KINETICS OF CHLOROPHYLL a AND PLASTOQUINONE A: CHANGES IN RESPONSE TO LIGHT INTENSITY1

The thermophilic blue-green Synechococcus lividus Y52 was grown at several light intensities between 200 and 2400 ft-c. A 3.4-fold change of cellular chlorophyll (Chl) a content was found. The concentration of Plastoquinone A (PQA) per Chl a varied by a factor of 7, whereas PQA per cell varied by 1.4. Adaptation to light intensity appeared to occur through changes in size of the light-gathering antenna of chlorophyll and phycocyanin while the concentration of PQA remained nearly constant.     

INFLUENCE OF ULTRAVIOLET RADIATION ON GROWTH AND PHOTOSYNTHESIS OF TWO COLD OCEAN DIATOMS1

The influence of chronic exposure to UV-B and UV-A radiation on growth and photosynthesis of two polar marine diatoms (Pseudonitzschia seriata and Nitzschia sp.) was investigated in cultures exposed to moderate photon fluences for 3–7 days. Population growth rates were diminished 50% by UV-B. Fluorescence induction kinetics of photo-system II (PSII) revealed that UV-B caused lower F_v/F_m ratios and half-rise times, indicating damage to the reaction center of PSII and to related elements of the photosynthetic electron transport chain. Carbon assimilation rates per cell and per chlorophyll a were nonetheless highest for UV-B—exposed populations, which also had the highest chlorophyll a content per cell. The UV-B—exposed cells were, however, more vulnerable to visible light-induced photoinhibition. Exposure to UV-A in the absence of UV-B had little effect on growth, fluorescence induction of PSII, or chlorophyll a contents but did have some inhibitory effects on carbon assimilation per chlorophyll a and per cell. The increased photosynthetic capacity of UV-B-exposed cells suggested some ability to compensate for damage to the photosynthetic apparatus.     

The Adaptation of Plankton Algae

The variation in Skeletonema cells grown at 3 klux continuous illumination and 20°C is reported. Four different types of lamps gave no difference in the photosynthetic characteristics. The average diameter of the cells decreased from 8–3.5 μ during their six months vegetative period. The ratio between the pigment content in the largest and the smallest cells was about 2:1. A good correlation between cell volume and chlorophyll a content was found for this species. The content of chlorophyll c generally varied between 4 and 17 per cent of the chlorophyll a content. — A distinct correlation between the chlorophyll a content and the rate of photosynthesis per unit of cells at low light intensity was found. The rate of photosynthesis, in mg C per mg chlorophyll a and hour at 1 klux, varied between 0.40 and 0.70 for all 60 experiments with an average value of 0.56. The corresponding value for cells deficient in phosophorus was 0.19 and for cells deficient in nitrogen 0.09. — The material also showed a good correlation between the rate of photosynthesis per cell at 1 klux and the light-saturated rate of photosynthesis. I_k varied between 7 and 13 klux.     

The interaction of light intensity and DDT concentration upon the marine diatom,Nitzschia delicatissima cleve

Summary The effects of p, p-DDT were determined on photosynthesis and chlorophyll a content in the marine diatom Nitzschia delicatissima Cleve at four light intensities. A consistent reduction in carbon fixation and chlorophyll a per cell over controls in a 24-hour period was observed with increasing DDT concentration between 9.4 ppb and 1000 ppb. The maximum reductions of carbon uptake, chlorophyll a and carbon/chlorophyll a uptake per cell occurred at the highest light intensities. Carbon fixation per cell was reduced by as much as 94% in water containing an initial DDT concentration of 100 ppb, and chlorophyll a per cell by as much as 86% in 220 ppb DDT. Above 100 ppb, further decreases of carbon fixation and chlorophyll a per cell were not observed. Distortion of the chloroplasts in the cells exposed to DDT was also observed at the lowest concentration of DDT used. At 1000 ppb, chloroplasts were totally destroyed within 24 hours.

