共查询到20条相似文献,搜索用时 15 毫秒
1.
The effects of growth temperature on the marine chlorophyte Dunaliella tertiolecta Butcher were studied to provide a more mechanistic understanding of the role of environmental factors in regulating bio-optical properties of phytoplankton. Specific attention was focused on quantities that are relevant for modeling of growth and photosynthesis. Characteristics including chlorophyll a (chl z)-specific light absorption (a*ph(λ)), C:chl a ratio, and quantum yield for growth (φμ) varied as functions of temperature under conditions of excess light and nutrients. As temperature increased over the range examined (12°-28°C), intracellular concentrations of chl a increased by a factor of 2 and a*ph(λ) values decreased by more than 50% at blue to green wavelengths. The lower values of a*ph(λ) were due to both a decrease in the abundance of accessory pigments relative to chl a and an increase in pigment package effects arising from higher intracellular pigment concentrations. Intracellular pigment concentration increased as a consequence of higher cellular pigment quotas combined with lower cell volume. At high growth temperatures, slightly more light was absorbed on a per-cell-C basis, but the dramatic increases in growth rate from μ= 0.5 d?1 at 12° C to μ= 2.2 d?1 at 28°C were primarily due to an increase in φμ (0.015–0.041 mol C (mol quanta)?1). By comparison with previous work on this species, we conclude the effects of temperature on a*ph(λ) and φμ are comparable to those observed for light and nutrient limitation. Patterns of variability in a*ph(λ)and φμ as a function of growth rate at different temperatures are similar to those previously documented for this species grown at the same irradiance but under a range of nitrogen-limited conditions. These results are discussed in the context of implications for bio-optical modeling of aquatic primary production by phytoplankton. 相似文献
2.
Hugh L. MacIntyre Todd M. Kana Tracy Anning Richard J. Geider 《Journal of phycology》2002,38(1):17-38
The photosynthesis‐irradiance response (PE) curve, in which mass‐specific photosynthetic rates are plotted versus irradiance, is commonly used to characterize photoacclimation. The interpretation of PE curves depends critically on the currency in which mass is expressed. Normalizing the light‐limited rate to chl a yields the chl a‐specific initial slope (αchl). This is proportional to the light absorption coefficient (achl), the proportionality factor being the photon efficiency of photosynthesis (φm). Thus, αchl is the product of achl and φm. In microalgae αchl typically shows little (<20%) phenotypic variability because declines of φm under conditions of high‐light stress are accompanied by increases of achl. The variation of αchl among species is dominated by changes in achl due to differences in pigment complement and pigment packaging. In contrast to the microalgae, αchl declines as irradiance increases in the cyanobacteria where phycobiliproteins dominate light absorption because of plasticity in the phycobiliprotein:chl a ratio. By definition, light‐saturated photosynthesis (Pm) is limited by a factor other than the rate of light absorption. Normalizing Pm to organic carbon concentration to obtain PmC allows a direct comparison with growth rates. Within species, PmC is independent of growth irradiance. Among species, PmC covaries with the resource‐saturated growth rate. The chl a:C ratio is a key physiological variable because the appropriate currencies for normalizing light‐limited and light‐saturated photosynthetic rates are, respectively, chl a and carbon. Typically, chl a:C is reduced to about 40% of its maximum value at an irradiance that supports 50% of the species‐specific maximum growth rate and light‐harvesting accessory pigments show similar or greater declines. In the steady state, this down‐regulation of pigment content prevents microalgae and cyanobacteria from maximizing photosynthetic rates throughout the light‐limited region for growth. The reason for down‐regulation of light harvesting, and therefore loss of potential photosynthetic gain at moderately limiting irradiances, is unknown. However, it is clear that maximizing the rate of photosynthetic carbon assimilation is not the only criterion governing photoacclimation. 相似文献
3.
