共查询到20条相似文献,搜索用时 29 毫秒
1.
Judith D. L. van Bleijswijk Rob S. Kempers Marcel J. Veldhuis Peter Westbroek 《Journal of phycology》1994,30(2):230-241
Two morphotypes of Emiliania huxleyi (Lohmann 1902) Hay et al. 1967, types A and B, known to be unequally distributed in the oceans, were grown in dilution cultures at a range of photon flux densities (PFDs) (1.5–155 μmol photons·m?2·s?1) and two temperatures (10° and 15° C). Calcite carbon and organic carbon content of the cells as well as instantaneous growth rate, cell size, chlorophyll fluorescence, and light-scatter properties clearly depended on growth conditions and differed considerably for the two morphotypes. The ratio between calcite carbon and organic carbon production showed an optimum of 0.65 in E. huxleyi type A cells at PFD = 17.5. The ratio increased slightly with a temperature increase from 10° to 15°C but remained < 1.0 at both temperatures in light-limited cells. In contrast, calcite carbon production exceeded organic carbon production (ratio: 1.4–2.2) in phosphate-deprived cultures. Emiliania huxleyi type B generally showed a higher calcite carbon/organic carbon ratio than E. huxleyi type A, but the relation with PFD was similar. The content of calcite carbon and organic carbon as well as the instantaneous growth rate, cell size, chlorophyll fluorescence, and light-scatter properties showed large diel variations that were closely related to the division cycle. Our results show the importance of mapping the structure of any sampled cell population with respect to the phase in the cell division cycle, as this largely determines the outcome of not only “per cell” measurements but also short time (less than 24 h) flux measurements. For instance, dark production of calcite by E. huxleyi was negatively affected by cell division. Slowly growing (phosphate-stressed) cultures produced calcite in the light and in the dark. In contrast, rapidly growing cultures at 10°C produced calcite only in the light, whereas in the dark there was a significant loss of calcite due to dissolution. 相似文献
2.
R.C. Anderson N.A. Krueger J.A. Byrd R.B. Harvey T.R. Callaway T.S. Edrington D.J. Nisbet 《Journal of applied microbiology》2009,107(4):1258-1268
Aims: To determine if the purported deaminase inhibitors diphenyliodonium chloride (DIC) and thymol reduce the growth and survivability of Campylobacter. Methods and Results: Growth rates of Campylobacter jejuni and Camp. coli were reduced compared to unsupplemented controls during culture in Muellar–Hinton broth supplemented with 0·25 μmol DIC or thymol ml?1 but not with 0·01 μmol monensin ml?1 or 1% ethanol. Recovery of Camp. jejuni and Camp. coli was reduced >5 log10 CFU from controls after 24 h pure culture in Bolton broth supplemented with 0·25 or 1·0 μmol DIC ml?1 or with 1·0 μmol thymol ml?1. Similarly, each test Campylobacter strain was reduced >3 log10 CFU from controls after 24 h mixed culture with porcine faecal microbes in Bolton broth supplemented with 0·25 or 1·0 μmol DIC ml?1 or with 1·0 μmol thymol ml?1. Treatments with 0·25 μmol thymol ml?1, 0·01 μmol monensin ml?1 or 1% ethanol were less effective. Ammonia production during culture or incubation of cell lysates was reduced by 0·25 or 1·0 μmol DIC ml?1 but only intermittently reduced, if at all, by the other treatments. Conclusions: Diphenyliodonium chloride and thymol reduced growth, survivability and ammonia production of Camp. jejuni and Camp. coli. Significance and Impact of the Study: Results suggest a potential physiological characteristic that may be exploited to develop interventions. 相似文献
3.
