Pigment Analysis Research Articles

Physiological responses of Amaranthus cruentus L. to drought stress under sufficient- and deficient-nitrogen conditions.

Water and nitrogen availability are two major environmental factors that can impair plant growth, and when combined, their effects on plant performance can be either intensified or reduced. The objective of this study was to analyze the influence of nitrogen availability on the responses of Amaranthus cruentus’s metabolism to water stress. The plants were cultivated in plastic pots filled with vermiculite, kept under greenhouse conditions, and were watered three times a week with 70% of a full strength nitrogen-free Long Ashton solution, containing 1.97 or 9.88 kg N ha−1 as ammonium nitrate. Photosynthetic parameters were evaluated in planta, and leaves were harvested for chemical analysis of photosynthetic pigments, proline, and phenolic contents. Higher nitrogen supply increased the shoot dry matter, photosynthetic pigments, photosynthesis, stomatal conductance, transpiration, total leaf nitrogen, proline, nitrate, and ammonium but reduced the concentration of flavonoids and total phenols. Six days of water stress did not affect dry matter, photosynthetic pigments, leaf nitrogen, ammonium, or specialized metabolites but increased the proline under high nitrogen and negatively affected stomatal conductance, transpiration, photosynthesis, relative water content, instantaneous water use efficiency, and leaf nitrate. The negative effect was more pronounced under high nitrogen supply. The results show that the addition of a high amount of nitrogen made the physiological processes of plants more sensitive to water stress, indicating that the plant response to water restriction depends on the interaction between the different environmental stressors to which the plants are subjected.

Xanthophyll cycles in the juniper haircap moss (Polytrichum juniperinum) and Antarctic hair grass (Deschampsia antarctica) on Livingston Island (South Shetland Islands, Maritime Antarctica)

The summer climate in Maritime Antarctica is characterised by high humidity and cloudiness with slightly above zero temperatures. Under such conditions, photosynthetic activity is temperature-limited and plant communities are formed by a few species. These conditions could prevent the operation of the photoprotective xanthophyll (VAZ) cycle as low irradiance reduces the excess of energy and low temperatures limit enzyme activity. The VAZ cycle regulates the dissipation of the excess of absorbed light as heat, which is the main mechanism of photoprotection in plants. To test whether this mechanism operates dynamically in Antarctic plant communities, we characterised pigment dynamics under natural field conditions in two representative species: the moss Polytrichum juniperinum and the grass Deschampsia antarctica. Pigment analyses revealed that the total VAZ pool was in the upper range of the values reported for most plant species, suggesting that they are exposed to a high degree of environmental stress. Despite cloudiness, there was a strong conversion of violaxanthin (V) to zeaxanthin (Z) during daytime. Conversely, the dark-induced enzymatic epoxidation back to V was not limited by nocturnal temperatures. In contrast with plants from other cold ecosystems, we did not find any evidence of overnight retention of Z or sustained reductions in photochemical efficiency. These results are of interest for modelling, remote sensing and upscaling of the responses of Antarctic vegetation to environmental challenges.

A Study on Replica Restoration Methods through Scientific Analysis of Seongju Lee Family’s Portraits

Materials and techniques u sed for two portraits ( Jo-nyeon L ee a nd S ung-in L ee) o f the Lee family from Seongju enshrined in Seongsan temple were scientifically analyzed, and based on the data, an optimal replica restoration method was designed. According to the expression technique investigation, both portraits were expressed mainly in line drawing, but there were differences in shoes, pupils, the color expression of flesh, overpainting, and traces of reinforcement. Pigment analysis revealed that a mixture of cinnabar and minium, organic pigment, azurite, malachite, lead white, and yellow pigment were used in common. In the case of Sung-in Lee’s portrait, seokganju and atacamite were also used. In addition, comparison with the contemporaneous portraits of gentry showed that the portrait style at the time was found in the two portraits, but the singularity was modified differently there. Based on the scientific analysis, it was decided to replicate the old color restoration for Jo-nyeon Lee’s portrait while for Sung-in Lee’s portrait, it was decided to replicate the phenomenon. Detailed coloring techniques were presented by supplementing the expression techniques that are difficult to confirm visually using scientific data. In addition, by measuring the chromaticity of representative positions in the portrait for each color and presenting the color reference value calculated as the average value, the current color of the artifact can be replicated and restored based on the objective data as much as possible.

Proteomic Time-Course Analysis of the Filamentous Anoxygenic Phototrophic Bacterium, Chloroflexus aurantiacus, during the Transition from Respiration to Phototrophy.

