Differences In Pigment Composition Research Articles

Differences in pigment composition and concentration between phototrophic, mixotrophic, and heterotrophic Chrysophyceae

Differences in pigment composition and concentration between phototrophic, mixotrophic, and heterotrophic Chrysophyceae

Abnormal expression of bHLH3 disrupts a flavonoid homeostasis network, causing differences in pigment composition among mulberry fruits

Mulberry fruits with high concentrations of anthocyanins are favored by consumers because of their good taste, bright color, and high nutritional value. However, neither the regulatory mechanism controlling flavonoid biosynthesis in mulberry nor the molecular basis of different mulberry fruit colors is fully understood. Here, we report that a flavonoid homeostasis network comprising activation and feedback regulation mechanisms determines mulberry fruit color. In vitro and in vivo assays showed that MYBA-bHLH3-TTG1 regulates the biosynthesis of anthocyanins, while TT2L1 and TT2L2 work with bHLH3 or GL3 and form a MYB-bHLH-WD40 (MBW) complex with TTG1 to regulate proanthocyanidin (PA) synthesis. Functional and expression analyses showed that bHLH3 is a key regulator of the regulatory network controlling mulberry fruit coloration and that MYB4 is activated by MBW complexes and participates in negative feedback control of the regulatory network to balance the accumulation of anthocyanins and proanthocyanidins. Our research demonstrates that the interaction between bHLH3 and MYB4 in the homeostasis regulatory network ensures that the fruits accumulate desirable flavonoids and that this network is stable in pigment-rich mulberry fruits. However, the abnormal expression of bHLH3 disrupts the balance of the network and redirects flavonoid metabolic flux in pale-colored fruits, resulting in differences in the levels and proportions of anthocyanins, flavones, and flavonols among differently colored mulberry fruits (red, yellow, and white). The results of our study reveal the molecular basis of the diversity of mulberry fruit colors.

Size fractionation, chemotaxonomic groups and bio-optical properties of phytoplankton along a transect from the Mediterranean Sea to the SW Atlantic Ocean

The relationships between the structure of the phytoplankton community and the bio-optical properties of surface waters were studied during the TransPEGASO cruise along a transect across the Atlantic Ocean that covered seven biogeographical provinces, from the Alborán Sea (SW Mediterranean) to the Patagonian Shelf. We characterized the composition of the phytoplankton community by means of high-performance liquid chromatography and CHEMTAX pigment analyses applied to whole water and two filtration size classes (< 3 and ≥ 3 μm), flow cytometric determinations and microscopic observations. Additionally, the study was complemented by measurements of the absorption of particulate matter and coloured dissolved organic matter (CDOM). The size class distribution of the chlorophyll a (Chl a) obtained from the size-fractionated filtration (SFF) was compared with that resulting from the diagnostic pigment algorithms (VU) developed by Vidussi et al. (2001) and Uitz et al. (2006), and the total Chl a–based expressions (HI) of Hirata et al. (2011). The seven provinces crossed by the transect could be divided into an oligotrophic group with Chl a < 0.25 mg m-3 comprising the tropical and subtropical Atlantic (including the Canary Current Coastal Province), and a eutrophic group (Chl a > 0.5 mg m-3) with a single Mediterranean (MEDI) sample and those from the southwestern Atlantic Shelf (SWAS). According to CHEMTAX, the most important taxa in the tropical and subtropical Atlantic were Prochlorococcus, haptophytes and Synechoccoccus, while the MEDI and SWAS were dominated by diatoms and haptophytes. Both the VU and HI algorithms, which are based on pigment composition or Chl a concentration, predicted for SWAS a high proportion of nano- and microphytoplankton, while the SFF indicated dominance of the < 3 μm size class. In addition, the CHEMTAX results indicated a high average diatom contribution in this province. However, at several SWAS stations with relatively high values of diatom Chl a estimated by CHEMTAX, the microscopic observations found only small concentrations of nano- or microplankton-sized cells. This discrepancy appeared to be due to the presence, confirmed by scanning electron microscopy, of picoplankton-sized cells of the diatom Minidiscus sp. and of Parmales (a group sharing the pigment composition with the diatoms). These findings caution against a routine assignment of diatom pigments to the microplankton size class. The total non-water absorption in the water column was dominated by CDOM. The average contribution of phytoplankton absorption for the different provinces ranged from 19.3% in the MEDI to 45.7% in the SWAS and 47% in the western tropical Atlantic (WTRA). The Chl a–specific phytoplankton absorption [aph*(443), m2 mg-1] was lower in the MEDI and SWAS than in the oligotrophic provinces. aph*(443) was negatively correlated with the first principal component derived from a principal component analysis based on the concentration of the main pigments and was not correlated with indicators of phytoplankton community size structure such as the proportion of Chl a in the < 3 μm class or a size index derived from the VU size class distribution. These findings indicate that the variability observed in aph*(443) was mainly related to differences in pigment composition and possibly to photoacclimation processes, and that any package effects due to cell size were probably masked by other factors, an outcome that may be related to the relatively small influence of size within the narrow range of Chl a concentrations (all ≤ 2.4 mg m-3) considered in our study.