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Zusammenfassung Die Wirkung von p, p-DDT auf Photosynthese und Chlorophyll a Gehalt der Meeresdiatomee Nitschia delicatissima Cleve wurde untersucht unter vier Lichtintensitäten. Bei DDT Konzentrationen, steigend von 9,4 ppb bis 1000 ppb, wurde eine fortschreitende Reduktion der Kohlenstoff bindung und des Chlorophyll a Gehaltes pro Zelle gefunden, wobei die höchtse Lichtintensität die stärkste Reduktion, sowie auch die niedrigste Kohlenstoff/Chlorophyll a Aufnahme pro Zelle zeigte. In Wasser mit anfänglichem DDT Gehalt von 100 ppb, wurde die Kohlenstoff bindung pro Zelle 94% reduziert und beim DDT Gehalt von 220 ppb, wurde der Chlorophyll a Gehalt mit 86% reduziert. Bei Konzentrationen über 100 ppb, fielen Kohlenstoff bindung und Chlorophyll a Gehalt pro Zelle nicht weiter ab.Schädigungen der Chloroplasten in der Zelle wurden schon bei den niedrigsten DDT Gehalten festgestelt. Bei 100 ppb wurden die Chloroplasten innerhalb 24 Stunden völlig zerstört.

     

Variations in biochemical parameters of Heterocapsa sp. and Olisthodiscus luteus grown in 12:12 light:dark cycles II. Changes in pigment composition

Photosynthetic pigment composition was studied in batch cultures of Heterocapsa sp. and Olisthodiscus luteus growing exponentially in a 12:12 light:dark cycle. Both species divided in the dark. The synthesis of pigments was continuous for both species. However for chlorophyll c and peridinin, in Heterocapsa sp., and chlorophyll c and fucoxanthin, in O. luteus, (pigments belonging to light harvesting complexes) the synthesis was significantly higher during the light period. Concentrations per total cell volume (TCV) of chlorophyll a, chlorophyll c, peridinin and diadinoxanthin in Heterocapsa sp., and chlorophyll a, chlorophyll c, fucoxanthin and violaxanthin in O. luteus, showed a maximum at the onset of light and decreased during the light period. The values of the chlorophyll a:chlorophyll c, chlorophyll a:peridinin and chlorophyll a:fucoxanthin ratios are compared with data reported in the literature.     

COMPARATIVE PHYSIOLOGICAL STUDY OF MARINE DIATOMS AND DINOFLAGELLATES IN RELATION TO IRRADIANCE AND CELL SIZE. II. RELATIONSHIP BETWEEN PHOTOSYNTHESIS,GROWTH, AND CARBON/CHLOROPHYLL a RATIO1,2

Photosynthetic rates, growth rates, cell carbon, cell protein, and chlorophyll a content of two diatom and two dinoflagellate species were measured. The microalgae were chosen to have one small and one large species from each phylogenetic group; the two size categories differed from each other by 1.5 orders of magnitude in terms of cell carbon or cell protein. The cultures for the experiments were grown under continuous light at an irradiance high enough for the light-saturation of growth for all four species. The four species were found to have similar maximum photosynthetic rates per unit chlorophyll a. The diatom species showed lower carbon/chlorophyll a ratios and higher photosynthetic rates per unit carbon than the dinoflagellates. The higher growth rates of the diatoms were shown to be related to their higher photosynthetic rates per unit carbon. The ecological significance of the physiological difference between these two groups of microalgae is discussed.     

Chloroplast development and the synthesis of chlorophyll a and b and chlorophyll protein complexes I and II in the dark in Tradescantia albiflora (Kunth)

Continued synthesis of chlorophyll a and chlorophyll b occurs in Tradescantia albiflora Kunth on transfer to darkness. This synthesis continues for several days and may result in a doubling of chlorophyll content per leaf. It is accompanied by continued cell division and development of normal chloroplast ultrastructure, including stacked thylakoids.     