Erik T. Buitenhuis Hein J. W. de Baar Marcel J. W. Veldhuis 《Journal of phycology》1999,35(5):949-959
To test the possibility of inorganic carbon limitation of the marine unicellular alga Emiliania huxleyi (Lohmann) Hay and Mohler, its carbon acquisition was measured as a function of the different chemical species of inorganic carbon present in the medium. Because these different species are interdependent and covary in any experiment in which the speciation is changed, a set of experiments was performed to produce a multidimensional carbon uptake scheme for photosynthesis and calcification. This scheme shows that CO2 that is used for photosynthesis comes from two sources. The CO2 in seawater supports a modest rate of photosynthesis. The HCO is the major substrate for photosynthesis by intracellular production of CO2 (HCO+ H+→ CO2+ H2O → CH2O + O2). This use of HCO is possible because of the simultaneous calcification using a second HCO, which provides the required proton (HCO+ Ca2+→ CaCO3+ H+). The HCO is the only substrate for calcification. By distinguishing the two sources of CO2 used in photosynthesis, it was shown that E. huxleyi has a K½ for external CO2 of “only” 1.9 ± 0.5 μM (and a Vmax of 2.4 ± 0.1 pmol·cell−1·d−1). Thus, in seawater that is in equilibrium with the atmosphere ([CO2]= 14 μM, [HCO]= 1920 μM, at fCO2= 360 μatm, pH = 8, T = 15° C), photosynthesis is 90% saturated with external CO2. Under the same conditions, the rate of photosynthesis is doubled by the calcification route of CO2 supply (from 2.1 to 4.5 pmol·cell−1·d−1). However, photosynthesis is not fully saturated, as calcification has a K½ for HCO of 3256 ± 1402 μM and a Vmax of 6.4 ± 1.8 pmol·cell−1·d−1. The H+ that is produced during calcification is used with an efficiency of 0.97 ± 0.08, leading to the conclusion that it is used intracellularly. A maximum efficiency of 0.88 can be expected, as NO uptake generates a H+ sink (OH− source) for the cell. The success of E. huxleyi as a coccolithophorid may be related to the efficient coupling between H+ generation in calcification and CO2 fixation in photosynthesis. 相似文献
4.
William M. Balch Katherine Kilpatrick Patrick M. Holligan Terry Cucci 《Journal of phycology》1993,29(5):566-575
Laboratory experiments were performed with the prymnesiophyte Emiliania huxleyi (Lohm.) Hay and Mohler, strain 88E, to quantify calcification per cell, coccolith detachment, and effects of coccolith production on optical scattering of individual cells. 14C incorporation into attached and detached coccoliths was measured using a bulk filtration technique. 14C-labeled cells also were sorted using a flow cytometer and analyzed for carbon incorporation into attached coccoliths. The difference between the bulk and flow cytometer analyses provided a 14C-based estimate of the rate of production of detached coccoliths. Coccolith production and detachment were separated in time in batch cultures, with most detachment happening well after calcification had stopped. Accumulation of coccoliths was maximum at the end of logarithmic growth with 50–80 coccoliths per cell (three to five complete layers of coccoliths around the cells). Net accretion rates of coccoliths were on the order of 7 coccoliths· cell?1·d?1 while net detachment rates were as high as 15 coccoliths· cell?1·d?1 for stationary phase cells. Equal numbers of coccoliths were attached and detached early in logarithmic growth, and as cells aged, the numbers of detached coccoliths exceeded the attached ones by a factor of 6. Our results demonstrate pronounced charges of forward angle light scatter and 90° light scatter of cells as they grow logarithmically and enter stationary phase. Counts of loose coccoliths in batch cultures are consistent with the detachment of coccoliths in layers rather than individual coccoliths. 相似文献
5.
6.
