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1.
Assimilation and release of 14C in a tropical strain of Cryptomonas obovata (Cryptophyceae) exposed to several irradiances 总被引:1,自引:0,他引:1
Carbon assimilation (14C) and dissolved organic
carbon (DO14C) release by a tropical strain of
Cryptomonas obovata was studied. Cells were exposed to
a range of irradiances (0-2000 mol
m-2 s-1) using axenic batch
cultures in the laboratory (Ek = 180 mol
m-2s-1). At up to 2000
mol m-2s-1, carbon
assimilation was not inhibited and an acclimation to low irradiances was
observed. DO14C release was dependent on carbon
fixation and no increase was detected under high irradiances. To determine
particulate organic carbon (PO14C) loss and
CO14C release cells acclimated to 350 mol
m-2 s-1 were incubated during
4 h at 35, 350, 850 and 1900 mol m-2
s-1. DO14C release was
responsible for 30% of the PO14C loss at 1900
mol m-2s-1. High-
and low-molecular-weight (HMW, LMW) compounds were released by
C.obovata under all irradiance conditions. However,
increased release with exposure time was observed only for the HMW
compounds.
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2.
Long-term phytoplankton studies in the Bahí Blanca estuary
showed a seasonal pattern characterized by a winter-early spring bloom of
diatoms dominated by Thalassiosira curviseriata.
Laboratory experiments were carried out to elucidate the influence of
irradiance, temperature and salinity on the growth rate of
T.curviseriata. The maximum daily growth rate was 1.93
divisions at 20C. The compensation point
(Ic) varied from approaching zero to 3.08 mol m-2
s-1, values were
-0.020-0.070 divisions mol-1, and the
calculated Ik (the irradiance at which initial slope
line reaches the maximum rate of growth) varied between 32 and 36
mol m-2 s-1. Growth
became light saturated (when max) between 70 and 80
mol m-2 s-1, and was
inhibited at -150 mol m-2
s-1 at all temperatures (5-20°C). The range
of temperatures at which T.curviseriata can grow
(5-20°C) coincides with the temperature range over which it is
found in the field. In contrast, the thermal optimum for growth,
20°C, was higher than the range of temperatures (between 5 and
10°C) characteristic of the winter-early spring bloom in
Bahí Blanca estuary. The mean specific growth rate of
T.curviseriata was not affected by salinity over the
tested range between 25 and 40 p.p.t. Field observations and experimental
data support the characterization of T.curviseriata as
a eurythermal and euryhaline species adapted to growth at relatively low
light intensity. These characteristics may explain the ability of
T.curviseriata to flourish seasonally when light
conditions are apparently limiting and its presence almost year round under
variable conditions of temperature and salinity.
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3.
Observations on the first red tide off Kuwait, Arabian Gulf, yielded high
biomass [55.4-262.7 g chlorophyll (Chl)
a l-1] and primary production
(507.9-571.2 g C
h-1l-1), comparable with some
of the highest values reported. There were contrasting changes in the
carbon assimilation ratios, composition of the phytoplankton and the
contribution of nanoplankton (<20 m) between 11 and 12 May.
On 11 May, carbon assimilation by nanoplankton was 2.2 g C
(g Chl a)-1
h-1, but increased to 9.2 g C (g C
(g Chl a)-1
h-1 the following day. Nanoplankton contributed 56
and 9% of Chl a and production, respectively, on 11
May, while net plankton (>20 m) accounted for >65%
of the biomass and primary production on 12 May. Picoplankton (<3
m) contributed <8% of Chl a and
<3% of production. Frequent sampling will be necessary to capture
such dynamic changes and ephemeral events in these waters.
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4.
Short communication. Carbon:nitrogen ratios of Baltic Sea copepods-indication of mineral limitation?