The Antenna System of Photosystem II From Thermosynechococcus elongatus at 3.2 Å Resolution

The content and type of cofactors harboured in the Photosystem II core complex (PS IIcc) of the cyanobacterium Thermosynechococcus elongatus has been determined by biochemical and spectroscopic methods. 17 ± 1 chlorophyll a per pheophytin a and 0.25 β-carotene per chlorophyll a have been found in re-dissolved crystals of dimeric PS IIcc. The X-ray crystal structure of PS IIcc from Thermosynechococcus elongatus at 3.2 Å resolution clearly shows chlorophyll a molecules arranged in two layers close to the cytoplasmic and lumenal sides of the thylakoid membrane. Each of the cytoplasmic layers contains 9 chlorophyll a, whose positions and orientations are related by a local twofold rotation pseudo-C2 axis passing through the non-haem Fe²⁺. These chlorophyll a are arranged comparably to those in the antenna domains of PsaA and PsaB of cyanobacterial Photosystem I affirming an evolutionary relation. The chlorophyll a in the lumenal layer are less well conserved between Photosystems I and II and even between CP43 and CP47 with 4 chlorophyll a in the former and 7 in the latter.     

Functional organization and plasticity of the photosynthetic unit of the cyanobacterium Anacystis nidulans

Anacystis nidulans grown under high and low light, 100 and 10 μE m^?2 s^?1, respectively, was analyzed with respect to chlorophyll/P700, phycobiliproteins/P700, chlorophyll/cell, and oxygen evolution parameters. The photosynthetic unit sizes of this cyanobacterium, measured as the ratio of total chromophores (chlorophyll and bilin) to P700, were shown to be similar to those of higher plants and green algae. High light grown cells possessed a photosynthetic unit consisting of a core of 157 ± 6 chlorophyll a molecules per P700 associated with a light harvesting system of 95 ± 3.5 biliprotein chromophores. Low light grown cells had substantially more biliprotein chromophores per P700 (125 ± 3.1) than high light cells, but showed no significant difference in the numbers of chlorophyll a molecules per P700 (149 ± 4). Analyses of aqueous biliprotein extracts indicate that low light grown cells produce proportionately more phycocyanin relative to allophycocyanin than high light cells. Calculations of the molecular weight of biliproteins per P700 suggest that there is less than one phycobilisome per reaction center I under both growth conditions. Differences in chlorophyll/cell ratios and oxygen evolution characteristics were also observed. High light cells contain 6.3 × 10^?12 mg chlorophyll cell^?1, while low light grown cells contain 12.8 × 10^?12 mg chlorophyll cell^?1. Photosynthetic oxygen evolution rate vs. light intensity curves indicate that high light grown cells reach maximal levels of oxygen evolution at higher light intensity than low light grown cells. Maximal rates of oxygen evolution were 16.6 μmol oxygen min^?1 (mg chlorophyll)^?1 for high and 8.4 μmol oxygen min^?1 (mg chlorophyll)^?1 for low light cells. Maximal oxygen evolution rates per cell were equivalent for both cell types, although the amount of P700 per cell was lower in high light cells. High light grown cells are therefore capable of producing more oxygen per reaction center I than low light grown cells.     

Conversion of chlorophyll b to chlorophyll a precedes magnesium dechelation for protection against necrosis in Arabidopsis

Chlorophyll is a deleterious molecule that generates reactive oxygen species and must be converted to non‐toxic molecules during plant senescence. The degradation pathway of chlorophyll a has been determined; however, that of chlorophyll b is poorly understood, and multiple pathways of chlorophyll b degradation have been proposed. In this study, we found that chlorophyll b is degraded by a single pathway, and elucidated the importance of this pathway in avoiding cell death. In order to determine the chlorophyll degradation pathway, we first examined the substrate specificity of 7‐hydroxymethyl chlorophyll a reductase. 7‐hydroxymethyl chlorophyll a reductase reduces 7‐hydroxymethyl chlorophyll a but not 7‐hydroxymethyl pheophytin a or 7‐hydroxymethyl pheophorbide a. These results indicate that the first step of chlorophyll b degradation is its conversion to 7‐hydroxymethyl chlorophyll a by chlorophyll b reductase, although chlorophyll b reductase has broad substrate specificity. In vitro experiments showed that chlorophyll b reductase converted all of the chlorophyll b in the light‐harvesting chlorophyll a/b protein complex to 7‐hydroxymethyl chlorophyll a, but did not completely convert chlorophyll b in the core antenna complexes. When plants whose core antennae contained chlorophyll b were incubated in the dark, chlorophyll b was not properly degraded, and the accumulation of 7‐hydroxymethyl pheophorbide a and pheophorbide b resulted in cell death. This result indicates that chlorophyll b is not properly degraded when it exists in core antenna complexes. Based on these results, we discuss the importance of the proper degradation of chlorophyll b.     

