a deep fjord on the west coast of Norway during April1996, May 1997 and November 1998. Eggs of C. finmarchicus andCalanus glacialis were collected during May 1989 in the BarentsSea. The sinking speeds of animals and eggs were measured ina homogeneous column with seawater of known density, and Stokeslaw was applied to estimate their mass density. Also the densitycontrast between the organisms and seawater was calculated.The mean mass density of C. finmarchicus ranged from 1.0274to 1.0452 g cm3. During spring copepodite stage CV hada significantly lower mean mass density (1.0345 g cm3)compared to CIV (1.0381 g cm3) and CVI females (1.0408g cm3). Copepods collected during winter had a distinctlylower mass density. The sinking speed of C. glacialis eggs followeda unimodal distribution, with a mean of 25.9 m day1,while sinking speeds of C. finmarchicus eggs were bimodal, thetwo groups of eggs having a mean sinking speed of 23.3 m day1and 35.4 m day1 respectively. Correspondingly the meanmass density was 1.0556 g cm3 for C. glacialis eggs andfor the two groups of C. finmarchicus eggs 1.0639 g cm3and 1.0812 g cm3. Results of earlier work, particularlyusing density gradient methods to determine mass density ofzooplankton, are critically reviewed, and it is suggested thatthis method should not be used to determine the mass densityof small organisms the size of C. finmarchicus. 相似文献
10.
Recent studies indicate that Oithona spp. contribute significantlyto total copepod biomass. Little is known, however, about theirecological significance, particularly in the case of the estuarineOithona nana. A study comprising three sites within SouthamptonWater was conducted to evaluate the late-stage copepodite/adult(stages IVVI) O. nana community, using 120-µm meshnets. Although present throughout the estuary, there was a strikingspatial gradient with O. nana most common in the upper estuary.A clear seasonal pattern was observed with O. nana as the mostabundant copepod species from late summer until early winter.It comprised 61% of all copepods recorded, with a biomass of757.22 mg C m3. Production estimates of O. nana werederived from the instantaneous-growth approach,using appropriate growth equations. The estimated productionof O. nana ranged from 1.50 mg C m3 year1 withinthe lower estuary to 146.77 mg C m3 year1 in theupper estuary. In the upper estuary, this compares with productionrates of 187.47 mg C m3 year1 for all Acartiacongeners (excluding nauplii), the most common calanoid genus.Throughout the estuary, O. nana annual production represented18% of total copepod production clearly indicating that, atleast in the upper estuary, O. nana production may be directlycomparable with calanoid production. 相似文献
11.
The production and ingestion of faecal pellets by nauplii of marine calanoid copepods 总被引:2,自引:0,他引:2
The downward transport of organic matter as zooplankton faecalmaterial is influenced by copepods which fragment, ingest andrecycle some of the pellet contents. Most of this activity hasbeen attributed to the later copepodite stages and the adults,but little is known about the role of nauplii. Stage-relateddefaecation rates during the naupliar development of two speciesof copepod, Calanus helgolandicus and Pseudocalanus elongatus,were quantified in a series of laboratory experiments. The productionof faecal material commenced soon after the appearance of theNIII in both species and increased throughout naupliar development.The causes of the increase were the formation of larger pelletsby later stages in Calanus and an increased rate of productionby Pseudocalanus. Calanus nauplii, when supplied with algalfood at concentrations that would support full naupliar development,ingested or broke up the pellets of the smaller Pseudocalanusspecies at rates of 1.15 pellets nauplius1 h1This consumption increased to 2.96 pellets nauplius1h1 when the concentration of algal food was reduced toa limiting level. Pseudocalanus was not able to consume thepellets of Calanus. Ingestion of Pseudocalanus faecal pelletsby Calanus could supply a nutritional benefit to a food-limitednauplius. 相似文献
12.
Feeding on natural plankton populations and respiration of thesmall cyclopoid copepod Oithona similis were measured duringthe warm season in Buzzards Bay, Massachusetts, USA. AlthoughO.similis did not significantly ingest small autotrophic andheterotrophic flagellates (28 µn), this copepodactively fed on >10 µm particles, including autotrophic/heterotrophic(dino)flagel-lates and ciliates, with clearance rates of 0.030.38ml animal1 h1. The clearance rates increased withthe prey size. O.similis also fed on copepod nauplii (mainlycomposed of the N1 stage of Acartia tonsa with a clearance rateof 0.16 ml animal1 h1. Daily carbon ration fromthe combination of these food items averaged 148 ng C animal1day1 (41% of body C day1), with ciliates and heterotrophicdino-flagellates being the main food source ({small tilde}69%of total carbon ration). Respiration rates were 0200.23µl O2 animal1 day1. Assuming a respiratoryquotient of 0.8 and digestion efficiency of 0.7, the carbonrequirement for respiration was calculated to be 125143ng C animal1 day1, close to the daily carbon rationestimated above. We conclude that predation on ciliates andheterotrophic dinoflagellates was important for O.similis tosustain its population in our study area during the warm season. 相似文献
13.
