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Chlorophyll
Kinds of Chlorophyll Terms modified by Chlorophyll Selected AbstractsLATERAL GENE TRANSFER IN THE CYANOBACTERIA: CHLOROPHYLLS, PROTEINS, AND SCRAPS OF RIBOSOMAL RNAJOURNAL OF PHYCOLOGY, Issue 3 2005B. R. Green First page of article [source] Fathers, fruits and photosynthesis: pollen donor effects on fruit photosynthesis in wild parsnipECOLOGY LETTERS, Issue 11 2003Arthur R. Zangerl Abstract Chlorophyll is frequently present in plant reproductive tissues and indicates that photosynthesis is occurring in these parts. Photosynthesis by a reproductive organ can contribute as much as 65% to its own growth. Given the advantages that increased photosynthetic rates might have on development of individual seeds competing for resources, selection can be expected to favour the ability of offspring to influence photosynthetic rates of the tissues surrounding them. We report in this study the first evidence that the pollen genotype can influence the rate of photosynthesis in the fruit tissues surrounding the developing offspring. Using a novel chlorophyll fluorescence imaging instrument to quantify quantum efficiency of photosystem II, we found significant differences in photosynthetic rates among fruits in wild parsnip, Pastinaca sativa L, associated with different pollen genotypes. [source] Chlorophyll fluorescence as a bioindicator of effects on growth in aquatic macrophytes from mixtures of polycyclic aromatic hydrocarbonsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2001Christopher A. Marwood Abstract Chlorophyll- a fluorescence induction is a rapid technique for measuring photosynthetic electron transport in plants. To assess chlorophyll- a fluorescence as a bioindicator of effects of polycyclic aromatic hydrocarbon mixtures, chlorophyll- afluorescence parameters and plant growth responses to exposure to the wood preservative creosote were examined in the aquatic plants Lemna gibba and Myriophyllum spicatum. Exposure to creosote inhibited growth of L. gibba (EC50 = 7.2 mg/L total polycyclic aromatic hydrocarbons) and M. spicatum (EC50 = 2.6 mg/L) despite differences in physiology. Creosote also diminished maximum PSII efficiency (Fv/Fm) (EC50 = 36 and 13 mg/L for L. gibba and M. spicatum) and the effective yield of photosystem II photochemistry (,F/F,m) (EC50 = 13 and 15 mg/L for L. gibba and M. spicatum). The similarity between growth and chlorophyll- a fluorescence EC50s and slopes of the response curves suggests a close mechanistic link between these end points. The predictive power of chlorophyll- a fluorescence as a bioindicator of whole-organism effects applied to complex contaminant mixtures is discussed. [source] Lipid biomarkers, pigments and cyanobacterial diversity of microbial mats across intertidal flats of the arid coast of the Arabian Gulf (Abu Dhabi, UAE)FEMS MICROBIOLOGY ECOLOGY, Issue 3 2008Raeid M.M. Abed Abstract Variations in morphology, fatty acids, pigments and cyanobacterial community composition were studied in microbial mats across intertidal flats of the arid Arabian Gulf coast. These mats experience combined extreme conditions of salinity, temperature, UV radiation and desiccation depending on their tidal position. Different mat forms were observed depending on the topology of the coast and location. The mats contained 63 fatty acids in different proportions. The increased amounts of unsaturated fatty acids (12,39%) and the trans/cis ratio (0.6,1.6%) of the cyanobacterial fatty acid n- 18:1,9 in the higher tidal mats suggested an adaptation of the mat microorganisms to environmental stress. Chlorophyll a concentrations suggested lower cyanobacterial abundance in the higher than in the lower intertidal mats. Scytonemin concentrations were dependent on the increase in solar irradiation, salinity and desiccation. The mats showed richness in cyanobacterial species, with Microcoleus chthonoplastes and Lyngbya aestuarii morphotypes as the dominant cyanobacteria. Denaturing gradient gel electrophoresis patterns suggested shifts in the cyanobacterial community dependent on drainage efficiency and salinity from lower to higher tidal zones. We conclude that the topology of the coast and the variable extreme environmental conditions across the tidal flat determine the distribution of microbial mats as well as the presence or absence of different microorganisms. [source] Diversity of planktonic photoautotrophic microorganisms along a salinity gradient as depicted by microscopy, flow cytometry, pigment analysis and DNA-based methodsFEMS MICROBIOLOGY ECOLOGY, Issue 2 2004Marta Estrada Abstract The diversity of prokaryotic and eukaryotic phytoplankton was studied along a gradient of salinity in the solar salterns of Bras del Port in Santa Pola (Alacant, Spain) using different community descriptors. Chlorophyll a, HPLC pigment composition, flow cytometrically-determined picoplankton concentration, taxonomic composition of phytoplankton (based on optical microscopy) and genetic fingerprint patterns of 16S (cyanobacteria- and chloroplast-specific primers) and 18S rRNA genes were determined for samples from ponds with salinities ranging from 4% to 37%. Both morphological and genetical descriptors of taxonomic composition showed a good agreement and indicated a major discontinuity at salinities between 15% and 22%. The number of classes and the Shannon diversity index corresponding to the different descriptors showed a consistent decreasing trend with increasing salinity. The results indicate a selective effect of extremely high salinities on phytoplanktonic assemblages. [source] Culture-based fisheries in non-perennial reservoirs in Sri Lanka: production and relative performance of stocked speciesFISHERIES MANAGEMENT & ECOLOGY, Issue 4 2005W. M. H. K. WIJENAYAKE Abstract, In Sri Lanka, there is a great potential for the development of culture-based fisheries because of the availability of around 12 000 non-perennial reservoirs in the dry zone (<187 cm annual rainfall) of the island. These reservoirs fill during the north-east monsoonal period in October to December and almost completely dry up during August to October. As these non-perennial reservoirs are highly productive, hatchery-reared fish fingerlings can be stocked to develop