Roel Riegman Willem Stolte Anna A. M. Noordeloos Doris Slezak 《Journal of phycology》2000,36(1):87-96
Emiliania huxleyi (strain L) expressed an exceptional P assimilation capability. Under P limitation, the minimum cell P content was 2.6 fmol P·cell?1, and cell N remained constant at all growth rates at 100 fmol N·cell?1. Both, calcification of cells and the induction of the phosphate uptake system were inversely correlated with growth rate. The highest (cellular P based) maximum phosphate uptake rate (VmaxP) was 1400 times (i.e. 8.9 h?1) higher than the actual uptake rate. The affinity of the P‐uptake system (dV/dS) was 19.8 L·μmol?1·h?1 at μ = 0.14 d?1. This is the highest value ever reported for a phytoplankton species. Vmax and dV/dS for phosphate uptake were 48% and 15% lower in the dark than in the light at the lowest growth rates. The half‐saturation constant for growth was 1.1 nM. The coefficient for luxury phosphate uptake (Qmaxt/Qmin) was 31. Under P limitation, E. huxleyi expressed two different types of alkaline phosphatase (APase) enzyme kinetics. One type was synthesized constitutively and possessed a Vmax and half‐saturation constant of 43 fmol MFP·cell?1·h?1 and 1.9 μM, respectively. The other, inducible type of APase expressed its highest activity at the lowest growth rates, with a Vmax and half‐saturation constant of 190 fmol MFP·cell?1·h?1 and 12.2 μM, respectively. Both APase systems were located in a lipid membrane close to the cell wall. Under N‐limiting growth conditions, the minimum N quotum was 43 fmol N·cell?1. The highest value for the cell N‐specific maximum nitrate uptake rate (VmaxN) was 0.075 h?1; for the affinity of nitrate uptake, 0.37 L·μmol?1·h?1. The uptake rate of nitrate in the dark was 70% lower than in the light. N‐limited cells were smaller than P‐limited cells and contained 50% less organic and inorganic carbon. In comparison with other algae, E. huxleyi is a poor competitor for nitrate under N limitation. As a consequence of its high affinity for inorganic phosphate, and the presence of two different types of APase in terms of kinetics, E. huxleyi is expected to perform well in P‐controlled ecosystems. 相似文献
7.
The toxigenic diatom Pseudo‐nitzschia cuspidata, isolated from the U.S. Pacific Northwest, was examined in unialgal batch cultures to evaluate domoic acid (DA) toxicity and growth as a function of light, N substrate, and growth phase. Experiments conducted at saturating (120 μmol photons · m?2 · s?1) and subsaturating (40 μmol photons · m?2 · s?1) photosynthetic photon flux density (PPFD), demonstrate that P. cuspidata grows significantly faster at the higher PPFD on all three N substrates tested [nitrate (NO3?), ammonium (NH4+), and urea], but neither cellular toxicity nor exponential growth rates were strongly associated with one N source over the other at high PPFD. However, at the lower PPFD, the exponential growth rates were approximately halved, and the cells were significantly more toxic regardless of N substrate. Urea supported significantly faster growth rates, and cellular toxicity varied as a function of N substrate with NO3?‐supported cells being significantly more toxic than both NH4+‐ and urea‐supported cells at the low PPFD. Kinetic uptake parameters were determined for another member of the P. pseudodelicatissima complex, P. fryxelliana. After growth of these cells on NO3? they exhibited maximum specific uptake rates (Vmax) of 22.7, 29.9, 8.98 × 10?3 · h?1, half‐saturation constants (Ks) of 1.34, 2.14, 0.28 μg‐at N · L?1, and affinity values (α) of 17.0, 14.7, 32.5 × 10?3 · h?1/(μg‐at N · L?1) for NO3?, NH4+ and urea, respectively. These labo‐ratory results demonstrate the capability of P. cuspidata to grow and produce DA on both oxidized and reduced N substrates during both exponential and stationary growth phases, and the uptake kinetic results for the pseudo‐cryptic species, P. fryxelliana suggest that reduced N sources from coastal runoff could be important for maintenance of these small pennate diatoms in U.S. west coast blooms, especially during times of low ambient N concentrations. 相似文献
8.