Trichoderma harzianum T6776 modulates a complex metabolic network to stimulate tomato cv. Micro-Tom growth

Trichoderma harzianum 6776 is a novel and beneficial tomato fungal isolate. To investigate the mechanisms underlying the T. harzianum 6776-tomato interaction, several physiological and biochemical responses were explored on dwarf tomato plants, cv. Micro-Tom. Growth of treated and untreated plants was evaluated by measuring the height and biomass production of plants. The leaf pigment content and sugar partitioning in plant organs were evaluated by biochemical analysis. The photosynthetic parameters were measured by a miniaturized PAM fluorometer and a portable gas-exchange system. The hormonal analysis in root and xylem sap was performed by gas cromatography- mass spectrometry (GC-MS). T. harzianum 6776 positively affected plant growth, increasing the leaf pigment content and improving the photosynthetic activity at both stomatal and non-stomatal levels. Differences in pigment composition and photosynthetic performance were reflected in the carbohydrate content and their partitioning. In the absence of a pathogen, root and xylem vessel stress and growth-related hormone balance were affected by the interaction with T. harzianum 6776, with an increase in jasmonic and indoleacetic acids and a decrease in salicylic acid content. This study shows the complex connection between increased hormone accumulation and transport, altered sugar partitioning and enhanced photosynthetic efficiency induced by T. harzianum 6776, and how growth promotion is the result of the combination of these drastic changes in Micro-Tom plants.

Assessing phytoplankton community composition from hyperspectral measurements of phytoplankton absorption coefficient and remote-sensing reflectance in open-ocean environments

Abstract This study assesses the ability of hyperspectral optical measurements to discriminate changes in the composition of phytoplankton communities in open-ocean non-bloom environments. A large set of in situ near-surface measurements, comprising phytoplankton pigment determinations and hyperspectral optical data of phytoplankton absorption coefficient, aph(λ), and remote-sensing reflectance, Rrs(λ), are used in the analysis. Measurements were collected in different ecological provinces in the Pacific and Atlantic Oceans with chlorophyll-a concentrations ranging from about 0.02 to 1.5 mg m− 3. Hierarchical cluster analysis was applied to measured spectra of aph(λ) and Rrs(λ) and the second-derivative spectra of these optical variables. The resulting optical-based classifications of the examined stations compared favorably (similarity index ≥ 0.73) with a classification of phytoplankton community composition calculated from pigment measurements. Similarities between pigment-based and optically-based classifications were better for the optical data of aph(λ) than Rrs(λ), with only slight improvements resulting from the use of the second derivative spectra as opposed to the non-differentiated spectra. An Empirical Orthogonal Function (EOF) analysis was applied to the optical spectra to examine the correlation of dominant modes of variability with several bio-optical and biogeochemical properties. This analysis supports the notion that the performance of the optical approach is strongly associated with the effects of differences in pigment composition, cell size, and intracellular pigment concentration among different phytoplankton communities on the optical properties of the ocean.

HPLC-MS(n) Identification of Betalain Profile of Different Beetroot (Beta vulgaris L. ssp. vulgaris) Parts and Cultivars.

