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1.
《Aquatic Botany》2005,81(2):157-173
The main photosynthesis and respiration parameters (dark respiration rate, light saturated production rate, saturation irradiance, photosynthetic efficiency) were measured on a total of 23 macrophytes of the Thau lagoon (2 Phanerogams, 5 Chlorophyceae, 10 Rhodophyceae and 6 Phaeophyceae). Those measurements were performed in vitro under controlled conditions, close to the natural ones, and at several seasons. Concomitantly, measurements of pigment concentrations, carbon, phosphorous and nitrogen contents in tissues were performed. Seasonal intra-specific variability of photosynthetic parameters was found very high, enlightening an important acclimatation capacity. The highest photosynthetic capacities were found for Chlorophyceae (e.g. Monostroma obscurum thalli at 17 °C, 982 μmol O2 g−1 dw h−1 and 9.1 μmol O2 g−1 dw h−1/μmol photons m−2 s−1, respectively for light saturated net production rate and photosynthetic efficiency) and Phanerogams (e.g. Nanozostera noltii leaves at 25 °C, 583 μmol O2 g−1 dw h−1 and 2.6 μmol O2 g−1 dw h−1/μmol photons m−2 s−1 respectively for light saturated net production rate and photosynthetic efficiency). As expected, species with a high surface/volume ratio were found to be more productive than coarsely branched thalli and thick blades shaped species. Contrary to Rd (ranging 6.7–794 μmol O2 g−1 dw h−1, respectively for Rytiphlaea tinctoria at 7 °C and for Dasya sessilis at 25 °C) for which a positive relationship with water temperature was found whatever the species studied, the evolution of P/I curves with temperature exhibited different responses amongst the species. The results allowed to show summer nitrogen limitation for some species (Gracilaria bursa-pastoris and Ulva spp.) and to propose temperature preferences based on the photosynthetic parameters for some others (N. noltii, Zostera marina, Chaetomorpha linum). 相似文献
2.
《Bioorganic & medicinal chemistry》2016,24(18):4410-4414
We have cloned, purified and investigated the catalytic activity and anion inhibition profiles of a full catalytic domain (358 amino acid residues) carbonic anhydrase (CA, EC 4.2.1.1) from Plasmodium falciparum, PfCAdom, an enzyme belonging to the η-CA class and identified in the genome of the malaria-producing protozoa. A truncated such enzyme, PfCA1, containing 235 residues was investigated earlier for its catalytic and inhibition profiles. The two enzymes were efficient catalysts for CO2 hydration: PfCAdom showed a kcat of 3.8 × 105 s−1 and kcat/Km of 7.2 × 107 M−1 × s−1, whereas PfCA showed a lower activity compared to PfCAdom, with a kcat of 1.4 × 105 s−1 and kcat/Km of 5.4 × 106 M−1 × s−1. PfCAdom was generally less inhibited by most anions and small molecules compared to PfCA1. The best PfCAdom inhibitors were sulfamide, sulfamic acid, phenylboronic acid and phenylarsonic acid, which showed KIs in the range of 9–68 μM, followed by bicarbonate, hydrogensulfide, stannate and N,N-diethyldithiocarbamate, which were submillimolar inhibitors, with KIs in the range of 0.53–0.97 mM. Malaria parasites CA inhibition was proposed as a new strategy to develop antimalarial drugs, with a novel mechanism of action. 相似文献
3.
