Effects of chlorophyll a, chlorophyll b, and xanthophylls on the in vitro assembly kinetics of the major light-harvesting chlorophyll a/b complex, LHCIIb

The major light-harvesting chlorophyll a/b complex (LHCIIb) of photosystem II in higher plants can be reconstituted with pigments in lipid-detergent micelles. The pigment-protein complexes formed are functional in that they perform efficient internal energy transfer from chlorophyll b to chlorophyll a. LHCIIb formation in vitro, can be monitored by the appearance of energy transfer from chlorophyll b to chlorophyll a in time-resolved fluorescence measurements. LHCIIb is found to form in two apparent kinetic steps with time constants of about 30 and 200 seconds. Here we report on the dependence of the LHCIIb formation kinetics on the composition of the pigment mixture used in the reconstitution. Both kinetic steps slow down when the concentration of either chlorophylls or carotenoids is reduced. This suggests that the slower 200 seconds formation of functional LHCIIb still includes binding of both chlorophylls and carotenoids. LHCIIb formation is accelerated when the chlorophylls in the reconstitution mixture consist predominantly of chlorophyll a although the complexes formed are thermally less stable than those reconstituted with a chlorophyll a:b ratio < or = 1. This indicates that although chlorophyll a binding is more dominant in the observed rate of LHCIIb formation, the occupation of (some) chlorophyll binding sites with chlorophyll b is essential for complex stability. The accelerating effect of various carotenoids (lutein, zeaxanthin, violaxanthin, neoxanthin) on LHCIIb formation correlates with their affinity to two lutein-specific binding sites. We conclude that the occupation of these two carotenoid binding sites but not of the third (neoxanthin-specific) binding site is an essential step in the assembly of LHCIIb in vitro.     

Synthesis of chlorophyll a regulates translation of chlorophyll a apoproteins P700, CP47, CP43 and D2 in barley etioplasts.

Accumulation of plastid-encoded chlorophyll apoproteins and chlorophyll synthesis are controlled by light in angiosperms. An in vitro system utilizing isolated and lysed barley (Hordeum vulgare L.) etioplasts revealed the specific accumulation of P700, CP47, CP43 and D2 triggered by de novo synthesis of chlorophyll. Accumulation rates of radiolabelled chlorophyll apoproteins were linear for about 30 min. Pulse/chase translation assays showed that synthesis of chlorophyll does not result in increased chlorophyll apoprotein stability. Instead turnover rates of chlorophyll apoproteins were higher in the presence than in the absence of chlorophyll. Chlorophyll-dependent accumulation of chlorophyll apoproteins must therefore be regulated on the level of translation. Translation of chlorophyll apoproteins was blocked to about 50% by addition of 30-50 microM aurintricarboxylic acid or 20 microM kasugamycin. The kinetics of chlorophyll-dependent translation indicated that the in vitro translation system is capable of translation initiation. The capability of translation initiation was lost in lysed etioplasts after preincubation for at least 5 min without chlorophyll synthesis. The results suggest that initiation is involved in chlorophyll-dependent regulation of translation.     

Differential Responses of Iron,Magnesium, and Zinc Deficiency on Pigment Composition,Nutrient Content,and Photosynthetic Activity in Tropical Fruit Crops

Photosynthetica - Fe, Mn, and Zn affected the chlorophyll (Chl) content whereas Fe deficiency caused larger reduction of total chlorophyll content than Mg and Zn deficiencies. Mg deficient mango...     

Pigment Degradation in Discs of the Thermophilic Cucumis sativus as Affected by Light, Temperature, Sugar Application and Inhibitors

Chlorophyll degradation in Cucumis leaf discs was measured at different temperatures between 1 and 25°C in the light and in darkness, and in the presence or absence of sucrose. Two different processes of chlorophyll degradation could be distinguished, a light-requiring process operating at 1 and 5°C and another, light and sucrose enhanced degradation process which was evident at 25°C. Degradation of leaf pigments at low temperatures was of a photo-oxidative nature since there was no degradation in the dark. The chlorophyll a/b ratio was decreased, carotene was degraded at a faster rate than chlorophyll, and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and triphenyltetrazolium chloride (TTC) which prevent photo-oxidation, protected against chlorophyll degradation. The light and sucrose enhanced chlorophyll degradation at 25°C was of an enzymatic nature since it occurred in the dark as well as in the light. The chlorophyll a/b ratio was not affected, and carotene and chlorophyll degradation occurred at the same rate. Since DCMU completely inhibited the light enhancement at 25°C and experimentation in a low oxygen atmosphere also protected chlorophyll against the effect of light and sugar application, it is suggested that the enhancement of chlorophyll degradation by light and sucrose at 25°C may be due to increased sugar uptake of the chloroplasts and consequently excessive starch formation in the organelles.     