Chloroflexus aurantiacus is a filamentous anoxygenic phototrophic bacterium that grows chemotrophically under oxic conditions and phototrophically under anoxic conditions. Because photosynthesis-related genes are scattered without any gene clusters in the genome, it is still unclear how this bacterium regulates protein expression in response to environmental changes. In this study, we performed a proteomic time-course analysis of how C. aurantiacus expresses proteins to acclimate to environmental changes, namely the transition from chemoheterotrophic respiratory to photoheterotrophic growth mode. Proteomic analysis detected a total of 2520 proteins out of 3934 coding sequences in the C. aurantiacus genome from samples collected at 13 time points. Almost all proteins for reaction centers, light-harvesting chlorosomes, and carbon fixation pathways were successfully detected during the growing phases in which optical densities and relative bacteriochlorophyll c contents increased simultaneously. Combination of proteomics and pigment analysis suggests that the self-aggregation of bacteriochlorophyllide c could precede the esterification of the hydrophobic farnesyl tail in cells. Cytoplasmic subunits of alternative complex III were interchanged between oxic and anoxic conditions, although membrane-bound subunits were used for both conditions. These data highlight the protein expression dynamics of phototrophy-related genes during the transition from respiration to phototrophy.

The chemistry behind the first Portuguese postage stamps (1853–1894). A non-destructive analytical and chemometric analysis of pigments, fillers and binders

The analysis of 28 specimens of some of the first Portuguese postage stamps, dated from 1853 to 1894, was undertaken with non-destructive techniques: X-Ray fluorescence (XRF), Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) and Ultraviolet–Visible Reflectance Spectroscopy (UV–Vis). Ink, paper and cancellation of the postage stamps were analysed, and the pigments, binders and fillers identified. Prussian blue was found present in all blue and also in green and brown specimens. Chrome and zinc yellow, lead sulphate and mars red were also found in other of the investigated postage stamps. Binders consist mostly of protein glue. Fillers such as calcite and kaolinite were found dominant. The presence of the latter served as an indicator for distinguishing between genuine and forged samples. UV–Vis spectra also proved useful for the same purpose. All the above information was processed and organized using chemometric techniques. These include mainly Hierarchical Cluster Analysis (HCA), for clustering stamps of similar composition, and Principal Component Analysis (PCA) for mapping the samples and identifying the more relevant variables. The latter are, in the paper, content of calcium, potassium, sulphur and silicon and, in the dye pigment area, of iron, zinc and lead content. The study introduces an approach in which, by combination of non-destructive multi analytical techniques with chemometric analysis, extensive information on different aspects of the composition of the studied postage stamps is provided, including that of paper and dyes.

The influences of nitrogen and phosphorus availability on periphytic algae in eutrophic experimental mesocosm

ABSTRACT To investigate the influence of nitrogen (N) and phosphorus (P) availability on the periphytic algal biomass and assemblage composition (by pigment analysis) in the eutrophic lake, natural littoral intact sediment cores in a subtropical eutrophic lake (Lake Taihu) were collected, and subjected to three levels of water N and P loading (N-P [mg. L−1]: 1.5, 0.075; 2.5, 0.125; 3.5, 0.175) in the tanks, eighteen artificial substances (glass slides) were fixed at three water depths (1, 17, and 33 cm above the surface sediment) for development of periphytic algae in each tank, respectively. The results showed that the biomass of periphytic algae on artificial substance was significantly enhanced with increasing N and P levels in water column and water depth (p < 0.05), while sediment-associated periphytic algae did not significantly increase with increasing N and P levels in water column. The development of sediment-associated periphytic algae changed the phosphorus form, calcium-bound phosphorus and inorganic phosphorus in the sediments decreased slightly, and the total phosphorus and organic phosphorus in the sediments increased. Our results suggest that N and P availability is conducive to the development of periphytic algae in subtropical eutrophic shallow lakes in spring.

The pigment analyses of Cambodian panel painting at national museum of Cambodia

Most of panel paintings in Cambodia were destroyed by climate, insects and war; especially during Khmer Rouge (1975–1979). A few paintings were studied for materials and techniques. In this research, we focus on the pigment analyses of the early 20th century Cambodian panel paintings on the wooden doors and windows in the gallery of bronze, National Museum of Cambodia. The EDX and XRD techniques were applied to determine the elemental compositions and identities of the pigments used in the paintings. The results suggested the presence of lead white, calcite, Prussian blue, red cinnabar, red ochre, red lead, gypsum, emerald green (clinoclase), organic black, organic brown with the base of blanc fixe and gold leaf in the paintings.The cross sections of paint samples showed various layers; wood support, ground and paint layers. The ground layer was composed of kaolin while various white pigments like calcite, lead white, blanc fixe and gypsum were found in the paint layer. This indicated the use of white pigment(s) in combination with another colored pigment(s).

