Action spectra for nitrate and nitrite assimilation in blue-green algae

Action spectra for the assimilation of nitrate and nitrite have been obtained for several blue-green algae (cyanobacteria) with different accessory pigment composition. The action spectra for both nitrate and nitrite utilization by nitrate-grown Anacystis nidulans L-1402-1 cells exhibited a clear peak at about 620 nanometers, corresponding to photosystem II (PSII) C-phycocyanin absorption, the contribution of chlorophyll a (Chl a) being barely detectable. The action spectrum for nitrate reduction by a nitrite reductase mutant of A. nidulans R2 was very similar. All these action spectra resemble the fluorescence excitation spectrum of cell suspensions of the microalgae monitored at 685 nanometers—the fluorescence band of Chl a in PSII. In contrast, the action spectrum for nitrite utilization by nitrogen-starved A. nidulans cells, which are depleted of C-phycocyanin, showed a maximum near 680 nanometers, attributable to Chl a absorption. The action spectrum for nitrite utilization by Calothrix sp. PCC 7601 cells, which contain both C-phycoerythrin and C-phycocyanin as PSII accessory pigments, presented a plateau in the region from 550 to 630 nanometers. In this case, there was also a clear parallelism between the action spectrum and the fluorescence excitation spectrum, which showed two overlapped peaks with maxima at 562 and 633 nanometers. The correlation observed between the action spectra for both nitrate and nitrite assimilation and the light-harvesting pigment content of the blue-green algae studied strongly suggests that phycobiliproteins perform a direct and active role in these photosynthetic processes.     

Fluorescence Properties of Guard Cell Chloroplasts: EVIDENCE FOR LINEAR ELECTRON TRANSPORT AND LIGHT-HARVESTING PIGMENTS OF PHOTOSYSTEMS I AND II

The presence of chloroplasts in guard cells from leaf epidermis, coleoptile, flowers, and albino portions of variegated leaves was established by incident fluorescence microscopy, thus confirming the notion that guard cell chloroplasts are remarkably conserved. Room temperature emission spectra from a few chloroplasts in a single guard cell of Vicia faba showed one major peak at around 683 nanometers. Low-temperature (77 K) emission spectra from peels of albino portions of Chlorophytum comosum leaves and from mesophyll chloroplasts of green parts of the same leaves showed major peaks at around 687 and 733 nanometers, peaks usually attributed to photosystem II and photosystem I pigment systems, respectively. Spectra of peels of V. faba leaves showed similar peaks. However, fluorescence microscopy revealed that the Vicia peels, as well as those from Allium cepa and Tulipa sp., were contaminated with non-guard cell chloroplasts which were practically undetectable under bright field illumination. These observations pose restrictions on the use of epidermal peels as a source of isolated guard cell chloroplasts. Studies on the 3-(3,4-dichlorophenyl)-1,1-dimethylurea-sensitive variable fluorescence kinetics of uncontaminated epidermal peels of C. comosum indicated that guard cell chloroplasts operate a normal, photosystem II-dependent, linear electron transport. The above properties in combination with their reported inability to fix CO₂ photosynthetically may render the guard cell chloroplasts optimally suited to supply the reducing and high-energy phosphate equivalents needed to sustain active ion transport during stomatal opening in daylight.     

Proton Fluxes Associated with Sugar Uptake in Vicia faba Leaf Tissues

Vicia faba leaf fragments bring the pH of their incubation medium to about 4.7, whatever the initial pH value. At this pH, addition of 20 millimolar sucrose causes a transient (20 to 40 minutes) alkalinization (0.05 to 0.10 pH unit) of the medium. The alkalinization is not observed in the presence of p-chloromercuribenzenesulfonic acid which blocks the sucrose carrier involved in phloem loading without affecting the ATPase (Delrot, Despeghel, Bonnemain 1980 Planta 149: 144-148). Addition of 20 millimolar glucose, fructose, or 3-O-methylglucose induces weaker alkalinization than sucrose. Sequential additions of sugars show that: (a) sucrose- and hexose-induced proton fluxes are nearly saturated at 20 millimolar sugar (b) there is no competition between sucrose and hexoses for inducing proton influxes whereas (c) glucose and 3-O-methylglucose are competing for a common system.     