Lotocka Maria; Styczynska-Jurewicz Ewa; Bledzki Leszek A. 《Journal of plankton research》2004,26(2):159-166
Carotenoid contents and composition were studied in three successivedevelopmental groups of copepod populations from the southernBaltic Sea. Samples were collected with >80% prevalence ofany one of three developmental groups: (i) nauplii, (ii) copepodidsIIII and (iii) copepodids IVV and also adultsof Pseudocalanus acuspes Giesbrecht and Acartia spp. (Copepoda:Calanoida). Samples were collected over the years 19911999from May to September at six sampling sites in the southernBaltic Sea. The carotenoids were analyzed by means of reverse-phasehigh-performance liquid chromatography (RP-HPLC). The mean totalcarotenoid concentrations (astaxanthin, astaxanthin esters,canthaxanthin and other carotenoid unidentified and derivedfrom the diet) found in three groups of developmental stagesfor P. acuspes were 556 µg g-1 dry weight (d.w.) in naupliarstages, 791 µg g-1 in copepodids IIII, and 868µg g-1 in copepodids IVV and adults. The averagecarotenoid concentrations in Acartia spp. were 619, 764 and872 µg g-1 d.w., respectively. Significant changes wereobserved in the proportion of carotenoids of separate developmentalgroups. Astaxanthin and canthaxanthin occurred in all developmentalgroups, with the evident dominance of astaxanthin. However,copepodid groups IIII, and especially IVV includingadults, showed an increased proportion of astaxanthin esters.This suggests that astaxanthin is the main active carotenoidin copepod metabolism. It acts most probably as an efficientfree radical quencher and may be involved in rapid metabolismof stored lipids in mostly unfeeding young nauplii. The feedingstages (late nauplii and copepodids IIII and IVV)are evidently able to metabolize this pigment by esterificationand further degradation. 相似文献
14.
Miralto A.; Ianora A.; Guglielmo L; Zagami G.; Buttino I. 《Journal of plankton research》1998,20(12):2369-2378
In situ rates of egg production and hatching success are reportedfor Calanus simillimus, one of the most abundant calanoid speciesin peri-Antarctic regions, during the Italian Italicscruise in the Straits of Magellan in March-April 1995. Low fecundity(8.6 eggs female1 day1) and fecal pellet production(0.8 fecal pellets female1 day1) in this periodindicate that the species was feeding very poorly. Sixty-sixof the 126 females sampled did not produce eggs and 80 of thesedid not produce any fecal pellets during the 24 h period ofincubation. Striking abnormal naupliar and embryonic developmentwas recorded in 81.8% of the eggs spawned. Aberrant eggs didnot undergo normal cleavage, and failed to develop to hatching.Deformed nauplii were asymmetrical and presented strong anatomicalanomalies in the total body length and number of swimming appendages.These results are discussed in the light of recent findingson the causes of low hatching success in copepods. 相似文献
15.
Eudiaptomus gracilis makes up 3040 and 8090% ofthe zooplankton in Lake Balaton during the summer and the winterrespectively. More than half of the species population consistsof nauplii We studied feeding and size selectivity of naupliiin suspensions which contained polystyrol latex beads in a concentrationdose to the natural seston. Guts of NI nauplii were free ofboth beads and remnants of natural food Of NIINVI nauplii,6787% took in beads. Older animals consumed more andlarger particles. The maximum diameter of ingested beads reached29 µm On an average, NII nauplii took in 128 µm3of beads in 10 min, whereas older animals consumed 615900µm3. The clearance rate remained below 0 01 µl h1NII nauplii strongly preferred 1 2 µm particles Oldernauplii did not show any preference or selected only slightlyfor the smallest particles. Nauplii rejected 411 µmbeads. In some cases a weak positive selection could be observedtoward 12 µm or larger beads. 相似文献
16.
Relationship Between N:P Ratio and Growth Rate During the Life Cycle of Calanoid Copepods: An in situ Measurement 总被引:3,自引:0,他引:3
Carrillo Presentacion; Villar-Argaiz Manuel; Medina-Sanchez Juan M. 《Journal of plankton research》2001,23(5):537-547
The mean nitrogen and phosphorus contents of the calanoid copepodMixodiaptomus laciniatus Lilljeborg were measured to the stagelevel throughout the ice-free period of a high mountain lake.Our results indicate large intraspecific variations in calanoidelemental composition. While mean N as dry weight increasedfrom 3.0 ± 1.3 in nauplii to 6.0 ± 2.1 in copepodites,mean P content showed the opposite trend, varying intraspecificallyfrom 0.98 ± 0.26% in nauplii, to 0.87 ± 0.21%in copepodites and 0.51 ± 0.16% in adults. Thus, themean N:P ratio increased ontogenetically from 3.3 in naupliito 13.3 in copepodites and 24.6 in adults. Two ontogenetic parameters,the growth rate and body size, were associated with zooplanktonstoichiometry. Among all 11 copepod stages, growth rate waspositively related to %P and negatively related to %N and N:Pratio. A two-part analysis of these relationships, before andafter metamorphosis, showed that the nauplii growth rate explainednearly all the variance in naupliar P content. A high P contentin nauplii may reflect a high content of RNA, translating intorapid growth rates. Overall, these results tend to support thehypothesis linking specific growth rate with P content for copepods,but these results also suggest that the validity of this hypothesisis robustness when differences in the life history of copepodsas a consequence of metamorphosis are accounted for. We suggestthat the intra-stage variation in P content is associated withpeaks of intensive metabolic activity during the process ofmolting in copepods, and we emphasize the importance of newempirical evidence to examine this hypothesis further. 相似文献
17.