《Process Biochemistry》2004,39(11):1599-1605
Fusarium oxysporum F3 produced N-acetyl-β-d-glucosaminidase when grown on wheat bran and chitin as carbon sources in solid-state fermentation. The initial moisture content and pH of growth medium were 65% and 6.0, respectively, and the enzyme yield 23.6 U g−1 carbon source. Two isozymes of N-acetyl-β-d-glucosaminidase, called N-acetyl-β-d-glucosaminidases I and II, were isolated from the culture filtrate of F. oxysporum F3. The filtrate was subjected to ammonium sulphate fractionation followed by anion exchange, gel filtration, hydrophobic interaction and cation exchange chromatography. The optimum pH of isozymes I and II was 5.0 and 6.0, respectively, whereas maximum activity of both isozymes was obtained at 40 °C. The Km of isozymes I and II was 49.6 and 48.6 μM and the Vmax 1.24 and 0.26 μmol mg−1 min−1, respectively, on p-nitrophenyl N-acetyl-β-d-glucosaminide as substrate. The molecular mass of isozymes I and II was calculated to be 67 kDa by SDS–PAGE. 相似文献
4.
《Bioorganic & medicinal chemistry》2014,22(20):5569-5577
AurF catalyzes the N-oxidation of p-aminobenzoic acid to p-nitrobenzoic acid in the biosynthesis of the antibiotic aureothin. Here we report the characterization of AurF under optimized conditions to explore its potential use in biocatalysis. The pH optimum of the enzyme was established to be 5.5 using phenazine methosulfate (PMS)/NADH as the enzyme mediator system, showing ∼10-fold higher activity than previous reports in literature. Kinetic characterization at optimized conditions give a Km of 14.7 ± 1.1 μM, a kcat of 47.5 ± 5.4 min−1 and a kcat/Km of 3.2 ± 0.4 μM−1 min−1. PMS/NADH and the native electron transfer proteins showed significant formation of the p-hydroxylaminobenzoic acid intermediate, however H2O2 produced mostly p-nitrobenzoic acid. Alanine scanning identified the role of important active site residues. The substrate specificity of AurF was examined and rationalized based on the protein crystal structure. Kinetic studies indicate that the Km is the main determinant of AurF activity toward alternative substrates. 相似文献
5.
《Systematic and applied microbiology》2019,42(6):126021
During long-term extra-terrestrial missions, food is limited and waste is generated. By recycling valuable nutrients from this waste via regenerative life support systems, food can be produced in space. Astronauts’ urine can, for instance, be nitrified by micro-organisms into a liquid nitrate fertilizer for plant growth in space. Due to stringent conditions in space, microbial communities need to be be defined (gnotobiotic); therefore, synthetic rather than mixed microbial communities are preferred. For urine nitrification, synthetic communities face challenges, such as from salinity, ureolysis, and organics.In this study, a synthetic microbial community containing an AOB (Nitrosomonas europaea), NOB (Nitrobacter winogradskyi), and three ureolytic heterotrophs (Pseudomonas fluorescens, Acidovorax delafieldii, and Delftia acidovorans) was compiled and evaluated for these challenges. In reactor 1, salt adaptation of the ammonium-fed AOB and NOB co-culture was possible up to 45 mS cm−1, which resembled undiluted nitrified urine, while maintaining a 44 ± 10 mg NH4+–N L−1 d−1 removal rate. In reactor 2, the nitrifiers and ureolytic heterotrophs were fed with urine and achieved a 15 ± 6 mg NO3−–N L−1 d−1 production rate for 1% and 10% synthetic and fresh real urine, respectively. Batch activity tests with this community using fresh real urine even reached 29 ± 3 mg N L−1 d−1. Organics removal in the reactor (69 ± 15%) should be optimized to generate a nitrate fertilizer for future space applications. 相似文献
6.
β-Glucosidase catalyzes the sequential breakdown of cyanogenic glycosides in cyanogenic plants. The β-glucosidase from Prunus armeniaca L. was purified to 8-fold, and 20% yield was obtained, with a specific activity of 281 U/mg protein. The enzyme showed maximum activity in 0.15 M sodium citrate buffer, pH 6, at 35 °C with p-nitrophenylglucopyranoside as substrate. The β-glucosidase from wild apricot was used successfully for the saccharification of cellobiose into D-glucose. This enzyme has a Vmax of 131.6 μmol min−1 mg−1 protein, Km of 0.158 mM, Kcat of 144.8 s−1, Kcat/Km of 917.4 mM−1 s−1, and Km/Vmax of 0.0012 mM min mg μmole−1, using cellobiose as substrate. The half-life, deactivation rate coefficient, and activation energy of this β-glucosidase were 12.76 h, 1.509 × 10−5 s−1, and 37.55 kJ/mol, respectively. These results showed that P. armeniaca is a potential source of β-glucosidase, with high affinity and catalytic capability for the saccharification of cellulosic material. 相似文献
7.