The distribution of betalains in peel, flesh, and petioles of yellow and red beetroot cultivars has been investigated using an High-performance liquid chromatography (HPLC) system with electrospray mass spectrometry. Differences in the levels of betacyanins and betaxanthins between different colored cultivars were individually determined for 3 plant parts. The content of almost all analyzed compounds decreased in the following order: peel > flesh > petiole. Betanin/isobetanin pigments comprised a major portion of the relative peak area measured in red beetroot peel. Isobetanin relative peak areas were also high in leaf petioles (68.94% to 74.16%) of red colored cultivars. However, betacyanins were completely absent from the extracts of all analyzed parts of yellow beet. Glutamine-bx represented a very high relative peak area (59.54% to 64.18%) in flesh of red-colored cultivars analyzed in the study. Our results indicate that red beet cultivars can be utilized as a potential source of red and yellow natural colorants. However, differences in pigment composition among different beetroot parts must be considered and in order to maximize the pigment yields petioles can also be used as a source rich in specific betalain compounds.

Light adaptation of the unicellular red alga, Cyanidioschyzon merolae, probed by time-resolved fluorescence spectroscopy.

Photosynthetic organisms change the quantity and/or quality of their pigment-protein complexes and the interactions among these complexes in response to light conditions. In the present study, we analyzed light adaptation of the unicellular red alga Cyanidioschyzon merolae, whose pigment composition is similar to that of cyanobacteria because its phycobilisomes (PBS) lack phycoerythrin. C. merolae were grown under different light qualities, and their responses were measured by steady-state absorption, steady-state fluorescence, and picosecond time-resolved fluorescence spectroscopies. Cells were cultivated under four monochromatic light-emitting diodes (blue, green, yellow, and red), and changes in pigment composition and energy transfer were observed. Cells grown under blue and green light increased their relative phycocyanin levels compared with cells cultured under white light. Energy-transfer processes to photosystem I (PSI) were sensitive to yellow and red light. The contribution of direct energy transfer from PBS to PSI increased only under yellow light, while red light induced a reduction in energy transfer from photosystem II to PSI and an increase in energy transfer from light-harvesting chlorophyll protein complex I to PSI. Differences in pigment composition, growth, and energy transfer under different light qualities are discussed.

High efficiency light harvesting by carotenoids in the LH2 complex from photosynthetic bacteria: unique adaptation to growth under low-light conditions.

Rhodopin, rhodopinal, and their glucoside derivatives are carotenoids that accumulate in different amounts in the photosynthetic bacterium, Rhodoblastus (Rbl.) acidophilus strain 7050, depending on the intensity of the light under which the organism is grown. The different growth conditions also have a profound effect on the spectra of the bacteriochlorophyll (BChl) pigments that assemble in the major LH2 light-harvesting pigment–protein complex. Under high-light conditions the well-characterized B800-850 LH2 complex is formed and accumulates rhodopin and rhodopin glucoside as the primary carotenoids. Under low-light conditions, a variant LH2, denoted B800-820, is formed, and rhodopinal and rhodopinal glucoside are the most abundant carotenoids. The present investigation compares and contrasts the spectral properties and dynamics of the excited states of rhodopin and rhodopinal in solution. In addition, the systematic differences in pigment composition and structure of the chromophores in the LH2 complexes provide an opportunity to explore the effect of these factors on the rate and efficiency of carotenoid-to-BChl energy transfer. It is found that the enzymatic conversion of rhodopin to rhodopinal by Rbl. acidophilus 7050 grown under low-light conditions results in nearly 100% carotenoid-to-BChl energy transfer efficiency in the LH2 complex. This comparative analysis provides insight into how photosynthetic systems are able to adapt and survive under challenging environmental conditions.