Three acylated anthocyanins and a flavone glycoside in violet-blue flowers of Saintpaulia ‘Thamires’

Three new acylated anthocyanidin 3-rutinoside-5-glucosides were isolated from the violet-blue flowers of Saintpaulia ‘Thamires’ (Saintpaulia sp.) along with a known flavone glycoside. Three new acetylated anthocyanins were determined to be 3-O-[6-O-(4-O-(acetyl)-α-rhamnopyranosyl)-β-glucopyranoside]-5-O-(β-glucopyranoside)s of malvidin (pigment 1), peonidin (pigment 2), and pelargonidin (pigment 3) by chemical and spectroscopic methods. HPLC analysis revealed that malvidin 3-O-acetylrutinoside-5-O-glucoside existed as a dominant pigment in the violet-blue flowers. Moreover, the isolated flavone was identified to be apigenin 4′-O-β-glucuronopyranoside (pigment 4).On the visible absorption spectral curves of fresh violet-blue petals and in their crude extracts in pH 5.0 buffer solution, two characteristic absorption maxima at 547 and 577 nm, with a shoulder near 620 nm, were observed. In contrast, the absorption curves of malvidin 3-O-acetylrutinoside-5-O-glucoside and its deacyl anthocyanin exhibited only one maximum at 535 nm in pH 5.0 buffer solution, and its color was violet and soon fell into decay.However, by addition of apigenin 4′-O-glucuronide, the color of malvidin 3-O-acetylrutinoside-5-O-glucoside changed from violet to violet-blue, similar to that of the fresh flower in pH 5.0 buffer solution. The absorption curve of its violet-blue solution exhibited two similar absorption maxima at 547 and 577 nm, with a shoulder near 620 nm. These results suggest that intermolecular copigmentation between malvidin 3-O-acetylrutinoside-5-O-glucoside and apigenin 4′-O-glucuronide may be responsible for the violet-blue flower color of S. ‘Thamires’.     

The blue anthocyanin pigments from the blue flowers of Heliophila coronopifolia L. (Brassicaceae)

Six acylated delphinidin glycosides (pigments 1-6) and one acylated kaempferol glycoside (pigment 9) were isolated from the blue flowers of cape stock (Heliophila coronopifolia) in Brassicaceae along with two known acylated cyanidin glycosides (pigments 7 and 8). Pigments 1-8, based on 3-sambubioside-5-glucosides of delphinidin and cyanidin, were acylated with hydroxycinnamic acids at 3-glycosyl residues of anthocyanidins. Using spectroscopic and chemical methods, the structures of pigments 1, 2, 5, and 6 were determined to be: delphinidin 3-O-[2-O-(β-xylopyranosyl)-6-O-(acyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside], in which acyl moieties were, respectively, cis-p-coumaric acid for pigment 1, trans-caffeic acid for pigment 2, trans-p-coumaric acid for pigment 5 (a main pigment) and trans-ferulic acid for pigment 6, respectively. Moreover, the structure of pigments 3 and 4 were elucidated, respectively, as a demalonyl pigment 5 and a demalonyl pigment 6. Two known anthocyanins (pigments 7 and 8) were identified to be cyanidin 3-(6-p-coumaroyl-sambubioside)-5-(6-malonyl-glucoside) for pigment 7 and cyanidin 3-(6-feruloyl-sambubioside)-5-(6-malonyl-glucoside) for pigment 8 as minor anthocyanin pigments. A flavonol pigment (pigment 9) was isolated from its flowers and determined to be kaempferol 3-O-[6-O-(trans-feruloyl)-β-glucopyranoside]-7-O-cellobioside-4′-O-glucopyranoside as the main flavonol pigment.On the visible absorption spectral curve of the fresh blue petals of this plant and its petal pressed juice in the pH 5.0 buffer solution, three characteristic absorption maxima were observed at 546, 583 and 635 nm. However, the absorption curve of pigment 5 (a main anthocyanin in its flower) exhibited only one maximum at 569 nm in the pH 5.0 buffer solution, and violet color. The color of pigment 5 was observed to be very unstable in the pH 5.0 solution and soon decayed. In the pH 5.0 solution, the violet color of pigment 5 was restored as pure blue color by addition of pigment 9 (a main flavonol in this flower) like its fresh flower, and its blue solution exhibited the same three maxima at 546, 583 and 635 nm. On the other hand, the violet color of pigment 5 in the pH 5.0 buffer solution was not restored as pure blue color by addition of deacyl pigment 9 or rutin (a typical flower copigment). It is particularly interesting that, a blue anthocyanin-flavonol complex was extracted from the blue flowers of this plant with H₂O or 5% HOAc solution as a dark blue powder. This complex exhibited the same absorption maxima at 546, 583 and 635 nm in the pH 5.0 buffer solution. Analysis of FAB mass measurement established that this blue anthocyanin-flavonol complex was composed of one molecule each of pigment 5 and pigment 9, exhibiting a molecular ion [M+1] ⁺ at 2102 m/z (C₉₃H₁₀₅O₅₅ calc. 2101.542). However, this blue complex is extremely unstable in acid solution. It really dissociates into pigment 5 and pigment 9.     