The separate or combined effects of Pichia membranaefaciens and salicylic acid (SA) on the control of blue and green mold decay in citrus fruits were investigated. Results indicate that combining P. membranaefaciens (1 × 108 CFU ml−1) with SA (10 μg ml−1) either in a point-inoculated or dipped treatment provided a more effective control of blue and green mold than separately applying yeast or SA. SA (10 μg ml−1) did not significantly affect P. membranaefaciens growth in vitro but slightly increased the yeast population in fruit wounds. P. membranaefaciens plus SA effectively enhanced the phenylalanine ammonia-lyase, peroxidase, polyphenoloxidase, chitinase, and β-1,3-glucanase activities and stimulated the synthesis of phenolic compounds. The combined treatment did not impair quality parameters such as weight loss or titratable acidity, but resulted in low average natural infection incidence and increased total soluble solids and ascorbic acid contents in citrus fruits after 14 d at 20 °C. 相似文献
8.
《Process Biochemistry》2014,49(10):1606-1611
The filamentous fungus Paecilomyces lilacinus was grown on n-hexadecane in submerged (SmC) and solid-state (SSC) cultures. The maximum CO2 production rate in SmC (Vmax = 11.7 mg CO2 Lg−1 day−1) was three times lower than in SSC (Vmax = 40.4 mg CO2 Lg−1 day−1). The P. lilacinus hydrophobin (PLHYD) yield from the SSC was 1.3 mg PLHYD g protein−1, but in SmC, this protein was not detected. The PLHYD showed a critical micelle concentration of 0.45 mg mL−1. In addition, the PLHYD modified the hydrophobicity of Teflon from 130.1 ± 2° to 47 ± 2°, forming porous structures with some filaments <1 μm and globular aggregates <0.25 μm diameter. The interfacial studies of this PLHYD could be the basis for the use of the protein to modify surfaces and to stabilize compounds in emulsions. 相似文献
9.
《Aquatic Botany》2005,81(4):326-342
The effects of NH4+ or NO3− on growth, resource allocation and nitrogen (N) uptake kinetics of two common helophytes Phragmites australis (Cav.) Trin. ex Steudel and Glyceria maxima (Hartm.) Holmb. were studied in semi steady-state hydroponic cultures. At a steady-state nitrogen availability of 34 μM the growth rate of Phragmites was not affected by the N form (mean RGR = 35.4 mg g−1 d−1), whereas the growth rate of Glyceria was 16% higher in NH4+-N cultures than in NO3−-N cultures (mean = 66.7 and 57.4 mg g−1 d−1 of NH4+ and NO3− treated plants, respectively). Phragmites and Glyceria had higher S/R ratio in NH4+ cultures than in NO3− cultures, 123.5 and 129.7%, respectively.Species differed in the nitrogen utilisation. In Glyceria, the relative tissue N content was higher than in Phragmites and was increased in NH4+ treated plants by 16%. The tissue NH4+ concentration (mean = 1.6 μmol g fresh wt−1) was not affected by N treatment, whereas NO3− contents were higher in NO3− (mean = 1.5 μmol g fresh wt−1) than in NH4+ (mean = 0.4 μmol g fresh wt−1) treated plants. In Phragmites, NH4+ (mean = 1.6 μmol g fresh wt−1) and NO3− (mean = 0.2 μmol g fresh wt−1) contents were not affected by the N regime. Species did not differ in NH4+ (mean = 56.5 μmol g−1 root dry wt h−1) and NO3− (mean = 34.5 μmol g−1 root dry wt h−1) maximum uptake rates (Vmax), and Vmax for NH4+ uptake was not affected by N treatment. The uptake rate of NO3− was low in NH4+ treated plants, and an induction phase for NO3− was observed in NH4+ treated Phragmites but not in Glyceria. Phragmites had low Km (mean = 4.5 μM) and high affinity (10.3 l g−1 root dry wt h−1) for both ions compared to Glyceria (Km = 6.3 μM, affinity = 8.0 l g−1 root dry wt h−1). The results showed different plasticity of Phragmites and Glyceria toward N source. The positive response to NH4+-N source may participates in the observed success of Glyceria at NH4+ rich sites, although other factors have to be considered. Higher plasticity of Phragmites toward low nutrient availability may favour this species at oligotrophic sites. 相似文献
10.