The carbon (C) and nitrogen (N) content and the C:N ratio of two common
calanoid copepods, Eurytemora affinis and
Acartia bifilosa were measured during spring and
summer at the SW coast of Finland, northern Baltic Sea. The C:N ratio of
both copepod species was slow and stable (4-4.5), irrespective of sampling
time, which implies N limitation at least during intermediate to high food
concentrations in spring and early summer. In addition, experiments were
conducted to reveal whether the diet of copepods affects their C and N
content. Adding green algae Brachiomonas submarina in
concentrations of 50-500 g C
l-1 to <100-m-filtered sea water did
not significantly increase copepod C or N content in 3 day experiments.
However, the C and N contents of E.affinis eggs were
2 times higher in high food concentration, which may increase
survival of eggs and nauplii.
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5.
The occurrence of early larval stages of Brama brama
and Coryphaena hippurus is reported for the first time
in Adriatic waters. Two larvae of B.brama between 4.36
and 5.00 mm, and two larvae of C.hippurus between 4.75
and 4.95 mm standard length, were found in ichthyoplankton collections
taken off the River Neretva estuary (43010N,
17°250E) and station Stoncica, island Vis
(43°000N,
16°20E) (eastern middle Adriatic),
respectively. The capture of both species (B.brama) in
August 1998; C.hippurus in May 1998) is in agreement
with their proposed seasonal life cycle in the Adriatic Sea.
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6.
The raphidophyte flagellate Chattonella marina was
successfully cultured from Boston Bay (South Australia), coincident with
mass mortality of farmed bluefin tuna (Thunnus
maccoyii) in April 1996. Grown under laboratory conditions at
150 mol m-2
s-1 irradiance, optimal growth (>0.5
day-1) occurred at a temperature of 25C and a salinity of 30 p.s.u., but good growth
(>0.3 day-1) also occurred between a
temperature of 10 and 30°C and at a salinity of 15-45 p.s.u.
However, cultures grow much faster at an irradiance of 450 mol
m-2 s-1 (1.08
day-1). While Australian
C.marina had similar temperature and salinity
requirements as well-studied Japanese cultures from the Seto Inland Sea,
the Australian strains exhibited a light saturation level for growth four
times higher than that reported from Japan (150 mol
m-2 s-1). An adaptation to
higher light intensities was reflected in higher concentrations of
microsporine-like amino acids in the Australian strains. The different
light adaptation phenotypes were still apparent after long-term culturing
under similar physiological conditions. Potential growth habitats for this
ichthyotoxic flagellate in the Australian region and implications for
finfish aquaculture industries are discussed.
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7.
Influence of nutrient ratios on the in vitro extracellular polysaccharide production by marine diatoms from the Adriatic Sea 总被引:4,自引:0,他引:4
Three different species of marine diatoms, Nitzschia
closterium (Ehr) Smith, Chaetoceros sp.
(Ehr) and Skeletonema costatum (Grev) Cleve, were
isolated from the Adriatic sea and studied in vitro
for the production of extracellular carbohydrates. Variations of the
nitrogen (N)/phosphorus (P)/silicon (Si) ratios in the growth medium affect
the accumulation and release of carbohydrates. In the
N.closterium cultures at high N/P ratio, the rate of
extracellular polysaccharide release was higher both in rapidly growing
cells (2.14 g per 106
cells day-1 and in stationary phase (1.0 g
per 106 cells day-1) compared
to S.costatum and Chaetoceros sp.
Instead, at low N/P ratios, S.costatum and
Chaetoceros sp. produced large amounts of
extracellular polysaccharides during the logarithmic phase, compared to
N.closterium, with values of 10 g per
106 cells day-1 for
S.costatum and 2.8 g per
106 cells day-1 for
Chaetoceros sp., respectively; in particular, only
S.costatum was able to produce extracellular
carbohydrates (1.2 g per 106 cells
day-1) during the stationary phase of growth. Under
Si limitation, any of the three diatom species produce extracellular
polysaccharides both in the logarithmic and stationary phase of growth. The
potential ecological significance of these findings is discussed.
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8.
