Photoprotective Compounds Research Articles

Effect of ultraviolet radiation on clearance rate of planktonic copepods with different photoprotective strategies

AbstractWe studied two populations of Boeckella gracilipes and two populations of Boeckella gibbosa that inhabit mountain lakes from North‐Patagonian Andes with different optical properties. We combined field and laboratory experiments to determine the effects of ultraviolet radiation (UVR) on clearance rate among these taxa that had different UVR defences. The copepod populations differed in photoprotective compounds (carotenoids and mycosporine‐like amino acids [MAAs]) and antioxidant enzymes (glutathione S‐transferase [GST]). These variations were related to elevation, dissolved organic carbon content and the optical features of the inhabited lakes. Laboratory experiments showed a decrease in the clearance rate (CR) in all populations exposed to UVR. Consistently, the long‐term field experiment showed a negative impact of UVR on CR. We conclude that UVR exposure affects feeding, however, the magnitude of this negative effect depends on the exposure intensity and the photoprotective mechanisms used by zooplankton.

Different response of photosynthetic apparatus to high-light stress in sporotrophophyll and nest leaves of Platycerium bifurcatum

Tropical forest deforestation leads to sudden changes in light conditions, which is a problem for the development of epiphytes, such as Platycerium bifurcatum. High light (HL) results in disturbances of the light phase of photosynthesis and changes in leaf pigment composition. The current study determined differences in fast chlorophyll fluorescence transients and changes in radiation reflectance in sporotrophophylls and nest leaves after one and seven days of HL. In addition, a spectral range was identified with the largest change in reflectance induced by HL. Sporotrophophylls exhibited a stronger response of the photosynthetic apparatus to photoinhibition than that of the nest leaves. Moreover, in sporotrophophylls, disorders of electron transport were visible in the whole O-P phase, and in the nest leaves mainly in the O-J phase. Higher accumulation of photoprotective compounds in sporotrophophylls underlined a different reaction to HL.

Mycosporine-Like Amino Acids for Skin Photoprotection.

Background: Excessive human exposure to solar ultraviolet radiation (UVR) con-tinues to be a major public health concern, with skin cancer rates increasing year on year. The major protective measure is the use of synthetic UVR filters formulated into sunscreens, but there is a growing concern that some of these chemicals cause damage to delicate marine ecosystems. One alternative is the use of biocompatible mycosporine-like amino acids (MAA), which occur naturally in a wide range of marine species. Their role within nature is mainly thought to be photoprotective. However, their potential for human photoprotection is largely understudied.Objective: To review the role of MAA in nature and assess their potential as natural sun-screens for human skin photoprotection.Method: A literature review of all relevant papers was conducted.Conclusion: MAA are natural photostable compounds that are thought to offer photopro-tection to marine species. Initially thought of as protective based on their absorption prop-erties in the solar UVR spectrum, it is clear that MAA are multifunctional photoprotective compounds acting as chemical and biological anti-oxidants. This suggests that MAA may offer a novel eco-friendly approach to human skin photoprotection. Most studies have been carried out in vitro and current data strongly suggest that MAA have potential for de-velopment as natural biocompatible sunscreens that protect against a diverse range of solar UVR induced adverse effects on human health.

Fernblock Prevents Dermal Cell Damage Induced by Visible and Infrared A Radiation

Sun overexposure leads to higher risk of photoaging and skin cancer. The contribution of infrared (IR) and visible light (VIS) radiation is currently being taken into account in their pathogenesis. Erythema, hyperpigmentation, genotoxicity or the increase of matrix metalloproteinases (MMPs) expression are some of the effects induced by these types of radiation. Extracts of various botanicals endowed with antioxidant activity are emerging as new photoprotective compounds. A natural extract from Polypodium leucotomos (Fernblock®, FB) has antioxidant and photoprotective properties and exhibits a strong anti-aging effect. In this study, we evaluated the protective capacity of FB against the detrimental effects of infrared A (IRA) and VIS radiation in human dermal fibroblasts. We analyzed the effects of FB on the morphology, viability, cell cycle and expression of extracellular matrix components of fibroblasts subjected to VIS and IRA. Our results indicate that FB prevents cell damage caused by VIS and IRA. Moreover, it reduces the increase in MMP-1 and cathepsin K expression induced by both VIS and IRA radiation, and curbs alterations in fibrillin 1, fibrillin 2 and elastin expression. All these findings support FB as a feasible approach to prevent or treat skin damage caused by IRA or VIS exposure.

