No description available.

Liposomes incorporating chlorophyll (Chl) have been used as a model system to study various aspects of photosynthesis (such as Chl photooxidation and acceptor reduction). Laser flash photolysis studies of this system have demonstrated that the Chl triplet state (Chl(t)) can transfer an electron to acceptors such as quinones, resulting in the formation of the Chl cation radical (Chl⁺.) and the semiquinone anion radical (Q¯.). Quenching of Chl(t) by quinones in liposomes is diffusion-controlled. The quenching rate is dependent upon bilayer viscosity. Chl(t) lifetimes in the absence of quinones also reflect bilayer viscosity. Radical decay occurs by reverse electron transfer. Although the decay is non-exponential, the decay rate is independent of laser intensity. This is presumably because radical pairs once formed do not become independent of one another and back react in a manner which can be likened to geminate recombination. The non-exponentiality is due to electron exchange between quinone molecules and the heterogeneity in the distribution of molecules among the vesicles. This electron exchange is also manifested in the radical formation process. At high quinone concentration the radical yield increases with quinone concentration in non-linear fashion with respect to the amount of triplet quenched. This positive cooperative effect is interpreted in terms of high quinone concentrations increasing the efficiency of radical production by providing a pathway (via electron hopping) for removal of the electron from the site of initial electron transfer. When ubiquinone is used, only a single fast decay is observed. However, when quinones which can partition between the aqueous and lipid phases are used, radical decay occurs via a fast and a slow process. This is interpreted in terms of electron transfers from Q¯. within the bilayer to Q at the bilayer-water interface which results in a stabilization of the electron transfer products and a slowly-decaying radical. The rate of this slow decay process is also quinone concentration dependent, which is a consequence of a facilitation of electron return to Chl⁺. by Q molecules within the bilayer via an electron hopping mechanism. That such a mechanism is, in fact, operative in radical production is shown also by the observation of electron transfer from UQ¯. to BQ molecules.

No description available.

Global climate change is predicted to alter the weather patterns around the world, as climatic zones shift, forest carbon sequestration projects (e.g. the UK woodland carbon code) need to take into account the specific requirements of planted species. In the UK, oaks are an important charismatic group of trees favoured in recent planting programmes. The English oak (Quercus robur L.), has poor water conservation, but is a major component of natural forests in lowland UK. On the other hand, Holm oak (Quercus ilex L.) is a Mediterranean oak that has high water conservation and can also tolerate cold despite being restricted by minimum temperatures. At local scales, there may be advantages of planting either evergreen or deciduous oak species for forestry and climate mitigation. Alternatively, a comparative assessment of non native versus native productivity, may give clues to the invasiveness potential of Holm oak and its ability to out compete the deciduous oak along an urban to upland gradient. This thesis documents a series of field based experiments intended to analyse differences in carbon sequestration potential and photosynthetic efficiency between these two species and in relation to their environment within the Southwest UK. 520 one year saplings were planted, half in pots and half in nursery field beds situated on Dart- moor, the east Devon Dartmoor fringe, Totnes, and Plymouth city centre. Originally two sites were chosen for their relative ‘urban’ qualities, two at ‘rural’ localities, one upland and a control site with access to a polytunnel for comparisons with well-watered and non nutrient limited trees. However, data analyses showed that sapling characteristics were site specific with the five sites falling along an urban, rural to upland gradient. The field experiments included monthly height and diameters (ground level diameter or DAG), monthly assimilation rates and analy- sis of chlorophyll fluorescence to aid interpretation of photosystem II functioning and sapling ‘vitality’. Further laboratory experiments analysed specific leaf area (SLA), mass based leaf Nitrogen (Nleaf ) and carbon (Cleaf), with differences between sun and shade leaves included, to aid comparisons between species and sites. The final experiment was a destructive harvest and this was used to find total biomass estimates and carbon allocation to different root shoot fractions. In order to quantify differences between saplings and adult trees a smaller experiment was con- ducted in the canopy using experienced climbers and leaf level productivity analysed. Intrinsic water use (iWUE), stomatal conductance (Gs), means net assimilation rates (An) and chloro- phyll fluorescence parameters; Variable fluorescence over maximum fluorescence (Fv/Fm) and performance index (PI) were measured and relative carbon assimilation rates and productivity assessed and compared between species at one urban , rural and upland site. Results showed that Q. ilex allocated relatively more carbon to branches and leaves as a sapling which in turn increased growth rate and whole tree assimilation rates to larger values than the deciduous oak despite Q. robur being able to increase maximum assimilation rates in response to increasing temperatures. This gives Q. ilex the advantage and overall biomass was higher at all sites than Q. robur apart from the upland site where there were no differences in biomass accumulation between species. However, despite no significant difference in biomass at this site Q. robur had greater survival and photosystem II functioning. In mature trees Q. ilex was under stress and Nleaf and carbon sequestration potential were higher in the deciduous species at the urban site. In contrast, Q. robur was under stress at the upland site at Castle Drogo where thin and nutrient poor soils have made it more vulnerable to drought stress. Here, mature Q. ilex showed reduced photosynthetic efficiency in relation to cold and drought, but was able to recover when milder temperatures occurred. The results were site specific, with a reduction in both SLA and relative allocation to the leaf weight fraction (LWF) in Q.robur the only common urban related effect seen. The potential for Q. ilex to perform well at sapling stage is due to its morphological plasticity and drought tolerance. This species may become more prevalent within the Southwest as local climates continue to push it northwards from its natural Mediterranean range. In contrast, if Q. robur continues to suffer from defoliation and fungal attack and this may leave it more vulnerable to competition throughout less fertile and drier areas of its natural range.