The goal of this study was to provide temporal information on the
generation time of Dolioletta gegenbauri and some of
the life cycle's components. At 20C and
90 g C l-1 of
ingestible phytoplankton. D.gegenbauri's life cycle is
completed in 20.5 days. Phorozooids 5 mm produce on average 11.0
gonozooids day-1 over a period of 8-18 days.
Utilizing field data on the abundance and size distribution of an
assemblage of phorozooids and nurses, in conjunction with experimentally
obtained rates, indicates that asexual production per cubic meter by
phorozooids with that of nurses should result in rapid colonization of a
wide shelf by doliolids, as observed during July and August 1981 on the
southeastern continental shelf of the USA.
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9.
High-light damage in air-dry thalli of Lobaria
pulmonaria were measured in the laboratory as reductions in
maximal PSII efficiency (Fv/Fm)
after a 48 h recovery in a hydrated state at low light to account for
permanent damage. Thalli treated with the lowest light dose (90 mol photons
m-2) recovered normal
Fv/Fm-values with increasing irradiances (400-700 nm)
up to 1000 mol photons
m-2 s-1. Doubling this dose
lowered the threshold level for damage from 1000 to 320 mol photons m-2
s-1, and reduced
Fv/Fm at 1000 mol
photons m-2 s-1 by more than
50%. A second doubling of the dose to 360 mol photons
m-2 caused damage at 200 mol photons
m-2 s-1, and a nearly
complete cessation of PSII efficiency occurred at 1000 mol photons
m-2 s-1. No reciprocity of
irradiance and duration of illumination for PSII function was found. The
measured time-dependent decrease in
Fv/Fm was remarkably similar for
the naturally coupled, but artificially separated, light and temperature
factors. Therefore, the damage of high light on desiccated L.
pulmonaria seemed to be an additive effect of high irradiance
and high temperatures. Air-dry thalli were highly heat susceptible, being
affected already at temperatures around 40C.
Logging operations in forests are likely to raise the solar radiation at
remaining lichen sites to destructive levels.Keywords:
Lichens, high-light damage, heat stress, poikilohydric
organisms, reciprocity.
相似文献
10.
Spatial variability of the photosynthetic parameters and biomass of the Gulf of California phytoplankton 总被引:2,自引:0,他引:2
Gaxiola-Castro G; Alvarez-Borrego S; Lavin M; Zirino A; Najera-Martinez S 《Journal of plankton research》1999,21(2):231-245
Spatial variability of the central Gulf of California (CGC) phytoplankton
biomass and photosynthetic parameters in relation to physical forcing was
studied. Sampling was carried out in November, and the surface
TC range was
20-27.5°C. Strong tidal mixing in the midrift islands regions
injects relatively cool, nutrient-rich waters to the euphotic zone. Some of
this water is transported via jets and cool filaments throughout the Gulf.
In general, chlorophyll a (Chl) of small phytoplankton
(<8 m) (up to >2.5 mg
m-3) was higher than that of large phytoplankton.
Highest values of phytoplankton assimilation numbers
(PBm) [3.17 mg C (mg
Chla)-1
h-1], and photosynthetic efficiency B) [0.23 mg C (mg
Chl a)-1
h-1 (W
m-2)-1] were determined for
the large phytoplankton cells (>8 m). Our hypothesis that
PBm values increase
from cooler to warmer waters is not supported by the data. We found a
27-fold spatial difference of Chl, compared with a 10-fold difference of
PBm and a 6-fold
difference of B. Thus, in our study
area, the major source of variability for primary productivity (PP) comes
from Chl, and not from
PBm and
B. Therefore, we propose that it is
possible to estimate late-fall PP for the CGC using average photosynthetic
parameters. Average values for
PBm and
B of total phytoplankton were 0.72
mg c (mg Chl a)-1
h-1 and 0.12 mg C (mg Chl
a-1 h-1,
(W m-2)-1, with standard
errors of 0.07 and 0.03, respectively.
相似文献
11.