Towards an efficient phenotypic classification of fungal cultures from environmental samples using digital imagery

The use of the analysis technique proposed here, based on functions of the digital imagery software eCognition professional 4.0, provides an objective and effective method for the assessment of fungal diversity in the context of environmental screening projects. It is demonstrated that strains of cultivated fungi can be quantitatively segregated with regard to specific false-color patterns, which reflect even the merest differences in pigment composition, indicating genotypic or phylogenetic disparities. Due to resolving subtle differences of phenotypic traits, a rapid recognition of (duplicate) genotypes is possible which allows the direct inference of the mycobial diversity of given environmental samples and a semi-quantitative or qualitative estimation of the fungal community structure. Two sets of image data from cultures were used in the current study: a minor set being applied for the definition of color classes and for usage in an image reference array, and a second, extended dataset for method validation. An objective assignment, based on false-color classification, was carried out by cluster analysis. High reproducibility using standardized methods makes this design an effective pre-screening option in the field of microbial environmental research. The application of false-color imagery may therefore be applied in fungal monitoring studies as a meaningful procedure supplementing molecular analyses by the identification of new strains irrespective of their relatedness.

Distinct differences in photoacclimation potential between prokaryotic and eukaryotic oceanic phytoplankton

Six (pico)phytoplankton strains typical for the open oligotrophic oceans were acclimated to different irradiance regimes mimicking stable (ranging from 10 to 125μmolphotonsm−2s−1) and dynamic (averaging at 50 and 125μmolphotonsm−2s−1) water column conditions. Photoacclimation potential of the different phytoplankton species was assessed by analysis of specific growth rates, pigment composition, pigment absorption, elemental composition, and photosynthetic characteristics. Results showed distinct differences between the studied prokaryotic species, Prochlorococcus marinus and Synechococcus sp. (two strains), and the eukaryotic species, Ostreococcus sp., Emiliania huxleyi, and Thalassiosira oceanica. Based on growth and photosynthetic characteristics, the photoacclimation potential of the eukaryotic species was significantly higher compared to that of the prokaryotic species under high and dynamic irradiance conditions. Likewise, the eukaryotic species performed better than the prokaryotic species after photoacclimation to low irradiance conditions. No consistent differences between constant and dynamic irradiance treatments were found. Differences in pigment composition, for example the presence of a xanthophyll cycle, may have played an important role in the success of photoacclimation of the studied phytoplankton species. These results imply that the high photoacclimation potential of eukaryotic oceanic phytoplankton offers a selective advantage over prokaryotic phytoplankton, in both the upper mixed layer and the deep chlorophyll maximum. Thus, factors other than photoacclimation potential, for example low nutrient availability, are likely to explain the high abundance of prokaryotic picophytoplankton in the open oligotrophic oceans.

Pigmentation and spectral absorbance in the deep-sea arctic amphipods Eurythenes gryllus and Anonyx sp.

As for many deep-sea animals, the red colouration of the two amphipods Eurythenes gryllus and Anonyx sp. has an important function providing camouflage, as the attenuation of the red wavelengths in seawater is higher than other colours within the visible range. Variation in colouration between different stages of colour intensity (related to size) is evident in both species. The red colour is caused by carotenoids, and the carotenoid composition was identified and quantified using spectral optical density signatures, high-performance liquid chromatography (HPLC) and liquid chromatography–mass spectrometry (LC–MS). The carotenoid astaxanthin was identified as the major carotenoid in both amphipods, both in pure and in esterified forms. In addition, minor amounts of lutein-like, canthaxanthin-like and several unidentified carotenoids were found in E. gryllus, while diatoxanthin, β,β-carotene and canthaxanthin-like carotenoids were detected in Anonyx sp. Generally, both species displayed an increase in the amount of carotenoids as a function of colour intensity and size. Shifts in λmax in the OD (Optical density; dimensionless, acronym absorbance) spectra were evident in both species between the different colour stages in both the in vivo and the in vitro material, probably caused by changes in pigment composition. Similar shifts in λmax were observed between the in vivo and in vitro pigment raw extracts in general, most likely caused by pigment-binding proteins. The differences in pigment composition and wavelength shifts suggest large intra- and inter-specific differences between the two species. Probable reasons for changes in pigment composition could be related to diet, season, moulting patterns, metabolic pathways and reproduction.