Pak-chung Leung. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 151-158). / Abstract --- p.i / Acknowledgments --- p.iii / Table of contents --- p.iv / List of Figures --- p.viii / List of Tables --- p.ix / List of Abbreviations --- p.xiv / Chapter / Chapter 1. --- General Introduction --- p.1 / Chapter 2. --- Literature Review: Greening process in higher plants --- p.4 / Chapter 3. --- Greening Bioassay in Excised Cucumber Cotyledons / Introduction --- p.13 / Materials and Methods / Plant material --- p.14 / Measurement of Ch1 synthesizing activity in excised cotyledons of different ages --- p.14 / Measurement of Ch1 accumulation in excised cotyledons after various pretreatment periods --- p.15 / Measurement of Ch1 accumulation in excised cotyledons under different light intensities and temperatures --- p.15 / Greening curve --- p.16 / Results and Discussion / Effect of seedling age on Ch1 accumulation --- p.16 / Effect of pretreatment period on Ch1 accumulation --- p.18 / Effects of light intensity and temperature on Ch1 accumulation --- p.18 / Effect of shaking (for oxygen replenishment) on Ch1 accumulation --- p.19 / Greening curve --- p.20 / Greening bioassay in excised cucumber cotyledons --- p.20 / Chapter 4. --- Regulation of Chlorophyll Accumulation in Excised Cucumber Cotyledons / Introduction --- p.27 / Materials and Methods / Materials --- p.28 / Seed germination --- p.28 / Harvesting and pretreatment --- p.28 / Illumination and Ch1 determination --- p.29 / Results / Effect of BA on Ch1 accumulation --- p.29 / Effect of Na2EGTA on Ch1 accumulation --- p.30 / "Effect of Na+, Ca2+ and K+ on Ch1 accumulation" --- p.32 / Effect of duration of pretreatment with Na+ ， Ca2+ and K+ on Ch1 accumulation --- p.34 / Effect of verapamil and Ca ionophore A23187 on Chl accumulation --- p.36 / Effect of TFP on Chl accumulation --- p.37 / Discussion / Effect of BA on Chl accumulation --- p.38 / "Effect of Na+, Ca2+ and K+ on Chl accumulation" --- p.39 / Demonstration of the involvement of Ca2+ in Chl accumulation --- p.43 / Chapter 5. --- The Calcium Effect on Benzyladenine-induced Stimulation of Chlorophyll Accumulation in Excised Cucumber Cotyledons / Introduction --- p.63 / Materials and Methods / Materials --- p.64 / Plant growth and treatment --- p.64 / Pretreatment experiment --- p.64 / Sequence experiment --- p.65 / Results / Pretreatment experiment --- p.65 / Sequence experiment --- p.66 / Discussion --- p.68 / Chapter 6. --- Regulation of 5-Aminolevulinic Acid and Chlorophyll Accumulation in Levulinic Acid-treated Cotyledons / Introduction --- p.80 / Materials and Methods / Materials --- p.81 / Plant growth and treatment --- p.81 / Chl determination and ALA assay --- p.82 / Measurement of ALA and Chl accumulation in LA-treated cotyledons --- p.83 / ALA accumulation curve --- p.83 / Measurement of Chl accumulation in 50 mM NaCl-treated cotyledons --- p.84 / "Measurement of ALA and Chl accumulation in BA-, cations-, Na2EGTA-, verapamil- and TFP-pretreated cotyledons" --- p.85 / Results / Concentrations effect of LA on ALA and Chl accumulation --- p.85 / ALA accumulation curve --- p.86 / Effect of 50 mM NaCl on Chl accumulation --- p.87 / Effect of BA on ALA and Chl accumulation in LA- treated cotyledons --- p.90 / "Effects of Na+, Ca2+ and K+ on ALA and Chl accumulation in LA-treated cotyledons" --- p.91 / "Effects of Na2EGTA, verapamil and TFP on ALA and Chl accumulation in LA-treated cotyledons" --- p.92 / Discussion / Measurement of ALA accumulation in LA-treated cotyledons --- p.93 / Effect of BA on ALA and Chl accumulation in LA-treated cotyledons --- p.96 / "Effects of Na+, Ca2+ and K+ on ALA and Chl accumulation in LA-treated cotyledons" --- p.98 / Demonstration of the involvement of Ca2+ in ALA accumulation --- p.99 / Chapter 7. --- Regulation of 5-Aminolevulinic Acid Accumulation in Isolated Developing Chloroplasts / Introduction --- p.123 / Materials and Methods / Materials --- p.124 / Plant materials --- p.124 / Chloroplast isolation --- p.125 / Incubation conditions --- p.126 / ALA assay --- p.127 / Measurement of ALA accumulation in LA-treated isolated developing chloroplasts --- p.128 / "Measurement of ALA accumulation in BA-, cations-, Na2EGTA-, verapamil- and TFP-treated isolated developing chloroplasts" --- p.128 / Results / Time course study of Chl accumulation in intact greening cotyledons of different ages --- p.129 / Measurement of ALA synthesizing activity in isolated developing chloroplasts incubated in the dark and light --- p.130 / Concentrations effect of LA on ALA accumulation in isolated developing chloroplasts --- p.130 / Effects of BA and the cations on ALA accumulation in isolated developing chloroplasts --- p.131 / "Effect of Na2EGTA, verapamil and TFP on ALA accumulation in isolated developing chloroplasts" --- p.132 / Discussion / Light regulation of ALA synthesizing activity in isolated developing chloroplasts --- p.132 / Regulation of ALA accumulation in isolated developing chloroplasts --- p.134 / Chapter 8. --- Conclusion --- p.147 / References --- p.151