The Faroe shelf water is separated from the offshore water by a persistent
tidal front, which surrounds the islands. This shelf water contains a
neritic zooplankton community, which, regarding species composition,
production, seasonal development and environmental conditions, is quite
different from that in the surrounding ocean. While during spring and
summer the zooplankton in the oceanic environment are dominated by the
copepod Calanus finmarchicus, the zooplankton in the
shelf water are largely dominated by neritic copepods, mainly
Acartia longiremis and Temora longicornis.
Calanus finmarchicus occurs in interannually highly variable
abundance in the Faroe shelf ecosystem. Meroplanktonic larvae, mainly
Balanus spp, and decapod larvae, are also common in
the shelf water during spring and summer. During the period presented
(1989-1997), the Faroe shelf ecosystem has undergone very large changes in
abundance of different zooplankton species. The midsummer abundance of
C.finmarchicus, which originally is advected into the
shelf from the open ocean, fluctuated from 400 copepods
m-3 in 1989 to 25 copepods
m-3 in 1994, and at the same time the neritic
zooplankton increased from 120 m-3 in 1989
to 450 m-3 in 1994. Consequently, the midsummer
biomass in the shelf fluctuated by a factor of 10 during the same period.
It is presumed that this variability between oceanic- and neritic-dominated
zooplankton, their sizes and their biomass has greatly affected the entire
pelagic ecosystem.
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12.
Response of Gonyaulax tamarensis to the presence of a pycnocline in an artificial water column 总被引:1,自引:0,他引:1
In nature, large concentrations of the toxic bloom-forming dinoflagellate,Gonyaulax tamarensis, are frequently observed in the vicinityof the pycnocline. In the absence of a pycnocline the organismis usually recorded near the surface, where light levels aremore advantageous for photosynthesis. In this paper we examinethe swimming behaviour of G.tamarensis when exposed to varyingdegrees of stratification and investigate whether the maintenanceof a subsurface (pycnocline) population is the result of retentionof the algae by a physical barrier or active accumulation ofthe organisms at a density interface. The study indicates thatG.tamarensis cells presented with a halocline of S<{smalltilde}67 (occurring over a few centimeters) cross thissalinity barrier and accumulate at the highest available photonflux density ({small tilde}100 µmol m2 s1).Cells exposed to a gradient of S>{small tilde}7remain atthe halocline (pfd={small tilde}40 µmol m2 s1).However, when light above the pycnocline is attenuated by theaddition of food colour to the medium, the cells cross a haloclineof S=10 and accumulate at the highest available photon fluxdensity. In the absence of added nutrients (inorganic N andP) the organism fails to exhibit a phototactic response. Thus,the presence of a strong halocline does not represent an inpenetrablephysical barrier for G.tamarensis and the development of pycnoclinepopulations of this organism is a function of density, lightand nutrient climate. 相似文献
13.
Resting egg production and oviducal cycling were investigatedfor the calanoid copepods Arctodiaptomus alpinus and Acanthodiaptomusdenticornis both in the laboratory and in a small karstic alpinelake by making a census of the number of eggs produced and theproportion of females in each of four morphologically distinguishedreproductive conditions each day in the laboratory or duringa 23 week period in lake enclosures. In the laboratory,individuals were maintained on a mixed diet of natural phytoplanktonat constant temperatures of 4, 10, 15 and 20C, respectively.Both species differed considerably in their temperature requirementsfor reproduction. Lifetime fecundity was highest at 10C in A.alpinusand at 20C in A.denticornis, with up to 327 eggs 1 spawnedin the former and up to 582 eggs 1 in the latter species.Unfavorable temperatures were further reflected in an increasein egg mortality and the allocation of time spent in a post-reproductivephase, as well as in a decrease of longevity. Increasing temperaturesenhanced egg production rates due to decreasing clutch productionperiods, although clutch size was negatively correlated withtemperature. Maximum rates reached 5.88 and 7.98 eggs 1day1 in the laboratory, and 0.73 and 0.55 eggs 1day1 in enclosures in A.alpinus and A.denticornis, respectively.Egg production rates and clutch size were clearly governed bynutritional conditions in the lake, but were less affected byfood supply in the laboratory. Here, rates of egg productionwere adapted to improving food supply by increasing the frequencyof spawning events, rather than the number of eggs per clutch.No correlation was found between female body size and reproductiveparameters in the laboratory. A very low proportion of totalclutch production resulted in clutches composed of subitaneouseggs, i.e. 0.14% in A.denticornis and 1.20% in A.alpinus. Oviducalphase duration allocations indicate that there exists a temperatureoptimum for gamete maturation. 相似文献
14.