culture-based fisheries during the water retention period of 7,9 months. The present study was conducted in 32 non-perennial reservoirs in five administrative districts in Sri Lanka. These reservoirs were stocked with fingerlings of Indian (catla Catla catla Hamilton and rohu Labeo rohita Hamilton) and Chinese (bighead carp Aristichthys nobilis Richardson) major carps, common carp Cyprinus carpio L., genetically improved farmed tilapia (GIFT) strain of Nile tilapia, Oreochromis niloticus (L.) and post-larvae of giant freshwater prawn, Macrobrachium rosenbergii De Man, at three different species combinations and overall stocking densities (SD) ranging from 218 to 3902 fingerlings ha,1, during the 2002,2003 culture cycle. Of the 32 reservoirs stocked, reliable data on harvest were obtained from 25 reservoirs. Fish yield ranged from 53 to 1801 kg ha,1 and the yields of non-perennial reservoirs in southern region were significantly (P < 0.05) higher than those in the northern region. Naturally-recruited snakehead species contributed the catches in northern reservoirs. Fish yield was curvilinearly related to reservoir area (P < 0.05), and a negative second order relationship was evident between SD and yield (P < 0.05). Chlorophyll- a and fish yield exhibited a positive second order relationship (P < 0.01). Bighead carp yield impacted positively on the total yield (P < 0.05), whereas snakehead yield impact was negative. Bighead carp, common carp and rohu appear suitable for poly-culture in non-perennial reservoirs. GIFT strain O. niloticus had the lowest specific growth rate among stocked species and freshwater prawn had a low return. [source] Sources and transport of algae and nutrients in a Californian river in a semi-arid climateFRESHWATER BIOLOGY, Issue 12 2007NOBUHITO OHTE Summary 1. To elucidate factors contributing to dissolved oxygen (DO) depletion in the Stockton Deep Water Ship Channel in the lower San Joaquin River, spatial and temporal changes in algae and nutrient concentrations were investigated in relation to flow regime under the semiarid climate conditions. 2. Chlorophyll- a (chl- a) concentration and loads indicated that most algal biomass was generated by in-stream growth in the main stem of the river. The addition of algae from tributaries and drains was small (c.15% of total chl- a load), even though high concentrations of chl- a were measured in some source waters. 3. Nitrate and soluble-reactive phosphorus (SRP) were available in excess as a nutrient source for algae. Although nitrate and SRP from upstream tributaries contributed (16.9% of total nitrate load and 10.8% of total SRP load), nutrients derived from agriculture and other sources in the middle and lower river reaches were mostly responsible (20.2% for nitrate and 48.0% for SRP) for maintaining high nitrate and SRP concentrations in the main stem. 4. A reduction in nutrient discharge would attenuate the algal blooms that accelerate DO depletion in the Stockton Deep Water Ship Channel. The N : P ratio, in the main stem suggests that SRP reduction would be a more viable option for algae reduction than nitrogen reduction. 5. Very high algal growth rates in the main stem suggest that reducing the algal seed source in upstream areas would also be an effective strategy. [source] Phytoplankton production and growth rate in Lake Tanganyika: evidence of a decline in primary productivity in recent decadesFRESHWATER BIOLOGY, Issue 11 2007STEPHANE STENUITE Summary 1. This study focused on phytoplankton production in Lake Tanganyika. We provide new estimates of daily and annual primary production, as well as growth rates of phytoplankton, and we compare them with values published in former studies. 2. Chlorophyll- a (chl- a) in the mixed layer ranged from 5 to 120 mg chl- a m,2 and varied significantly between rainy and dry seasons. Particulate organic carbon concentrations were significantly higher in the south basin (with 196 and 166 mg C m,3 in the dry and the rainy season, respectively) than in the north basin (112 and 109 mg C m,3, respectively). 3. Carbon : phosphorus (C : P) ratios varied according to season. Phosphorus limitation seemed to occur more frequently than nitrogen limitation, especially during the rainy season. Severe P deficiencies were rare. 4. Measured particulate daily primary production ranged from 110 to 1410 mg C m,2 day,1; seasonal contrasts were well marked in the north basin, but less in the south basin, where primary production peaks occurred also in the rainy season. Estimates of annual primary production, based on daily primary production calculated from chl- a and water transparency, gave values lower than those reported in previous studies. Picophytoplankton accounted on average for 56% of total particulate production in the south basin during the wet season of 2003. 5. Phytoplankton growth rates, calculated from primary production, ranged from 0.055 to 0.282 day,1; these are lower than previously published values for Lake Tanganyika. [source] Distribution and growth of benthic macroinvertebrates among different patch types of the littoral zones of two arctic lakesFRESHWATER BIOLOGY, Issue 12 2006STEVEN R. BEATY Summary 1. To evaluate the effect of habitat patch heterogeneity on abundance and growth of macroinvertebrates in arctic lakes, macroinvertebrate abundance, individual biomass, and potential food resources were studied in three patch types in two arctic lakes on the Alaskan North Slope near the Toolik Lake Field Station. An experiment was conducted to determine which sediment patch type supported higher growth rates for Chironomus sp., a commonly occurring macroinvertebrate. 2. Potential organic matter (OM) resources were significantly higher in both rock and macrophyte patches than in open-mud patches. Total macroinvertebrate densities in both lakes were highest in rock patches, intermediate in macrophytes and lowest in open-mud. The open-mud patches also had lower species richness compared with other patch types. Additionally, individual biomass for one clam species and two chironomid species was significantly greater in rock patches than in open-mud. 3. In a laboratory experiment, Chironomus showed two to three times greater mass increase in sediments from macrophyte and rock patches than from open-mud patches. Rock and macrophyte experimental sediments had at least 1.5 × the percentage OM as open-mud sediments. 