Chlorophyll-a (chl-a) concentration is an indicator of the trophic status and is extensively used as a measurement of the algal biomass which affects the level of eutrophication in aquatic systems. High concentration of chl-a may indicate high biomass of phytoplankton which can decrease the quality of water or eliminate important functional groups in the ecosystem. Predicting chl-a concentrations is desirable to understand how great impact chl-a may have in aquatic systems for different scenarios during long-time periods and seasonal variation. Several models of predicting annual or summer chl-a concentration have been designed using total phosphorus, total nitrogen or both in combination as in-parameters. These models have high predictive power but are not constructed for evaluating the long-term change or predicting the seasonal variation in a system since the input parameters often are annual values or values from other specific periods. The models are in other words limited to the range where they were constructed. The aim with this thesis was to complement these models with other methods and models which gives a more appropriate image of how the chl-a concentration in an aquatic system acts, both in a short as well as a long-time perspective. The results showed that with a new method called Statistically meaningful trend the Baltic Proper have not had any change in chl-a concentrations for the period 1975 to 2007 which contradicts the old result observing the p-value from the trend line of the raw data. It is possible to predict seasonal variation of median chl-a concentration in lakes from a wide geographically range using summer total phosphorus and latitude as an in-parameter. It is also possible to predict the probability of reaching different monthly median chl-a concentrations using Markov chains or a direct relationship between two months. These results give a proper image of how the chl-a concentration in aquatic systems vary and can be used to validate how different actions may or may not reduce the problem of potentially harmful algal blooms. / Koncentrationen av klorofyll-a (chl-a) är en indikator på vilken trofinivå ett akvatiskt system har och används som ett mått på algbiomassa som påverkar övergödningen i akvatiska system. Höga koncentrationer av chl-a i sjöar kan indikera hög biomassa av fytoplankton och försämra kvalitén i vattnet eller eliminera viktiga funktionella grupper i ett ekosystem. Det är önskvärt att kunna prediktera chl-a koncentrationer för att förstå hur stor påverkan chl-a kan ha för olika scenarier i akvatiska system under längre perioder samt under säsongsvariationer. Flera modeller har tagits fram som predikterar årsvärden eller sommarvärden av chl-a koncentrationer och i dessa ingår totalfosfor, totalkväve eller en kombination av båda som inparametrar. Dessa modeller har hög prediktiv kraft men är inte utvecklade för att kunna utvärdera förändringar över längre perioder eller prediktera säsongsvariationer i ett system eftersom inparametrarna ofta är årsmedelvärden eller värden från andra specifika perioder. Modellerna är med andra ord begränsade till den domän som de togs fram för. Målet med denna avhandling var att komplettera dessa modeller med andra metoder och modeller vilket ger en bättre förståelse för hur chl-a koncentrationer i akvatiska system varierar, både i ett kortsiktigt och ett längre perspektiv. Resultaten visade att med en ny metod som kallas för Statistiskt meningsfull trend så har egentliga Östersjön inte haft någon förändring av chl-a koncentrationer under perioden 1975 till 2007 vilket motsäger tidigare resultat då p-värdet tas fram från en trendlinje av rådata. Det är möjligt att prediktera säsongsvariationer av median chl-a koncentrationer i sjöar från en bred geografisk domän med totalfosfor från sommar och latitud som inparametrar. Det är även möjligt att beräkna sannolikhetenav ett predikterat värde för olika månadsmedianer av chl-a koncentrationer med Markovkedjor eller ett direkt samband mellan två månader. Dessa resultat ger en reell förståelse för hur chl-a koncentrationer i akvatiska system varierar och kan användas till att validera hur olika åtgärder kan eller inte kan reducera problemet av de potentiellt skadliga algblomningarna.