Assimilation of Fe and carbon by marine copepods from Fe-limited and Fe-replete diatom prey 总被引:1,自引:0,他引:1
Previous studies have demonstrated that growth of marine phytoplankton,
bacteria and protozoa can be limited by the availability of Fe. We report
evidence that the amount of Fe assimilated by crustacean grazers is
affected by the Fe status of their pry. 59Fe and
14C radiotracers were used to follow the fate of Fe
and carbon during trophic transfer from diatoms to copepods. Fe
assimilation efficiency was higher for copepods ingesting Fe-limited
Thalassiosira weissflogii (17%) compared to diatoms
that were not limited by Fe (10%), but assimilated Fe was lost more rapidly
by copepods ingesting Fe-limited prey. Fe:C assimilation ratios were lower
in copepods (5-12 mol Fe:mol C) than the
cellular ratios of the phytoplankton prey (17-35 mol Fe:mol C),
suggesting that copepods do not accumulate Fe relative to C during grazing.
The largest single fate for Fe and C after grazing was regeneration to
dissolved pools. Fe:C ratios in dissolved pools were approximately equal to
the ratios in the original prey, but Fe:C ratios were higher in particular
pools (largely fecal pellets), which should facilitate the export of Fe
from the euphotic zone relative to C. Although copepod grazing does recycle
cellular Fe and C, our results indicate that grazing may also tend to
enhance Fe stress for lower trophic levels by removing Fe from the euphotic
zone faster than C.
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15.
Egg production of a brackish water calanoid copepod Acartia
bifilosa was measured in the laboratory in different chlorophyll
(Chl) a concentrations (0-24 mgr;
l-1) and temperatures 4-24C), and the cephalothorax length and carbon content
of females were determined. Egg production was positively correlated both
with Chl a concentration and with temperature; highest
egg production was obtained with 14-20 g Chl
a l-1 and at 13-18°C.
There was also a significant positive correlation between egg production
and female length-specific carbon content (g C
m-1). However, no correlation was observed
between egg production and cephalothorax length of females. Female carbon
content changed during the 3 day experiments; carbon content was positively
related to Chl a concentration and negatively related
to temperature. We conclude that food availability (Chl
a concentration), rather than temperature, limits the
egg production of A.bifilosa in the present study area
in the northern Baltic Sea. Further, both food concentration and
temperature affect egg production not only through the direct effect on the
numbers of eggs produced per female, but also through their effect on
female carbon content.
相似文献
16.
Are copepods important grazers of the spring phytoplankton bloom in the western Irish Sea? 总被引:3,自引:0,他引:3
Gowen R; McCullough G; Kleppel G; Houchin L; Elliott P 《Journal of plankton research》1999,21(3):465-483
The spring phytoplankton bloom and copepod grazing were studied at a
coastal and offshore station in the western Irish Sea during 1997. Maximum
chlorophyll standing stocks of 132.8 mg m-2 inshore
and 199.4 mg m-2 offshore were measured in late
April. At that time, mean water column temperatures were 10 and 8C at the coastal and offshore station, respectively.