Micropropagation of Baccharis antioquensis (Asteraceae) and photoinduction of polyphenols by UV radiation

Polyphenols are a large diversity of chemical types and interactions that can be responsible for a multiplicity of protective functions ranging from toxicity and light/UV shielding to signal transduction. Bacharis antioquensis has been described as a potential source of new photoprotective compounds with antioxidant capacity associated to polyphenols compounds. The aim of the present work was to develop a micropropagation protocol of B. antioquensis and evaluate the production of polyphenols by in vitro plants exposure to UVB radiation. Branches in juvenile stage of B. antioquensis were collected, desinfected and cultured on half strength Murashige and Skoog medium, supplemented or not with growth regulators (TDZ, BA or GA3) on light/darkness conditions and liquid/solid media. After UV treatments, the absorption coefficient in the UVA-UVB range, the antioxidant capacity and the total phenol content (TPC) from all tissue cultures and the wild tissue were evaluated. Growth regulators, light conditions and type of culture medium (solid or liquid) had a favorable effect on the response of explants. Treatments containing BA + GA3 regulators (2 and 0.5 mg/L respectively) and TDZ (0.5 mg/L) showed positive results in bud growth in liquid medium and darkness. Results showed that UVR exhibited promoting effects on the accumulation of polyphenols, enhancing the absorption coefficient in the UVA-UVB range, the antiradical capacity and the TPC of B. antioquensis in vitro plants. Rev. Biol. Trop. 66(2): 754-764. Epub 2018 June 01.

Accumulation of Potential Photo-Protective Compound Groups in Mangrove (Sonneratia caseolaris (L.) Engler.) Leaves

Objective: To analyze the accumulation of potential photo-protective compound groups, include phenol, flavonoid, and tannin in the leaf tissues of Sonneratia caseolaris (L.) Engler. Methods: The research used Sonneratia caseolaris (L.) Engler leaves as materials. The total of compound groups and photo-protective ability level of each tissue was measured using spectrophotometry, while detection of compound group accumulations in the leaf tissue were observed using histochemical assay. Results: Epidermis extract contained the highest content of total phenolic compounds (phenol, flavonoid, and tannin), followed by those of mesophyll and whole leaf. Moreover, Sun Protection Factor (SPF) value of epidermis was also higher than those of mesophyll and whole leaf, considering that there were no significant difference of SPF value between mesophyll and whole leaf. Result of histochemical assay of S. caseolaris fresh leaf sections showed that phenol, flavonoid, and tannin were highly accumulated in the epidermis and some parts of mesophyll. Conclusion: Potential photo-protective compound groups of S. caseolaris leaves were accumulated in epidermis and mesophyll. However, epidermis showed the highest level of potential photo-protective compound groups than those of other tissues. Photo-protective ability of epidermis also showed higher value than those of mesophyll.

Physiological responses of Pterocladiella capillacea (Rhodophyta, Gelidiales) under two light intensities

Macroalgae must be able to survive in conditions of different light intensities with no damage to their physiological performance or vital processes. Irradiance can stimulate the biosynthesis of certain photoprotective compounds of biotechnological interest, such as pigments and proteins. Pterocladiella capillacea is a shade-grown alga, which play a role key in the balance of marine ecosystems. In addition, it is considered one of the best sources of bacteriological agar and agarose with a wide pharmacological potential. In order to evaluate the photosensitivity in P. capillacea under 60 (control) and moderate light intensity of 300 μmol(photon) m-2 s-1, photosynthetic performance and chemical composition were assessed. P. capillacea showed photosensitivity without evidence of photodamage. The results indicate the possibility to increase a growth rate and probably infer productivity in long-term cultivation by stimulation at moderate light intensity. Increasing photosynthetic pigment and protein contents were also observed under medium light, an interesting result for functional ingredient approaches.

Temporal changes in environmental conditions of a mid-latitude estuary (southern Chile) and its influences in the cellular response of the euryhaline anemone Anthopleura hermaphroditica