Tada Kuninao; Pithakpol Santiwat; Yano Rumiko; Montani Shigeru 《Journal of plankton research》2000,22(6):1203-1211
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 cell1 witha mean value of 353 ng C cell1, or 1.12 to 2.67 fg Cµm3 with a mean value of 1.98 fg C µm3.The nitrogen content ranged from 36.0 to 232 ng N cell1with a mean value of 131 ng N cell1, or 0.499 to 0.910fg N µm3 with a mean value of 0.694 fg N µm3.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 cell1,41.8 ng N cell1) for starved cells, whereas it was extremelyhigh (528 ng C cell1, 205 ng N cell1) 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. 相似文献
18.
Biomass, feeding and production of Noctiluca scintillans in the Seto Inland Sea, Japan 总被引:1,自引:0,他引:1
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 1345 cells 11(temporalaverage = 93 cell11) and 0.149.6 µg C l1(temporalaverage = 13.8 µg C l1; 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 >0.15.2 µg C l1 day1(temporalaverage = 1.4 µg C l1 day1; 64% of the productionof calanoid copepods during the same period). Diatom clearancerates by N.scintillans were in the range 0.100.35 mlcell1 day1, and the phytoplankton population clearanceby N.scintillans was >12% day1. 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. 相似文献
19.
Nodulated white clover plants (Trifolium repens L. cv. Huia)were grown as simulated swards for 71 d in flowing nutrientsolutions with roots at 11 C and shoots at 20/15 C, day/night,under natural illumination. Root temperatures were then changedto 3, 5, 7, 11, 13, 17 or 25 C and the total N2, fixation over21 d was measured in the absence of a supply mineral N. Alltreatments were subsequently supplied with 10 mmol m2NO2 in the flowing solutions for 14 d, and the relativeuptake of N by N2, fixation and NO3 uptake was compared.Net uptake of K+ was measured on a daily basis. Root temperature had little effect on root d. wt over the 35-dexperimental period, but shoot d. wt increased by a factor of3.5 between 3 and 25 C, with the sharpest increase occurringat 711 C. Shoot: root d. wt ratios increased from 25to 68 with increasing temperature at 725 C. N2-fixationper plant (in the absence of NO2 ) increased with roottemperature at 313C, but showed little change above13 C. The ratios of N2 fixation: NO2 uptake over 14d (mol N: mol N) were 0.470.77 at 37 C, 092154at 1117 C, and 046 at 25 C, reflecting the dominanceof NO3 uptake over N2 fixation at extremes of high andlow root temperature. The total uptake of N varied only slightlyat 1125 C (095110 mmol N plant1),the decline in N2 fixation as root temperature increased above11 C was compensated for by the increase in NO 3 uptake.The % N in shoot dry matter declined with decreasing root temperature,from 32% at 13 C to 15% at 3 C. In contrast, concentrationsof N expressed on a shoot water content basis showed a modestdecrease with increasing temperature, from 345 mol m3at 3 C to 290 mol m3 at 25 C. Trifolium repens L, white clover, root temperature, N2 fixation, potassium uptake, nitrate uptake, flowing solution culture 相似文献
20.
The nutritional value of different sized fractions of naturalplankton was investigated for the growth of Eodiaptomus japonicusBurckhardt by comparing the development of its naupliar andcopepodid stages fed on differentially fractionated planktonicassemblages of a eutrophic pond, at 20°C. Water filteredthrough a 0.8 µm Nuclepore filter, containing mainly smallcoccoid bacteria (0.450.6 µm in cell diameter),at a concentration of 82.7 µg C 11 could not supportthe development of E.japonicus. The 3 µm filtered water,containing bacteria and picoalgae. at a total concentrationof 259 µg C 11, supported development but not eggproduction. The 20 µm filtered water, containing bacteria,picoalgae and large algae, at a total concentration of 2600µg C 11, supported rapid development of the juvenilesand continuous egg production by the adults. The separated 320µm fraction, containing only large algae, could not supportthe development at concentrations of 131 and 196 µg C11. However, the same rapid development of the juvenilesand continuous egg production by adults occurred at all of thetested concentrations between 261 and 3920 µg C11of the large algae. The results suggest that E.japonicus favoursalgae larger than 3 µm during its complete lifespan, andthat the threshold food concentration for its development variesbetween 200 and 250 µg C 11. 相似文献