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1.
The photon use efficiencies and maximal rates of photosynthesis in Dunaliella salina (Chlorophyta) cultures acclimated to
different light intensities were investigated. Batch cultures were grown to the mid-exponential phase under continuous low-light
(LL: 100 μmol photon m-2 s-1) or high-light (HL: 2000 μmol photon m-2 s-1) conditions. Under LL, cells were normally pigmented (deep green) containing ∼500 chlorophyll (Chl) molecules per photosystem
II (PSII) unit and ∼250 Chl molecules per photosystem I (PSI). HL-grown cells were yellow-green, contained only 60 Chl per
PSII and 100 Chl per PSI and showed signs of chronic photoinhibition, i.e., accumulation of photodamaged PSII reaction centers
in the chloroplast thylakoids. In LL-grown cells, photosynthesis saturated at ∼200 μmol photon m-2 s-1 with a rate (Pmax) of ∼100 mmol O2 (mol Chl)-1 s-1. In HL-grown cells, photosynthesis saturated at much higher light intensities, i.e. ∼2500 μmol photon m-2 s-1, and exhibited a three-fold higher Pmax (∼300 mmol O2 (mol Chl)-1 s-1) than the normally pigmented LL-grown cells. Recovery of the HL-grown cells from photoinhibition, occurring prior to a light-harvesting
Chl antenna size increase, enhanced Pmax to ∼675 mmol O2 (mol Chl)-1 s-1. Extrapolation of these results to outdoor mass culture conditions suggested that algal strains with small Chl antenna size
could exhibit 2–3 times higher productivities than currently achieved with normally pigmented cells.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
The responses to irradiance of photosynthetic CO2 assimilation and photosystem 2 (PS2) electron transport were simultaneously studied by gas exchange and chlorophyll (Chl) fluorescence measurement in two-year-old apple tree leaves (Malus pumila Mill. cv. Tengmu No.1/Malus hupehensis Rehd). Net photosynthetic rate (P
N) was saturated at photosynthetic photon flux density (PPFD) 600-1 100 (mol m-2 s-1, while the PS2 non-cyclic electron transport (P-rate) showed a maximum at PPFD 800 mol m-2 s-1. With PPFD increasing, either leaf potential photosynthetic CO2 assimilation activity (Fd/Fs) and PS2 maximal photochemical activity (Fv/Fm) decreased or the ratio of the inactive PS2 reaction centres (RC) [(Fi – Fo)/(Fm – Fo)] and the slow relaxing non-photochemical Chl fluorescence quenching (qs) increased from PPFD 1 200 mol m-2 s-1, but cyclic electron transport around photosystem 1 (RFp), irradiance induced PS2 RC closure [(Fs – Fo)/Fm – Fo)], and the fast and medium relaxing non-photochemical Chl fluorescence quenching (qf and qm) increased remarkably from PPFD 900 (mol m-2 s-1. Hence leaf photosynthesis of young apple leaves saturated at PPFD 800 mol m-2 s-1 and photoinhibition occurred above PPFD 900 mol m-2 s-1. During the photoinhibition at different irradiances, young apple tree leaves could dissipate excess photons mainly by energy quenching and state transition mechanisms at PPFD 900-1 100 mol m-2 s-1, but photosynthetic apparatus damage was unavoidable from PPFD 1 200 mol m-2 s-1. We propose that Chl fluorescence parameter P-rate is superior to the gas exchange parameter P
N and the Chl fluorescence parameter Fv/Fm as a definition of saturation irradiance and photoinhibition of plant leaves. 相似文献
3.
Photosynthetic parameters, growth, and pigment contents were determined during expansion of the fourth leaf of in vitro photoautotrophically cultured Nicotiana tabacum L. plants at three irradiances [photosynthetically active radiation (400–700 nm): low, LI 60 μmol m−2 s−1; middle, MI 180 μmol m−2 s−1; and high, HI 270 μmol m−2 s−1]. During leaf expansion, several symptoms usually accompanying leaf senescence appeared very early in HI and then in MI plants.
Symptoms of senescence in developing leaves were: decreasing chlorophyll (Chl) a+b content and Chl a/b ratio, decreasing both maximum (FV/FM) and actual (ΦPS2) photochemical efficiency of photosystem 2, and increasing non-photochemical quenching. Nevertheless, net photosynthetic
oxygen evolution rate (P
N) did not decrease consistently with decrease in Chl content, but exhibited a typical ontogenetic course with gradual increase.