Changes in the species composition, photosynthesis, calcification and size-fractionated carbon metabolism by natural phytoplankton assemblages were monitored in three mesocosms under different nutrient conditions during May 1993. In the 3 enclosures, the decline of the diatom-dominated assemblages was followed by the development of a bloom of the coccolithoporid Emiliania huxleyi. Highest growth of E. huxleyi was observed in the mesocosm with a high N : P ratio, suggesting this species is a good competitor at low phosphate concentrations. The transition from diatom- to E. huxleyi-dominated assemblages brought about a sharp reduction of the phytoplankton standing stock and carbon-specific photosynthetic rate. The relative contribution of the smaller size fraction to total photosynthesis increased as the succession progressed. Calcification rate and E. huxleyi cell-specified calcite production were highest during the early stages of development of the E. huxleyi bloom. Distinct changes in the patterns of 14C allocation into biomolecules were noticed during the diatom-E. huxleyi succession. The diatom-dominated assemblage showed high relative 14C incorporation into low molecular weight metabolites (LMWM), whereas proteins and, specially, lipids accounted for the largest proportion of carbon incorporation in the E. huxleyi bloom. The patterns of photoassimilated carbon metabolism proved to be strongly dependent on cellular size, as protein relative synthesis was significantly higher in the smaller than in the larger size fraction, irrespective of the nutrient regime and the successional stage. These results are discussed in relation to the ecological and physiological features of small phytoplankton. 相似文献
9.
The main effects and interactions between light (Io, full incident sunlight to 0.07 Io) and NO3? loading (0.4 to 4.3 mmol · g dry weight?1· d?1) on growth rate, photosynthesis and biochemical constituents of Gracilaria tikvahiae McLachlan were studied using a factorial design experiment in outdoor, continuous-flow seawater cultures. Incipient nitrogen limitation in the low NO3? loading, Io and 0.57 Io treatments occurred after 2.5 weeks of growth under the experimental conditions and resulted in decreased tissue NO3? and R-phycoerythrin. Tissue NO3? and R-phycoerythrin accounted for up to ca. 15 and 20%, respectively, of the total N in G. tikvahiae suggesting a N reserve role for these N pools. Under light and NO3? limitation, growth rate was a parabolic function of the C:N ratio. As light limitation increased, growth rate and the C:N ratio decreased as levels of Chl-a, R-phycoerythrin, percent N and percent protein increased. As NO3? limitation increased, growth rate and levels of Chl-a, R-phycoerythrin, percent N and percent protein all decreased with parallel increases in the C:N ratio. In contrast to the inverse relationship between pigment content and light, ribulose bisphosphate carboxylase (RuBPCase) activity (on both a protein and dry weight basis) varied directly with light. This biochemical acclimation of G. tikvahiae to light and N availability appears to be a process directed towards maximizing photo synthetic capacity and growth. 相似文献
10.
Induction of nitrate uptake and nitrate reductase activity in trembling aspen and lodgepole pine 总被引:3,自引:0,他引:3
X. Min M. Y. Siddiqi R. D. Guy A. D. M. Glass & H. J. Kronzucker 《Plant, cell & environment》1998,21(10):1039-1046
13NO3– influx into the roots and in vivo nitrate reductase activity (NRA) in the roots and leaves have been measured in trembling aspen (Populus tremuloides Michx.) and lodgepole pine (Pinus contorta Dougl.) seedlings after exposure to either 0·1 or 1·5 mol m–3 NO3– for varying periods up to 20 d. Both NO3– influx and NRA were inducible in these species and, in trembling aspen, peak induction of nitrate influx and NRA were achieved within 12 h, compared to 2–4 d for influx and 4–12 d for NRA in lodgepole pine. In trembling aspen, ≈ 30% of the total 13N absorbed during a 10 min influx period followed by 2 min of desorption was translocated to the shoot. In lodgepole pine, by contrast, translocation of 13N to the shoot was undetectable during the same time period. Root NRA as well as NO3– influx from 0·1 mol m–3 NO3– were substantially higher in trembling aspen than in lodgepole pine at all stages of NO3– exposure, i.e. during the uninduced, the peak induction, and steady-state stages. In order to examine whether the lower rates of NO3– influx and NRA were related to proportionately fewer young (unsuberized) roots in lodgepole pine, we determined these parameters in young and old (suberized) roots of this species separately. Induction of influx and NRA were initially greater in young roots but at steady-state there were only minor differences between the young and the old roots. However, even the elevated initial rates in the young roots of lodgepole pine were substantially lower than those of aspen. In pine, influx at 1·5 mol m–3 NO3– was ~ 6-fold higher than at 0·1 mol m–3 NO3– and appeared to be mostly via a constitutive system. By contrast, in aspen, steady-state influxes at 0·1 and 1·5 mol m–3 were not significantly different, being similar to the rate attained by pine at only the higher [NO3–]. In aspen, leaf NRA was ~ 2-fold higher than that of roots. In lodgepole pine NRA of the needles was below the detection limit. These results show that trembling aspen seedlings are better adapted for NO3– acquisition and utilization than lodgepole pine seedlings. 相似文献
11.