The maximum quantum yield (Fv/Fm), zooxanthellae density, chlorophyll a concentration and protein concentration of non-bleached and bleached colonies of the reef coral Acropora intermedia were measured in inlet of The Third Nuclear Power Plant of Nanwan Bay in southern Taiwan. A significant positive correlation was found between Fv/Fm and chlorophyll a concentration per zooxanthellae of non-bleached colonies. The chlorophyll a concentration per zooxanthellae and zooxanthellae density of non-bleached colonies were lowest in summer, and were significantly negative correlated with total radiant heat and seawater temperature, respectively. This suggests that the seasonal variation exist, and they maybe regulated by seasonal fluctuation of radiation and temperature. The Fv/Fm, chlorophyll a concentration per cm-2, chlorophyll a concentration per zooxanthellae, zooxanthellae density and protein were significantly lower than those of the non-bleached colonies in the bleaching events. However, compared to the non-bleached colonies, zooxanthellae density, chlorophyll a concentration per cm-2 and protein of bleached colonies were increased and significantly higher than those of non-bleached colonies, then decreased to similar level. However, Fv/Fm increased to similar level, but chlorophyll a concentration per zooxanthellae remained lower. It suggests that number of zooxanthellae rapidly increased while remained stable chlorophyll a concentration during recovery.

In this study, a one-dimensional model based on the Mellor and Yamada level 2.5 turbulence closure model was coupled with a biogeochemical model to investigate the inter-annual variation of biogeochemistry at the South-East Asian Time-series Study (SEATS) Site in the northern South China Sea (SCS) from 1997 to 2003. During the study period there were two El Niño Events and two La Niña Events. This study was focused on the hydrographic and biogeochemical conditions during these events. In order to better understand the model performance in the physical and biogeochemical aspects, numerical experiments were conducted to investigate the key processes. Numerical experiments by using idealized forcing conditions revealed that stronger wind stresses resulted in stronger cooling and deeper mixed layer. The model results were as sensitive to the initial density structure of the water column as to wind stress. Numerical experiments with the coupled model revealed that the biogeochemical results are insensitive to the initial biogeochemical conditions except the nitrate profile. Sensitivity tests indicated that primary production was sensitive to the remineralization rate constant for the detritus and parameters related to zooplankton, such as growth rate, grazing constant and mortality rate constant. It is less sensitive to iv aggregation constant of phytoplankton. The SEATS project of the National Center for Ocean Research provided data of sea surface chlorophyll-a (S-chl) concentrations, which were derived from SeaWiFS data for the period from Jan. 1997 to Dec. 2003 by calibrating against shipboard observations. The time-series showed decreases of mean S-chl by 35% and 9% below the climatological mean in the winter months (DJF) of the two El Niño Events. The negative S-chl anomalies corresponded to elevated sea surface temperature (SST) by 1.4oC and 0.4oC above the climatological mean, while the mean wind speed (WS) was reduced by 20% and 13%, and the surface heat exchange reverted from net loss to net gain or null. It is hypothesized that the anomalously low S-chl may have been caused by the weakened wind mixing and strengthened stratification. A 1-dimensional coupled physical-biogeochemical model was developed to test this hypothesis. The model driven by wind stress and surface heat fluxes successfully reproduced the seasonal cycles of S-chl and integrated primary productivity (IPP) as compared to shipboard observations and SeaWiFS data derived values, and predicted the negative anomalies of S-chl and IPP under the 1997-98 and 2002-03 El Niño conditions. However, the model-predicted strong positive anomalies of S-chl and IPP under the 1998-99 and 1999-2000 La Niña conditions, which brought v stronger wind and heat loss, were not substantiated by observations. Hydrographic conditions at the SEATS station indicated that, under La Niña conditions, unusual accumulation of warm and nutrient-depleted water occurred in the upper water column cancelled out the effect of stronger mixing. Therefore, the biogeochemical responses of the northern SCS to surface forcing during the recent El Niño/La Niña conditions displayed in a highly asymmetrical manner.