P
N reached its maximum before full leaf expansion and then tended to decline. Thus excess irradiance during in vitro cultivation did not cause early start of leaf senescence, but impaired photosynthetic performance and Chl content in leaves
and changed their typical ontogenetic course. 相似文献
4.
Adam M. Gilmore Theodore L. Hazlett Peter G. Debrunner Govindjee 《Photosynthesis research》1996,48(1-2):171-187
Photosystem II (PS II) chlorophyll (Chl) a fluorescence lifetimes were measured in thylakoids and leaves of barley wild-type and chlorina f104 and f2 mutants to determine the effects of the PS II Chl a+b antenna size on the deexcitation of absorbed light energy. These barley chlorina mutants have drastically reduced levels of PS II light-harvesting Chls and pigment-proteins when compared to wild-type plants. However, the mutant and wild-type PS II Chl a fluorescence lifetimes and intensity parameters were remarkably similar and thus independent of the PS II light-harvesting antenna size for both maximal (at minimum Chl fluorescence level, Fo) and minimal rates of PS II photochemistry (at maximum Chl fluorescence level, Fm). Further, the fluorescence lifetimes and intensity parameters, as affected by the trans-thylakoid membrane pH gradient (pH) and the carotenoid pigments of the xanthophyll cycle, were also similar and independent of the antenna size differences. In the presence of a pH, the xanthophyll cycle-dependent processes increased the fractional intensity of a Chl a fluorescence lifetime distribution centered around 0.4–0.5 ns, at the expense of a 1.6 ns lifetime distribution (see Gilmore et al. (1995) Proc Natl Acad Sci USA 92: 2273–2277). When the zeaxanthin and antheraxanthin concentrations were measured relative to the number of PS II reaction center units, the ratios of fluorescence quenching to [xanthophyll] were similar between the wild-type and chlorina f104. However, the chlorina f104, compared to the wild-type, required around 2.5 times higher concentrations of these xanthophylls relative to Chl a+b to obtain the same levels of xanthophyll cycle-dependent fluorescence quenching. We thus suggest that, at a constant pH, the fraction of the short lifetime distribution is determined by the concentration and thus binding frequency of the xanthophylls in the PS II inner antenna. The pH also affected both the widths and centers of the lifetime distributions independent of the xanthophyll cycle. We suggest that the combined effects of the xanthophyll cycle and pH cause major conformational changes in the pigment-protein complexes of the PS II inner or core antennae that switch a normal PS II unit to an increased rate constant of heat dissipation. We discuss a model of the PS II photochemical apparatus where PS II photochemistry and xanthophyll cycle-dependent energy dissipation are independent of the Peripheral antenna size.Abbreviations Ax
antheraxanthin
- BSA
bovine serum albumin
- cx
lifetime center of fluorescence decay component x
- CP
chlorophyll binding protein of PS II inner antenna
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- DTT
dithiothreitol
- fx
fractional intensity of fluorescence lifetime component x
- Fm, Fm
maximal PS II Chl a fluorescence intensity with all QA reduced in the absence, presence of thylakoid membrane energization
- Fo
minimal PS II Chl a fluorescence intensity with all QA oxidized
- Fv=Fm–Fo
variable level of PS II Chl a fluorescence
- HPLC
high performance liquid chromatography
- kA
rate constant of all combined energy dissipation pathways in PS II except photochemistry and fluorescence
- kF
rate constant of PS II Chl a fluorescence
- LHCIIb
main light harvesting pigment-protein complex (of PS II)
- Npig
mols Chl a+b per PS II
- NPQ=(Fm/Fm–1)
nonphotochemical quenching of PS II Chl a fluorescence
- PAM
pulse-amplitude modulation fluorometer
- PFD
photon-flux density, mols photons m–2 s–1
- PS II
Photosystem II
- P680
special-pair Chls of PS II reaction center
- QA
primary quinone electron acceptor of PS II
- Vx
violaxanthin
- wx
width at half maximum of Lorentzian fluorescence lifetime distribution x
- Zx
zeaxanthin
- pH
trans-thylakoid proton gradient
- % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqef0uAJj3BZ9Mz0bYu% H52CGmvzYLMzaerbd9wDYLwzYbItLDharqqr1ngBPrgifHhDYfgasa% acOqpw0xe9v8qqaqFD0xXdHaVhbbf9v8qqaqFr0xc9pk0xbba9q8Wq% Ffea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dme% GabaqaaiGacaGaamqadaabaeaafiaakeaacqGH8aapcqaHepaDcqGH% +aGpdaWgaaWcbaGaamOraiaad2gaaeqaaaaa!4989!\[< \tau > _{Fm}\],% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqef0uAJj3BZ9Mz0bYu% H52CGmvzYLMzaerbd9wDYLwzYbItLDharqqr1ngBPrgifHhDYfgasa% acOqpw0xe9v8qqaqFD0xXdHaVhbbf9v8qqaqFr0xc9pk0xbba9q8Wq% Ffea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dme% GabaqaaiGacaGaamqadaabaeaafiaakeaacqGH8aapcqaHepaDcqGH% +aGpdaWgaaWcbaGaamOraiaad+gaaeqaaOGaeyypa0Zaaabqaeaaca% WGMbWaaSbaaSqaaiaadIhaaeqaaOGaam4yamaaBaaaleaacaWG4baa% beaaaeqabeqdcqGHris5aaaa!50D3!\[< \tau > _{Fo} = \sum {f_x c_x }\]
average lifetime of Chl a fluorescence calculated from a multi-exponential model under Fm, Fo conditions 相似文献
5.