The cellular response of the estuarine anemone Anthopleura hermaphroditica was assessed during a tidal cycle (low tide at noon) and compared between organisms acclimated to summer and winter environmental conditions (UV-B and PAR levels, salinity and temperature), with the aim of understanding the strategies used by this dominant invertebrate in an estuary of southern Chile. Anemones were gathered every two hours from 8:00 to 20:00 h from the low intertidal area of the Quempillén estuary and immediately snap frozen to carry out biochemical analyses (oxidative damage, antioxidant capacity, photo-protective compounds). Additionally, levels of environmental radiation (UV-B and PAR), salinity and water temperature were recorded during the field survey. Our results indicate that during summer, lipid peroxidation and protein carbonyl levels in A. hermaphroditica were 3.72 and 16.51 folds higher than during winter, respectively. Maximum lipid peroxidation levels in A. hermaphroditica during summer occurred after UV-B radiation peaked (14:00 h) when water temperatures reached 31 °C. Carbonyl protein levels increased progressively reaching maximum levels at the end of the day. On the contrary, during winter when radiation levels are low and water temperature remained almost constant in the estuary throughout the day, significant variation in salinity levels occurred due to oxidative damage levels that increased significantly at the end of the day. Surprisingly, the mean antioxidant capacity level in A. hermaphroditica during winter was 1.7 folds higher than in summer, a situation that was positively correlated to total phenolic compounds content. Mycosporine 2-glycine (λmax: 331 nm) was the only mycosporine like amino acid (MAA) found in A. hermaphroditica, a photo-protective compound with constant levels throughout the year. Anthopleura hermaphroditica, is an estuarine anemone that are adapted to tolerate rapid fluctuations in the environmental parameters during tidal changes. Those fluctuations are highly affected by seasonal components that expose this invertebrate to different intensity and duration of stress factors between summer and winter. Thus, an efficient antioxidant strategy added to the use of secondary metabolites (phenolic compounds and MAA) may efficiently intercept and neutralize ROS in this animal that lacks of physical protection, allowing it to succeed in a very unstable environment characterized by strong fluctuations of salinity, temperature and environmental radiation through the year.

Seasonal plasticity in photoprotection modulates UV-induced hsp gene expression in copepods from a clear lake.

Zooplankton from clear alpine lakes is exposed to stressful levels of solar UV radiation (UVR). As these pelagic organisms experience high UVR and large changes in solar radiation conditions between ice‐free and ice‐cover periods, they have evolved various strategies to minimize UVR exposure and damage. Here, we studied the relation between photoprotection levels (mycosporine‐like amino acids, carotenoids), antioxidant capacities, and gene expression of heat shock proteins (hsps) as indicator of stress in the copepod Cyclops abyssorum tatricus during the course of a year. Expression of hsp60, hsp70, and hsp90 was measured in the field (baseline expression [BE]) and after UVR exposure in the laboratory. The BE differed among genes and seasons (hsp60: high during summer, hsp70 and hsp90: high during the ice‐cover period). The gene expression of hsp70 was upregulated after exposure to UVR (up to 5.2‐fold change), while hsp60 and hsp90 were only constitutively expressed. A strong seasonal pattern was found in the photoprotective compounds and antioxidant capacities, with highest levels during the ice‐free period. The extent of upregulation of hsp70 gene expression increased with decreasing photoprotection levels and peaked 24 h post UVR exposure (9.6‐fold change) at the time of lowest photoprotection (February). Our data suggest that hsp70 gene expression is modulated by seasonal plasticity in photoprotection. This ability of adequate stress response is essential for survival in highly variable ecosystems such as alpine lakes.

Dietary Photoprotective Compounds Ameliorate UV Tolerance in Shrimp (Pleoticus muelleri) through Induction of Antioxidant Activity

AbstractThe aim of this study was to determine the effects of ultraviolet radiation (UVR) on bioaccumulation of UV‐absorbing compounds acquired through the diet, in larvae and postlarvae of Pleoticus muelleri, and to assess tissue antioxidant activity, survival, and development. Mysis stage I were exposed to two artificial radiation treatments: M‐PAR (photosynthetically active radiation, range = 400–700 nm) and M‐PAR + UVR (280–700 nm). The experimental larvae received a mixed dietary treatment of Artemia persimilis and the microalga Pavlova lutheri, reared under two radiation regimes: PAR (D‐PAR) and PAR + UVR (D‐PAR + UVR). Shrimp from all treatments reached 8 d postlarval stage (PL8), except those under M‐PAR + UVR treatment fed the D‐PAR‐cultured algae, which had 0% survival. Larvae in M‐PAR + UVR and M‐PAR treatments fed with D‐PAR + UVR diet presented the highest survival rates (70 and 75%, respectively), with 37 and 41% increase in PL size. UV‐absorbing compounds were detected in microalgae and PL subject to PAR + UVR treatments. Antioxidant activity, quantified by measuring the free‐radical 1,1‐diphenyl‐2‐picrylhydrazyl in homogenates of PL8, decayed drastically under radiation treatment M‐PAR + UVR fed with algae of the D‐PAR + UVR treatment. It is concluded that the bioaccumulation of UV‐absorbing compounds and the highest antioxidant activity in PL could improve the biochemical and photophysiological responses of shrimp under UVR stress.