CHLOROPHYLL A VERSUS ADENOSINE TRIPHOSPHATE AS ALGAL BIOMASS INDICATORS IN LAKES1

The relation between phyloplankton chlorophyll a and adenosine triphosphate (ATP) was investigated during a yearly cycle in Lake Tahoe, California–Nevada, and a variety of North American and New Zealand lakes of ranging trophic state. Since cellular concentrations of ATP have been shown as acceptable indicators of live biomass among natural microbial populations, the ratio of chlorophyll a to cellular ATP reveals the extent of pigment production per unit biomass under diverse environmental conditions. In general, mixed systems, i.e., epilimnion of most lakes sampled, showed good consistency of cellular chlorophyll a:ATP ratios. Under thermally stratified conditions at Lake Tahoe extensive modifications of the ratio occurred, leading to a 10-fold increase in the ratio at the bottom of the euphotic zone by late summer. Thus, the applicability of chlorophyll a as a quantitative algal biomass indicator is greatly restricted in lakes having thermally stratified euphotic zones.     

The use of dialysis culture in a study of chlorophyll budget in a brackish lagoon,Japan

Growth rates of the entire phytoplankton community of a brackish lagoon in northeastern Japan were estimated by measuring increasing chlorophyll a content in dialysis bags during the summer and early autumn of 1986. The chlorophyll a contents of lagoon water fluctuated between 20 and 200 mg m^–3. At lower densities of phytoplankton (20–50 mg chl. a m^–3), growth rates (the rate of increase of chlorophyll a) exceeded 1 turnover per day, while at higher densities (more than 50 mg chl. a m^–3), the growth rate decreased rapidly. Tidal exchanges of chlorophyll a showed net exports of chlorophyll a from the lagoon to adjacent waters. The exchange rate of chlorophyll a was estimated to be 0.65 d^–1. At about 140 mg m^–3 of chlorophyll a concentration, the increase of chlorophyll in the lagoon water compensated for tidal export. Only a small proportion of primary production was consumed by zooplankton in the lagoon. There were also net exports of ammonium and phosphate from the lagoon. Nutrient flux from sediment exceeded the phytoplankton requirement and was the major source of the ammonium and phosphate exports from the lagoon. The low inorganic N/P atom supply ratio in the lagoon suggests that nitrogen is a major nutrient limiting phytoplankton growth.     

Response of Tetraselmis suecica to nutrient and grazer manipulation

Three methods of algal quantification (direct cell counts, chlorophyll a extraction, in vivo fluorescence) were used to evaluate the response of the unicellular green flagellate Tetraselmis suecica to nutrients and grazers. Nutrient enrichment enhanced total cell counts, chlorophyll a concentration and in vivo and DCMU-fluorescence. Photosynthetic efficiency was reduced in the complete F2 medium as indicated by the high level of in vivo fluorescence, whereas photosynthetic efficiency was increased by the introduction of mussels to the F2 medium. The addition of mussels significantly increased the proportion of non-motile cells, but did not reduce the total cell count. The effect of mussel grazing on algae could be underestimated if only total cells were counted or only the chlorophyll a concentration was measured. The results indicate that these three methods measure different properties of an algal culture and are complementary to each other in assessing the quality and quantity of an algal population. Direct algal counting offers a reliable numerical assessment for cell population abundance. Chlorophyll a concentration was closely correlated to the total cell count. In the presence of mussels, in vivo fluorescence did not correlate with either algal cell counts or chlorophyll a concentration, indicating that the measurement of in vivo fluorescence may be misleading for estimating algal abundance under different culture conditions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Accumulation of Plastoquinone A during Low Temperature Growth of Winter Rye