Rates of net CO2 uptake were examined in developing leaves of Hydrocotyle bonariensis. Leaves that developed under high photosynthetically active radiation (48 mol m-2 day-1 PAR) were smaller, thicker, and reached maximum size sooner than did leaves that developed under low PAR (4.8 mol m-2 day-1). Maximum net CO2 uptake rates were reached after 5 to 6 days expansion for both the low and the high PAR leaves. Leaves grown at high PAR had higher maximum photosynthetic rates and a higher PAR required for light saturation but showed a more rapid decline in rate with age than did low PAR leaves. To assess the basis for the difference observed in photosynthetic rates, CO2 diffusion conductances and the mesophyll surface available for CO2 absorption were examined for mature leaves. Stomatal conductance was the largest conductance in all treatments and did not vary appreciably with growth PAR. Mesophyll conductance progressively increased with growth PAR (up to 48 mol m-2 day-1) as did the mesophyll surface area per unit leaf area, but the cellular conductance exhibited most of its increase at low PAR (up to 4.8 mol m-2 day-1). 相似文献
6.
Field experiments were conducted in Sicily (south Italy) to assess chlorophyll (Chl) fluorescence parameters in response of
potato crop to nitrogen dose, to variation in genotype and in plant age, and to detect relationships between Chl content,
fluorescence parameter Fv/Fm, and tuber yield. The experiment included five nitrogen doses (0, 10, 20, 30, and 40 g m−2) and four genotypes (Spunta, Sieglinde, Daytona, and Igea). Chl fluorescence parameters (initial fluorescence, F0, maximum fluorescence, Fm, variable fluorescence, Fv, Fv/Fm, Tmax (the time required to reach Fm), and Chl content were measured weekly between the appearance of the fifth and sixth leaves and the onset of plant senescence.
A positive linear relationship was established between nitrogen supply and Chl content, F0, and Tmax. Nitrogen supply up to 10 g m−2 also had a positive effect on Fm and Fv, but above this rate it reduced Fv/Fm. Spunta had the highest Chl content, Fm, Fv, and Fv/Fm, but the lowest F0, whereas Sieglinde had the lowest Chl content, Fv, Fv/Fm, and Tmax and the highest F0. The cvs. Igea and Daytona exhibited intermediate Chl fluorescence parameters. Chl content and Tmax decreased with increasing plant age, whereas F0, Fm, and Fv increased until complete canopy development and thereafter declined until crop maturity. Tuber and plant dry matter yield
were significantly correlated with Chl content, F0, and Tmax. Thus Chl fluorescence and content detect differences in the response of potato to N supply, can discriminate between genotypes,
predict plant age, and yield performance under field conditions. 相似文献
7.
Two rice chlorophyll (Chl) b-less mutants (VG28-1, VG30-5) and the respective wild type (WT) plant (cv. Zhonghua No. 11) were analyzed for the changes
in Chl fluorescence parameters, xanthophyll cycle pool, and its de-epoxidation state under exposure to strong irradiance,
SI (1 700 μmol m−2 s−1). We also examined alterations in the chloroplast ultrastructure of the mutants induced by methyl viologen (MV) photooxidation.