The phytoplankton community structure of a hypertrophic lake was quantitatively determined with the aid of flow cytometry. The flow cytometry signals were calibrated to obtain cell‐specific information, such as the chl a content and the biovolume per cell. The reliability of this method was tested with laboratory cultures. The results of the phytoplankton structure in a hypertrophic lake with respect to chl distribution in the different algal groups obtained by flow cytometry were compared with the results from HPLC pigment fingerprinting. Both methods yield the percentage contribution of the different algal groups to total chl a. The chl a specific absorption coefficient of the phytoplankton (a*Phy) was determined via visible (VIS) spectroscopy of samples taken from a hypertrophic lake (Auensee) in 2003. The results indicated that a*Phy of the total cell suspension is dependent on the phytoplankton structure as well as on environmental factors. The linear relationship between a*Phy at 675 nm and the product of the chl a content per cell and the biovolume offered the possibility to normalize phytoplankton absorption spectra to acquire the taxon‐specific a*Phy. The estimated a*Phy (675 nm) values were used to normalize single cell absorption spectra at this wavelength to obtain the a*Phy between 400 and 750 nm for representatives of the major algal groups. Our measurements show that the absorption coefficient for the whole phytoplankton community varies within the season. Finally, we used the a*Phy and the chl a distribution to calculate the light absorption of each algal group in the hypertrophic lake. 相似文献
4.
Calcifying and a noncalcifying strains of Emiliania huxleyi were cultured in nutrient replete turbidostats under a photon flux density (PFD) gradient from 50 to 600 μmol E·m?2·s?1. For both strains, growth was PFD‐saturated at 300 μmol E·m?2·s?1. The strains, although with clearly different physiological properties due to the presence or absence of calcification, showed the same trends and magnitude of change in their pigment compliment as a function of PFD. Light‐controlled pigment composition and the trends of change in pigment composition were identical in both strains. Fucoxanthin (Fuco) was the major carotenoid in the calcifying strain, while in the noncalcifying strain this role was assumed by 19′ hexanoyloxyfucoxanthin (19 Hex). The photoprotective pigments and 19 Hex, normalized to chl a, increased with increasing light, while chl a content per cell and chl c's and Fuco, normalized to chl a, decreased with increasing PFD. The sum of all carotenoids normalized to chl a was remarkably similar in all PFDs used. Collectively, our results suggest that 19 Hex was synthesized from Fuco with light as a modulating factor and that the total amount of carotenoids is strain‐specific and synthesized/catabolized in tandem with chl a to a genetically predefined level independent of PFD. 相似文献
5.
The psychrophilic diatom Fragilariopsis cylindrus (Grunow) Krieger in Helmcke & Krieger was used to investigate photosynthesis and growth under freezing temperatures. Gene expression during a temperature shift from +5° C to ?1.8° C was studied under 3 and 35 μmol photons·m?2·s?1 by using a macroarray. These measurements were paralleled by determination of fluorescence induction at PSII and pigment analysis. The shift to ?1.8° C at 35 μmol photons·m?2·s?1 caused a marginal decrease of photosynthetic quantum yield (Fv/Fm) from 0.61 to 0.52 with fast recovery after 1 day. The ratio of chl c to chl a increased from 3.1 to 5.5, and the ratio of diatoxanthin to diadinoxanthin increased from 0.7 to 5.0. Genes encoding proteins of PSII (psbA, psbC) and for carbon fixation (rbcL) were down‐regulated, whereas genes encoding chaperons (hsp70) and genes for plastid protein synthesis and turnover (elongation factor EfTs, ribosomal protein rpS4, ftsH protease) were up‐regulated. In contrast, cold exposure at 3 μmol photons·m?2·s?1 induced a marginal increase in Fv/Fm from 0.61 to 0.63 and a strong increase in fucoxanthin concentrations from 0.04 up to 0.12 pg·cell?1. This was paralleled by up‐regulation of fcp genes. The ratio of chl c to chl a also increased from 3.1 to 4.2, as did the ratio of diatoxanthin to diadinoxanthin from 0.7 to 2.2. Down‐regulation of psbA, psbC, and rbcL could also be measured but not up‐regulation of hsp70, EfTs, rpS4, and the ftsH protease. The latter genes are probably necessary to avoid cold shock photoinhibition only at higher light intensities. 相似文献
6.