Physiological properties of photosynthesis were determined in the marine diatom, Phaeodactylum tricornutum UTEX640, during acclimation from 5% CO2 to air and related to H2CO3 dissociation kinetics and equilibria in artificial seawater. The concentration of dissolved inorganic carbon at half maximum rate of photosynthesis (K0·5[DIC]) value in high CO2‐grown cells was 1009 mmol m ? 3 but was reduced three‐fold by the addition of bovine carbonic anhydrase (CA), whereas in air‐grown cells K0·5[DIC] was 71 mmol m ? 3, irrespective of the presence of CA. The maximum rate of photosynthesis (Pmax) values varied between 300 and 500 μ mol O2 mg Chl ? 1 h ? 1 regardless of growth pCO2. Bicarbonate dehydration kinetics in artificial seawater were re‐examined to evaluate the direct HCO3 ? uptake as a substrate for photosynthesis. The uncatalysed CO2 formation rate in artificial seawater of 31·65°/oo of salinity at pH 8·2 and 25 °C was found to be 0·6 mmol m ? 3 min ? 1 at 100 mmol m ? 3 DIC, which is 53·5 and 7·3 times slower than the rates of photosynthesis exhibited in air‐ and high CO2‐grown cells, respectively. These data indicate that even high CO2‐grown cells of P. tricornutum can take up both CO2 and HCO3 ? as substrates for photosynthesis and HCO3 ? use improves dramatically when the cells are grown in air. Detailed time courses were obtained of changes in affinity for DIC during the acclimation of high CO2‐grown cells to air. The development of high‐affinity photosynthesis started after a 2–5 h lag period, followed by a steady increase over the next 15 h. This acclimation time course is the slowest to be described so far. High CO2‐grown cells were transferred to controlled DIC conditions, at which the concentrations of each DIC species could be defined, and were allowed to acclimate for more than 36 h. The K0·5[DIC] values in acclimated cells appeared to be correlated only with [CO2(aq)] in the medium but not to HCO3 ? , CO32 ? , total [DIC] or the pH of the medium and indicate that the critical signal regulating the affinity of cells for DIC in the marine diatom, P. tricornutum, is [CO2(aq)] in the medium. 相似文献
12.
T.P. Chang 《欧洲藻类学杂志》2013,48(3):207-210
Gloeotrichia echinulata, isolated in axenic culture, grows in medium free of combined nitrogen but better growth occurs in the presence of low levels of combined nitrogen (5–12 mm NO- 3; 0·1–2·0 mm NH+ 4). The addition of 5–40 mm glucose and the addition of soil extract also stimulate growth. Heterocyst frequency declines in the presence of high levels of combined nitrogen, but the effect of added glucose on heterocyst frequency is equivocal. Soil extract inhibits heterocyst production. Significant acetylene reduction activity is found only in the light with rates in the presence of NO- 3 and in the presence of exogenous glucose being higher than on N2. NH+ 4 inhibited nitrogenase activity. 相似文献
13.