During HI (0–3.5 h), the photoinactivation of photosystem 2 (PS2) appeared earlier and more severely in Chl b-less mutants than in the WT. The decreases in maximal photochemical efficiency of PS2 in the dark (Fv/Fm), quantum efficiency of PS2 electron transport (ΦPS2), photochemical quenching (qP), as well as rate of photochemistry (Prate), and the increases in de-epoxidation state (DES) and rate of thermal dissipation of excitation energy (Drate) were significantly greater in Chl b-mutants compared with the WT plant. A relatively larger xanthophyll pool and 78–83 % conversion of violaxanthin into antheraxanthin
and zeaxanthin in the mutants after 3.5 h of HI was accompanied with a high ratio of inactive/total PS2 (0.55–0.73) and high
1–qP (0.57–0.68) which showed that the activities of the xanthophyll cycle were probably insufficient to protect the photosynthetic
apparatus against photoinhibition. No apparent difference of chloroplast ultrastructure was found between Chl b-less mutants and WT plants grown under low, LI (180 μmol m−2 s−1) and high, HI (700 μmol m−2 s−1) irradiance. However, swollen chloroplasts and slight dilation of thylakoids occurred in both mutants and the WT grown under
LI followed by MV treatment. These typical symptoms of photooxidative damage were aggravated as plants were exposed to HI.
Distorted and loose scattered thylakoids were observed in particular in the Chl b-less mutants. A greater extent of photoinhibition and photooxidation in these mutants indicated that the susceptibility to
HI and oxidative stresses was enhanced in the photosynthetic apparatus without Chl b most likely as a consequence of a smaller antenna size. 相似文献
8.
Chrococcoid cyanobacteria of the genus Synechococcus are the important component of marine and freshwater ecosystems. Picocyanobacteria comprise even 80% of total cyanobacterial biomass and contribute to 50% of total primary cyanobacterial bloom production. Chlorophyll (Chl) fluorescence and photosynthetic light response (P-I) curves are commonly used to characterize photoacclimation of Synechococcus strains. Three brackish, picocyanobacterial strains of Synechococcus (BA-132, BA-124, BA-120) were studied. They were grown under 4 irradiances [10, 55, 100, and 145 μmol(photon) m?2 s?1] and at 3 temperatures (15, 22.5, and 30°C). Photosynthetic rate was measured by Clark oxygen electrode, whereas the Chl fluorescence was measured using Pulse Amplitude Modulation fluorometer. Based on P-I, two mechanisms of photoacclimation were recognized in Synechococcus. The maximum value of maximum rate of photosynthesis (P max) expressed per biomass unit at 10 μmol(photon) m?2 s?1 indicated a change in the number of photosynthetic units (PSU). The constant values of initial slope of photosynthetic light response curve (α) and the maximum value of P max expressed per Chl unit at 145 μmol(photon) m?2 s?1 indicated another mechanism, i.e. a change in PSU size. These two mechanisms caused changes in photosynthetic rate and its parameters (compensation point, α, saturation irradiance, dark respiration, P max) upon the influence of different irradiance and temperature. High irradiance had a negative effect on fluorescence parameters, such as the maximum quantum yield and effective quantum yield of PSII photochemistry (φPSII), but it was higher in case of φPSII. 相似文献
9.
《Chemical Speciation and Bioavailability》2013,25(4):213-223
AbstractMost current electrostatic surface complexation models describing ionic binding at the particle/water interface rely on the use of Poisson–Boltzmann (PB) theory for relating diffuse layer charge densities to diffuse layer electrostatic potentials. PB theory is known to contain a number of implicit assumptions whose significance in environmental applications is largely unknown. This study seeks to better quantify the impact of these assumptions by: (1) comparing potentials obtained from planar analytical solutions to the PB with those obtained from Hypernetted Chain (HNC) theory (Attard, 2006), (2) assessing the accuracy of the Ohshima et al. (1982) spherical approximate analytical solution to the PB equation by comparison with published numerical values (Loeb et al., 1961), and (3) comparing interfacial potential estimates obtained from the spherical approximate analytical solution to the PB equation at and adjacent to the particle surface with potential estimates obtained from the Entropic Balanced Surface Potential (EB) model (Loux, 1985; Loux and Anderson, 2001) and published potential estimates obtained from the Hypernetted Chain/Mean Spherical Approximation procedure (HNC/MSA; Gonzalez-Tovar and Lozada-Cassou, 1989). EB potential estimates were obtained assuming a surface volume thickness equal to the Bjerrum length (0.357 nm in a room temperature monovalent electrolyte solution). Findings from the study included: (1) the planar, surficial HNC estimates compared favourably with planar surficial PB relationships at charge densities equal to or less than 0.05 C m?2, (2) the Ohshima et al. (1982) approximate spherical analytical solution to the PB equation replicated the numerical charge density estimates required to obtain 72 datapoints over an e<img>/kT range of one to four with a maximum error of 3.37% and a coefficient of variation of 0.92%, (3) for a 0.1 μm radius particle in a room temperature 0.01 M (1 : 1) ionic strength solution, potential estimates over a surface charge density range of 0 to 0.3C m?2 occurred in the following order: ψHNC/MSA,R >ψPB,R >ψHNC/MSA,R+0.2125nm >ψPB,R+0.2nm ~ ψEB >ψHNC/MSA,R+0.425nm ~ ψPB,R+0.4nm and (4) with 45 datapoints including both 1 μm and 10 nm radius particles over an ionic strength range of 1.0 to 0.001 M, the PB potential estimates 0.2 nm from the particle surface (ψPBR+02nm) closely tracked the corresponding EB estimates (ψEB) with a 5.3% coefficient of variation. If one assumes that interfacial potential values adjacent to the particle surface are most relevant for describing environmental phenomena and that a 10% coefficient of variation in potential estimates is acceptable, then presumably any of the non-surficial charge/potential relationships would be useful below an absolute charge density of 0.125 C m ?2 (with monovalent electrolyte solutions). 相似文献
10.