Apoplastic pH and growth in expanding leaves of Vicia faba under salinity

Salinity affects water availability in the soil and subsequently the plant uptake capacity. Upon exposure to salt stress, leaf growth in monocot plants has been shown to be reduced instantaneously, followed by a gradual acclimation. The growth reactions are caused by an initial water deficit and an accompanied osmotic effect, followed by an IAA-induced sequestration of protons into the apoplast that increases leaf growth again as explained by the acid growth theory. In this study, we investigated the dynamics of growth reactions and apoplastic pH in leaves of the dicot Vicia faba in the presence of NaCl during the initiation of salt stress. Concurrent changes in apoplastic pH were detected by ratiometric fluorescence microscopy using the fluorescent dye fluorescein tetramethylrhodamine dextran. To elucidate the possible relation between the dynamics of leaf growth and apoplastic pH, results of the ratio imaging technique were combined with an in vivo growth analysis imaging approach. Leaf growth rate of V. faba was highest in the dusk and the early night phase; at this time a concomitant decrease of the apoplastic pH was observed. Under salinity, the apoplastic pH in leaves of V. faba increased with a simultaneous decrease of leaf growth towards increasing developmental stages, but with complex aberrations in the 24-h-leaf-growth pattern compared to control leaves. In conclusion, these results show that salt stress leads to an increase in apoplastic pH and to a declined leaf growth activity with complex 24-h-interactions of growth and pH in V. faba.     

Biosynthesis of the phytoalexin wyerone in Vicia faba

In contrast to earlier results [1-¹⁴C] acetate, [2-¹⁴C] malonate and [n 9,10-³H] oleate show significant incorporations into wyerone and related Vicia faba phytoalexins, following infection by Botrytis cinerea.     

Isolation of 4′-dihydroabscisic acid from immature seeds of Vicia faba

4′-Dihydroabscisic acid [1′, 4′-cis-diol of (+)-ABA] was isolated from immature seeds of Vicia faba. Its identity was proved by TLC and MS.     

Covalent anthocyanin–flavonol complexes from the violet-blue flowers of Allium ‘Blue Perfume’

Three covalent anthocyanin–flavonol complexes (pigments 1–3) were extracted from the violet-blue flower of Allium ‘Blue Perfume’ with 5% acetic acid-MeOH solution, in which pigment 1 was the dominant pigment. These three pigments are based on delphinidin 3-glucoside as their deacylanthocyanin and were acylated with malonyl kaempferol 3-sophoroside-7-glucosiduronic acid or malonyl-kaempferol 3-p-coumaroyl-tetraglycoside-7-glucosiduronic acid in addition to acylation with acetic acid.By spectroscopic and chemical methods, the structures of these three pigments 1–3 were determined to be: pigment 1, (6^I-O-(delphinidin 3-O-(3^I-O-(acetyl)-β-glucopyranoside^I)))(2^VI-O-(kaempferol 3-O-(2^II-O-(3^III-O-(β-glucopyranosyl^V)-β-glucopyranosyl^III)-4^II-O-(trans-p-coumaroyl)-6^II-O-(β-glucopyranosyl^IV)-β-glucopyranoside^II)-7-O-(β-glucosiduronic acid^VI))) malonate; pigment 2, (6^I-O-(delphinidin 3-O-(3^I-O-(acetyl)-β-glucopyranoside^I)))(2^VI-O-(kaempferol 3-O-(2^II-O-β-glucopyranosyl^III)-β-glucopyranoside^II)-7-O-(β-glucosiduronic acid^VI))); and pigment 3, (6^I-O-(delphinidin 3-O-(3^I-O-(acetyl)-β-glucopyranoside^I)))(2^VI-O-(kaempferol 3-O-(2^II-O-(3^III-O-(β-glucopyranosyl^V)-β-glucopyranosyl^III)-4^II-O-(cis-p-coumaroyl)-6^II-O-(β-glucopyranosyl^IV)-β-glucopyranoside^II)-7-O-(β-glucosiduronic acid^VI))) malonate.The structure of pigment 2 was analogous to that of a covalent anthocyanin–flavonol complex isolated from Allium schoenoprasum where delphinidin was observed in place of cyanidin. The three covalent anthocyanin–flavonol complexes (pigment 1–3) had a stable violet-blue color with three characteristic absorption maxima at 540, 547 and 618 nm in pH 5–6 buffer solution. From circular dichroism measurement of pigment 1 in the pH 6.0 buffer solution, cotton effects were observed at 533 (+), 604 (−) and 638 (−) nm. Based on these results, these covalent anthocyanin–flavonol complexes were presumed to maintain a stable intramolecular association between delphinidin and kaempferol units closely related to that observed between anthocyanin and hydroxycinnamic acid residues in polyacylated anthocyanins. Additionally, an acylated kaempferol glycoside (pigment 4) was isolated from the same flower extract, and its structure was determined to be kaempferol 3-O-sophoroside-7-O-(3-O-(malonyl)-β-glucopyranosiduronic acid).     