The photoprotective response in the dinoflagellate Glenodinium foliaceum F. Stein exposed to ultraviolet‐A (UVA) radiation (320–400 nm; 1.7 W · m2) and the effect of nitrate and phosphate availability on that response have been studied. Parameters measured over a 14 d growth period in control (PAR) and experimental (PAR + UVA) cultures included cellular mycosporine‐like amino acids (MAAs), chls, carotenoids, and culture growth rates. Although there were no significant effects of UVA on growth rate, there was significant induction of MAA compounds (28 ± 2 pg · cell?1) and a reduction in chl a (9.6 ± 0.1 pg · cell?1) and fucoxanthin (4.4 ± 0.1 pg · cell?1) compared to the control cultures (3 ± 1 pg · cell?1, 13.3 ± 3.2 pg · cell?1, and 7.4 ± 0.3 pg · cell?1, respectively). In a second investigation, MAA concentrations in UVA‐exposed cultures were lower when nitrate was limited (P < 0.05) but were higher when phosphate was limiting. Nitrate limitation led to significant decreases (P < 0.05) in cellular concentration of chls (chl c1, chl c2, and chl a), but other pigments were not affected. Phosphate availability had no effect on final pigment concentrations. Results suggest that nutrient availability significantly affects cellular accumulation of photoprotective compounds in G. foliaceum exposed to UVA. 相似文献
7.
Finding of 132, 173‐cyclopheophorbide a enol as a degradation product of chlorophyll in shrunk zooxanthellae of the coral Montipora digitata
下载免费PDF全文
![点击此处可从《Journal of phycology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Toshiyuki Suzuki Beatriz Estela Casareto Yuzo Shioi Yoshio Ishikawa Yoshimi Suzuki 《Journal of phycology》2015,51(1):37-45
We examined the morphology and pigment composition of zooxanthellae in corals subjected to normal temperature (27°C) and thermal stress (32°C). We observed several normal and abnormal morphological types of zooxanthellar cells. Normal cells were intact and their chloroplasts were unbroken (healthy); abnormal cells were shrunken and had partially degraded or broken chloroplasts, or they were bleached and without chloroplasts. At 27°C, most healthy zooxanthellar cells were retained in the coral tissue, whereas shrunken zooxanthellae were expelled. Under thermal stress, the abundance of healthy zooxanthellae declined and the proportion of shrunken/abnormal cells increased in coral tissues. The rate of algal cell expulsion was reduced under thermal stress. Within the shrunken cells, we detected the presence of a chl‐like pigment that is not ordinarily found in healthy zooxanthellae. Analysis of the absorption spectrum, absorption maxima, and retention time (by HPLC) indicated that this pigment was 132, 173‐cyclopheophorbide a enol (cPPB‐aE), which is frequently found in marine and lacustrine sediments, and in protozoans that graze on phytoplankton. The production of cPPB‐aE in shrunken zooxanthellae suggests that the chls have been degraded to cPPB‐aE, a compound that is not fluorescent. The lack of a fluorescence function precludes the formation of reactive oxygen species. We therefore consider the formation of cPPB‐aE in shrunken zooxanthellae to be a mechanism for avoiding oxidative stress. 相似文献
8.