Submerged macrophytes, zooplankton and the predominance of low- over high-chlorophyll states in western boreal, shallow-water wetlands

1. Shallow‐water (<2 m deep) wetlands in northern Alberta's western boreal forest tend to have either extremely high‐chlorophyll, pea‐green water or water that is low in chlorophyll and clear. The relative importance of top‐down processes (e.g. zooplankton grazing) compared with bottom‐up processes (e.g. nutrient limitation) for regulating the existence of these alternate states has yet to be explicitly investigated in these poorly studied waterbodies. 2. To assess the relationship between chemical and biological factors and the predominance of low‐chlorophyll over high‐chlorophyll states, a survey of 24 shallow‐water wetlands in northern Alberta was conducted over the summers of 2001 and 2002. 3. In wetlands without fish, statistical analysis indicated that high‐ and low‐chlorophyll sites could be differentiated with 82% accuracy based solely on whether submerged aquatic vegetation (SAV) coverage was greater or less than 25%. Further, high‐SAV lakes with zooplankton communities dominated by large cladocerans were clear 96% of the time. 4. In the few wetlands that supported stickleback populations, large cladocerans were absent. However, the development of zooplankton communities dominated by small cladocera (Bosmina) with calanoid copepods in fish‐containing wetlands corresponded with a shift from high‐ to low‐chlorophyll states. 5. Results suggest that in fishless wetlands high‐SAV coverage and grazing by large, SAV‐associated cladocerans promotes low‐chlorophyll states. Results also suggest that suppression of macroinvertebrate predators by sticklebacks allowing Bosmina to flourish may also promote low‐chlorophyll, clear‐water conditions.     

Chlorophyll content of seston in a regulated Rocky Mountain river,Idaho, USA

The chlorophyll content of seston at four sites in a regulated mid-order Rocky Mountain river, Henry's Fork of the Snake River, Idaho, USA, was examined. Spectrometry was used to determine the amount of chlorophyll a, b, c and in seston and potential organic matter sources including macrophytes, algae, plankton, and terrestial plant litter. The amount of chlorophyll in seston varied among size fractions, sites, and seasons. Coarse seston (6–1 mm) contained the most chlorophyll a (2.3 mg g^–1 ashfree dry mass [AFDM]) followed by ultra fine seston (53–0.3 µm; 1.9 mg g^–1 AFDM), very coarse seston (> 6 mm, 1.8 mg g^–1 AFDM), very fine seston (250–53 µm; 1.3 mg g^–1 AFDM), and fine seston (1–0.25 mm; 0.7 mg g^–1 AFDM). Chlorophyll content of coarse seston was similar at all sites reflecting a common source, aquatic macrophyte debris. Chlorophyll content of coarse and fine seston were highest in fall reflecting the importance of phenology of aquatic plants on sestonic pigment levels. Very fine seston from below a reservoir contained more chlorophyll than seston from downstream and tributary sites suggesting a reservoir source. Terrestial plant litter was chlorophyll depleted compared to autochthonous materials and seston. Most seston was autochthonously-derived from a variety of macrophyte, algal, and planktonic sources. The chlorophyll content of Henry's Fork seston was higher than that reported for similar rivers. Island Park Dam moderates river temperature and flow, enhances autotrophy, and accounts for the consistently high sestonic chlorophyll levels.     

Chlorophyll, Ribulose-1,5-diphosphate Carboxylase, and Hill Reaction Activity in Developing Leaves of Populus deltoides

The synthesis of chlorophyll and ribulose diphosphate carboxylase as well as the development of Hill reaction activity were followed in expanding Populus deltoides leaves and related to photosynthetic patterns. Total chlorophyll, which was not correlated with photosynthetic rate in expanding leaves, decreased slightly with age in very young leaves, due to a decrease in chlorophyll b, but then increased linearly. The ratio of chlorophyll a to b, which rose sharply in young leaves, was highly correlated with the onset of net photosynthesis. Hill reaction activity was very low in young leaves and did not increase significantly until leaves were about half expanded. Ribulose diphosphate carboxylase activity increased in a sigmoid fashion with leaf ontogenesis and closely paralleled development of the photosynthetic system. The study demonstrates the importance of chlorophyll a and Calvin cycle enzyme synthesis to photosynthetic development in expanding leaves.     