The aim of the work was to find the optimal photon irradiance for the growth of green cells of Haematococcus pluvialis and to study the interrelations between changes in photochemical parameters and pigment composition in cells exposed to photon irradiances between 50 and 600?µmol?m?2?s?1 and a light:dark cycle of 12:12?h. Productivity of cultures increased with irradiance. However, the rate of increase was higher in the range 50–200?µmol??2?s?1. The carotenoid content increased with increasing irradiance, while the chlorophyll content decreased. The maximum quantum yield of PSII (Fv/Fm) gradually declined from 0.76 at the lowest irradiance of 50?µmol??2?s?1 to 0.66 at 600?µmol??2?s?1. Photosynthetic activity showed a drop at the end of the light period, but recovered fully during the following dark phase. A steep increase in non-photochemical quenching was observed when cultures were grown at irradiances above 200?µmol??2?s?1. A sharp increase in the content of secondary carotenoids also occurred above 200?µmol?m?2?s?1. According to our results, with H. pluvialis green cells grown in a 5-cm light path device, 200?µmol??2?s?1 was optimal for growth, and represented a threshold above which important changes in both photochemical parameters and pigment composition occurred. 相似文献
14.
Growth rate, pigment composition, and noninvasive chl a fluorescence parameters were assessed for a noncalcifying strain of the prymnesiophyte Emiliania huxleyi Lohman grown at 50, 100, 200, and 800 μmol photons·m?2·s?1. Emiliania huxleyi grown at high photon flux density (PFD) was characterized by increased specific growth rates, 0.82 d?1 for high PFD grown cells compared with 0.38 d?1 for low PFD grown cells, and higher in vivo chl a specific attenuation coefficients that were most likely due to a decreased pigment package, consistent with the observed decrease in cellular photosynthetic pigment content. High PFD growth conditions also induced a 2.5‐fold increase in the pool of the xanthophyll cycle pigments diadinoxanthin and diatoxanthin responsible for dissipation of excess energy. Dark‐adapted maximal photochemical efficiency (Fv/Fm) remained constant at around 0.58 for cells grown over the range of PFDs, and therefore the observed decline, from 0.57 to 0.33, in the PSII maximum efficiency in the light‐adapted state, (Fv′/Fm′), with increasing growth PFD was due to increased dissipation of excess energy, most likely via the xanthophyll cycle and not due to photoinhibition. The PSII operating efficiency (Fq′/Fm′) decreased from 0.48 to 0.21 with increasing growth PFD due to both saturation of photochemistry and an increase in nonphotochemical quenching. The changes in the physiological parameters with growth PFD enable E. huxleyi to maximize rates of photosynthesis under subsaturating conditions and protect the photosynthetic apparatus from excess energy while supporting higher saturating rates of photosynthesis under saturating PFDs. 相似文献
15.
Nitric oxide, a gaseous free radical, is poorly reactive with most biomolecules but highly reactive with other free radicals. Its ability to scavenge peroxyl and other damaging radicals may make it an important antioxidant in vivo, particular in the cardiovascular system, although this ability has been somewhat eclipsed in the literature by a focus on the toxicity of peroxynitrite, generated by reaction of O·-2 with NO· (or of NO- with O2). On balance, experimental and theoretical data support the view that ONOO- can lead to hydroxyl radical (OH·) generation at pH 7.4, but it seems unlikely that OH· contributes much to the cytotoxicity of ONOO-. The cytotoxicity of ONOO- may have been over-emphasized: its formation and rapid reaction with antioxidants may provide a mechanism of using NO· to dispose of excess O·-2, or even of using O·-2 to dispose of excess NO·, in order to maintain the correct balance between these radicals in vivo. Injection or instillation of “bolus” ONOO- into animals has produced tissue injury, however, although more experiments generating ONOO- at steady rates in vivo are required. The presence of 3-nitrotyrosine in tissues is still frequently taken as evidence of ONOO- generation in vivo, but abundant evidence now exists to support the view that it is a biomarker of several “reactive nitrogen species”. Another under-addressed problem is the reliability of assays used to detect and measure 3-nitrotyrosine in tissues and body fluids: immunostaining results vary between laboratories and simple HPLC methods are susceptible to artefacts. Exposure of biological material to low pH (e.g. during acidic hydrolysis to liberate nitrotyrosine from proteins) or to H2O2 might cause artefactual generation of nitrotyrosine from NO-2 in the samples. This may be the origin of some of the very large values for tissue nitrotyrosine levels quoted in the literature. Nitrous acid causes not only tyrosine nitration but also DNA base deamination at low pH: these events are relevant to the human stomach since saliva and many foods are rich in nitrite. Several plant phenolics inhibit nitration and deamination in vitro, an effect that could conceivably contribute to their protective effects against gastric cancer development. 相似文献
16.
