Phenotypic Plasticity and Genetic Variation of Leaf Pigment Content in a Southern Beech

Physiological, morphological and phenological attributes are potentially adaptive traits that determine functional responses to certain environmental conditions. They are crucial for understanding adaptations to environmental variation along a species natural range. In particular, leaf pigment content can be a good proxy to the physiological and phenological tree state. Our goal was to evaluate the variation in pigment traits among Nothofagus alpina populations in a common garden trail during two years to infer local adaptation and/or phenotypic plasticity. We also aim to analyse the correlation between pigment traits and phenological traits and climatic data from the geographic location of the populations. To comprise the entire range of the species in Argentina, we analysed 400 individuals from eight natural populations coming from four lake watersheds. Pigment traits were estimated using a spectrophotometer and analysed with linear mixed model (LMM). Significant differences among fixed factors (populations - years and watershed – years) were found in chlorophyl a, b, total, carotenoids and anthocyanins concentrations. Higher concentrations were found for 2018, year with the highest number of rainy days and accumulated precipitation. Two populations (Boquete and Tren Tren) were always the most contrasting ones. At population level, the correlation between the means of pigment concentrations and phenological traits was significant in almost all cases. Conversely, the correlation between the means of population pigment concentrations and the main geographic, climatic and bioclimatic variables of the home range were not significant. The significance of the environmental factor (year) in the linear mixed models tested is evidence of phenotypic plasticity of pigment content, suggesting flexibility for acclimatization to moderate inter-annual changes in climatic conditions. The significance of population and watershed and the influence of the family factor on the variance of the pigment traits are evidence of the genetic control as well as the potential adaptive value of leaf pigment content in N. alpina, giving a base for adaptation to a long-lasting change in climate. High correlations between phenological and pigment traits indicate that, in N. alpina, the determination of only one pigment concentration could be used as a proxy of bud burst, senescence and growing degree days.

Chlorophyll pigment and needle macronutrient responses and interactions to soil moisture and atmospheric CO2 treatments of eight pine and spruce species

Key message Large differences were detected between genera and among species in chlorophyll pigment and macronutrient concentrations. Pines have greater variances than spruces and showed less downregulation of chlorophyll pigment concentrations than spruces in response to eCO2 and DRT. There was strong genetic control of chlorophyll pigments and most macronutrients. Abstract Chlorophyll pigment and needle macronutrient concentrations were quantified for eight tree species in two commercially important genera, Pinus and Picea grown in a 2 × 2 factorial of atmospheric CO2 (370 and 740 ppm) and soil moisture stress (− 0.1 to − 0.5 and − 0.7 to − 1.0 MPa) treatments. Four of the pines and three of the spruces are native to eastern North America, while a fourth spruce, Norway spruce (NS: Picea abies), is from Europe but has been widely used for reforestation in northeastern North America. Overall, spruces had significantly greater chlorophyll a, b, (CHLa, CHLb), and total chlorophyll concentration (TCC) and carotenoid concentration (CAR) than pines. Ambient CO2 (aCO2) had significantly greater TCC than in response to elevated CO2 (eCO2), and TCC and CAR was significantly downregulated more in spruces than in pines in response to eCO2. Pines had equal or greater TCC and CAR in response to drought treatment (DRT) than well-watered treatment, whereas spruces had significantly lower values in response to DRT. Needle N, P and Ca concentrations were greater for spruces than pines. Needle N concentrations declined in response to both eCO2 and DRT. Needle P increased in response to eCO2 but declined in response to DRT. Using total biomass as a covariate, needle N showed no response in pines; whereas spruces showed a slight positive response to increasing total biomass. Covariate analysis showed that TCC had a significant positive relationship to needle N and Mg, with greater TCC in spruces than in pines for a given needle N. Photosynthetic quantum efficiency (QE), derived from light response curves, had a significant positive relationship to TCC that was greater in pines than in spruces for a given TCC. Photosynthetic light convexity had a significant positive relationship to TCC that was also greater in pines than in spruces for a given TCC, indicating a sharper curvature compared to a more progressive curve for spruce. Pine species have greater variances than spruce species. While Pinus strobus (white pine, subgenus Strobus) stands out as having greater chlorophyll and nutrient concentrations than the other three pines (subgenus Pinus). Overall, pines showed less downregulation of chlorophyll pigment concentrations than spruces in response to eCO2 and DRT. There was strong genetic control for chlorophyll pigments and most macronutrients.