A Cyanobacteria Enriched Layer of Shark Bay Stromatolites Reveals a New Acaryochloris Strain Living in Near Infrared Light.

The genus Acaryochloris is unique among phototrophic organisms due to the dominance of chlorophyll d in its photosynthetic reaction centres and light-harvesting proteins. This allows Acaryochloris to capture light energy for photosynthesis over an extended spectrum of up to ~760 nm in the near infra-red (NIR) spectrum. Acaryochloris sp. has been reported in a variety of ecological niches, ranging from polar to tropical shallow aquatic sites. Here, we report a new Acarychloris strain isolated from an NIR-enriched stratified microbial layer 4–6 mm under the surface of stromatolite mats located in the Hamelin Pool of Shark Bay, Western Australia. Pigment analysis by spectrometry/fluorometry, flow cytometry and spectral confocal microscopy identifies unique patterns in pigment content that likely reflect niche adaption. For example, unlike the original A. marina species (type strain MBIC11017), this new strain, Acarychloris LARK001, shows little change in the chlorophyll d/a ratio in response to changes in light wavelength, displays a different Fv/Fm response and lacks detectable levels of phycocyanin. Indeed, 16S rRNA analysis supports the identity of the A. marina LARK001 strain as close to but distinct from from the A. marina HICR111A strain first isolated from Heron Island and previously found on the Great Barrier Reef under coral rubble on the reef flat. Taken together, A. marina LARK001 is a new cyanobacterial strain adapted to the stromatolite mats in Shark Bay.

Diversity of Dinoflagellate Symbionts in Scyphozoan Hosts From Shallow Environments: The Mediterranean Sea and Cabo Frio (Rio de Janeiro, Brazil)

Symbiotic scyphozoan jellyfish are poorly understood in terms of their symbionts and traits, as well as the ecological significance of this association. Dinoflagellate symbionts of the medusae Cotylorhiza tuberculata, Phyllorhiza punctata, and Cassiopea xamachana collected in the Mediterranean Sea and Cabo Frio (Rio de Janeiro, Brazil) were phylogenetically identified based on 28S rDNA and ITS2 haplotypes. The studied medusae harbour only one phylotype of symbionts in a time, but scyphozoan jellyfishes can associate with several types of symbionts. This study confirmed that the main symbionts of investigated scyphozoans belong to the genera Symbiodinium, Philozoon, and Breviolum. The associations between dinoflagellate symbionts and Cotylorhiza tuberculata changed from year to year, hosting Philozoon one year and Breviolum another. Invasive species in the Mediterranean Sea Phyllorhiza punctata harboured dinoflagellate symbionts of genus Symbiodinium as in the native areal. Pigment analysis of two shallow-water symbiont species Breviolum sp. and Philozoon medusarum revealed characteristic profiles for each genus.

Application of Intelligent Image Color Technology in Teaching Chinese Painting Color

This paper presents an in-depth analysis and research on the application of intelligent image color technology in teaching Chinese painting color. A feature reorganization-based approach to Chinese painting image style migration is proposed. Using the connection between depth features in neural networks and image semantics, the artistic style expression method of traditional Chinese painting is combined with existing methods to match the feature matrix in the generative network by feature reorganization, and finally, the migrated image is generated using a decoder. The texture of the target image is input to the generator as an additional condition, and the discriminator is changed to a relativistic discriminator to build a new generative adversarial network. To demonstrate the effectiveness of the method, a large number of Chinese ink and wash style landscape paintings and natural landscape photos are used as experimental data. The experimental results show that the obtained generated images after style migration are 8% better in realism and quality. An image color intelligent analysis system was designed, which integrates a color classification module, a pigment analysis module, an output saving module, and a pigment sample library to achieve the automatic classification of different color areas in Chinese painting, and ultimately allows a judgment to be made on the most likely pigment to be used for each type of color. In the teaching of Chinese painting, the system can transform the traditional “ear-listening” color transmission through vision into eye perception, which makes the teaching of Chinese painting vivid, arouses the enthusiasm of the classroom, and greatly promotes the color teaching of Chinese painting.