Maruin W. Fawley 《Journal of phycology》1989,25(3):601-604
Three chlorophyll c-type pigments were separated by reversed-phase high Performance liquid chromatography and thin-layer chromatography from pigment extracts of the prymnesiophyte, Prymnesium parvum Carter. Based on spectral characteristics, retention times, and comparison with reference pigments isolated from the diatom Phaeodactylum tricornutum Bohlin, two of these pigments were identijied as chlorophyll c1 and c2. The other pigment was identified by its absorption spectrum and thin-layer chromatography retention times as the newly described chlorophyll c3. However, in other prymnesiophytes so far examined, chlorophyll c1 and chlorophyll c3 were present with no chlorophyll cl. The discovery of chlorophyll c3 with chlorophyll c1 and chlorophyll c3 in Prymnesium parvum therefore represents the first report of this combination of pigments in prymnesiophytes. 相似文献
9.
Nathalie Korbee Peinado Roberto T. Abdala Díaz Flix L. Figueroa E. Walter Helbling 《Journal of phycology》2004,40(2):248-259
The combined effects of ammonium concentration and UV radiation on the red alga Porphyra columbina (Montagne) from the Patagonian coast (Chubut, Argentina) was determined using short‐term (less than a week) experimentation. Discs of P. columbina were incubated with three ammonium concentrations (0, 50, and 300 μM NH4Cl) in anilluminated chamber (PAR=300 μmol photons·m?2·s?1, UVA=15 W·m?2, UVB=0.7 W·m?2) at 15°C. Algae incubated at 300 μM ammonium showed a significant increase (P<0.05) in the concentration of mycosporine‐like amino acids (MAAs) compared with the initial value or with the other ammonium treatments. The increase of MAAs was, however, a function of the quality of irradiance received, with a higher increase in samples exposed to UVA compared with UVB (29% and 5% increase, respectively). However, UVB radiation was more effective in inducing MAA synthesis per unit energy received by the algae. Samples exposed to PAR only had an intermediate increase in MAA concentration of 16%. Chl a concentration decreased through the incubation with the greatest decrease at high ammonium concentration. Phycobiliprotein (BP) decreased through time with the smallest decrease occurring at high ammonium concentration. Photoinhibition (as a decrease of optimal quantum yield) was significantly greater under nitrogen‐deprived conditions than that under replete ammonium levels. Maximal gross photosynthesis (GPmax), as oxygen evolution, and maximal electron transport rate (ETRmax), as chl fluorescence, increased with the ammonium concentration. Positive relationships between maximal GP or ETR and pigment ratios (BP/chl a and MAAs/chl a) and negative relationships with chl a concentration were found. 相似文献
10.
Kees Van Lenning Mikel Latasa Marta Estrada Alberto G. Sez Linda Medlin Ian Probert Benoît Vron Jeremy Young 《Journal of phycology》2003,39(2):379-389
Variations in the HPLC‐derived pigment composition of cultured Pavlovophyceae (Cavalier‐Smith) Green et Medlin were compared with phylogenetic relationships inferred from 18S rDNA sequencing, morphological characteristics, and current taxonomy. The four genera described for this haptophyte class (Diacronema Prauser emend. Green et Hibberd, Exanthemachrysis Lepailleur, Pavlova Butcher, and Rebecca Green) were represented by nine different species (one of which with data from GeneBank only). Chlorophylls a, c1, c2 and MgDVP (Mg‐[3,8‐divinyl]‐phytoporphyrin‐132‐methylcarboxylate) and the carotenoids fucoxanthin, diadinoxanthin, diatoxanthin, and β,β‐carotene were detected in all cultures. Species only differed in the content of an unknown (diadinoxanthin‐like) xanthophyll and two polar chl c forms, identified as a monovinyl (chl c1‐like) and a divinyl (chl c2‐like) compound. This is the first observation of the monovinyl form in haptophytes. Based on distribution of these two chl c forms, species were separated into Pavlovophyceae pigment types A, B, and C. These pigment types crossed taxonomic boundaries at the generic level but were in complete accordance with species groupings based on molecular phylogenetic relationships and certain ultrastructural characteristics (position and nature of pyrenoid, stigma, and flagella). These results suggest that characterization of the pigment signature of unidentified culture strains of Pavlovophyceae can be used to predict their phylogenetic affinities and vice versa. Additional studies have been initiated to evaluate this possibility for the haptophyte class Prymnesiophyceae. 相似文献
11.