Zooplankton species diversity in Lake St. Clair,Ontario, Canada

Zooplankton species diversity and selected chemical parameters were investigated at three stations in Lake St. Clair, Ontario, Canada, from 15 June–26 August, 1971. Primary productivity and zooplankton species diversity were greatest at stations 1 and 2 which were enriched by the Thames River drainage. No significant correlation between total zooplankton diversity and chlorophyll a was found, however, within the Cladocera and Copepoda, positive correlations with chlorophyll a, reactive silicate and nitrate were shown at stations 2 and 3. Rotifer species diversity showed negative correlation with chlorophyll a, nitrate and reactive silicate.     

Ammonium Ion, Ethylene, and Abscisic Acid in Polyethylene Glycol-treated Rice Leaves

Polyethylene glycol (PEG)-treatment decreased chlorophyll and protein contents and increased NH₄ ⁺ content due to decreased glutamine synthetase activity in detached rice leaves. PEG-treatment also increased abscisic acid (ABA) content and decreased ethylene production. Addition of fluridone, an inhibitor of ABA biosynthesis, reduced ABA content in rice leaves but did not prevent chlorophyll and protein loss in rice leaves induced by PEG. Silver thiosulfate, an inhibitor of ethylene action, was effective in preventing PEG-promoted chlorophyll and protein loss, but had no effect on PEG-induced NH₄ ⁺ accumulation. The current results suggest that NH₄ ⁺ accumulation in rice leaves induced by PEG increases leaf sensitivity to ethylene, which in turn results in an enhancement of chlorophyll and protein loss. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spectrophotometric measurement of carotenes, xanthophylls, and chlorophylls in extracts from plant seeds

The method of spectrophotometric measurement of carotenoid and chlorophyll content in extracts from plant seeds was modified. The pigments were extracted with a mixture of petroleum ether (PE) and tetrahydrofuran (THF) (PE to THF ratio 4: 1). Equations for calculations of β-carotene, lutein, chlorophyll a and b content in PE: THF mixture were obtained using specific absorption coefficients of solutions of particular pigments. It was shown that subtraction of chlorophyll contribution from the absorption spectrum of seed extracts yields spectra, which could be used in some cases for calculation of carotene and xanthophyll contents.     

Chlorophyll Destruction in Lemon Fruit by Light and 2',4'Dichloro 1-Cyanoethane-sulphonanilide

Chlorophyll content decreased when excised lemon fruits were exposed to light. A quantitative model for the photodestruction of chlorophyll exhibited reasonable agreement with data on in vivo destruction of chlorophyll. Photodestruction of chlorophyll was enhanced by treating fruit with 2′,4′-dichloro-l-cyanoethane-sulphonanilide (R33417). Measurable enhancement of chlorophyll destruction was observed with concentrations of R33417 as low as 10 μg/l. Maximum activity was achieved at approximately 600 μg/1. R33417 treatment enhanced photodestruction of chlorophyll to a greater extent at higher photon flux densities.     

Effect of anthocyanins, carotenoids, and flavonols on chlorophyll fluorescence excitation spectra in apple fruit: signature analysis, assessment, modelling, and relevance to photoprotection

Whole apple fruit (Malus domestica Borkh.) widely differing in pigment content and composition has been examined by recording its chlorophyll fluorescence excitation and diffuse reflection spectra in the visible and near UV regions. Spectral bands sensitive to the pigment concentration have been identified, and linear models for non-destructive assessment of anthocyanins, carotenoids, and flavonols via chlorophyll fluorescence measurements are put forward. The adaptation of apple fruit to high light stress involves accumulation of these protective pigments, which absorb solar radiation in broad spectral ranges extending from UV to the green and, in anthocyanin-containing cultivars, to the red regions of the spectrum. In ripening apples the protective effect in the blue region could be attributed to extrathylakoid carotenoids. A simple model, which allows the simulation of chlorophyll fluorescence excitation spectra in the visible range and a quantitative evaluation of competitive absorption by anthocyanins, carotenoids, and flavonols, is described. Evidence is presented to support the view that anthocyanins, carotenoids, and flavonols play, in fruit with low-to-moderate pigment content, the role of internal traps (insofar as they compete with chlorophylls for the absorption of incident light in specific spectral bands), affecting thereby the shape of the chlorophyll fluorescence excitation spectrum.     