Chloroplasts isolated from rye (Secale cereale L. cv Puma) grown at 5°C (RH) accumulated 260% more plastoquinone A (PQA) per plastid than chloroplasts isolated from rye grown at 20°C (RNH). The number of plastoglobuli increased by 270% in RH chloroplasts compared with RNH plastids. When RH plastids were lysed and washed, the number of plastoglobuli associated with thylakoid membranes decreased significantly, yet the PQA levels remained high. Room temperature fluorescence induction indicated that (a) there is no change in the size of the PQA pool immediately available for photochemistry in RNH and RH thylakoids and (b) there is a pool of oxidized PQA present in RNH and RH thylakoids which is not available for photochemistry. The accumulated PQA in RH thylakoids may reflect an increased nonphotochemical function such as regulation of thylakoid protein phosphorylation or protection against photoinhibition.     

Light absorption by marine macrophytes

Tissues of 338 marine macrophytes comprising 103 species, collected from the Atlantic, Mediterranean, South China, and Caribbean Seas, and encompassing a broad range in thallus form and pigmentation, were examined to quantify the importance of phylogenetic differences, spectral variability, and plant form and pigment content to account for differences in the absorption of light by marine macrophytes. Phylogenetic differences accounted for 2.5% of the variance in absorption observed, non-phylogenetic spectral differences being much larger (26%). Differences among individual specimens were much larger (72%), absorption at 675 nm increasing non-linearly as chlorophyll a density^1/2, indicating that light absorption increases with increasing chlorophyll a density following a law of diminishing returns, as predicted by theory. The energy return per unit tissue produced (i.e. light absorption per unit plant weight) increased linearly with increasing chlorophyll a concentration. However, the light absorbed per unit weight decreased, for a given chlorophyll a concentration, as plant thickness increased. This indicates that while increasing thickness may increase chlorphyll a density and, hence, the light absorbed by marine macrophyte thalli, this strategy represents a burden limiting potential carbon turnover and plant growth. These results indicate that the diverse repertoire of light absorption by marine macrophytes can be adequately modeled as a continuum, dependent on plant thickness and pigment content, independent of phylogenetic differences.     

Growth light level and photon absorption by cells of Chlamydomonas rheinhardii,Dunaliella tertiolecta (Chlorophyceae,Volvocales), Scenedesmus obliquus (Chlorophyceae,Chlorococcales) and Euglena viridis (Euglenophyceae,Euglenales)

Reductions in the growth light level (40 to 6 μmol m^-2 s^-1) resulted in increases in chlorophyll and protein per cell for all of the species examined. Only Dunaliella tertiolecta exhibited a reduction in chlorophyll a:b ratio with decreases in the photon flux density. However, the specific absorption coefficient (ā? _i ) normalized to chlorphyll a (ā? _a remained invariant for all of the microalgae studied. Constant values for the specific absorption coefficient normalized to the total pigment content (ā? _a+b ) were also found for the species Chlamydomonas rheinhardii, Euglena viridis and Scenedesmus obliquus. In contrast ā? _a+b for D. tertiolecta decreased with a reduction in light level due to an increase in the proportion of chlorophyll b. Differences in ā? _i were related to cell size and pigment content and possible reasons for the constancy of ā? _a discussed. Increases in the absorption cross sections (¯sQ _a ) were also found at reduced light levels due to an increase in the absorptance per cell (α_cell). The lower α_cell for D. tertiolecta, compared with C. rheinhardii was exactly compensated for by a larger light-capturing area. Although the increase in α_cell does not compensate for the reduction in the incident light level, it does reduce this range by half on an absorbed light basis.     