《Harmful algae》2016
Marine toxic dinoflagellates of the genus Gambierdiscus are the causative agents of ciguatera fish poisoning (CFP), a form of seafood poisoning that is widespread in tropical, subtropical and temperate regions worldwide. The distributions of Gambierdiscus australes, Gambierdiscus scabrosus and two phylotypes of Gambierdiscus spp. type 2 and type 3 have been reported for the waters surrounding the main island of Japan. To explore the bloom dynamics and the vertical distribution of these Japanese species and phylotypes of Gambierdiscus, the effects of light intensity on their growth were tested, using a photoirradiation-culture system. The relationship between the observed growth rates and light intensity conditions for the four species/phylotypes were formulated at R > 0.92 (p < 0.01) using regression analysis and photosynthesis-light intensity (P-L) model. Based on this equation, the optimum light intensity (Lmax) and the semi-optimum light intensity range (Ls-opt) that resulted in the maximum growth rate (μmax) and ≥80% μ max values of the four species/phylotypes, respectively, were as follows: (1) the Lmax and Ls-opt of G. australes were 208 μmol photons m−2 s−1 and 91–422 μmol photons m−2 s−1, respectively; (2) those of G. scabrosus were 252 and 120–421 μmol photons m−2 s−1, respectively; (3) those of Gambierdiscus sp. type 2 were 192 and 75–430 μmol photons m−2 s−1, respectively; and (4) those of Gambierdiscus sp. type 3 were ≥427 and 73–427 μmol photons m−2 s−1, respectively. All four Gambierdiscus species/phylotypes required approximately 10 μmol photons m−2 s−1 to maintain growth. The light intensities in coastal waters at a site in Tosa Bay were measured vertically at 1 m intervals once per season. The relationships between the observed light intensity and depth were formulated using Beer’s Law. Based on these equations, the range of the attenuation coefficients at Tosa Bay site was determined to be 0.058–0.119 m−1. The values 1700 μmol photons m−2 s−1, 500 μmol photons m−2 s−1, and 200 μmol photons m−2 s−1 were substituted into the equations to estimate the vertical profiles of light intensity at sunny midday, cloudy midday and rainy midday, respectively. Based on the regression equations coupled with the empirically determined attenuation coefficients for each of the four seasons, the ranges of the projected depths of Lmax and Ls-opt for the four Gambierdiscus species/phylotypes under sunny midday conditions, cloudy midday conditions, and rainy midday conditions were 12–38 m and 12–54 m, 1–16 m and 1–33 m, and 0 m and 0–16 m, respectively. These results suggest that light intensity plays an important role in the bloom dynamics and vertical distribution of Gambierdiscus species/phylotypes in Japanese coastal waters. 相似文献
11.