The effects of different spectral region of excitation and detection of chlorophyll (Chl) a fluorescence at room temperature on the estimation of excitation energy utilization within photosystem (PS) 2 were studied
in wild-type barley (Hordeum vulgare L. cv. Bonus) and its Chl b-less mutant chlorina f2 grown under low and high irradiances [100 and 1 000 μmol(photon) m−2 s−1]. Three measuring spectral regimes were applied using a PAM 101 fluorometer: (1) excitation in the red region (maximum at the wavelength of 649 nm) and detection in the far-red region beyond 710 nm, (2) excitation in the blue region (maximum at the wavelength of 461 nm) and detection beyond 710 nm, and (3) excitation in the blue region and detection in the red region (660– 710 nm). Non-photochemical quenching of maximal (NPQ)
and minimal fluorescence (SV0), determined by detecting Chl a fluorescence beyond 710 nm, were significantly higher for blue excitation as compared to red excitation. We suggest that
this results from higher non-radiative dissipation of absorbed excitation energy within light-harvesting complexes of PS2
(LHC2) due to preferential excitation of LHC2 by blue radiation and from the lower contribution of PS1 emission to the detected
fluorescence in the case of blue excitation. Detection of Chl a fluorescence originating preferentially from PS2 (i.e. in the range of 660–710 nm) led to pronounced increase of NPQ, SV0, and the PS2 photochemical efficiencies (FV/FM and FV′/FM′), indicating considerable underestimation of these parameters using the standard set-up of PAM 101. Hence PS1 contribution to the minimal fluorescence level in the irradiance-adapted state may reach up to about 80 %. 相似文献
11.
Pisum sativum (L.) plants were grown under “white” luminescent lamps, W [45 μ mol(quantum) m−2 s−1] or under the same irradiation supplemented with narrow spectrum red light-emitting diodes (LEDs), RE [λmax = 660 nm, Δλ = 20 nm, 40 μmol(quantum) m−2 s−1]. Significant differences in the chlorophyll (Chl) a fluorescence parameters, degree of State 1–State 2 transition, and the pigment-protein contents were found in plants grown
under differing spectral composition. Addition of red LEDs to the “white light” resulted in higher effective quantum yield
of photosystem 2 (PS2), i.e. F′v/F′m, linear electron transport (ϕPS2), photochemical quenching (qP), and lower non-photochemical quenching (qN as well as NPQ). The RE plants were characterised by higher degree State 1–State 2 transition, i.e. they were more effective in radiant energy utilisation. Judging from the data of “green” electrophoresis of Chl containing
pigment-protein complexes of plants grown under various irradiation qualities, the percentage of Chl in photosystem 2 (PS2)
reaction centre complexes in RE plants was higher and there was no difference in the total Chl bound with Chl-proteins of
light-harvesting complexes (LHC2). Because the ratio between oligomeric and monomeric LHC2 forms was higher in RE plants,
we suggest higher LHC2 stability in these ones. 相似文献
12.