基于小波分析的大豆叶绿素a含量高光谱反演模型

 2003和2004年分别在长春市良种场和中国科学院海伦黑土生态实验站实测了大田耕作与水肥耦合作用下大豆（Glycine max）冠层高光谱反射率 与叶绿素a含量数据,对光谱反射率、微分光谱与叶绿素a含量进行了相关分析;采用归一化植被指数(Normalized diffe rence vegetation index, NDVI)、土壤调和植被指数(Soil-adjusted vegetation index, SAVI)、再归一植被指数(Renormalized difference vegetation index, RDVI)、第二修正比值植被指数(Modified second ratio index, MSRI)等建立了大豆叶绿素a反演模型;应用小波分析对采集的光谱反 射率数据进行了能量系数提取,并以小波能量系数作为自变量进行了单变量与多变量回归分析,对大豆叶绿素a进行了估算。研究结果表明,大 豆叶绿素a 与可见光光谱反射率相关性较好,并在红光波段取得最大值(R²>0.70),但在红边处,微分光谱与大豆叶绿素a的相关性较反射率好 得多,在其它波段则相反;由NDVI、SAVI、RDVI、MSRI等植被指数建立的估算模型可以提高大豆叶绿素a的估算精度（R²>0.75）;小波能量系 数回归模型可以进一步提高大豆叶绿素a含量的估算水平,以一个特定小波能量系数作为自变量的回归模型,大豆叶绿素a回归决定系数R²高达 0.78;多变量回归分析结果表明,大豆叶绿素a实测值与预测值的线性回归决定系数R²均高达0.85。以上结果表明, 小波分析可以对高光谱进 行特征变量提取,并可在一定程度上提高大豆生理参数反演精度。     

Citrus chlorophyllase dynamics at ethylene-induced fruit color-break: a study of chlorophyllase expression, posttranslational processing kinetics, and in situ intracellular localization

Fruit color-break is the visual manifestation of the developmentally regulated transition of chloroplasts to chromoplasts during fruit ripening and often involves biosynthesis of copious amounts of carotenoids concomitant with massive breakdown of chlorophyll. Regulation of chlorophyll breakdown at different physiological and developmental stages of the plant life cycle, particularly at fruit color-break, is still not well understood. Here, we present the dynamics of native chlorophyllase (Chlase) and chlorophyll breakdown in lemon (Citrus limon) fruit during ethylene-induced color-break. We show, using in situ immunofluorescence on ethylene-treated fruit peel (flavedo) tissue, that citrus Chlase is located in the plastid, in contrast to recent reports suggesting cytoplasmic localization of Arabidopsis (Arabidopsis thaliana) Chlases. At the intra-organellar level, Chlase signal was found to overlap mostly with chlorophyll fluorescence, suggesting association of most of the Chlase protein with the photosynthetic membranes. Confocal microscopy analysis showed that the kinetics of chlorophyll breakdown was not uniform in the flavedo cells. Chlorophyll quantity at the cellular level was negatively correlated with plastid Chlase accumulation; plastids with reduced chlorophyll content were found by in situ immunofluorescence to contain significant levels of Chlase, while plastids containing still-intact chlorophyll lacked any Chlase signal. Immunoblot and protein-mass spectrometry analyses were used to demonstrate that citrus Chlase initially accumulates as an approximately 35-kD precursor, which is subsequently N-terminally processed to approximately 33-kD mature forms by cleavage at either of three consecutive amino acid positions. Chlase plastid localization, expression kinetics, and the negative correlation with chlorophyll levels support the central role of the enzyme in chlorophyll breakdown during citrus fruit color-break.     