Christine Schimek Igor N. Stadnichuk Rosemarie Knaust Werner Wehrmeyer 《Journal of phycology》1994,30(4):621-627
Three different chlorophyll (chl) c-type pigments were isolated from two cryptophyte species by silica thin-layer chromatography or polyethylene high-performance liquid chromatography. Chroomonas sp. Hansgirg contained chl c1 and magnesium-2,4-divinylpheoporphyrin a, mono-methylester; chl c2 and magnesium-2,4-divinylpheoporphyrin a5 monomethylester were found in Cryptomonas maculata (syn. Rhodomonas maculata Butcher). These identifications were based on spectral characteristics and on comparison with reference pigments isolated from the synurophycean Synura petersenii Korshikov and the prasinophyte Mantoniella squamata Manton & Park. Neither of the cryptophyte species contained chl c1 and chl c2. The significance of chl c1 as a major pigment and the occurrence of magnesium-2,4-divinylpheoporphyrin a5 monomethylester in cryptophytes are discussed. 相似文献
12.
Silvia M. Nascimento Duncan A. Purdie Emily L. Lilly Jacob Larsen Steven Morris 《Journal of phycology》2005,41(2):343-353
Paralytic shellfish toxins, pigment composition, and large subunit (LSU) rDNA sequence were analyzed for a clonal culture of Alexandrium minutum Halim isolated in 2000 from the coastal Fleet Lagoon, Dorset, United Kingdom. The HPLC pigment analysis revealed the presence of chl a, peridinin, and diadinoxanthin as major pigments and chl c1+c2 and c3, diatoxanthin, and β‐carotene as minor components. The toxins responsible for paralytic shellfish poisoning were analyzed by HPLC with postcolumn derivatization and fluorescence detection. The paralytic shellfish poisoning toxin profile of the Fleet Lagoon strain of A. minutum in exponential growth phase was dominated by gonyautoxin‐3 up to 54%, whereas gonyautoxin‐2 made up 10% and saxitoxin (STX) 36%. The average toxicity of the culture was 3.8 pg STX Eq·cell?1, and total toxin content varied from 5.6 fmol·cell?1 on day 1 to a maximum of 16.8 fmol·cell?1 during the early stationary phase. Sequence analysis of the LSU rDNA revealed the strain to be closely related to several European strains of A. minutum and one isolated from Australian waters, although most of these do not produce STX. The shallow Fleet Lagoon may provide a favorable environment for A. minutum to bloom, and the presence of highly potent saxitoxins in this strain indicates potential for future shellfish contamination. 相似文献
13.
Richard J. Geider Julie La Roche Richard M. Greene Miguel Olaizola 《Journal of phycology》1993,29(6):755-766
The effects of nitrate, phosphate, and iron starvation and resupply on photosynthetic pigments, selected photosynthetic proteins, and photosystem II (PSII) photochemistry were examined in the diatom Phaeodactylum tricornutum Bohlin (CCMP 1327). Although cell chlorophyll a (chl a) content decreased in nutrient-starved cells, the ratios of light-harvesting accessory pigments (chl c and fucoxanthin) to chl a were unaffected by nutrient starvation. The chl a-specific light absorpition coefficient (a*) and the functional absorption cross-section of PSII (σ) increased during nutrient starvation, consistent with reduction of intracellular self-shading (i.e. a reduction of the “package effect”) as cells became chlorotic. The light-harvesting complex proteins remained a constant proportion of total cell protein during nutrient starvation, indicating that chlorosis mirrored a general reduction in cell protein content. The ratio of the xanthophylls cycle pigments diatoxanthin and diadinoxanthin to chl a increased during nutrient starvation. These pigments are thought to play a photo-protective role by increasing dissipation of excitation energy in the pigment bed upstream from the reaction centers. Despite the increase in diatoxanthin and diadinoxanthin, the efficiency of PSII photochemistry, as measured by the ration of variable to maximum fluorescence (Fv/Fm) of dark-adapted cells, declined markedly under nitrate and iron starvation and moderately under phosphate starvation. Parallel to changes in Fv/Fm were decreases in abundance of the reaction center protein D1 consistent with damage of PSII reaction centers in nutrient-starved cells. The relative abundance of the carboxylating enzyme, ribulose bisphosphate carboxylase/oxygenase (RUBISCO), decreased in response to nitrate and iron starvation but not phosphate starvation. Most marked was the decline in the abundance of the small subunit of RUBISCO in nitrate-starved cells. The changes in pigment content and fluorescence characteristics were typically reversed within 24 h of resupply of the limiting nutrient. 相似文献
14.