Amino acid incorporation on 80s plant ribosomes: The complete system

A cell-free system directed by poly U or turnip yellow mosaic virus (TYMV)-RNA was obtained from imbibed seeds of Phaseolus aureus; this in vitro system was dependent upon exogenous tRNA. The poly U-directed system functioned in the presence of tRNAs from P. aureus, Vicia faba and yeast, whereas TYMV-RNA was translated only in the presence of tRNAs from P. aureus or V. faba. The pH and Mg²⁺ optima for aminoacylation of tRNAs of P. aureus, V. faba and yeast by leucine and phenylalanine were related to the overall pH and ionic concentration optima for the complete system.     

Polyphenol Oxidation by Vicia faba Chloroplast Membranes: STUDIES ON THE LATENT MEMBRANE-BOUND POLYPHENOL OXIDASE AND ON THE MECHANISM OF PHOTOCHEMICAL POLYPHENOL OXIDATION

The mechanism whereby light effects polyphenol oxidation was examined with Vicia faba chloroplast membranes known to contain a bound latent polyphenol oxidase. Results obtained with the inhibitors 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-idopropyl-p-benzoquinone (DBMIB) indicated an involvement of the non-cyclic electron transport pathway in the light-dependent oxidation of polyphenols, such as dihydroxyphenylalanine (DOPA). Further evidence was provided by experiments in which (a) DOPA replaced H₂O as electron donor for the photoreduction of NADP, (b) NADP replaced O₂ as electron acceptor in the photochemical oxidation of DOPA, and (c) the variable fluorescence associated with photosystem II was increased by DOPA. The photochemical oxidation of DOPA by V. faba chloroplast membranes was insensitive to KCN and to antibodies against purified latent polyphenol oxidase. The results are consistent with the conclusion that the light-dependent oxidation of polyphenols by V. faba chloroplast membranes is achieved independently of the latent membrane-bound polyphenol oxidase. Electrons derived from polyphenols seem to enter the noncyclic electron transport chain on the oxidizing side of photosystem II and to react with O₂ at an unidentified site on the photosystem I side of the DCMU/DBMIB blocks.     

Comparative electrophoretical analysis of plasmid-like mitochondrial DNAs in Vicia faba and in some other legumes

Minicircular DNAs found in mitochondria of 6-d-old etiolated seedlings of Vicia faba L. were also present in mitochondria isolated from cell suspension cultures and from green leaves of this plant. These results support the suggestion that the plasmid-like molecules found in mitochondria of V. faba are an essential component of the mitochondrial genome. The minicircular DNAs were, apparently, peculiar for the species V. faba since they were found in all three cultivars of this species which were studied. The distribution pattern of plasmid-like DNAs in Vicia villosa L. was completely different and mitochondria from Medicago sativa L. also contained specific minicircular DNAs. Thus, minicircular DNAs are typical for the mitochondrial genomes of several legumes and different plant species have their specific mitochondrial plasmid-like DNAs     