《Process Biochemistry》2014,49(10):1647-1655
A yellow laccase from the culture filtrate of Trametes hirsuta MTCC-1171 has been purified. The purification methods involved concentration of the culture filtrate by ammonium sulphate precipitation and an anion exchange chromatography on diethylaminoethyl cellulose. The sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and native polyacrylamide gel electrophoresis gave single protein band indicating that the enzyme preparation was pure. The molecular mass of the enzyme determined from SDS-PAGE analysis was 55.0 kDa. Using 2,6-dimethoxyphenol, 2,2′[azino-bis-(3-ethylbonzthiazoline-6-sulphonic acid) diammonium salt] and 3,5-dimethoxy-4-hydroxybenzaldehyde azine as the substrates, the Km, kcat and kcat/Km values of the laccase were found to be 420 μM, 13.04 s−1, 3.11 × 104 M−1 s−1, 225 μM, 13.03 s−1, 1.3 × 105 M−1 s−1 and 100 μM, 13.04 s−1, 5.8 × 104 M−1 s−1, respectively. The pH and temperature optima were 4.5 and 60 °C, respectively while pH and temperature stabilities were pH 4.5 and 50 °C. The activation energy for thermal denaturation of the enzyme was 18.6 kJ/mol/K. The purified laccase has yellow colour and does not show absorption band around 610 nm like blue laccases. The purified laccase transforms toluene, 3-nitrotoluene, 4-nitrotoluene, 3-chlorotoluene, 4-chlorotoluene and 3,4-dimethoxytoluene to benzaldehyde, 3-nitrobenzaldehyde, 4-nitrobenzaldehyde, 3-chlorobenzaldehyde, 4-chlorobenzaldehyde and 3,4-dimethoxybenzaldehyde in the absence of mediator molecules in high yields. 相似文献
12.
《Inorganica chimica acta》2006,359(7):2271-2274
Two dinuclear nickel(II) complexes, [Ni2(L-Et)(N3)(H2O)3](NO3)2 · 2H2O (1) and [Ni2(L-Et)(μ-1,3-N3)(H2O)2](NO3)2 · 4H2O (2) containing (HL-Et = N,N,N′,N′-tetrakis[(1-ethyl-2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane), have been synthesized and characterized by their IR and UV–Vis spectra and magnetic susceptibilities. The crystal structures of [Ni2(L-Et)(N3)(H2O)3](NO3)2 · CH3OH (1′) and [Ni2(L-Et)(μ-1,3-N3)(H2O)2](NO3)2 · 2C2H5OH (2′) similar to 1 and 2 were determined by X-ray crystallography. In 1′, the two nickel(II) ions are bridged by only an alkoxo group of L-Et−, while an azido and an alkoxo connect two nickel(II) ions in 2′. Magnetic susceptibility measurements (2–300 K) showed a weak ferromagnetic exchange coupling between the two nickel(II) ions (2J = 10.1 cm−1) for 1. On the other hand, antiferromagnetic interactions were observed for 2 (2J = −15.8 cm−1). 相似文献
13.