A comparative analysis of the relationship between phytoplankton standing crops and environmental parameters in four eutrophic prairie reservoirs

An analysis was performed with multivariate statistical methods of the relationship between chlorophyll a concentrations and eighteen physico-chemical parameters measured over a six year period in four eutrophic Nebraska reservoirs. In the reservoirs with relatively clear water early in the growing season, physical factors (Secchi depth, turbidity, temperature) and non-nutrient chemical factors (alkalinity, hardness, C. O. D.) were significantly related to chlorophyll a concentrations, but macronutrients (nitrogen and phosphorus) were not. In the reservoir with persistent abiogenic turbidity, chemical factors including nitrogen and phosphorus were significant but physical factors were not. Six models based upon intercorrelations between measured parameters and chlorophyll a are evaluated for their usefulness in accounting for chlorophyll a variance. The best model accounts for 67–70 percent of the total variation in chlorophyll a in the four reservoirs.     

Using Phytoplankton to Assess the Trophic Status of German Rivers

We introduce the German multi‐metric assessment method PhytoFluss for large rivers, based on phytoplankton, which can be used to implement the European Water Framework Directive (WFD). First, we examined the response of chlorophyll a concentration to total phosphorus (TP) at 220 German river sites. Rivers could be assigned to one of four groups, based on the response curves: a) streams with high specific run‐off (Rhine, Danube) had the lowest yield of chlorophyll a per unit of TP, followed by b) low yield in small lowland rivers (Trave, Stepenitz), c) medium‐sized lowland rivers (Spree) and large central mountain rivers (Main) had intermediate yields of chlorophyll a, and d) streams with low specific run‐off (Elbe, Weser) and Baltic tributaries (Penne, Warnow) had the highest yield of chlorophyll a per unit of TP. To define the five trophic status classes of phytoplankton biomass according the WFD, the chlorophyll a boundaries were derived from these response curves at the 75% percentile level. All selected sites were pre‐classified with the combined trophic boundaries for TP and chlorophyll a to create the new four taxa composition metrics: The proportions of Chlorophytes, Cyanobacteria, or Pennales and of indicator taxa were selected as indicative parameters. When applying the final PhytoFluss method to 418 years of investigation from 150 German river sites, the percentages in each status according to the bio‐ component phytoplankton were: high 3%, good 19%, moderate 42%, poor 30%, and bad 5%. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

CHLOROPLASTS OF MONOPLOID AND DIPLOID OENOTHERA HOOKERI

Comparison of leaves from diploid Oenothera hookeri plants with leaves of their monoploid derivatives revealed the following differences: the leaves of the diploids are almost twice as thick as those of the monoploids; the diploids have only one-fifth as many cells per unit leaf area as do the monoploids; leaf tissue of the diploids has an average of 36.3 chloroplasts per cell compared with 27.4 for the monoploids; chloroplasts of the diploids average 4.68 μm in length, those of the monoploids, 3.74 μm; chloroplasts from the diploids contain about seven times more chlorophyll than those of the monoploids and have an average of seven thylakoids per granum compared with an average of only three for the monoploids; the average chlorophyll a/b ratio for the diploid chloroplasts is 2.98 compared with 3.48 for the monoploids.     

Use of natural polymers as immobilizing agents and effects on the growth of Dunaliella salina and its glycerol production

Agar-agar, agarose, carrageenan and calcium alginate were used for the immobilization of Dunaliella salina cells. Out of the four, agar-agar was found to be the most effective and therefore the study was carried out on it using different pH values ranging from 6 to 10 and cell densities from 0.1 to 0.8 μg chlorophyll (chl, a) per bead to find which are is best suited for glycerol production. The maximum glycerol production of 9.2 μM/mg chl a was recorded in agar-agar immobilized algae and this was followed by 8.4 μM/mg chl a in calcium alginate. The maximum cell number 6.2 × 10⁹/ml and the specific growth rate (μ) of 0.80 l/day were reached at pH 8 in agar-agar immobilized algae. It was shown that the maximum amount of glycerol was produced when the cell density was 0.8 μg chl a/ block. Changing the medium after 24 hours affected the rate of glycerol production at different pH values. Using a cell density of 0.8 μg chl a/block at 16 W/m² light intensity increased the glycerol production in comparison with the use of free living cells.