Advances in the biotechnological glycosylation of valuable flavonoids

The natural flavonoids, especially their glycosides, are the most abundant polyphenols in foods and have diverse bioactivities. The biotransformation of flavonoid aglycones into their glycosides is vital in flavonoid biosynthesis. The main biological strategies that have been used to achieve flavonoid glycosylation in the laboratory involve metabolic pathway engineering and microbial biotransformation. In this review, we summarize the existing knowledge on the production and biotransformation of flavonoid glycosides using biotechnology, as well as the impact of glycosylation on flavonoid bioactivity. Uridine diphosphate glycosyltransferases play key roles in decorating flavonoids with sugars. Modern metabolic engineering and proteomic tools have been used in an integrated fashion to generate numerous structurally diverse flavonoid glycosides. In vitro, enzymatic glycosylation tends to preferentially generate flavonoid 3- and 7-O-glucosides; microorganisms typically convert flavonoids into their 7-O-glycosides and will produce 3-O-glycosides if supplied with flavonoid substrates having a hydroxyl group at the C-3 position. In general, O-glycosylation reduces flavonoid bioactivity. However, C-glycosylation can enhance some of the benefits of flavonoids on human health, including their antioxidant and anti-diabetic potential.     

Synthesis of Flavonoid O-Pentosides by Escherichia coli through Engineering of Nucleotide Sugar Pathways and Glycosyltransferase

Plants produce two flavonoid O-pentoses, flavonoid O-xyloside and flavonoid O-arabinoside. However, analyzing their biological properties is difficult because flavonoids are not naturally produced in sufficient quantities. In this study, Escherichia coli was used to synthesize the plant-specific flavonoid O-pentosides quercetin 3-O-xyloside and quercetin 3-O-arabinoside. Two strategies were used. First, E. coli was engineered to express components of the biosynthetic pathways for UDP-xylose and UDP-arabinose. For UDP-xylose biosynthesis, two genes, UXS (UDP-xylose synthase) from Arabidopsis thaliana and ugd (UDP-glucose dehydrogenase) from E. coli, were overexpressed. In addition, the gene encoding ArnA (UDP-l-Ara4N formyltransferase/UDP-GlcA C-4″-decarboxylase), which competes with UXS for UDP-glucuronic acid, was deleted. For UDP-arabinose biosynthesis, UXE (UDP-xylose epimerase) was overexpressed. Next, we engineered UDP-dependent glycosyltransferases (UGTs) to ensure specificity for UDP-xylose and UDP-arabinose. The E. coli strains thus obtained synthesized approximately 160 mg/liter of quercetin 3-O-xyloside and quercetin 3-O-arabinoside.     

Maintenance of plant cell membrane integrity and function by the immobilisation of protoplasts in alginate matrices

Isolated protoplasts (Vicia faba) suspended in a mannitol solution over a time period of about 10 d undergo a process of aging characterised by increased ethane formation, decrease in oxygen evolution and CO₂ uptake, pigment degradation and a change in certain enzyme activities (ribulose-1,5-bisphosphate carboxylase and protease). The technique of immobilisation of protoplasts in a cross-linked alginate matrix offers a way to delay the appearance of the indicators mentioned. Various possible mechanisms for the increased stability of protoplasts are discussed.     

Apigenin and amentoflavone glycosides in the psilotaceae and their phylogenetic significance

Documentation of amentoflavone O-glucosides as the predominant flavonoid glycosides in both genera of the Psilotaceae clearly distinguishes this family from all other families of vascular plants. Psilotum and Tmesipteris also possess apigenin C- and O-glycosides as common flavonoid types. Apigenin 7-O-rhamnoglucoside occurs in both genera and the previously undocumented apigenin 7-O-rhamnoglucoside-4′-O-glucoside, although identified only in Tmesipteris, may also be present in Psilotum. The existence of flavone C-glycosides in both genera may provide a phytochemical relationship between the Psilotaceae and some ferns. The phylogenetic significance of these results is discussed.     

Tetra-acylated cyanidin 3-sophoroside-5-glucosides from the flowers of Iberis umbellata L. (Cruciferae)