《Harmful algae》2014
Benthic dinoflagellates of the genus Ostreopsis are found all over the world in temperate, subtropical, and tropical coastal regions. Our recent studies revealed that a putative “cryptic” species of Ostreopsis ovata is present widely along Japanese coasts. This organism, Ostreopsis sp. 1, possesses palytoxin analogs and thus its toxic blooms may be responsible for potential toxification of marine organisms. To evaluate the bloom dynamics of Ostreopsis sp. 1, the present study examined the growth responses of Ostreopsis sp. 1 strain s0716 to various light intensities (photon flux densities: μmol photons m−2 s−1) using a newly devised photoirradiation-culture system. This novel system has white light-emitting diodes (LEDs) capable of more closely simulating the wavelength spectrum of light entering the oceanic water column than do fluorescent tubes and halogen lamps. In this system, the light intensity of the white LEDs was reduced through two polarizing filters by varying the rotation angles of the filters. Thereby, the new system was capable of culturing microalgae under well-controlled light intensity conditions. Ostreopsis sp. 1 grew proportionally when light intensity was increased from 49.5 to 199 μmol photons m−2 s−1, but its growth appeared to be inhibited slightly at ≥263 μmol photons m−2 s−1. The relationship between observed growth rates and light intensity was calculated at R > 0.99 (P < 0.01) using a regression analysis with a modified equation of the photosynthesis-light intensity (P-L) model. The equation determined the critical light intensities for growth of Ostreopsis sp. 1 and the organism's growth potential as follows: (1) the threshold light intensity for growth: 29.8 μmol photons m−2 s−1; (2) the optimum light intensity (Lm) giving the maximum growth rate (μmax = 0.659 divisions day−1): 196 μmol photons m−2 s−1; (3) the optimum light intensity range (Lopt) giving ≥95% μmax: 130–330 μmol photons m−2 s−1; (4) the semi-optimum range (Lsopt) giving ≥80% μmax: 90 to over 460 μmol photons m−2 s−1. The Lsopt represents 4.5–23% ambient light intensity present in surface waters off of a temperate region of the Japanese coast, Tosa Bay; putatively, this semi-optimum range of light intensity appears at depth of 12.9–27.8 m. Considering these issues, our data indicate that Ostreopsis sp. 1 in coastal environments may form blooms at ca. ∼28 m depth in regions along Japanese coasts. 相似文献
14.
《Bioorganic & medicinal chemistry》2016,24(16):3413-3417
Among the numerous metalloenzymes known to date, carbonic anhydrase (CA, EC 4.2.1.1) was the first zinc containing one, being discovered decades ago. CA is a hydro-lyase, which catalyzes the following hydration–dehydration reaction: CO2 + H2O ⇋ HCO3− + H+. Several CA classes are presently known, including the α-, β-, γ-, δ-, ζ- and η-CAs. In prokaryotes, the existence of genes encoding CAs from at least three classes (α-, β- and γ-class) suggests that these enzymes play a key role in the physiology of these organisms. In many bacteria CAs are essential for the life cycle of microbes and their inhibition leads to growth impairment or growth defects of the pathogen. CAs thus started to be investigated in detail in bacteria, fungi and protozoa with the aim to identify antiinfectives with a novel mechanism of action. Here, we investigated the catalytic activity, biochemical properties and anion inhibition profiles of the three CAs from the bacterial pathogen Vibrio cholera, VchCA, VchCAβ and VchCAγ. The three enzymes are efficient catalysts for CO2 hydration, with kcat values ranging between (3.4 − 8.23) × 105 s−1 and kcat/KM of (4.1 − 7.0) × 107 M−1 s−1. A set of inorganic anions and small molecules was investigated for inhibition of these enzymes. The most potent VchCAγ inhibitors were N,N-diethyldithiocarbamate, sulfamate, sulfamide, phenylboronic acid and phenylarsonic acid, with KI values ranging between 44 and 91 μM. 相似文献
15.
《Process Biochemistry》2007,42(4):704-709
Four immobilized forms of glucose oxidase (GOD) were used for biotransformation removal of glucose from its mixture with dextran oligosaccharides. GOD was biospecifically bound to Concanavalin A-bead cellulose (GOD-ConA-TBC) and covalently to triazine-bead cellulose (GOD-TBC). Eupergit C and Eupergit CM were used for preparation of other two forms of immobilized GOD: GOD-EupC and GOD-EupCM. GOD-ConA-TBC and GOD-EupC exhibited the best operational and storage stabilities. pH and temperature optima of these two immobilized enzyme forms were broadened and shifted to higher values (pH 7 and 35 °C) in comparison with those of free GOD. The decrease of Vmax values after immobilization was observed, from 256.8 ± 7.0 μmol min−1 mgGOD−1 for free enzyme to 63.8 ± 4.2 μmol min−1 mgGOD−1 for GOD-ConA-TBC and 45 ± 2.7 μmol min−1 mgGOD−1 for GOD-EupC, respectively. Depending on the immobilization mode, the immobilized GODs were able to decrease the glucose content in solution to 3.8–15.6% of its initial amount The best glucose conversion, was achieved by an action of GOD-EupCM on a mixture of 100 g dextran with 9 g of glucose (i.e. 98.7% removal of glucose). 相似文献
16.