Spring bloom production at the coastal station was estimated as 31.2 g C
m-2 and was dominated by the diatom
Guinardia delicatula. Offshore, production was 28.2 g
C m-2 and the bloom was composed of small (10 m) phytoflagellates
and the silicoflagellate Dictyocha speculum. Maximum
copepod abundance (189 and 544 x 103 individuals
m-2, inshore and offshore, respectively) coincided
with the spring bloom. Pseudocalanus and
Temora ingestion rates were derived from measurements
of gut pigment fluorescence, and were found to vary during the course of
the spring bloom as a result of changes in gut content. Grazing by late
copepodite and adult Pseudocalanus and
Temora was variable inshore, but overall accounted for
17% of bloom production. Offshore, 22% of bloom production was grazed with
maximum grazing (76% of daily production) occurring at the end of the
bloom. Large copepod species were not major grazers of the spring bloom.
Greater utilization of spring bloom production by copepods in the western
Irish Sea compared to regions of the North Sea is attributed to differences
in population size at the time of the bloom.
相似文献
17.
Growth and toxin production of a highly toxic clone of the marine
dinoflagellate Alexandrium tamarense, isolated from
the lower St Lawrence estuary (Quebec) in eastern Canada, were studied in
unialgal batch cultures under different conditions. Controlled experiments
were conducted on the production of paralytic shellfish poisoning (PSP)
toxins under conditions of varying light (40, 60, 150, 230 and 470 mol m-21
s-1), salinity (10, 15, 20, 25 and 30)
and nitrate concentrations (0, 88, 364, 528 and 880 mol
l-1). The effects of variable environmental factors
on both toxin composition (% molar) and cell toxicity [pg STXeq (saxitoxin
equivalents) cell-1] were determined through the
culture cycle. The toxin profile (% molar; mean SD), determined by high-performance liquid
chromatography with fluorescence detection (HPLC-FD), remained stable and
was consistently dominated by the low-potency
N-sulfocarbamoyl toxins C1/C2 (64.0 ± 3%).
There were also substantial relative amounts of the high-toxicity carbamate
derivatives gonyautoxin 1-4 (GTX1-4) (1.7 ± 0.5%), neosaxitoxin
(NEO) (16.2 ± 2%) ans saxitoxin (STX) (17.8 ± 2%).
The cellular toxicity (mean ± SD: 58.8 ± 7 pg STXeq
cell-1) was essentially independent of light,
salinity and nitrate concentration throughout the exponential growth phase,
but varied over the growth stages in cultures. A positive correlation was
observed between cellular toxicity and salinity-dependent growth rate,
indicating that cell toxin quota may be affected by extrinsic factors, but
it is not always a direct functional response to specific environmental
stress.
相似文献
18.
Temperature and salinity effect on growth and chemical composition of Gyrodinium aureolum Hulburt in culture 总被引:1,自引:0,他引:1
A factorial experiment shows highly significant effects of temperature(12 522.5°C) and salinity (17.834 S) on thegrowth rate of Gyrodinium aureolum, with a significant temperature-salinityinteraction. The maximum growth rate of G aureolum is measuredto 0.61 div. day1 at 20°C and 22.3 S. Gyrodiniumaureolum does not grow at temperatures :10 °C or 25°Cand at salinities 12 S. The cellular content of carbon (C) andnitrogen (N) and the elemental ratios N/C, P/C and N/P are significantlyaffected by the temperature The cellular content of phosphorus(P) and the elemental ratios P/C and N/P vary significantlywith salinity Significant temperature-salinity interactionsare found for the cellular content of carbon, nitrogen and phosphorus.Variations in the N/P ratio indicate that G.aureolum has a largestorage capacity for phosphorus It is suggested that temperatureis one important limiting factor in the initiation of bloomsof G.aureolum in north European waters. 相似文献
19.
Egg production rates of eight calanoid copepod species during summer 1997 off Newport, Oregon, USA 总被引:3,自引:0,他引:3
Measurements of hydrography, water transparency, chlorophyll (Chl)
a and egg production rates (EPRs) by females of
Calanus marshallae Frost, Calanus
pacificus Brodsky, Eucalanus californicus
Johnson, Epilabidocera longipedata Sato,
Pseudocalanus mimus Frost, Centropages
abdominalis Sato, Acartia longiremis
Lilljerborg and Paracalanus parvus (Claus) were
estimated at weekly intervals between 17 July and 2 September 1997.