The effect of ethylenediurea (EDU) was tested using the chlorophyll (Chl) a fluorescence transient analysis, performed with JIP-test, to assess ambient ozone (O3) effects on photosynthesis of adult trees under natural conditions. Twelve adult European ash (Fraxinus excelsior L.) trees, known to be sensitive or tolerant to O3, determined by presence symptomatic (S) or absence asymptomatic (AS) trees of foliar symptoms in previous years, were treated
either with distilled water containing 450 g m−3 EDU or with distilled water. Once a month across the growing season [the accumulated exposure over a threshold of 40 nmol(O3) mol−1 was 32.49 μmol mol−1 h−1], Chl a fluorescence transients were measured in vivo on dark-adapted leaves of 1-year-old labeled shoots, from the lower crown part. Twenty-five parameters were calculated. The
maximum quantum yield of primary photochemistry (ϕPo or Fv/Fm) did not differentiate between S-and AS-trees, while increased Chl content and de-excitation rates suggested compensation
of O3 injury in S-trees. Seasonal reductions in absorbing fluxes and increase in heat and fluorescence dissipation processes was
due to leaf ageing and drought, the latter suggesting water deficit influenced Chl a fluorescence stronger than ambient O3 exposure. AS-trees showed elevated probability of connectivity among photosystem 2 units, a mechanism to stimulate energy
dissipation and reduce photo-oxidative injury. EDU prevented the inactivation of reaction centers. This slight effect does
not warrant EDU as a tool to assess O3 effects on photosynthesis, while the JIP-test is suggested for a quantitative assessment in adult trees. 相似文献
13.
Cells of potato (Solanum tuberosum L.) were obtained which were capable of photoautotrophic growth in liquid suspension culture under a photon flux density of 90–110 μmol m?2 s?1 PAR and in an atmosphere enriched with 2% CO2. These photoautotrophic cells contained between 100 to 200 μg Chl (g fresh weight)?1 and fixed CO2 at a maximum rate of 16 μmol CO2 (g fresh weight)?1h?1. In order to obtain cells capable of photoautotrophic growth it was necessary to adapt highly chlorophyllous heterotrophic cells (>50 μg Chl (g fresh weight)?1) for growth in medium with 2.5 g sucrose 1?1 (photomixotrophic cells). The photomixotropic cells had a Chl content of ca 100 μg Chl (g fresh weight)?1 and were capable of photosynthetic activity which allowed them to survive after sugars had been depleted from the medium. It was from the photomixotrophic cells that cells capable of photoautotrophic growth were obtained. Heterotrophic cells initially established in liquid medium with 25 g sucrose I?1 from chlorophyllous callus contained about 50 to 150 μg Chl (g fresh weight)?1. However, after 5 to 10 passages the Chl content decreased to a maximum of 15 μg Chl (g fresh weight)?1. These cells could not be adapted to photomixotrophic or photoautotrophic growth. These cells also were not able to regain Chl or initiate high rates of CO2 fixation during the stationary phase of growth as did photomixotrophic cells or chlorophyllous heterotrophic cells. The loss of Chl exhibited by the cells during adaption to heterotrophic growth could be attributed at least in part to unbalanced growth (when cell division and growth exceeds Chl accumulation). Sucrose appeared to have an inhibitory effect directly on photosynthesis independent of Chl accumulation. 相似文献
14.
The Status and Characteristics of Eutrophication in the Yangtze River (Changjiang) Estuary and the Adjacent East China Sea, China 总被引:19,自引:0,他引:19
Eutrophication has become increasingly serious and noxious algal blooms have been of more frequent occurrence in the Yangtze
River Estuary and in the adjacent East China Sea. In 2003 and 2004, four cruises were undertaken in three zones in the estuary
and in the adjacent sea to investigate nitrate (NO3–N), ammonium (NH4–N), nitrite (NO2–N), soluble reactive phosphorus (SRP), dissolved reactive silica (DRSi), dissolved oxygen (DO), phytoplankton chlorophyll
a (Chl a) and suspended particulate matter (SPM). The highest concentrations of DIN (NO3–N+NH4–N+NO2–N), SRP and DRSi were 131.6, 1.2 and 155.6 μM, respectively. The maximum Chl a concentration was 19.5 mg m−3 in spring. An analysis of historical and recent data revealed that in the last 40 years, nitrate and SRP concentrations increased
from 11 to 97 μM and from 0.4 to 0.95 μM, respectively. From 1963 to 2004, N:P ratios also increased from 30–40 up to 150. In parallel with the N and P enrichment,
a significant increase of Chl a was detected, Chl a maximum being 20 mg m−3, nearly four times higher than in the 1980s. In 2004, the mean DO concentration in bottom waters was 4.35 mg l−1, much lower than in the 1980s. In comparison with other estuaries, the Yangtze River Estuary was characterized by high DIN
and DRSi concentrations, with low SRP concentrations. Despite the higher nutrient concentrations, Chl a concentrations were lower in the inner estuary (Zones 1 and 2) than in the adjacent sea (Zone 3). Based on nutrient availability,
SPM and hydrodynamics, we assumed that in Zones 1 and 2 phytoplankton growth was suppressed by high turbidity, large tidal
amplitude and short residence time. Furthermore, in Zone 3 water stratification was also an important factor that resulted
in a greater phytoplankton biomass and lower DO concentrations. Due to hydrodynamics and turbidity, the open sea was unexpectedly
more sensitive to nutrient enrichment and related eutrophication processes. 相似文献
15.