《Aquatic Botany》2005,81(3):265-275
Palatability to snail herbivory (Radix swinhoei H. Adams) and C/N ratios were assessed for Vallisneria natans (Lour.) Hara, in three different experimental light regimes (midday fluxes respectively 280 μmol m−2 s−1, 15 μmol m−2 s−1, and a variable intensity between these two). Higher light intensity as well as prolonged photoperiods increased palatability and growth, and improved C/N ratio by decreasing N content. Snail growth was slightly increased but juvenile survivorship decreased under higher light. The results suggest that the availability of light may affects intraspecific variation in palatability of V. natans. 相似文献
17.
《Aquatic Botany》2005,83(3):187-192
We investigated the effect of intraspecific competition on growth parameters and photosynthesis of the salt marsh species Atriplex prostrata Boucher in order to distinguish the effects of density-dependent growth inhibition from salt stress. High plant density caused a reduction of 30% in height, 82% in stem dry mass, 80% in leaf dry mass, and 95% in root dry mass. High density also induced a pronounced 72% reduction in leaf area, 29% decrease in length of mature internodes and 50% decline in net photosynthetic rate. The alteration of net photosynthesis paralleled growth inhibition, decreasing from 7.6 ± 0.9 μmol CO2 m−2 s−1 at low density to 3.5 ± 0.4 μmol CO2 m−2 s−1 at high density, indicating growth inhibition caused by intraspecific competition is mainly due to a decline in net photosynthesis rate. Plants grown at high density also exhibited a reduction in stomatal conductance from 0.7 ± 0.1 mol H2O m−2 s−1 at low density to 0.3 ± 0.1 mol H2O m−2 s−1 at high density and a reduction in transpiration rate from 6.0 ± 0.3 mmol H2O m−2 s−1 at low density to 4.3 ± 0.3 mmol H2O m−2 s−1 at high density. Biomass production was inhibited by an increase in plant density, which reduced the rate of photosynthesis, stomatal conductance and leaf area of plants. 相似文献
18.
《Aquatic Botany》2005,83(2):129-140
Bisexual populations of the charophyte Chara canescens (Desv. et Loisel. in Loisel., 1810) containing male and female individuals are rarely found. Two experiments were carried out to study whether male and female algae from the same site exhibit different physiological capacities, especially with respect to light acclimation.Algae from two different shore levels and from laboratory cultures acclimated to six irradiance conditions (35–500 μmol photons m−2 s−1) were compared. Field measurements showed that both female and male algae of C. canescens are able to acclimate to daily changes in solar irradiance. The quantum yield of Photosystem II (PSII) decreased with increasing irradiance in the morning and increased with decreasing irradiance in the afternoon. Growth experiments showed increasing growth rates from 35 μmol photons m−2 s−1 (∼7 mg FW) up to 500 μmol photons m−2 s−1 (∼27 mg FW) in female and male C. canescens. The irradiance saturation point for photosynthesis (Ek) was about 140 μmol m−2 s−1 for both sexes within the whole range of acclimation irradiances. The maximum photosynthesis rate at saturating irradiances (Pmax) of male algae was highest at Ek, whereas Pmax of female algae was highest at 500 μmol photons m−2 s−1. The photosynthetic efficiency in the light-limited range (α) increased in female C. canescens and decreased in male C. canescens. The ratio of the non-photochemical quenching parameter (NPQ) to the relative electron transport rates rETR(MT) increased in both sexes with irradiance, but showed a steeper increase in male than in female algae. Pigment analysis showed similar acclimation pattern for male and female C. canescens. Chl a/Chl b ratios of both sexes were constant over the whole range of Eg, whereas Chl a/carotenoid ratios in male and female C. canescens decreased from 70 μmol photons m−2 s−1 upwards. Pigment analysis pointed out that the carotenes α-, β- and γ-carotene were more prominent in male than in female algae.Our results indicate that female C. canescens are more efficient in light acclimation than male algae from the same site. Nevertheless, further investigations of bisexual C. canescens populations resolving CO2-uptake mechanisms and/or genetic differences are needed. 相似文献
19.