Abstract The aim of this study was to quantify algal colonisation on anthropogenic surfaces (viz. building facades and roof tiles) using chlorophyll a (chl a) as a specific biomarker. Chl a was estimated as the initial fluorescence F0 of ‘dark adapted’ algae using a pulse-modulated fluorometer (PAM-2000). Four isolates of aeroterrestrial green algae and one aquatic isolate were included in this study. The chl a concentration and F0 showed an exponential relationship in the tested range between 0 and 400 mg chl a m?2. The relationship was linear at chl a concentrations <20 mg m?2. Exponential and linear models are presented for the single isolates with large coefficients of determination (exponential: r2 > 0.94, linear: r2 > 0.92). The specific power of this fluorometric method is the detection of initial algal colonisation on surfaces in thin or young biofilms down to 3.5 mg chl a m?2, which corresponds to an abundances of the investigated isolates between 0.2 and 1.5 million cells cm?2. 相似文献
15.
The chl a specific absorption coefficients [a* (λ), m2·mg chl a ? 1] were examined in chemostat culture of the Prymnesiophyceae Isochrysis galbana (Parke) under a 12:12‐h light:dark cycle at low light (75 μmol photons·m ? 2·s ? 1) and high light (500 μmol photons· m ? 2·s ? 1) conditions. Other associated measurements such as pigment composition, cell density, and diameter as the measure of cell size were also made at the two light regimes every 2 h for 2 days to confirm the periodicity. A distinct diel variability was observed for the a* (λ) with maxima near dawn and minima near dusk. The magnitude of diel variation in a* (440) was 15% at low light and 22% at high light. Pronounced diel patterns were observed for cell size with minima near dawn and maxima near dusk. The magnitude of diel variation in cell size was 9.3% at low light and 21% at high light. The absorption efficiency factors [Q a (440)] were determined by reconstruction using intracellular concentrations of pigments and cell size. The Q a (440) also showed a distinct diel variability, with minima near dawn and maxima near dusk. The diel variation in a* (λ) and Q a (λ) was primarily caused by changes in cell size due to growth, although there was some influence from diel variations in the intracellular pigment concentrations. The results presented here indicated that diel variation in a* (λ) was an important component of the optical characterization of phytoplankton. 相似文献
16.
The measurement of Photosynthetic rates of algae growing on the undersurface of 1. 7 m thick ice in the Canadian Arctic (Resolute Passage. N.W.T.) presents several problems. During the preparation of samples for physiological measurements, the ice algae may he exposed to salinity and temperature shocks. Fluorescence induction (the rise in in vivo Chl a fluorescence intensity during a period of millineconds) and photosynthesis-irradiance (PI) experiments examined the potential effects of salinity and temperature on the physiology of ice algae. Experimental suspensions were routinely prepared by scraping one part ire crystals (11–14%0 salinity) and attached algae from the bottom ice into four parts filtered seawater (32%0 salinity). giving a final salinity of 28–31%0. Post-dilution of melted ice scrapings with seawater suppressed photosynthetic 14C-fixation and decreased ADCMU (the area above the fluorescence induction curve measured in the presence of the inhibitor DCMC: an estimate of photosynthetic capacity) by a factor of 3–16. due to the low salinity of the melted ice scrapings. Fluorescence induction and PI experiments showed that the ice algae had a salinity optimum near 30%0, close to the ambient seawater salinity, Experiments in which the Chl a concentration was manipulated showed that ADCMU, Pam (Chl a-normalized rate of photosynthesis at light saturation), and a (photosynthetic efficiency) declined with increasing Chl a concentration. Ice algae tolerated heating (l.5°C-min-1) up to 17° C, above which ADCMU’decreased with sample temperature. 相似文献
17.