4. Chlorophyll a appeared to be the best predictor for invertebrate abundances across all patch types measured, whereas OM content appeared to be the variable most closely associated with Chironomus growth. 5. Our results combined with previous studies show that the relationships between macroinvertebrate community structure, individual growth, and habitat heterogeneity are complex, reflecting the interaction of multiple resources, and biotic interactions, such as the presence or absence of a selective vertebrate predator (lake trout, Salvelinus namaycush). [source] Priming the productivity pump: flood pulse driven trends in suspended algal biomass distribution across a restored floodplainFRESHWATER BIOLOGY, Issue 8 2006DYLAN S. AHEARN Summary 1. Chlorophyll a (Chl a) distribution across a 0.36 km2 restored floodplain (Cosumnes River, California) was analysed throughout the winter and spring flood season from January to June 2005. In addition, high temporal-resolution Chl a measurements were made in situ with field fluorometers in the floodplain and adjacent channel. 2. The primary objectives were to characterise suspended algal biomass distribution across the floodplain at various degrees of connection with the channel and to correlate Chl a concentration and distribution with physical and chemical gradients across the floodplain. 3. Our analysis indicates that periodic connection and disconnection of the floodplain with the channel is vital to the functioning of the floodplain as a source of concentrated suspended algal biomass for downstream aquatic ecosystems. 4. Peak Chl a levels on the floodplain occurred during disconnection, reaching levels as high as 25 ,g L,1. Chl a distribution across the floodplain was controlled by residence time and local physical/biological conditions, the latter of which were primarily a function of water depth. 5. During connection, the primary pond on the floodplain exhibited low Chl a (mean = 3.4 ,g L,1) and the shallow littoral zones had elevated concentrations (mean = 4.6 ,g L,1); during disconnection, shallow zone Chl a increased (mean = 12.4 ,g L,1), but the pond experienced the greatest algal growth (mean = 14.7 ,g L,1). 6. Storm-induced floodwaters entering the floodplain not only displaced antecedent floodplain waters, but also redistributed floodplain resources, creating complex mixing dynamics between parcels of water with distinct chemistries. Incomplete replacement of antecedent floodplain waters led to localised hypoxia in non-flushed areas. 7. The degree of complexity revealed in this analysis makes clear the need for high-resolution spatial and temporal studies such as this to begin to understand the functioning of dynamic and heterogeneous floodplain ecosystems. [source] Effects of the non-indigenous cladoceran Cercopagis pengoi on the lower food web of Lake OntarioFRESHWATER BIOLOGY, Issue 12 2003Corey L. Laxson Summary 1. In North America, the invasive predatory cladoceran Cercopagis pengoi was first detected in Lake Ontario. We explored the impact of Cercopagis on the lower food web of Lake Ontario through assessments of historical and seasonal abundance of the crustacean zooplankton, by conducting feeding experiments on the dominant prey of the invader, and by estimating its food requirements. 2. Between 1999 and 2001, a decrease in the abundance of dominant members of the Lake Ontario zooplankton community (Daphnia retrocurva, Bosmina longirostris and Diacyclops thomasi) coincided with an increase in the abundance of Cercopagis. Daphnia retrocurva populations declined despite high fecundity in all 3 years, indicating that food limitation was not responsible. Chlorophyll a concentration generally increased, concomitant with a decline in the herbivorous cladoceran zooplankton in the lake. 3. Laboratory experiments demonstrated that Cercopagis fed on small-bodied species including D. retrocurva and B. longirostris. 4. Consumption demand of mid-summer populations of Cercopagis, estimated from a bioenergetic model of the confamilial Bythotrephes, was sufficient to reduce crustacean abundance, although the degree of expected suppression varied seasonally and interannually. 5. Predatory effects exerted by Cercopagis on the Lake Ontario zooplankton, while initially very pronounced, have decreased steadily as the species became established in the lake. [source] Lake age and water level affect the turbidity of floodplain lakes along the lower RhineFRESHWATER BIOLOGY, Issue 3 2003F. C. J. M. Roozen SUMMARY 1. We sampled a set of 93 lakes situated in the floodplains of the lower River Rhine in search for morphometric and other factors that explain their variation in clarity. 2. Lakes with a drop in summer water level were less turbid at the time of sampling, mainly because of a lower concentration of inorganic suspended solids (ISS). 3. We also found that older lakes were more turbid than younger lakes and that this was largely because of an increase in phytoplankton. 4. Water clarity was positively related to lake depth and the presence of vegetation. 5. Model calculations indicated that the underwater light climate was strongly affected by chlorophyll and ISS, the latter being the dominant factor affecting Secchi depth. Dissolved organic carbon (DOC) was less important. 6. The high concentration of ISS suggests that intensive resuspension occurs in most of the lakes. Using a simple wave model, and assuming that vegetation protects sediments against resuspension, we could eliminate wind resuspension as an important process in 90% of the lakes, leaving resuspension by benthivorous fish as probably the most important factor determining transparency. 7. Chlorophyll a concentration showed a strong positive correlation to ISS concentration, suggesting that resuspension may also have a positive effect on phytoplankton biomass in these lakes. 