Photosystem 2 photochemistry and pigment composition of a yellow mutant of rice (Oryza sativa L.) under different irradiances

A yellow leaf colouration mutant (named ycm) generated from rice T-DNA insertion lines was identified with less grana lamellae and low thylakoid membrane protein contents. At weak irradiance [50 µmol(photon) m-2 s-1], chlorophyll (Chl) contents of ycm were ≈20 % of those of WT and Chl a/b ratios were 3-fold that of wild type (WT). The leaf of ycm showed lower values in the actual photosystem 2 (PS2) efficiency (ΦPS2), photochemical quenching (qP), and the efficiency of excitation capture by open PS2 centres 1 (Fv'/Fm') than those of WT, except no difference in the maximal efficiency of PS2 photochemistry (Fv/Fm). With progress in irradiance [100 and 200 µmol(photon) m-2 s-1], there was a change in the photosynthetic pigment stoichiometry. In ycm, the increase of total Chl contents and the decrease in Chl a/b ratio were observed. ΦPS2, qP, and Fv'/Fm' of ycm increased gradually along with the increase of irradiance but still much less than in WT. The increase of xanthophyll ratio [(Z+A)/(V+A+Z)] associated with non-photochemical quenching (qN) was found in ycm which suggested that ycm dissipated excess energy through the turnover of xanthophylls. No significant differences in pigment composition were observed in WT under various irradiances, except Chl a/b ratio that gradually decreased. Hence the ycm mutant developed much more tardily than WT, which was caused by low photon energy utilization independent of irradiance.

Differences in pigment composition, photosynthetic rates and chlorophyll fluorescence images of sun and shade leaves of four tree species

The differential pigment composition and photosynthetic activity of sun and shade leaves of deciduous ( Acer pseudoplatanus, Fagus sylvatica, Tilia cordata) and coniferous ( Abies alba) trees was comparatively determined by studying the photosynthetic rates via CO 2 measurements and also by imaging the Chl fluorescence decrease ratio ( R Fd), which is an in vivo indicator of the net CO 2 assimilation rates. The thicker sun leaves and needles in all tree species were characterized by a lower specific leaf area, lower water content, higher total chlorophyll (Chl) a+ b and total carotenoid (Cars) content per leaf area unit, as well as higher values for the ratio Chl a/ b compared to the much thinner shade leaves and needles that possess a higher Chl a+ b and Cars content on a dry matter basis and higher values for the weight ratio Chls/Cars. Sun leaves and needles exhibited higher rates of maximum net photosynthetic CO 2 assimilation ( P Nmax) measured at saturating irradiance associated with higher maximum stomatal conductance for water vapor efflux. The differences in photosynthetic activity between sun and shade leaves and needles could also be sensed via imaging the Chl fluorescence decrease ratio R Fd, since it linearly correlated to the P Nmax rates at saturating irradiance. Chl fluorescence imaging not only provided the possibility to screen the differences in P N rates between sun and shade leaves, but in addition permitted detection and quantification of the large gradients in photosynthetic rates across the leaf area existing in sun and shade leaves.

Extraction and quantification of main pigments in pesto sauces

Pesto is a widely diffused Italian pasta sauce, whose main ingredient is basil. Since its appearance is a key factor for marketing, the determination of its pigment content is of fundamental interest. To this aim, a method for the determination of pesto pigments by C18-HPLC is proposed. Only β-carotene was determined directly by Vis-spectrophotometry, as a consequence of sample purification over a silica cartridge. The proposed method is reliable allowing, for the first time, an easy determination of chlorophylls, pheophytins, lutein and β-carotene in a complex matrix such as pesto. The results show great differences in pigment composition among the samples, with pheophytins as the main components. Only non-thermally processed product show appreciable chlorophyll content as a consequence of the different production technique. Principal Component Analysis performed on the pigment contents showed great variability among the different samples.

Micro X-ray diffraction for painting and pigment analysis

Micro-X-ray diffraction (Micro-XRD) offers many opportunities for non-destructive, in situ crystalline phase composition analysis of varied artworks. This paper discusses the application of this technique to paintings. Painting surfaces and cross-sections can be examined to characterise pigments and provide additional information complementary to existing investigative analyses, which often rely only on elemental information. This study was completed in three parts: proprietary tube paints were examined showing differences in pigment composition on the basis of paint quality; analysis of cross-sections from Tiepolo’s Banquet of Cleopatra provided information on ground layer composition; and a small panel painting was examined non-destructively by placement within the instrument. Through these examples the utility and versatility of the technique is demonstrated.