Kasper Hancke Torunn B. Hancke Lasse M. Olsen Geir Johnsen Ronnie N. Glud 《Journal of phycology》2008,44(2):501-514
Short‐term temperature effects on photosynthesis were investigated by measuring O2 production, PSII‐fluorescence kinetics, and 14C‐incorporation rates in monocultures of the marine phytoplankton species Prorocentrum minimum (Pavill.) J. Schiller (Dinophyceae), Prymnesium parvum f. patelliferum (J. C. Green, D. J. Hibberd et Pienaar) A. Larsen (Coccolithophyceae), and Phaeodactylum tricornutum Bohlin (Bacillariophyceae), grown at 15°C and 80 μmol photons · m?2 · s?1. Photosynthesis versus irradiance curves were measured at seven temperatures (0°C–30°C) by all three approaches. The maximum photosynthetic rate (PCmax) was strongly stimulated by temperature, reached an optimum for Pro. minimum only (20°C–25°C), and showed a similar relative temperature response for the three applied methods, with Q10 ranging from 1.7 to 3.5. The maximum light utilization coefficient (αC) was insensitive or decreased slightly with increasing temperature. Absolute rates of O2 production were calculated from pulse‐amplitude‐modulated (PAM) fluorometry measurements in combination with biooptical determination of absorbed quanta in PSII. The relationship between PAM‐based O2 production and measured O2 production and 14C assimilation showed a species‐specific correlation, with 1.2–3.3 times higher absolute values of PCmax and αC when calculated from PAM data for Pry. parvum and Ph. tricornutum but equivalent for Pro. minimum. The offset seemed to be temperature insensitive and could be explained by a lower quantum yield for O2 production than the theoretical maximum (due to Mehler‐type reactions). Conclusively, the PAM technique can be used to study temperature responses of photosynthesis in microalgae when paying attention to the absorption properties in PSII. 相似文献
18.
Sébastien Mas Suzanne Roy Frédérick Blouin Behzad Mostajir Jean‐Claude Therriault Christian Nozais Serge Demers 《Journal of phycology》2008,44(3):551-563
Diel variations of cellular optical properties were examined for cultures of the haptophyte Imantonia rotunda N. Reynolds and the diatom Thalassiosira pseudonana (Hust.) Hasle et Heimdal grown under a 14:10 light:dark (L:D) cycle and transferred from 100 μmol photons · m?2 · s?1 to higher irradiances of 250 and 500 μmol photons · m?2 · s?1. Cell volume and abundance, phytoplankton absorption coefficients, flow‐cytometric light scattering and chl fluorescence, and pigment composition were measured every 2 h over a 24 h period. Results showed that cell division was more synchronous for I. rotunda than for T. pseudonana. Several variables exhibited diel variability with an amplitude >100%, notably mean cell volume for the haptophyte and photoprotective carotenoids for both species, while optical properties such as flow‐cytometric scattering and chl a–specific phytoplankton absorption generally showed <50% diel variability. Increased irradiance induced changes in pigments (both species) and mean cell volume (for the diatom) and amplified diel variability for most variables. This increase in amplitude is larger for pigments (factor of 2 or more, notably for cellular photoprotective carotenoid content in I. rotunda and for photosynthetic pigments in T. pseudonana) than for optical properties (a factor of 1.5 for chl a–specific absorption, at 440 nm, in I. rotunda and a factor of 2 for the absorption cross‐section and the chl a–specific scattering in T. pseudonana). Consequently, diel changes in optical properties and pigmentation associated with the L:D cycle and amplified by concurrent changes in irradiance likely contribute significantly to the variability in optical properties observed in biooptical field studies. 相似文献
19.