川西贡嘎山峨眉冷杉成熟林生态系统CO2通量特征 总被引:1,自引:0,他引:1
成熟森林的碳收支对陆地生态系统碳循环研究具有重要意义。目前,我国关于西南亚高山暗针叶林成熟林碳通量的研究还相对较少,尚不明确对碳循环的作用。以涡度相关技术为基础,对川西贡嘎山东坡峨眉冷杉成熟林生态系统尺度的CO_2通量进行长期定位观测。利用2015年6月至2016年5月观测数据,分析了峨眉冷杉成熟林净生态系统CO_2交换量(NEE)、生态系统呼吸(Re)和总生态系统生产力(GPP)的季节变异特征及其源汇状况,并结合环境因子,分析CO_2通量的主要控制因子。结果表明:(1)峨眉冷杉成熟林NEE具有明显的日变化特征,呈现"U"形变化,白天为负值,夜间为正值,中午前后CO_2通量达到最大;各月间日平均NEE变化差异显著,NEE峰值最大出现在2015年6月(-0.64 mg CO_2m~(-2)s~(-1)),峰值最小出现在2016年1月(-0.08 mg CO_2m~(-2)s~(-1));日平均NEE由正值变为负值的时间夏季最早,冬季最晚,NEE由负值变为正值的时间冬季最早,夏季最晚。(2)峨眉冷杉成熟林NEE、Re和GPP具有明显的月变化。2015年6月和12月NEE分别达到最大值(-46.02 g C m~(-2)月~(-1))和最小值(-1.42 g C m~(-2)月~(-1));Re呈现单峰变化,最大和最小值分别出现在2015年6月(84.78 g C m~(-2)月~(-1))和2016年1月(12.82 g C m~(-2)月~(-1));GPP最大值和最小值分别出现在2015年6月(130.81 g C m~(-2)月~(-1))与2016年1月(16.15 g C m~(-2)月~(-1))。(3)空气温度(T_a)、5 cm土壤温度(T_(s5))和光合有效辐射(PAR)是影响峨眉冷杉成熟林CO_2通量的主要环境因子。T_a与CO_2通量呈指数相关(R~2=0.5283,P0.01);白天CO_2通量与PAR显著相关(R~2=0.4373,P0.01);夜晚CO_2通量与T_(s5)显著相关(R~2=0.4717,P0.01)。(4)全年NEE、Re和GPP分别为-241.87、564.81 g C m~(-2)和806.68 g C m~(-2),表明川西贡嘎山峨眉冷杉成熟林具有较强的碳汇功能。 相似文献
16.
M. Moynul Haque A. Hamid M. Khanam D. K. Biswas M. A. Karim Q. A. Khaliq M. A. Hossain D. C. Uprety 《Biologia Plantarum》2006,50(1):69-73
The effect of elevated CO2 concentration (CE) on leaf chlorophyll (Chl) and nitrogen (N) contents and photosynthetic rate (PN) was evaluated during the post-flowering stages of rice grown at CE (570 ± 50 μmol mol−1) in open top chamber (OTC), at ambient CO2 concentration (∼ 365 μmol mol−1) in OTC and at open field. Thirty-five day old seedlings were transplanted in OTCs or in field and allowed to grow till maturity.
Chl and N contents were highest at the time of flowering and thereafter it started to decline. The rate of decline in Chl
and N contents was faster in plants grown under CE mostly in later part of growth. Irrespective of treatment difference, flag
leaf contained the highest amount of Chl and N than penultimate and third leaf. The higher PN was observed in leaves under CE than in the leaves in other two growing conditions. Considering growth stage, PN was the highest at flowering which reduced at the later part of growth due to degradation of Chl and N content of the leaf.
Under CE it was 40.02 μmol m−2 s−1 at flowering and it reduced to only 14.77 μmol m−2 s−1 at maturity stage. The beneficial effect of CE in increasing leaf PN may be maintained by applying extra dose of nitrogen at the later stages of plant growth. 相似文献
17.