《Saudi Journal of Biological Sciences》2017,24(7):1672-1678
This study was carried out to determine the median lethal concentrations (LC50) of Zinc nanoparticles (ZnNPs) on Oreochromis niloticus and Tilapia zillii. The biochemical and molecular potential effects of ZnNPs (500 and 2000 μg L−1) on the antioxidant system in the brain tissue of O. niloticus and T. zillii were investigated. Four hundred fish were used for acute and sub-acute studies. ZnNP LC50 concentrations were investigated in O. niloticus and T. zillii. The effect of 500 and 2000 μg L−1 ZnNPs on brain antioxidants of O. niloticus and T. zillii was investigated. The result indicated that 69 h LC50 was 5.5 ± 0.6 and 5.6 ± 0.4 for O. nilotica and T. zillii, respectively. Fish exposed to 500 μg L−1 ZnNPs showed a significant increase in reduced glutathione (GSH), total glutathione (tGSH) levels, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activity and gene expression. On the contrary, malondialdehyde (MDA) levels significantly decreased. Meanwhile, fish exposed to 2000 μg L−1 ZnNPs showed a significant decrease of GSH, tGSH levels, SOD, CAT, GR, GPx and GST activity and gene expression. On the contrary, MDA levels significantly increased. It was concluded that, the 96 h LC50 of ZnNPs was 5.5 ± 0.6 and 5.6 ± 0.4 for O. nilotica and T. zillii, respectively. ZnNPs in exposure concentrations of 2000 μg/L induced a deleterious effect on the brain antioxidant system of O. nilotica and T. zillii. In contrast, ZnNPs in exposure concentrations of 500 μg L−1 produced an inductive effect on the brain antioxidant system of O. nilotica and T. zillii. 相似文献
20.
PurposeTo analyse the correlations between the eye lens dose estimates performed with dosimeters placed next to the eyes of paediatric interventional cardiologists working with a biplane system, the personal dose equivalent measured on the thorax and the patient dose.MethodsThe eye lens dose was estimated in terms of Hp(0.07) on a monthly basis, placing optically stimulated luminescence dosimeters (OSLDs) on goggles. The Hp(0.07) personal dose equivalent was measured over aprons with whole-body OSLDs. Data on patient dose as recorded by the kerma-area product (PKA) were collected using an automatic dose management system. The 2 paediatric cardiologists working in the facility were involved in the study, and 222 interventions in a 1-year period were evaluated. The ceiling-suspended screen was often disregarded during interventions.ResultsThe annual eye lens doses estimated on goggles were 4.13 ± 0.93 and 4.98 ± 1.28 mSv. Over the aprons, the doses obtained were 10.83 ± 0.99 and 11.97 ± 1.44 mSv. The correlation between the goggles and the apron dose was R2 = 0.89, with a ratio of 0.38. The correlation with the patient dose was R2 = 0.40, with a ratio of 1.79 μSv Gy−1 cm−2. The dose per procedure obtained over the aprons was 102 ± 16 μSv, and on goggles 40 ± 9 μSv. The eye lens dose normalized to PKA was 2.21 ± 0.58 μSv Gy−1 cm−2.ConclusionsMeasurements of personal dose equivalent over the paediatric cardiologist’s apron are useful to estimate eye lens dose levels if no radiation protection devices are typically used. 相似文献