In spring 2005, monthly sampling was carried out at a sublittoral site near Tautra Island. Microphytobenthic identification, abundance (ABU), and biomass (BIOM), were performed by microscopic analyses. Bacillariophyceae accounted for 67% of the total ABU, and phytoflagellates constituted 30%. The diatom floristic list consisted of 38 genera and 94 species. Intact light‐harvesting pigments chl a, chl c, and fucoxanthin and their derivatives were identified and quantified by HPLC. Photoprotective carotenoids were also observed (only as diadinoxanthin; no diatoxanthin was detected). Average fucoxanthin content was 4.57 ± 0.45 μg fucoxanthin · g sediment dry mass?1, while the mean chl a concentration was 2.48 ± 0.15 μg · g?1 dry mass. Both the high fucoxanthin:chl a ratio (considering nondegraded forms) and low amounts of photoprotective carotenoids indicated that the benthic microalgal community was adapted to low light. Microphytobenthic primary production was estimated in situ (MPPs, from 0.15 to 1.28 mg C · m?2 · h?1) and in the laboratory (MPPp, from 6.79 to 34.70 mg C · m?2 · h?1 under light saturation) as 14C assimilation; in April it was additionally estimated from O2‐microelectrode studies (MPPO2) along with the community respiration. MPPO2 and the community respiration equaled 22.9 ± 7.0 and 7.4 ± 1.8 mg C · m?2 · h?1, respectively. A doubling of BIOM from April to June in parallel with a decreasing photosynthetic activity per unit chl a led us to suggest that the microphytobenthic community was sustained by heterotrophic metabolism during this period. 相似文献
20.
Yuki Watanabe Gregory N. Nishihara Shigemitsu Tokunaga Ryuta Terada 《Phycological Research》2014,62(3):187-196
The effect of irradiance and temperature on the photosynthesis of the red alga, Pyropia tenera, was determined for maricultured gametophytes and sporophytes collected from a region that is known as one of the southern limits of its distribution in Japan. Macroscopic gametophytes were examined using both pulse‐amplitude modulated fluorometry and/or dissolved oxygen sensors. A model of the net photosynthesis–irradiance (P‐E) relationship of the gametophytes at 12°C revealed that the net photosynthetic rate quickly increased at irradiances below the estimated saturation irradiance of 46 μmol photons m?2 s?1, and the compensation irradiance was 9 μmol photons m?2 s?1. Gross photosynthesis and dark respiration for the gametophytes were also determined over a range of temperatures (8–34°C), revealing that the gross photosynthetic rates of 46.3 μmol O2 mgchl‐a?1 min?1 was highest at 9.3 (95% Bayesian credible interval (BCI): 2.3–14.5)°C, and the dark respiration rate increased at a rate of 0.93 μmol O2 mgchl‐a?1 min?1°C?1. The measured dark respiration rates ranged from ?0.06 μmol O2 mgchl‐a?1 min?1 at 6°C to ?25.2 μmol O2 mgchl‐a?1 min?1 at 34°C. The highest value of the maximum quantum yield (Fv/Fm) for the gametophytes occurred at 22.4 (BCI: 21.5–23.3) °C and was 0.48 (BCI: 0.475–0.486), although those of the sporophyte occurred at 12.9 (BCI: 7.4–15.1) °C and was 0.52 (BCI: 0.506–0.544). This species may be considered well‐adapted to the current range of seawater temperatures in this region. However, since the gametophytes have such a low temperature requirement, they are most likely close to their tolerable temperatures in the natural environment. 相似文献