Estimation of chlorophyll content and daily primary production of the major algal groups by means of multiwavelength-excitation PAM chlorophyll fluorometry: performance and methodological limits

The performance and methodological limits of the Phyto-PAM chlorophyll fluorometer were investigated with laboratory grown algae cultures and natural phytoplankton from the rivers Saar and Saale. The Phyto-PAM is a 4-wavelength chlorophyll fluorometer with the functional combination of chlorophyll (Chl) estimation and assessment of photosynthetic activity, both differentiated into the main algal groups. The reliability of fluorescence-based Chl estimation strongly depends on the group specific calibration of the instrument and the resulting chlorophyll/fluorescence (Chl/F) ratios in reference algal cultures. A very high reliability of the Chl estimation was obtained in the case of constant Chl/F-ratios. Algae grown at different light intensities showed marked differences in Chl/F-ratios, reflecting differences in pigment composition and Chl a specific absorption (a*). When the Phyto-PAM was calibrated with laboratory grown diatoms, the Chl a in river grown diatoms was underestimated, due a lower content of accessory pigments and stronger pigment packaging. While this aspect presently limits the application of PAM fluorometry in limnology, this limitation may be overcome by future technical progress in the detection of dynamic changes in Chl/F-ratio via fluorescence-based measurements of the functional PS II absorption cross-section. Practically identical Chl/F-ratios were found for the diatom-dominated waters of the rivers Saar and Saale, suggesting that the same instrument calibration parameters may be applied for hydrographically similar surface waters. For this particular case, despite of the present methodological limitations, the potential of PAM fluorometry in limnology could be demonstrated. Light response curves were measured to estimate primary production with a spectrally resolved model in daily courses at two sampling sites. Fluorescence based primary production was closely correlated with measured oxygen evolution rates until midday. In the afternoon, at the water surface the fluorescence approach gave higher rates than the measured oxygen evolution. Possible explanations for the observed differences are discussed.

Analysis of planktonic community structure and trophic interactions using refined isotopic signatures determined by combining fluorescence‐activated cell sorting and isotope‐ratio mass spectrometry

Summary1. Thermally assisted hydrolysis and methylation of cellular lipids, by means of Curie‐point pyrolysis of intact whole cells in the presence of a quaternary ammonium hydroxide reagent, provided analytical access (pyrolysis‐gas chromatography; Py‐GC) to the very small amounts of algal carbon delivered by fluorescence‐activated cell sorting. Based on differences in pigment composition, population‐specific in situ fatty acid profiles could be obtained of the major taxa present in the phytoplankton of Lake Loosdrecht (The Netherlands).2. By combining Py‐GC and compound‐specific isotope‐ratio mass spectrometry (Py‐GC‐IRMS) the in situ carbon isotopic signatures could be established of the fatty acid profiles retrieved by flow cytometry. Colonial phytoplankton not amenable to cell sorting and zooplankton specimens were also isotopically characterised with this technique by subjecting handpicked samples to pyrolytic methylation. In this way proxies could be obtained in great detail for isotopic end‐members delineating important carbon sources and sinks in the pelagic food web of Lake Loosdrecht.3. These analyses suggested a significant isotopic heterogeneity among major representatives of the phytoplankton in Lake Loosdrecht. This heterogeneity was also reflected in the isotopic composition of the zooplankton, implying the occurrence of preferential grazing. A differential labelling of the phytoplankton using 13C‐CO2 in a laboratory confinement, and subsequent monitoring of label transfer to the zooplankton, corroborated selective feeding in some rotifer species. The large‐bodied rotifer Asplanchna, previously thought to be predaceous, apparently mainly fed on algae rather than small rotifers, whereas Euchlanis dilatata actively selected filamentous cyanobacteria. Flow cytometric cell sorting in concert with Py‐GC‐IRMS offers new possibilities in carbon isotope‐based food web studies.