Efficient Green Light Acclimation of the Green Algae Picochlorum sp. Triggering Geranylgeranylated Chlorophylls.

In analogy to higher plants, eukaryotic microalgae are thought to be incapable of utilizing green light for growth, due to the “green gap” in the absorbance profiles of their photosynthetic pigments. This study demonstrates, that the marine chlorophyte Picochlorum sp. is able to grow efficiently under green light emitting diode (LED) illumination. Picochlorum sp. growth and pigment profiles under blue, red, green and white LED illumination (light intensity: 50–200 μmol m−2 s−1) in bottom-lightened shake flask cultures were evaluated. Green light-treated cultures showed a prolonged initial growth lag phase of one to 2 days, which was subsequently compensated to obtain comparable biomass yields to red and white light controls (approx. 0.8 gDW L−1). Interestingly, growth and final biomass yields of the green light-treated sample were higher than under blue light with equivalent illumination energies. Further, pigment analysis indicated, that during green light illumination, Picochlorum sp. formed unknown pigments (X1-X4). Pigment concentrations increased with illumination intensity and were most abundant during the exponential growth phase. Mass spectrometry and nuclear magnetic resonance data indicated, that pigments X1-X2 and X3-X4 are derivatives of chlorophyll b and a, which harbor C=C bonds in the phytol side chain similar to geranylgeranylated chlorophylls. Thus, for the first time, the natural accumulation of large pools (approx. 12 mg gDW −1) of chlorophyll intermediates with incomplete hydrogenation of their phytyl chains is demonstrated for algae under monochromatic green light (Peak λ 510 nm, full width at half maximum 91 nm). The ability to utilize green light offers competitive advantages for enhancing biomass production, particularly under conditions of dense cultures, long light pathways and high light intensity. Green light acclimation for an eukaryotic microalgae in conjunction with the formation of new aberrant geranylgeranylated chlorophylls and high efficiency of growth rates are novel for eukaryotic microalgae. Illumination with green light could enhance productivity in industrial processes and trigger the formation of new metabolites–thus, underlying mechanisms require further investigation.

Characterization of Seasonal Phytoplankton Pigments and Functional Types around Offshore Island in the East/Japan Sea, Based on HPLC Pigment Analysis

In this study, we investigated the seasonal phytoplankton community and phytoplankton functional types (PFTs) in the vicinity of Dokdo Island, located in the East/Japan Sea, in 2019. With strong seasonal winds, the water column was well mixed in winter. In spring and autumn, the upper mixed layer depth (MLD) was relatively deep, and the Subsurface Chlorophyll Maximum (SCM) formed in the middle layer. Small phytoplankton were dominant in the summer, which is a time of high water temperatures and strong stratification associated with a shallower MLD. Based on CHEMTAX analysis, in spring, the high phytoplankton biomass was mainly derived from cyanobacteria, diatoms, and dinoflagellates. In summer, &gt;73.2% of the surface biomass was comprised of cyanobacteria. In autumn, pelagophytes accounted for the highest proportion of the biomass. The fraction of microphytoplankton (fmicro) was highest in winter and spring, whereas the fraction of nanophytoplankton (fnano) was highest in autumn and summer. A high fraction of picophytoplankton (fpico) was evident in the surface layers in summer. Values for both the photoprotection index (PI) and the ratio of photoprotective carotenoids (PPC) to photosynthetic carotenoids (PSC) indicate that this study area had high primary productivity in 2019. In order to predict long-term changes in marine food webs due to climate change, it is important to evaluate the size and composition of phytoplankton.

Method development for PPB culture screening, pigment analysis with UPLC-UV-HRMS vs. spectrophotometric methods, and spectral decomposition-based analysis

PPB carotenoids are usually measured through spectrophotometric analysis, measuring total carotenoids (TCs) which has low accuracy and cannot identify individual carotenoids or isomers. Here, we developed an ultra-performance liquid chromatography method with ultraviolet and high-resolution mass spectrometry detection (UPLC-UV-HRMS) to quantify neurosporene, lycopene, and bacteriochlorophyll a contents in PPB cultures. The method exhibited satisfactory recoveries for individual pigments (between 82.1% and 99.5%) and was applied to a range of mixed PPB cultures. The use of a C30 column also enabled the detection of three different isomers of lycopene. In addition, a method for anaerobic photoheterotrophic PPB cultivation to acquire live-cell spectrophotometric information was developed and tested by modifying a standard microbial culture microplate system. A rapid, and relatively low effort principal component analysis (PCA) based decomposition of the whole-cell spectra for pigment analysis in the microplates was also developed. Analysing whole-cell spectra via PCA allowed more accurate prediction of individual pigments compared to absorption methods, and can be done non-destructively, during live-cell growth, but requires calibration for new media and microbial matrices.