The structures of 11 acylated cyanidin 3-sophoroside-5-glucosides (pigments 1-11), isolated from the flowers of Iberis umbellata cultivars (Cruciferae), were elucidated by chemical and spectroscopic methods. Pigments 1-11 were acylated with malonic acid, p-coumaric acid, ferulic acid, sinapic acid and/or glucosylhydroxycinnamic acids.Pigments 1-11 were classified into four groups by the substitution patterns of the linear acylated residues at the 3-position of the cyanidin. In the first group, pigments 1-3 were determined to be cyanidin 3-O-[2-O-(2-O-(acyl)-β-glucopyranosyl)-6-O-(trans-p-coumaroyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside], in which the acyl moiety varied with none for pigment 1, ferulic acid for pigment 2 and sinapic acid for pigment 3. In the second one, pigments 4-6 were cyanidin 3-O-[2-O-(2-O-(acyl)-β-glucopyranosyl)-6-O-(4-O-(β-glucopyranosyl)-trans-p-coumaroyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside], in which the acyl moiety varied with none for pigment 4, ferulic acid for pigment 5 and sinapic acid for pigment 6. In the third one, pigments 7-9 were cyanidin 3-O-[2-O-(2-O-(acyl)-β-glucopyranosyl)-6-O-(4-O-(6-O-(trans-feruloyl)-β-glucopyranosyl)-trans-p-coumaroyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside], in which the acyl moiety varied with none for pigment 7, ferulic acid for pigment 8, and sinapic acid for pigment 9. In the last one, pigments 10 and 11 were cyanidin 3-O-[2-O-(2-O-(acyl)-β-glucopyranosyl)-6-O-(4-O-(6-O-(4-O-(β-glucopyranosyl)-trans-feruloyl)-β-glucopyranosyl)-trans-p-coumaroyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside], in which acyl moieties were none for pigment 10 and ferulic acid for pigment 11.The distribution of these pigments was examined in the flowers of four cultivars of I. umbellata by HPLC analysis. Pigment 1 acylated with one molecule of p-coumaric acid was dominantly observed in purple-violet cultivars. On the other hand, pigments (9 and 11) acylated with three molecules of hydroxycinnamic acids were observed in lilac (purple-violet) cultivars as major anthocyanins. The bluing effect and stability on these anthocyanin colors were discussed in relation to the molecular number of hydroxycinnamic acids in these anthocyanin molecules.     

Antheraxanthin, a light harvesting carotenoid found in a chromophyte alga

The pigments of the chromophyte freshwater alga, Chrysophaera magna Belcher were analyzed by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) to reveal the presence of chlorophylls a and c, β-carotene, fucoxanthin, and antheraxanthin. The presence of antheraxanthin was verified by comparison of TLC R_F values, HPLC retention times, and absorption features to those of authentic, synthetic antheraxanthin. Antheraxanthin accounted for about 15% of the total carotenoid content of C. magna. The molar ratio of the major carotenoids was antheraxanthin:fucoxanthin:β-carotene, 1:2.3:3.3. The whole-cell absorption spectrum revealed a broad band between 470 and 520 nanometers which was attributed to fucoxanthin and antheraxanthin in vivo. Upon extraction in hydrocarbon, this broad absorption region was lost. The in vivo fluorescence excitation spectrum for 680 nm emission revealed the energy transfer activities and light harvesting roles of chlorophylls a and c, and fucoxanthin. In addition, an excitation band was resolved at 487 nanometers which could be attributed only to antheraxanthin. Comparison of whole-cell fluorescence excitation spectra of C. magna with the diatom Phaeodactylum tricornutum, which possesses fucoxanthin but not antheraxanthin, supports the assignment of the 487 nm band to antheraxanthin. This is the first report of a photosynthetic light harvesting function of the xanthophyll, antheraxanthin. This carotenoid broadens the absorption cross-section for photosynthesis in C. magna and extends light harvesting into the green portion of the spectrum.     

Flavonoids of Sullivantia: Taxonomic implications at the generic level within the saxifraginae

Sullivantia species were found to produce quercetin 3-O-glycosides, several of which contain glucuronic acid, as well as pedalitin (6-hydroxy-7-O-methyl luteolin), pedalitin 6-O-glycosides, and small amounts of luteolin. Sullivantia has a unique combination of compounds that distinguishes it from other genera in the Saxifraginae for which flavonoid data are available. The nature of the flavonoid compounds is in accordance with a general trend within the Saxifragaceae of reduction and replacement of flavonols by flavones.     

The flavonoids of ferns in the isolated genera Loxsoma and Loxsomopsis

Kaempferol and quercetin 3-O-glucosides and 3-O-rhamnoglucosides are common to both Loxsoma cunninghamii and Loxsomopsis costaricensis, but in the former the new flavonoid glycosides, kaempferol and quercetin 3-O-glucoside-7-O-arabinoside have also been identified. The data are consistent with the proposed taxonomic relationship between these geographically isolated genera. Comparative flavonoid chemistry indicates that the Loxsomaceae may be a primitive family, not closely related to the Hymenophyllaceae or the Cyatheaceae.