8. In conclusion, in-lake processes, rather than river dynamics, seem to be driving the turbidity of floodplain lakes along the lower River Rhine. [source] Cell Lysis of Cyanobacteria and Its Implications for Nutrient DynamicsINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2010Linlin Ye Abstract The dynamics of nutrients, such as phosphorus, nitrogen, and carbohydrates, during cyanobacteria cell lysis was investigated under darkness incubation in the laboratory. The cell lysis rate of cyanobacteria sampled from Lake Taihu was measured using an esterase assay. Based on particulate esterase activity, the calculated cyanobacteria lysis rate was 0.094 d,1. During 30 days of darkness incubation, Chlorophyll a concentration decreased from 56 ,g L,1 to 2.0 ,g L,1. Parallel to this, total particulate carbohydrate concentration decreased rapidly. The fluctuation of dissolved organic carbon concentration was a function of the production of non-carbohydrate by cyanobacteria and the decomposition of carbohydrate by bacteria. Total dissolved carbohydrates and dissolved polysaccharides concentrations showed a similar pattern, declining at the beginning of the experiment and keeping relatively stable, thereafter. In contrast, the concentration of dissolved monosaccharides remained constant during the entire process. The concentrations of NH4+ and PO43, increased at the early stage, and then decreased afterwards. A gradual decrease in NO3, concentration after day 8 indicated that anaerobic conditions might be produced during the cell lysis process. The present results demonstrated cyanobacteria cell lysis has a big influence on the nutrient status of the surrounding water. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Temporal Coherence of Chlorophyll a during a Spring Phytoplankton Bloom in Xiangxi Bay of Three-Gorges Reservoir, ChinaINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 6 2009Yao-Yang Xu Abstract Algal bloom phenomenon was defined as "the rapid growth of one or more phytoplankton species which leads to a rapid increase in the biomass of phytoplankton", yet most estimates of temporal coherence are based on yearly or monthly sampling frequencies and little is known of how synchrony varies among phytoplankton or of the causes of temporal coherence during spring algal bloom. In this study, data of chlorophyll a and related environmental parameters were weekly gathered at 15 sampling sites in Xiangxi Bay of Three-Gorges Reservoir (TGR, China) to evaluate patterns of temporal coherence for phytoplankton during spring bloom and test if spatial heterogeneity of nutrient and inorganic suspended particles within a single ecosystem influences synchrony of spring phytoplankton dynamics. There is a clear spatial and temporal variation in chlorophyll a across Xiangxi Bay. The degree of temporal coherence for chlorophyll a between pairs of sites located in Xiangxi Bay ranged from ,0.367 to 0.952 with mean and median values of 0.349 and 0.321, respectively. Low levels of temporal coherence were often detected among the three stretches of the bay (Down reach, middle reach and upper reach), while high levels of temporal coherence were often found within the same reach of the bay. The relative difference of DIN between pair sites was the strong predictor of temporal coherence for chlorophyll a in down and middle reach of the bay, while the relative difference in Anorganic Suspended Solids was the important factor regulating temporal coherence in middle and upper reach. Contrary to many studies, these results illustrate that, in a small geographic area (a single reservoir bay of approximately 25 km), spatial heterogeneity influence synchrony of phytoplankton dynamics during spring bloom and local processes may override the effects of regional processes or dispersal. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effects of Moisture Stress and Anti-transpirants on Leaf Chlorophyll,JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2000M. Prakash Brinjal plants (Solanum melongena L.) grown under moisture stress conditions in a glasshouse were treated with three anti-transpirants, namely cycocel, limewash and potassium chloride, to study their influence on chlorophyll content, soluble protein and photosynthetic rate. Moisture stress imposed at each of the three growth stages decreased chlorophyll content, soluble protein and photosynthetic rate. Of the anti-transpirants investigated, cycocel performed better than limewash and po-tassium chloride. Zusammenfassung Eierfruchtpflanzen (Solanum melongena L.), die unter Feuchtigkeitsstre ßbedingungen im Glashaus angezogen wurden, wurden mit drei Transpirationshemmern: Cycocel, Kalkbrühe und Kaliumchlorid behandelt, um deren Einfluß auf Chlorophyllgehalt, lösliches Protein und Photosyntheserate zu untersuchen. Feuchtigkeitsstreß in drei Entwicklungsstadien führte zur Abnahme von Chlorophyll,-löslichem Protein und Photosyntheserate. Von den Transpirationshemmern erwies sich Cycocel besser als Kalkbrühe und Kaliumchlorid. [source] Trophic state, fish community and intensive production of salmonids in Alicura Reservoir (Patagonia, Argentina)LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 4 2001P. F. Temporetti Abstract The Governments of the Provinces located in Patagonia, Argentina, promote the intensive breeding of salmonids in the Andean Patagonian region. Although annual production is low (450 ton ha,1 year,1), some effects are significant. Waste produced by salmonid breeding (feed losses, faeces and excretion) increases nutrient and organic matter concentrations, which cause modifications of water quality, sediments and biota. A consequent risk is the elevation of eutrophication levels. Possible changes in water composition, sediments, algae and wild fish populations were studied. Sites affected by fish farming showed increased nutrient concentration, and phytoplankton and periphyton biomass. Chlorophyll a was similar at both sites (affected and unaffected by fish farm sites). Sediments clearly reflect fish farm waste inputs: total phosphorus and organic matter increased 12-fold and fourfold, respectively. The species present in the gill-net catches were the autochthonous Percichthys trucha, Odontesthes hatcheri, Diplomystes viedmensis, and the introduced salmonids Oncorhynchus mykiss, Salmo trutta, Salmo salar sebago and Salvelinus fontinalis. About 50% of the total catch was salmonids. A major portion of the catch per unit weight was composed of rainbow trout, followed by perch. The catch per unit weight obtained for this reservoir agrees with the range of values previously