Blue-green light is required for a maximized fatty acid unsaturation and pigment concentration in the microalga Acutodesmus obliquus.

Blue-green light is known to maximize the degree of fatty acid (FA) unsaturation in microalgae. However, knowledge on the particular waveband responsible for this stimulation of FA desaturation and its impact on the pigment composition in microalgae remains limited. In this study, Acutodesmus obliquus was cultivated for 96 h at 15°C with different light spectra (380-700 nm, 470-700 nm, 520-700 nm, 600-700 nm, and dark controls). Growth was monitored daily, and qualitative characterization of the microalgal FA composition was achieved via gas chromatography coupled with electron impact ionization mass spectrometry (GC-EI/MS). Additionally, a quantitative analysis of microalgal pigments was performed using high-performance liquid chromatography with diode array detection (HPLC-DAD). Spectra that included wavelengths between 470 and 520 nm led to a significantly higher percentage of the polyunsaturated fatty acids (PUFA) 18:3 and 16:4, compared to all other light conditions. However, no significant differences between the red light cultivations and the heterotrophic dark controls were observed for the FA 18:3 and 16:4. These results indicate, that exclusively the blue-green light waveband between 470 and 520 nm is responsible for a maximized FA unsaturation in A. obliquus. Furthermore, the growth and production of pigments were impaired if blue-green light (380-520 nm) was absent in the light spectrum. This knowledge can contribute to achieving a suitable microalgal pigment and FA composition for industrial purposes and must be considered in spectrally selective microalgae cultivation systems.

Portable Raman and XRF analyses of pigments in a 15th-century Mallorcan altarpiece from the Oratorio de Santa Ana in Alcúdia, Spain

To identify pigments used in a Mallorcan Gothic painting and to investigate their provenance, portable Raman and X-ray fluorescence spectrometers were used to examine in situ the 15th-century Retablo de la Virgen, san Sebastián y san Bernardino, formerly an altarpiece in the Oratorio de Santa Ana in Alcúdia, Spain. The historical pigments vermilion, ultramarine, lead white, orpiment, and hematite were found in pigmented surface layers of the altarpiece, and the elements gold and iron were detected in the expansive gold-colored background areas of the triptych. Two relatively modern pigments, phthalocyanine green and lithopone, were found in a portion of the first small painting in the predella underneath the triptych suggesting a restoration sometime after the late 1930s. Calcium sulfate, as gypsum or anhydrite, was found in the preparation ground layer, as expected for late medieval Mallorcan panel paintings. Known degradation products, weddellite and possibly whewellite, were found. Anglesite was found in an area with lead white and is likely another degradation product. Although spectral markers indicative of the provenance of the historical pigments were not detected, this work contributes to a greater understanding of the composition of late Gothic Mallorcan altarpieces.

Comparative Transcriptome Analysis of Anthocyanin Biosynthesis in Pansy (Viola × wittrockiana Gams.)

Pansy (Viola × wittrockiana Gams.) is an important and attractive ornamental plant with a wide variety of flower colors. To date, the molecular genetic understanding of its colorful petal pigment patterns remains largely unknown. In this study, we analyzed the bicolor petals of “Mengdie” in cytological, physiological, and transcriptomic aspects. Results showed that the difference of flower colors was mainly determined by the pigment distribution in the epidermal cells. Pigment analysis indicated that anthocyanins had strong correlations with color parameters, which acted as the main factor in flower coloration. Comparative transcriptome analysis found a total of 43,908 unigenes with the mean length of 682 bp. There were 24,323, 16,668, 8507, and 7680 unigenes annotated in the Nr, Swiss-Prot, KOG, and KEGG databases, respectively. Differential expression genes (DEGs) showed that the expression of anthocyanin late biosynthesis genes (LBGs), VwF3′H, VwF3′5′H, and VwUFGT, would be likely to play a major role in the color formation of pansy. The expression patterns of selected DEGs were verified by qRT-PCR. This study contributes an excellent insight into molecular mechanism of pigment biosynthesis and provides some useful information for flower color modification in pansy.