不同叶色红栌叶片中色素含量、酶活性及内含物差异的研究

为明确秋季不同叶色美国红栌叶片的生理差异,以秋季同一植株上红色、中间色、绿色三种颜色的美国红栌叶片为试材,测定了叶片中色素物质含量、酶活性以及叶片可溶性内含物的含量,结果表明：在红色叶片中,叶绿素含量较低,PAL、POD酶活性较高,花青素苷/叶绿素的比值较大,从而使叶色显现红色;而在绿色叶片中,叶绿素含量较高,PAL、POD酶活性较小,花青素苷/叶绿素的比值较低,叶片显现绿色。通过可溶性内含物测定可知,在红色叶片中的可溶性糖和蛋白质含量相对较高,均与花青素苷/叶绿素的比值达到显著相关水平,表明这些内含物的积累有利于花色素苷的合成。     

NaCl对4种荒漠豆科植物幼苗生理参数的影响

以塔中沙漠植物园引种成功的4种豆科植物紫穗槐(Amorpha fruticosa)、花棒(Hedysarum scoparium)、白柠条(Caragana korshinskii)和骆驼刺(Alhagi sparsifolia)的幼苗为实验材料, 研究不同NaCl浓度处理30天其叶绿素荧光参数、叶绿素含量及叶片水势的变化特征。结果表明: 在不同浓度NaCl处理下, 骆驼刺和白柠条幼苗的叶绿素荧光参数、叶绿素含量及叶片水势的变化程度均低于紫穗槐和花棒; NaCl处理后骆驼刺和白柠条均具有较稳定的光合生理特征, 紫穗槐和花棒的稳定性则相对较差; 在NaCl处理时, 植物叶片水势的变化规律与叶绿素荧光参数具有一定的相关性, 它们可以反映幼苗对NaCl处理的不同响应。     

Studies on chlorophyll formation in Chlorella protothecoides III. Effects of chloramphenicol, cycloheximide, and ethionine on chlorophyll formation

Effects of chloramphenicol, cycloheximide, puromycin and ethionineon the light-independent and subsequent light-dependent processesof chlorophyll formation in "glucose-bleached" cells of Chlorellaprotothecoides were studied. These substances, except puromycin,strongly suppressed different phases of chlorophyll formation.Ethionine most strongly suppressed the light-independent phaseand chloramphenicol an early, relatively short process in thelight-dependent phase of chlorophyll formation. Cycloheximideseverely suppressed all phases of chlorophyll formation. Possibleimplications of these results for the biosynthesis of chlorophyllin algal cells are discussed. ¹ Present address: National Food Research Institute, Ministryof Agriculture and Forestry, Koto-ku, Tokyo 135, Japan. ² Laboratory of Entomology, Faculty of Agriculture, TamagawaUniversity, Machida-shi, Tokyo, Japan (Received October 5, 1972; )     

Pigments, light penetration, and photosynthetic activity in the multi-layered microbial mats of Great Sippewissett Salt Marsh, Massachusetts

The multi-layered microbial mats in the sand flats of Great Sippewissett Salt Marsh were found to have five distinct layers of phototrophic organisms. The top 1–3 mm contained oxygenic phototrophs. The lower 3–4 mm contained anoxygenic phototrophic bacteria. The uppermost gold layer contained diatoms and cyanobacteria, and chlorophyll a was the major chlorophyll. The next layer down was green and was composed of primarily filamentous cyanobacteria containing chlorophyll a. This was followed by a bright pink layer of bacteriochlorophyll b-containing purple sulfur bacteria. The lowest layer was a thin dull green layer of green sulfur bacteria containing bacteriochlorophyll c. The distribution of the chlorophylls with depth revealed that two-thirds of the total chlorophyll in the mat was composed of bacteriochlorophylls present in the anoxygenic phototrophys. The cyanobacterial layers and both purple sulfur bacterial layers had photoautotrophic activity. Light was attenuated in the uppermost layers so that less than 5% of the total radiation at the surface penetrated to the layers of anoxygenic phototrophys.     

Microscale vertical profiles of n(2) fixation, photosynthesis, o(2), chlorophyll a, and light in a cyanobacterial assemblage

Profiles of N(2) fixation, O(2) production (gross photosynthesis), O(2) concentration, chlorophyll a concentration, and photon fluence rates were measured with 50-mum resolution in colonies of the heterocyst-forming cyanobacterium Nostoc parmelioides. Microelectrode measurements were made after 20 h of incubation under N(2) gas. Colonies were frozen, and 50-mum sections were prepared by using a freezing microtome and analyzed for N enrichment and chlorophyll a concentration. Colonies exhibited steep spatial gradients in rates of gross photosynthesis, O(2) concentration, and irradiance, with the highest values generally occurring at the surface. O(2) concentration, photosynthesis, and irradiance all showed positive correlations, but chlorophyll a concentrations varied independently of photosynthesis and irradiance. Forty-four percent of the variation in N incorporation was explained by gross photosynthesis (a positive correlation) when incorporation of N was expressed per unit of biomass (chlorophyll a).