determined (Quiros 1990) for Patagonian reservoirs. Compared with previous studies by Freyre et al. (1991), a variation in catch composition exists. This consists mainly of an increase in the numbers and condition of O. mykiss and a decrease in P. trucha. Presence of fish that escaped from hatcheries, recognizable by their eroded fins, was observed; particularly in a sampling station near the fish cage systems. Variations in catches could be caused by cyclical changes in fish populations (Wooton 1991), by direct and indirect effects of intensive fish farming, or by a combination of both events, and can only be understood through long-term studies of catch variation. [source] Nutrients, Chlorophyll a and Phytoplankton in the ,skenderun Bay (Northeastern Mediterranean)MARINE ECOLOGY, Issue 2 2002Sevim Polat Abstract. The monthly changes in chlorophyll a, phytoplankton abundance and nutrient concentrations at two stations, one at the inshore and the other at the deep waters of the northern part of ,skenderun Bay, were investigated between 1994,,,1995. The vertical distribution of nutrients and phytoplankton biomass were also studied at the deep station. The concentrations of NO3+NO2 -N, PO4 -P and SiO4 -Si of surface water at both stations were 0.31,,,1.63 µg-at · l -1, 0.08,,,0.60 µg-at · l -1 and 0.50,,,2.7 µg-at · l -1, respectively. The highest concentrations were measured at the inshore station and clear differences were found between the inshore and deep-water stations. Chlorophyll a concentrations ranged from 0.17 to 2.78 µg · l -1 and the highest value was measured in March. At the inshore station, which was affected by land run-off, phytoplankton abundance reached the highest value (21,308 cells · l -1) in October 1995, with a marked dominance of Pseudonitzschia pungens (20,200 cells · l -1). The nutrient and chlorophyll a concentrations at the inshore station were higher than those at the deep station. One reason for this is the land-based nutrient input into the coastal area here. In spite of these effects, the bay is not eutrophicated because of circulation events in the northeastern Mediterranean. [source] Exclusive Observation of the (132R)-Enantiomer of Chlorophyll- c from a Diatom Chaetoseros calcitransPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2010Tadashi Mizoguchi Chiral high-performance liquid-chromatography (HPLC) for quantitative analysis of optically active chlorophyll(Chl)- c molecules, which are seen in many marine photosynthetic organisms, was developed. Chls- c have a single asymmetric carbon at the 132 -position, so their stereoisomers are (132R)- and (132S)-enantiomers. After the separation of each enantiomer, the stereochemistry was unambiguously characterized using its circular dichroism spectrum in comparison with that of the structure-related compound, protochlorophyllide- a. Moreover, Chls- c were carefully extracted from the cells of a diatom Chaetoseros calcitrans without racemization and were subjected to the chiral HPLC. The results clearly demonstrated that naturally occurring Chl- c molecules are enantiomerically pure (132R)-forms, which are generally found in photosynthetically active chlorophyllous pigments. [source] Chlorophyll a Self-assembly in Polar Solvent,Water Mixtures ,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2000Radka Vladkova ABSTRACT The conversion of chlorophyll a (Chl a) monomers into large aggregates in six polar solvents upon addition of water has been studied by means of absorption, fluorescence spectroscopy and fluorescence lifetime measurements for the purpose of elucidating the various environmental factors promoting Chl a self-assembly and determining the type of its organization. Two empirical solvent parameter scales were used for quantitative characterization of the different solvation properties of the solvents and their mixtures with water. The mole fractions of water f1/2 giving rise to the midpoint values of the relative fluorescence quantum yield were determined for each solvent, and then various solvent,water mixture parameters for the f1/2 values were compared. On the basis of their comparison, it is concluded that the hydrogen-bonding ability and the dipole,dipole interactions (function of the dielectric constant) of the solvent,water mixtures are those that promote Chl a self-assembly. The influence of the different nature of the nonaqueous solvents on the Chl aggregation is manifested by both the different water contents required to induce Chl monomer , aggregate transition and the formation of two types of aggregates at the completion of the transition: species absorbing at 740,760 nm (in methanol, ethanol, acetonitrile, acetone) and at 667,670 nm (in pyridine and tetrahydrofuran). It is concluded that the type of Chl organization depends on the coordination ability and the polarizability (function of the index of refraction) of the organic solvent. The ordering of the solvents with respect to the f1/2 values,methanol < ethanol < acetonitrile < acetone < pyridine < tetrahydrofuran,yielded a typical lyotropic (Hofmeister) series. On the basis of this solvent ordering and the disparate effects of the two groups of solvents on the Chl a aggregate organization, it is pointed out that the mechanism of Chl a self-assembly in aqueous media can be considered a manifestation of the Hofmeister effect, as displayed in the lipid-phase behavior (Koynova et al., Eur. J. Biophys. 