Production of eggs was determined in 24 h incubations to examine the
effects of environmental variability on EPR, to detect the possibility of
food limitation of EPR, and to evaluate the hypothesis that growth rates of
females are size dependent. During the study, an anomalous downwelling
event occurred, possibly in response to the 1997 El Niño, which
allowed us to determine how El Niño events affect EPRs of
coastal copepods. The larger copepods Calanus marshallae, Calanus
pacificus and Centropages abdominalis
showed the highest egg production and specific growth rates during the
period of active upwelling (18 July-13 August, water temperatures
8-13C, Chl a
concentration 4.7-16.2
l-1 and water transparency 3-5 m). After 27 August,
the 1997-98 El Niño arrived off Oregon, creating a downwelling
situation. Upwelling winds ceased, the thermocline intensified, temperature
and transparency increased (to >18°C and 16 m), and Chl
a declined to <2 g
l-1. Densities of the common coastal species
declined greatly as well. Paracalanus parvus became
the dominant species, and Eucalanus californicus, Epilabidocera
longipedata and Corycaeus anglicus became
common in our samples. EPRs for the larger boreal copepods
(Calanus and Centropages)
declined greatly during El Niño;; the smaller copepods,
Pseudocalanus mimus, A.longiremis and
Paracalanus parvus, showed low but relatively constant
egg production and specific growth rates during both upwelling and
downwelling events. Over the entire study period, only three species
produced eggs at its maximum rate (24-28 eggs
female-1 day-1),
Pseudocalanus mimus which averaged 4 eggs
day-1. All other species had EPRs that were two or
five times below their maximum EPR. Thus, EPRs were not related to body
size, contrary to our expectations. Hatching success was variable among
species. Values as low as 20-40% were found for all species at least once
during the study period, suggesting that occasionally a substantial portion
of egg production may not be viable.
相似文献
20.
The effect of rhizosphere dissolved inorganic carbon on gas exchange characteristics and growth rates of tomato seedlings 总被引:2,自引:0,他引:2
The possibility that an enhanced supply of dissolved inorganic carbon
(DIC=CO2+HCO3-) to the root solution could increase
the growth of Lycopersicon esculentum (L.) Mill. cv.
F144 was investigated under both saline and non-saline root medium
conditions. Tomato seedlings were grown in hydroponic culture with and
without NaCl and the root solution was aerated with CO2 concentrations in
the range between 0 and 5000 mol
mol-1. The biomass of both control and
salinity-stressed plants grown at high temperatures (daily maximum of
37C) and an irradiance of 1500 mol m-2
s-1 was increased by up to 200% by enriched
rhizosphere DIC. The growth rates of plants grown with irradiances of less
than 100 mol m-2 s-1
were increased by elevated rhizosphere DIC concentrations only when grown
at high shoot temperatures (35C) or with
salinity 28°C). At high light intensities, the photosynthetic rate,
the CO2 and light-saturated photosynthetic rate (jmax)
and the stomatal conductance of plants grown at high light intensity were
lower in plants supplied with enriched compared to ambient DIC. This was
interpreted as 'down-regulation' of the photosynthetic system in plants
supplied with elevated DIC. Labelled organic carbon in the xylem sap
derived from root DI14C incorporation was found to
be sufficient to deliver carbon to the shoot at rates equivalent to 1% and
10% of the photosynthetic rate of the plants supplied with ambient- and
enriched-DIC, respectively. It was concluded that organic carbon derived
from DIC incorporation and translocated in the xylem from the root to the
shoot may provide a source of carbon for the shoots, especially under
conditions where low stomatal conductance may be advantageous, such as
salinity stress, high shoot temperatures and high light
intensities. 相似文献