Chilling stress and chilling tolerance of sweet potato as sensed by chlorophyll fluorescence 总被引:2,自引:0,他引:2
We studied changes in the chlorophyll (Chl) fluorescence components in chilling-stressed sweet potato (Ipomoea batatas L. Lam) cv. Tainung 57 (TN57, chilling-tolerant) and cv. Tainung 66 (TN66, chilling-susceptible). Plants under 12-h photoperiod
and 400 μmol m−2 s−1 irradiance at 24/20 °C (day/night) were treated by a 5-d chilling period at 7/7 °C. Compared to TN66, TN57 exhibited a significantly
greater basic Chl fluorescence (F0), maximum fluorescence (Fm), maximum fluorescence yield during actinic irradiation (Fm′ ), and the quantum efficiency of electron transport through photosystem 2, PS2 (ΦPS2). Chilling stress resulted in decrease in the potential efficiency of PS2 (Fv/Fm), ΦPS2, non-photochemical fluorescence quenching (NPQ), non-photochemical quenching (qN), and the occurrence of chilling injury in TN66. Chilling increased the likelihood of photoinhibition, characterized by a
decline in the Chl fluorescence of both cultivars, and photoinhibition during low temperature stress generally occurred more
rapidly in TN66. 相似文献
18.
Isoxaflutole [5-cyclopropyl-4-(2-methylsulphonyl-4-trifluromethylbenzoyl)isoxazole] is a new preemergence herbicide for broad-spectrum weed control in maize. The effect of isoxaflutole on chlorophyll (Chl) and carotenoid (Car) biosynthesis was investigated in cucumber (Cucumis sativus L.) cotyledons. Etiolated tissue was incubated with 5 mM isoxaflutole for 24 h and irradiated (60 mol m-2 s-1). The irradiation for 3 h did not reduce Chl a, Chl b, and Car contents, but after a 28-h irradiation the contents of Chl a and Car decreased by 35 and 15 %, respectively, and the content of Chl b increased by 24 %. Increasing the concentration of isoxaflutole beyond 5 mM resulted in reduction of Chl a (71 %), Chl b (20 %), and Car (31 %) contents. Similarly, increase in irradiance from 60 to 180 mol m-2 s-1 resulted in larger reduction of Chl and Car contents. Exogenously supplied 5-aminolevulinic acid did not reverse the isoxaflutole-inhibited Chl synthesis, whereas an exogenously supplied homogentisic acid lactone reversed the inhibition of pigment synthesis due to isoxaflutole. 相似文献
19.
为评价日本荚蒾(Viburnum japonicum)的耐盐雾能力,对4 a生实生苗用不同盐雾浓度处理(盐雾NaCl质量浓度分别为0%、1%、2%、3%),测定叶片净光合速率、最大光化学效率(Fv/Fm)和叶绿素含量(Chl)等指标的变化。结果表明,1%盐雾处理的日本荚蒾植株能够存活,但生长不良,大于2%的盐雾处理的植株全部死亡。随着浓度的升高,日本荚蒾叶片的最大光合速率、Fv/Fm及Chl含量下降,而光饱和点及光补偿点总体呈上升趋势。这说明盐雾胁迫通过伤害光系统Ⅱ反应中心、改变植物可利用光能范围及降低叶绿素含量影响植物的光合作用。 相似文献
20.
Chlorophyll a (Chl a) accumulation in the cotyledons of Scots pine seedlings (Pinus sylvestris L.) is much higher in the light than in darkness where it ceases 6 days after germination. When these darkgrown seedlings are treated with continuous white light (3,500 lx) a 3 h lag phase appears before Chl a accumulation is resumed. The lag phase can be eliminated by pretreating the seedlings with 7 h of weak red light (0.14 Wm-2) or with 14 red light pulses separated by relatively short dark periods (<100 min). The effect of 15s red light pulses can be fully reversed by 1 min far-red light pulses. This reversibility is lost within 2 min. In addition, the amount of Chl a formed within 27 h of continuous red light is considerably reduced by the simultaneous application of far-red (RG 9) light. It is concluded that phytochrome (Pfr) is required not only for the elimination of the lagphase but also to maintain a high rate of Chl a accumulation in continuous light. Since accumulation of 5-aminolevulinate (ALA) responds in the same manner as Chl a accumulation to a red light pretreatment it is further concluded that ALA formation is the point where phytochrome regulates Chl biosynthesis in continuous light. No correlation has been found between ALA and Chl a formation in darkness. This indicates that in a darkgrown pine seedling ALA formation is not rate limiting for Chl a accumulation.Abbreviations Chl
chlorophyll(ide)
- PChl
protochlorophyll(ide)
- ALA
5-aminolevulinate
- Pr
the red absorbing form of phytochrome
- Pfr
the far-red absorbing form of phytochrome
- Ptot
total phytochrome ([Pr]+[Pfr]) 相似文献