There is still considerable uncertainty about the relationship between calcification and photosynthesis. It has been suggested that since calcification in coccolithophorids is an intracellular process that releases CO2, it enhances photosynthesis in a manner analogous to a carbon‐concentrating mechanism (CCM). The ubiquitous, bloom‐forming, and numerically abundant coccolithophorid Emiliania huxleyi (Lohmann) W. W. Hay et H. Mohler was studied in nutrient‐replete, pH and [CO2] controlled, continuous cultures (turbidostats) under a range of [Ca2+] from 0 to 9 mM. We examined the long‐term, fully acclimated photosynthesis‐light responses and analyzed the crystalline structure of the coccoliths using SEM. The E. huxleyi cells completely lost their coccosphere when grown in 0 [Ca2+], while thin, undercalcified and brittle coccoliths were evident at 1 mM [Ca2+]. Coccoliths showed increasing levels of calcification with increasing [Ca2+]. More robust coccoliths were noted, with no discernable differences in coccolith morphology when the cells were grown in either 5 or 9 mM (ambient seawater) [Ca2+]. In contrast to calcification, photosynthesis was not affected by the [Ca2+] in the media. Cells showed no correlation of their light‐dependent O2 evolution with [Ca2+], and in all [Ca2+]‐containing turbidostats, there were no significant differences in growth rate. The results show unequivocally that as a process, photosynthesis in E. huxleyi is mechanistically independent from calcification. 相似文献
17.
M. ASHRAF 《The Annals of applied biology》1999,135(2):509-513
The effects of the ammonium (NH4+) and nitrate (NO3-) forms of nitrogen and NaCl on the growth, water relations and photosynthesis performance of sunflower (Helianthus annuus L.) were examined under glasshouse conditions. Eight-day-old plants of cv. Hisun 33 were subjected for 21 days to Hoagland's nutrient solution containing 8 mol m-3N as NH4+or NO3-, and salinised with 0, 60, or 120 mol m-3NaCl. Fresh weights of shoots and roots, and leaf area of NO3-supplied non-salinised plants were significantly greater than those of NH4+-supplied non-salinised plants. But addition of NaCl to the rooting medium of these plants had more inhibitory effect on the growth of NO3--supplied plants than on NH4+-supplied plants. Both leaf water and osmotic potentials of plants grown with NH4+were lower than those of plants given NO3-under both non-saline and saline conditions. Chlorophylls a and b concentrations were higher in plants grown with NH4+than N03--supplied plants at the lower two levels of salinisation. The rate of photosynthesis in plants was considerably higher in non-salinised plants grown with NO3-than with NH4+, but with increase in salinisation the photosynthesis rate decreased in NO3--supplied plants, but not in those given NH4+. The rate of transpiration was increased significantly by salinisation in NO3--supplied plants, but not consistently so in NH4+-supplied plants. The stomatal conductances were much higher in plants given NO3-than with NH4+when grown under non-saline conditions, but not when salinised. As a consequence, water-use efficiency in NO3--supplied control plants was better than in NH4+-supplied under non-saline conditions, but worse under saline conditions. The different forms of nitrogen and the addition of NaCl to the growing medium did not affect the relative intercellular concentrations of CO2 (Ci/Ca). Overall, the NH4+form of nitrogen inhibited the growth of sunflowers under non-saline conditions, but NO3-and NaCl interacted to inhibit growth more than did NH4+under saline conditions. 相似文献
18.