Highly Productive Ice Algal Mats in Arctic Melt Ponds: Primary Production and Carbon Turnover

Arctic summer sea ice extent is decreasing and thinning, forming melt ponds that cover more than 50% of the sea ice area during the peak of the melting season. Despite of this, ice algal communities in melt ponds are understudied and so are their contribution to the Arctic Ocean primary production and carbon turnover. While melt ponds have been considered as low productive, recent studies suggest that accumulated ice algal potentially facilitate high and yet overlooked rates of carbon turnover. Here we report on ice algal communities forming dense mats not previously described, collected from melt ponds in the northern Barents Sea in July. We document on distinct layered and brown colored mats with high carbon assimilation and net primary production rates compared to ice algal communities and aggregates, in fact comparable to benthic microalgae at temperate tidal flats. Rates of gross and net primary production, as well as community respiration rates were obtained from oxygen micro profiling, and carbon assimilation calculations were supported by 14C incubations, pigment analysis and light microscopy examinations. The melt pond algal mats consisted of distinct colored layers and differed from aggregates with a consisted layered structure. We accordingly propose the term melt pond algal mats, and further speculate that these dense ice algal mats may provide an important yet overlooked source of organic carbon in the Arctic food-web. A foodweb component likely very sensitive to climate driven changes in the Arctic Ocean and pan-Arctic seas.

Raman Spectroscopy Analysis of the Mural Pigments in Lam Rim Hall of Wudang Lamasery, Baotou Area, Inner Mongolia, China

This paper presents scientific analyses of the wall paintings in Wudang Lamasery, which is located in the Baotou area of Inner Mongolia, China. Raman spectroscopy was used to analyze the pigments of the mural of the Lam rim Hall. The results show that vermilion, red lead, chrome yellow, emerald green and synthetic ultramarine were used. The existence of synthetic pigments provides a clue for the date the mural was painted.

Spectral technology and multispectral imaging for estimating the photosynthetic pigments and SPAD of the Chinese cabbage based on machine learning

• The estimation models constructed by spectra and multispectral imaging combined with various machine learning algorithms were compared. • A one-dimensional convolutional neural network model based on spectral data was established. • A two-dimensional convolutional neural network model based on multispectral images was established. • Spectra and multispectral images were combined with deep learning to achieve the estimation of multiple indicators, such as photosynthetic pigments and SPAD. The contents of photosynthetic pigment, which directly affect the growth of crops, could be evaluated with spectral and multispectral imaging technologies in an accurate and rapid way. For commodity germplasm resources on the market, the estimation of photosynthetic pigments and soil and plant analyzer development (SPAD) value was accomplished using the two techniques combined with machine learning. The spectrometer used in this study employed 781 bands from 320 nm to 1100 nm, and a multispectral imaging camera was used to acquire images in visible and near-infrared. Convolutional neural network (CNN), multiple linear regression (MLR) and generalized linear model (GLM) were used to establish the machine learning models, which established by preprocessed spectral data or 4-channel multispectral images. For estimating photosynthetic pigments (chlorophyll a , chlorophyll b , total chlorophyll and carotenoids), the GLM model established by spectral data was the optimal among all the models. For the SPAD optimal estimation model, the GLM model established by the spectral data and CNN model established by the multispectral images were fair. The R 2 and RMSE of the CNN model validation set in estimating SPAD were 0.87 and 2.31, respectively. The R 2 and RMSE of the GLM model validation set in estimating SPAD were 0.88 and 2.39, respectively. By combining two techniques with different machine learning methods, a comprehensive analysis of photosynthetic pigments and SPAD was accomplished in this paper.

Pigments identification and analysis of the state of conservation of the decorative elements of the castle of Coca (XV-XVI AC, Segovia, Spain) by Raman Spectroscopy

Abstract The castle of Coca (Coca, Segovia, Spain) is one of the summits of the Gothic-Mudejar architecture on the Iberian Peninsula. Among other extraordinary features, this castle presents unique Mudejar decorative elements, which have been partially lost due to this abandonment. In addition, the remaining elements are in danger due to ongoing degradation processes. However, there is no available information about the pigments employed in these decorative elements, nor any analytical study about their state of conservation. This study applies the Raman spectroscopy technique to identify, for the first time, the pigments and ongoing degradation processes on these endangered decorative elements of extraordinary cultural and historical relevance. Red hues were achieved using hematite, whereas the black hues come from the use of carbon black of vegetal origin. Additionally, dispersed carbonaceous particles were also generally found in the walls of the castle, probably related to the use of candles or torches to illuminate the rooms of the castle. Finally, monohydrate and dihydrate calcium oxalates (i.e., whewellite and weddellite, respectively) were detected as degradation products, probably related to biological processes.