25, 261,274, 1997). It relates to the solvent ability to modify the bulk structure and to distribute unevenly between the Chl,water interface and bulk liquid. [source] Effects of prolonged restriction in water supply on photosynthesis, shoot development and storage root yield in sweet potatoPHYSIOLOGIA PLANTARUM, Issue 1 2008Philippus Daniel Riekert Van Heerden Besides the paucity of information on the effects of drought stress on photosynthesis and yield in sweet potato [Ipomoea batatas (L.) Lam.], available reports are also contradictory. The aim of this study was to shed light on the effects of long-term restricted water supply on shoot development, photosynthesis and storage root yield in field-grown sweet potato. Experiments were conducted under a rainout shelter where effects of restricted water supply were assessed in two varieties (Resisto and A15). Large decreases in stomatal conductance occurred in both varieties after 5 weeks of treatment. However, continued measurements revealed a large varietal difference in persistence of this response and effects on CO2 assimilation. Although restricted water supply decreased leaf relative water content similarly in both varieties, the negative effects on stomatal conductance disappeared with time in A15 (indicating high drought acclimation capacity) but not in Resisto, thus leading to inhibition of CO2 assimilation in Resisto. Chlorophyll a fluorescence measurements, and the relationship between stomatal conductance, intercellular CO2 concentration and CO2 assimilation rate, indicated that drought stress inhibited photosynthesis primarily through stomatal closure. Although yield loss was considerably larger in Resisto, it was also reduced by up to 60% in A15, even though photosynthesis, expressed on a leaf area basis, was not inhibited in this variety. In A15 yield loss appears to be closely associated with decreased aboveground biomass accumulation, whereas in Resisto, combined effects on biomass accumulation and photosynthesis per unit leaf area are indicated, suggesting that research aimed at improving drought tolerance in sweet potato should consider both these factors. [source] Innentitelbild: Hypermodifizierte fluoreszierende Chlorophyllkataboliten als Quelle blauer Lumineszenz in seneszenten Blättern (Angew. Chem.ANGEWANDTE CHEMIE, Issue 30 201030/2010) Der typische Abbau von Chlorophyll in alternden Blättern führt zu farblosen und schwer detektierbaren Kataboliten. Wie B. Kräutler et,al. in ihrer Zuschrift auf S.,5300,ff. berichten, häufen sich aber blau fluoreszierende Chlorophyll-Kataboliten in gelb werdenden Bananenblättern an, die dann unter UV-Licht blau lumineszieren. Mit den fluoreszierenden Kataboliten steht eine neue molekulare In-vivo-Sonde für Seneszenzprozesse in Pflanzen zur Verfügung. [source] Threadfin shad impacts phytoplankton and zooplankton community structures in channel catfish pondsAQUACULTURE RESEARCH, Issue 10 2010Bartholomew W Green Abstract Plankton community structure and chlorophyll a concentration were compared in twelve 0.1 ha earthen ponds co-stocked with channel catfish (Ictalurus punctatus Rafinesque, 1818) in a multiple-batch culture (initial biomass=5458 kg ha,1) and a planktivore, threadfin shad (Dorosoma petenense Güther, 1867; initial biomass=449 kg ha,1), during the April,November growing season. We used a completely randomized design in a 2 × 2 factorial arrangement to test the planktivore level (presence or absence of threadfin shad) and channel catfish feeding frequency (daily or every third day). Channel catfish were fed a 32% protein feed to apparent satiation on days fed. The presence of threadfin shad affected phytoplankton and zooplankton community structure more than did feeding frequency, and the impact in ponds was more pronounced after 1 July. The numbers of all major groups of zooplankton were lower in ponds with threadfin shad, but were unaffected by the feeding frequency. Chlorophyll a concentration before 1 July was higher in ponds with threadfin shad and unaffected by the feeding frequency, whereas after 1 July it was higher in ponds without threadfin shad and that were fed daily. Phytoplankton community structure after 1 July was dominated by nuisance algal bloom genera of cyanobacteria in ponds without threadfin shad and by Bacillariophyceae in ponds with threadfin shad. [source] Mechanisms and Factors for Edible Oil OxidationCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 4 2006Eunok Choe ABSTRACT:,Edible oil is oxidized during processing and storage via autoxidation and photosensitized oxidation, in which triplet oxygen (3O2) and singlet oxygen (1O2) react with the oil, respectively. Autoxidation of oils requires radical forms of acylglycerols, whereas photosensitized oxidation does not require lipid radicals since 1O2 reacts directly with double bonds. Lipid hydroperoxides formed by 3O2 are conjugated dienes, whereas 1O2 produces both conjugated and nonconjugated dienes. The hydroperoxides are decomposed to produce off-flavor compounds and the oil quality decreases. Autoxidation of oil is accelerated by the presence of free fatty acids, mono- and diacylglycerols, metals such as iron, and thermally oxidized compounds. Chlorophylls and phenolic compounds decrease the autoxidation of oil in the dark, and carotenoids, tocopherols, and phospholipids demonstrate both antioxidant and prooxidant activity depending on the oil system. In photosensitized oxidation chlorophyll acts as a photosensitizer for the formation of 1O2; however, carotenoids and tocopherols decrease the oxidation through 1O2 quenching. Temperature, light, oxygen concentration, oil processing, and fatty acid composition also affect the oxidative stability of edible oil. [source] Variable photosynthetic acclimation in consecutive cohorts of Scots pine needles during 3 years of growth at elevated CO2 and elevated temperaturePLANT CELL & ENVIRONMENT, Issue 5 2003E.-M. LUOMALA ABSTRACT In this experiment, the photosynthetic acclimation of successive needle cohorts of Scots pine were studied during 3 years of growth at elevated CO2 and temperature. Naturally regenerated Scots pine (Pinus sylvestris L.) trees were subjected to elevated CO2 concentration (+CO2, 700 p.p.m), elevated temperature (+T, ambient +2 to +6 °C) and to a combination of elevated CO2 and temperature (+CO2 + T) in closed-top chambers, starting in August 1996. Trees growing in chambers with ambient CO2 and ambient temperature served as controls (AmbC). Elevated CO2 influenced the dark reactions more than the light reactions of photosynthesis, as in the 1996 and 1997 cohorts the carboxylation capacity of Rubisco was reduced in the first and second year of exposure, but there was no consistent change in chlorophyll fluorescence. Net photosynthesis measured at growth concentration of CO2 was higher at +CO2 than at AmbC on only one measuring occasion, was generally lower at +T and was not changed at +CO2 + T. However, trees grown at +T tended to invest more nitrogen (N) in Rubisco, as Rubisco/chlorophyll and the proportion of the total needle N bound to Rubisco occasionally increased. The interaction of +CO2 and +T