Data of various marine environmental factors collected and integrated by the National Center of Ocean Research (NCOR) were used to search for possible statistics relationship with chlorophyll concentration of the Kuroshio and its adjacent waters off eastern Taiwan. The seaWiFS chlorophyll concentration in natural logarithm were used as dependent variable in General Linear Model¡]GLM¡^analysis, followed by least square means (lsmeans) and cluster analysis. Study area ranged from 21.5¡CN and 121¡CE to 26.5¡CN and 125¡CE eastern Taiwan. Data were first assembled, screened, transformed to natural logarithm and reorganized into monthly averages for individual geographical grid points of 10¡¦X 10¡¦. The result of GLM analysis shows that all factors have significant relationship with chlorophyll concentration, more than 20 regression formulae were found with different combination of variable. Results of standard regression analysis show their order of importance as: latitude, depth, longitude, light, sst, east and west current on upper 20 meter(c20EW), north and south current on upper 20 meter(c20NS) and eddy kinetic energy(EKE), respectively. Results of lsmeans listing by latitude and by longitude showed that area with higher chlorophyll concentration are on high-latitude and low-longitude area but not between and area near east Taiwan tend to have high concentration and decreased eastward. Results of cluster analysis indicated that chlorophyll concentration of western longitude, and northern as well as southern latitude are different from other area.

This study focused on the spatial and temporal variation of water qualities and the phytoplankton and zooplankton standing crop of southwestern Taiwan. Data were collected from 30 cruises of research and fishermen vessels between August 1999 and December 2002. The yield of sergestid shrimp in this area was also analyzed for possible relationship with physical environment. Concentrations of phosphate and ammonia in the study area were highest in autumn, while the concentration of dissolved silicon peaked in winter; In spring, the concentration of all three nutrients similarly dropped to their lowest level. Regardless of seasonal variation, the concentration of dissolved silicon positively correlated with the water depth around the year. Positive correlation was found between phosphate and river discharge rates of Kao-Ping River in autumn. Negative correlation was found in spring, summer and autumn for ammonia, negative correlation in spring and autumn for dissolved silicon, respectively. Variations of phytoplankton in seasons and locations were also studied. Chlorophyll a blooms in winter but was at lowest level in summer. Concentration of total-chlorophyll a decreased with distance from the shoreline. Concentration of total-chlorophyll a negatively correlated with the river discharge rate in summer, but was positively correlated in winter. Nanophytoplankton (< 10 £gm) appeared to be the major component of phytoplankton. High standing crop of copepods was found at regions near the Liu-Chiu Yu, the estuary of Kao-Ping River, and near the coast. Significant positive correlation between phytoplankton and Copepoda standing crop indicates possible feeding and grazing relationship between them. Changes of the concentration of chlorophyll a corresponds with relative levels of phosphate and ammonia in some seasons. The period with the highest phytoplanktonic standing crop also coincides with the high yield season of sergestid shrimp (from November to March). Variation of Copepoda standing crop does not follow seasonal changes of phytoplankton. Based on the results from General Linear Model analysis, lunar phases, river discharge rates of Kao-Ping River, and the Fishing Effort (hrs/haul-boat) have significant effects on the yield (kgs/haul-boat) of sergestid shrimp respectively. The yield of sergestid shrimp in the full moon period and the last quarter of a lunar month is higher than other periods. The occurrence of thick thermocline water layer matched with the period of high CPUE of sergestid shrimp.