Environmental gradients predict the ratio of environmentally acquired carotenoids to self-synthesised pteridine pigments

Carotenoids are important pigments producing integument coloration; however, their dietary availability may be limited in some environments. Many species produce red to yellow hues using a combination of carotenoids and self-synthesised pteridine pigments. A compelling but untested hypothesis is that pteridines replace carotenoids in environments where carotenoid availability is limited. Based on a phylogenetic comparative analysis of pigment concentrations in agamid lizards, we show that environmental gradients predict the ratio of carotenoids to pteridines; carotenoid concentrations are lower and pteridine concentrations higher in arid environments with low vegetation productivity. Both carotenoid and pteridine pigments were present in all species, but only pteridine concentrations explained colour variation among species and there were no correlations between carotenoid and pteridine pigments with similar hue. These results suggest that pteridine pigments replace carotenoids in carotenoid-limited environments, irrespective of skin hue, presumably because it is metabolically cheaper to synthesise pteridines than to acquire and sequester carotenoids when carotenoids are rare.

Pteridine pigments compensate for environmental availability of carotenoids

Carotenoid-based colours are a textbook example of honest signalling because carotenoids must be acquired from the environment. However, many species produce similar colours using self-synthesised pteridine pigments. A compelling but untested hypothesis is that pteridines compensate for low environmental availability of carotenoids because it is metabolically cheaper to synthesise pteridines than to acquire and sequester carotenoids. Based on a phylogenetic comparative analysis of 11 pigment concentrations in skin tissue of agamid lizards, we show that pteridine concentrations are higher and carotenoid concentrations lower in less productive environments. Both carotenoid and pteridine pigments were present in all species, but only pteridine concentrations explained colour variation among species. Furthermore, pigment concentrations were uncorrelated with indices of sexual selection. These results suggest that variation among species in pteridine synthesis compensates for environmental availability of carotenoids and challenge the paradigm of honest carotenoid signalling in vertebrates with complex colour production mechanisms.

Estimating Pigment Concentrations from Spectral Images Using an Encoder‐Decoder Neural Network

A method is proposed to estimate the concentration of pigments mixed in a painting, using the encoder‐decoder model of neural networks. The model is trained to output a value that is the same as its input, and its middle output extracts a certain feature as compressed information about the input. In this instance, the input and output are spectral data of a painting. The model is trained with pigment concentration as the middle output. A dataset containing the scattering coefficient and absorption coefficient of each of 19 pigments was used. The Kubelka‐Munk theory was applied to the coefficients to obtain many patterns of synthetic spectral data, which were used for training. The proposed method was tested using spectral images of 33 paintings, which showed that the method estimates, with high accuracy, the concentrations that have a similar spectrum of the target pigments.

Estimation of phytoplankton pigments from ocean-color satellite observations in the Senegalo–Mauritanian region by using an advanced neural classifier

We processed daily ocean-color satellite observations to construct a monthly climatology of phytoplankton pigment concentrations in the Senegalo–Mauritanian region. Our proposed new method primarily consists of associating, in well-identified clusters, similar pixels in terms of ocean-color parameters and in situ pigment concentrations taken from a global ocean database. The association is carried out using a new self-organizing map (2S-SOM). Its major advantage is allowing the specificity of the optical properties of the water to be taken into account by adding specific weights to the different ocean-color parameters and the in situ measurements. In the retrieval phase, the pigment concentration of a pixel is estimated by taking the pigment concentration values associated with the 2S-SOM cluster presenting the ocean-color satellite spectral measurements that are the closest to those of the pixel under study according to some distance. The method was validated by using a cross-validation procedure. We focused our study on the fucoxanthin concentration, which is related to the abundance of diatoms. We showed that the fucoxanthin starts to develop in December, presents its maximum intensity in March when the upwelling intensity is maximum, extends up to the coast of Guinea in April and begins to decrease in May. The results are in agreement with previous observations and recent in situ measurements. The method is very general and can be applied in every oceanic region.