The growth of heterocystous bluegreen algae in various concentrations of sodium, was examined in axenic culture as well as in situ studies. Anabaena cylindrica Lemm. with no Na+ added, suffered from decreased rates of acetylene reduction, 14C, assimilation, excretion of organic C as well as lower concentrations of chlorophyll a and particulate organic C compared to cultures supplied with 5, 10, and 50 mg Na+·l−1 Sodium deficient algae released, extracellularly a higher percentage of previously fixed C as organic C. No differences in any parameter measured were demonstrable among cultures grown with 5, 10, and 50 mg Na+·l−1 High nitrate concentrations (20 mg NO3−·l−1) resulted in decreased rates of acetylene reduction and heterocyst numbers in. Na sufficient, and Na deficient cultures: however, decreased, cellular Na content at high NO3− levels occurred only in N deficient, cultures. Higher percentages of excreted organic C occurred with increasing NO3− concentrations in Na deficient cultures. Sodium enrichment of natural bluegreen populations with the addition of 50, 100, and 200 mg Na+·l−1 elicited neither a stimulatory nor an inhibitory response in photosynthetic C fixation. In contrast, the addition of small amounts of Na+ (5 mg·l−) resulted in increased C fixation. However, since the Na. concentration of the lake water, at ca. 5 mg Na+·l−1, was sufficient for growth of the bluegreens present, sodium, is not assumed to be limiting under most natural conditions. No increase in in situ acetylene reduction rates occurred with additions of sodium. 相似文献
19.
马尾松属高氮需求树种,然而在苗木培育中马尾松对氮素,尤其是不同形态氮素的需求尚不明确.该文以马尾松组培苗为试验材料,采用基质培养方法,针对硝态氮、铵态氮两种氮素形态均分别设置了2、4、8、16 mmol·L-14个处理,以不添加氮素为对照,对苗木的高径生长、根构型参数(总根长、总表面积、总体积、平均直径和根尖数)以及生... 相似文献
20.
Kre Lindstrm 《Journal of phycology》1991,27(2):207-219
Optimum nutrient conditions for growth and photosynthesis of Peridinium gatunense (Nygaard) (Peridinium cinctum fa. westii) were investigated using axenic clones in batch cultures. Selenium (Se) had previously been found to be an indispensable growth factor for P. gatunense. Optimal, suboptimal, and supraoptimal concentrations of HCO3?, N, Ca, Cl, Mg, P, K, S, Si, EDTA-Na, Fe, Mo, Zn, Mn, Co, Se, B, Br, I, and various trace element mixtures were determined by measuring biomass development, growth rates, 14C uptake, and/or oxygen production at various concentration gradients of these elements. The general characteristics of the best formulation, medium-L 16, relative to other media, are its high content of NaHCO3 (1 meq · L?1) and Mo (0.2 μM) but low concentrations of NO3-N (150 μM), PO4-P (10 μM), and Fe (0.4 μM), in addition to its content of Se. The total content of trace metals, except for Se, may be reduced to one-fourth of that in medium-L 16 without altering the major growth-promoting properties of the medium. Medium-L 16 deviated considerably from Lake Kinneret (Israel) water, being much lower in macroelements except for N and P. The pH (8.1–8.4) was in the same range, but the values of conductivity (140 μS · cm?1), alkalinity (1 meq · L?1) and NaCl (200 μM) were > 8, 2, and 30 times higher, respectively, in the lake water. Selenium deficiency may limit the growth of P. gatunense in this lake. 相似文献