on Rubisco was mostly negative; consequently, in the second and third year of the experiment the carboxylation capacity decreased at +CO2 + T. In the 1996, 1997 and 1998 cohorts, the structural N concentration of needles was lower at +CO2 than at AmbC. Elevated CO2 and elevated temperature generally had a positive interaction on N concentration; consequently, N concentration in needles decreased less at +CO2 + T than at +CO2. At +CO2 + T, the acclimation response of needles varied between years and was more pronounced in the 1-year-old needles of the 1997 cohort than in those of the 1998 cohort. Thus, acclimation was not always greater in 1-year-old needles than in current-year needles. In the +CO2 + T treatment, elevated temperature had a greater effect on acclimation of needles than elevated CO2. [source] Ecotype adaptation and acclimation of leaf traits to rainfall in 29 species of 16-year-old Eucalyptus at two common gardensFUNCTIONAL ECOLOGY, Issue 6 2006C. R. WARREN Summary 1Relationships of leaf traits with rainfall at the place of origin of seed (RPO) are a function of acclimation and adaptation. To disentangle these effects we studied 29 species of 16-year-old Eucalyptus at a productive and an unproductive common garden (mean annual increments of above-ground stem volume = 21 ± 11 and 8 ± 5 m3 ha,1 years,1, respectively). We tested three hypotheses: (i) leaf traits vary between sites, but relationships among them do not; (ii) relationships of leaf traits with RPO do not vary between sites; and (iii) ecotypes originating from low-rainfall areas allocate a small fraction of nitrogen to thylakoid proteins and Rubisco, and have small SLA, small and narrow leaves, and large water-use efficiency (WUE). 2Eleven leaf traits (leaf area, leaf thickness, leaf width/length, specific leaf area, fresh weight/dry weight, N, chlorophyll a/b, carotenoids/chlorophyll, thylakoid N%, Rubisco N%, WUE derived from 13C content) were measured in 1-year-old sun leaves. 3Site had a large effect on not only the absolute values of leaf traits, but also relationships between pairs of traits. There were 20 significant correlations between pairs of traits. Three of the correlations had different slopes between sites, while a further nine had different intercepts. Hence the majority of significant correlations were not independent of site. 4Leaf area and leaf width/length were the only traits related to RPO. There was no evidence that N allocation to Rubisco or thylakoid proteins was related to RPO, or that WUE was greater in ecotypes from dry areas. 5For Eucalyptus, and perhaps other genera, physiological leaf traits may play a minor role in adaptation to water availability. There is large phenotypic plasticity in many leaf traits affecting not only the absolute values of traits, but also relationships among them. [source] Numerical simulation of sediment-associated water quality processes for a Mississippi delta lakeECOHYDROLOGY, Issue 3 2009Xiaobo Chao Abstract Three major sediment-associated processes were presented to describe the effects of sediment on the water quality processes, including the effect of sediment on the light intensity for the growth of phytoplankton (PHYTO), the adsorption,desorption of nutrients by sediment and the release of nutrients from the bed sediment layer. A formula was generated from field measurements to calculate the light attenuation coefficient by considering the effects of concentrations of chlorophyll and suspended sediment (SS). The concentrations of adsorbed and dissolved nutrients because of adsorption,desorption were calculated using two formulas that were derived based on the Langmuir Equation. The release rates of nutrients from the bed sediment were calculated by considering the effects of the concentration gradient across the water-sediment interface, pH, temperature and dissolved oxygen (DO) concentration. Model algorithms describing the adsorption and desorption of nutrients from sediment particles as well as the release of nutrients from bed sediment were tested using experimental data. These sediment-associated water quality processes were included in a three-dimensional (3D) water quality model, CCHE3D_WQ, developed by the National Center for Computational Hydroscience and Engineering (NCCHE), to simulate the concentrations of PHYTO and nutrients in a shallow Mississippi Delta lake with special emphasis on sediment-related processes. The simulated concentration of PHYTO (as chlorophyll) and nutrients were generally in good agreement with field observations. This study shows that there are strong interactions between sediment-associated processes and water quality constituents. Copyright © 2009 John Wiley & Sons, Ltd. [source] Dynamics of marine bacterial and phytoplankton populations using multiplex liquid bead array technologyENVIRONMENTAL MICROBIOLOGY, Issue 4 2010Xavier Mayali Summary Heterotrophic bacteria and phytoplankton dominate the biomass and play major roles in the biogeochemical cycles of the surface ocean. Here, we designed and tested a fast, high-throughput and multiplexed hybridization-based assay to detect populations of marine heterotrophic bacteria and phytoplankton based on their small subunit ribosomal DNA sequences. The assay is based on established liquid bead array technology, an approach that is gaining acceptance in biomedical research but remains underutilized in ecology. End-labelled PCR products are hybridized to taxon-specific oligonucleotide probes attached to fluorescently coded beads followed by flow cytometric detection. We used ribosomal DNA environmental clone libraries (a total of 450 clones) and cultured isolates to design and test 26 bacterial and 10 eukaryotic probes specific to various ribotypes and genera of heterotrophic bacteria and eukaryotic phytoplankton. Pure environmental clones or cultures were used as controls and demonstrated specificity of the probes to their target taxa. The quantitative nature of the assay was demonstrated by a significant relationship between the number of target molecules and fluorescence signal. Clone library sequencing and bead array fluorescence from the same sample provided consistent results. We then applied the assay to a 37-day time series of coastal surface seawater samples from the Southern California