Photosynthetic pigment composition and photosystem II photochemistry of wheat ears

The characteristics of pigment composition and photosystem II (PSII) photochemistry in the flag leaf and ear parts of wheat ( Triticum aestivum L.) grown in the field was compared. At the early stage of flowering, awns and the flag leaf showed the highest values in the maximal efficiency of PSII photochemistry ( F v/ F m), actual PSII efficiency (Φ PSII), photochemical quenching ( q P), and the efficiency of excitation capture by open PSII centres ( F ′ v / F ′ m ), followed by glumes, lemmas, and paleae, respectively except that no differences in F ′ v / F ′ m were observed among glumes, leamms, and paleae. With progressing grain filling, there was a change in the photosynthetic pigment stoichiometry. In the ear parts, neoxanthin and antheraxanthin decreased equally with chlorophyll levels. Lutein and zeaxanthin decreased less than chlorophyll levels while β-carotene and violaxanthin decreased faster than chlorophyll levels. No big differences in pigment composition were observed among different ear parts. For the flag leaf, neoxanthin and β-carotene decreased concomitantly with chlorophyll, whereas lutein and xanthophyll cycle pigment were less affected, leading to increases in lutein/chlorophyll and xanthophyll cycle pigment/chlorophyll ratios. F v/ F m, Φ PSII, q P, and F ′ v / F ′ m decreased gradually in the flag leaf and ear parts but to different extents. The largest changes were observed in awns, followed by the lemmas of floret 2, the lemmas of floret 1, glumes, and the flag leaf, respectively. The results suggest that during grain filling, a down-regulation of PSII associated with an increase of the de-epoxidation state of the xanthophyll cycle carotenoids occurred in the flag leaf but not in the ear parts.

Is the Lower Shade Tolerance of Scots Pine, Relative to Pedunculate Oak, Related to the Composition of Photosynthetic Pigments?

Foliage of Scots pine (Pinus sylvestris L.) and pedunculate oak (Quercus robur L.) was collected in a mixed pine/oak forest at canopy positions differing in radiation environment. In both species, chlorophyll (Chl) a/b ratios were higher in foliage of canopy positions exposed to higher irradiance as compared to more shaded crown layers. Throughout the growing season, pine needles exhibited significantly lower Chl a/b ratios than oak leaves acclimated to a similar photon availability. Hence, pine needles showed shade-type pigment characteristics relative to foliage of oak. At a given radiation environment, pine needles tended to contain more neoxanthin and lutein per unit of Chl than oak leaves. The differences in pigment composition between foliage of pine and oak can be explained by a higher ratio of outer antennae Chl to core complex Chl in needles of P. sylvestris which enhances the efficiency of photon capture under limiting irradiance. The shade-type pigment composition of pine relative to oak foliage could have been due to a reduced mesophyll internal photon exposure of chloroplasts in needles of Scots pine, resulting from their xeromorphic anatomy. Hence, the higher drought tolerance of pine needles could be achieved at the expense of shade tolerance.

Discrimination of coral reflectance spectra in the Red Sea

Benthic populations can potentially be mapped from remotely acquired spectral imagery, provided that they have distinctive reflectance signatures. We examined the spectral reflectance characteristics of 14 genera of Red Sea coral using a submersible spectroradiometer. Coral spectra varied quantitatively and qualitatively over the depth interval 5–20 m. Tissue pigment content had a larger effect on reflectance than colony morphology. Ten coral genera could be discriminated with a statistical probability of 52% on the basis of their absolute reflectance. Six groups of two to three coral genera could be discriminated with a probability of 60% on the basis of their rates of change in reflectance at specific wavelengths. All coral genera could be discriminated with a minimum probability of 59% on the basis of their proportionate reflectance at one wavelength as compared with another. Ratio analysis holds significant potential for interpretation of remotely sensed imagery because measurement of reflectance at six wavelengths generates 15 different parameters that can be used to identify and discriminate the component classes. The method distinguishes spectra on the basis of their shape rather than their amplitude, which helps to factor out light-induced variation in pigment concentration, exposing taxon-specific differences in pigment composition and morphology.