Bight to examine the temporal dynamics of microbial communities on the scale of days to weeks. As expected, several bacterial phylotypes were positively correlated with total bacterial abundances and chlorophyll a concentrations, but others were negatively correlated. Bacterial taxa belonging to the same broad taxonomic groups did not necessarily correlate with one another, confirming recent results suggesting that inferring ecological role from broad taxonomic identity may not always be accurate. [source] Environmental determinants correlated to Vibrio harveyi -mediated death of marine gastropodsENVIRONMENTAL MICROBIOLOGY, Issue 1 2010Youhei Fukui Summary Vibrio harveyi is an emerging pathogen that causes mass mortality in a wide variety of marine animal species; however, it is still unclear which environmental determinants correlate V. harveyi dynamics and the bacterium-mediated death of marine animal life. We conducted a correlation analysis over a 5-year period (2003,2007) analysing the following data: V. harveyi abundance, marine animal mortality and environmental variables (seawater temperature, salinity, pH, chlorophyll a, rainfall and total viable bacterial counts). The samples were collected from a coastal area in northern Japan, where deaths of a marine gastropod species (Haliotis discus hannai) have been reported. Our analysis revealed significant positive correlations between average seawater temperature and average V. harveyi abundance (R = 0.955; P < 0.05), and between average seawater temperature and V. harveyi -mediated abalone death (R = 0.931; P < 0.05). Based on the regression model, n°C rise in seawater temperature gave rise to a 21n -fold increase in the risk of mortality caused by V. harveyi infection. This is the first report providing evidence of the strong positive correlation between seawater temperature and V. harveyi -mediated death of marine species. [source] Diversity and abundance of freshwater Actinobacteria along environmental gradients in the brackish northern Baltic SeaENVIRONMENTAL MICROBIOLOGY, Issue 8 2009Karin Holmfeldt Summary Actinobacteria are highly abundant in pelagic freshwater habitats and also occur in estuarine environments such as the Baltic Sea. Because of gradients in salinity and other environmental variables estuaries offer natural systems for examining factors that determine Actinobacteria distribution. We studied abundance and community structure of Bacteria and Actinobacteria along two transects in the northern Baltic Sea. Quantitative (CARD-FISH) and qualitative (DGGE and clone libraries) analyses of community composition were compared with environmental parameters. Actinobacteria accounted for 22,27% of all bacteria and the abundance changed with temperature. Analysis of 549 actinobacterial 16S rRNA sequences from four clone libraries revealed a dominance of the freshwater clusters acI and acIV, and two new subclusters (acI-B scB-5 and acIV-E) were assigned. Whereas acI was present at all stations, occurrence of acII and acIV differed between stations and was related to dissolved organic carbon (DOC) and chlorophyll a (Chl a) respectively. The prevalence of the acI-A and acI-B subclusters changed in relation to total phosphorus (Tot-P) and Chl a respectively. Community structure of Bacteria and Actinobacteria differed between the river station and all other stations, responding to differences in DOC, Chl a and bacterial production. In contrast, the composition of active Actinobacteria (analysis based on reversely transcribed RNA) changed in relation to salinity and Tot-P. Our study suggests an important ecological role of Actinobacteria in the brackish northern Baltic Sea. It highlights the need to address dynamics at the cluster or subcluster phylogenetic levels to gain insights into the factors regulating distribution and composition of Actinobacteria in aquatic environments. [source] Distribution of Roseobacter RCA and SAR11 lineages and distinct bacterial communities from the subtropics to the Southern OceanENVIRONMENTAL MICROBIOLOGY, Issue 8 2009Helge-Ansgar Giebel Summary We assessed the composition of the bacterioplankton in the Atlantic sector of the Southern Ocean in austral fall and winter and in New Zealand coastal waters in summer. The various water masses between the subtropics/Agulhas,Benguela boundary region and the Antarctic coastal current exhibited distinct bacterioplankton communities with the highest richness in the polar frontal region, as shown by denaturing gradient gel electrophoresis of 16S rRNA gene fragments. The SAR11 clade and the Roseobacter clade-affiliated (RCA) cluster were quantified by real-time quantitative PCR. SAR11 was detected in all samples analysed from subtropical waters to the coastal current and to depths of > 1000 m. In fall and winter, this clade constituted < 3% to 48% and 4,28% of total bacterial 16S rRNA genes respectively, with highest fractions in subtropical to polar frontal regions. The RCA cluster was only present in New Zealand coastal surface waters not exceeding 17°C, in the Agulhas,Benguela boundary region (visited only during the winter cruise), in subantarctic waters and in the Southern Ocean. In fall, this cluster constituted up to 36% of total bacterial 16S rRNA genes with highest fractions in the Antarctic coastal current and outnumbered the SAR11 clade at most stations in the polar frontal region and further south. In winter, the RCA cluster constituted lower proportions than the SAR11 clade and did not exceed 8% of total bacterial 16S rRNA genes. In fall, the RCA cluster exhibited significant positive correlations with latitude and ammonium concentrations and negative correlations with concentrations of nitrate, phosphate, and for near-surface samples also with chlorophyll a, biomass production of heterotrophic prokaryotes and glucose turnover rates. The findings show that the various water masses between the subtropics and the Antarctic coastal current harbour distinct bacterioplankton communities. They further indicate that the RCA cluster, despite the narrow sequence similarity of > 98% of its 16S rRNA gene, is an abundant component of the heterotrophic bacterioplankton in the Southern Ocean, in particular in its coldest regions. [source] | |||||||||||||||||||||||||||||||||||||||||||