UVR and PAR absorbing compounds of marine brown macroalgae along a latitudinal gradient of the Brazilian coast

Absorption spectra are indicative of biological sample chemical composition and can be used as a basis for the construction of descriptive and predictive models for biotechnological screening or assays. In marine algae, chemical composition can vary due to species-specific differences in biochemistry, as well as intra-specific responses to unique environmental variables. Different indices (UVCi, UVB+Ai and PARi) were proposed and calculated to evaluate how photoprotective compounds vary in 18 species of Phaeophyceae. In addition, they were correlated to abiotic factors. Through this technique, seven main peaks were detected in the absorbing spectra of marine brown algal extracts. The highest photoprotective indices values were found in species collected in tropical areas, where higher solar radiation is observed compared to the southern Brazilian coast. Considering additional abiotic factors, water temperature and nitrate concentration were negatively correlated with UV indices. PARi's indices were positively affected by nitrate. All species collected on the Brazilian coast have absorption peaks in the region of phenolic compounds and carotenoids, suggesting that tropical marine brown macroalgae may have developed an effective antioxidant defense system, suggesting adaptation to environments characterized by high solar radiation. UVR/PAR indices congregated essential information to possible future biotechnological screening, facilitating selection of high priority species or sites, fostering actions to enhance alternative sustainable management strategies of coastal environments.

UV-B radiation and temperature stress-induced alterations in metabolic events and defense mechanisms in a bloom-forming cyanobacterium Microcystis aeruginosa

The present investigation is aimed to understand how a bloom-forming cyanobacterium Microcystis aeruginosa adapts to changing climatic conditions. The cyanobacterium was exposed to stresses of UV-B (2 Wm−2) radiation and temperature (45 °C) for desired time intervals. Results showed that both the stresses affect growth and photosynthetic efficiency of M. aeruginosa. More than 50% loss of survival and content of photosynthetic pigments was noted after 4 h treatment of both the above stresses. Such changes were mainly due to the generation of reactive oxygen species which cause damage to proteins, DNA, lipids, and modulation of the membrane stability. An increase in the proline accumulation was noted in the cells which probably negates the harmful effects. In addition, activity of antioxidative enzymes namely, catalase, superoxide dismutase, ascorbate peroxidase, and peroxidase was induced by 1.5–3.0-fold on 3 h of UV-B and temperature treatment indicating their possible role in protection. Interestingly, induction of photoprotective compound, mycosporine-like amino acids (MAAs) were also found under UV-B stress which might be an additional strategy of defense mechanism for the survival of the cyanobacterium. Analysis of photoprotective compound revealed shinorine as the main MAA synthesized by the cyanobacterium.

Applications for Marine Resources in Cosmetics

Marine resources represent an interesting source of active ingredients for the cosmetics industry. Algae (macro and micro) are rich in proteins, amino acids, carbohydrates, vitamins (A, B, and C) and oligo-elements such as copper, iron and zinc. All those active principles play roles in hydration, firming, slimming, shine and protection. Marine organisms inhabit a wide spectrum of habitats. Photo-protective compounds can be obtained from organisms subjected to strong light radiation, such as in tropical systems or in shallow water. In the same way, molecules with antioxidant potential can be obtained from microorganisms inhabiting extreme systems such as hydrothermal vents. For example, marine bacteria collected around deep-sea hydrothermal vents produce complex and innovative polysaccharides in the laboratory which are useful in cosmetics. There are many properties that will be put forward by the cosmetic industries.

Anthocyanin Complex Improves Stability with In Vitro Localized UVA Protective Effect

Background: Anthocyanins are water-soluble photo-protective compounds which rapidly degrade in aqueous environments. Stability as well as skin permeation and UV protection are of concern in the development of sunscreen products from anthocyanins. An anthocyanin complex (AC) was developed and tested for its feasible applications as a sunscreen in in vitro. Keywords: Anthocyanins, complex, stability, cytotoxicity, skin permeation, UV protection, attenuated total reflectance infrared (ATR-IR).

Cyanobacteria growing on tree barks possess high amount of sunscreen compound mycosporine-like amino acids (MAAs)

The present study describes cyanobacterial species composition and their dominance in biological crusts from barks of different trees, roof top of building and soil of agricultural field. An attempt was also made to explore the presence of photoprotective compounds such as mycosporine-like amino acids (MAAs) in the crust samples. Microscopic examination and growth studies revealed the presence of Oscillatoria species in all the crust samples excluding the crust of roof top of a building. Study on the abundance of dominant genera showed marked differences among various crust samples but Hapalosiphon, Lyngbya, Oscillatoria and Scytonema sp. were the most dominant genera, Oscillatoria being dominant in three crust samples. Screening for the presence of photoprotective compounds showed the presence of major peaks in the range of 308–334 nm thereby pointing to the presence of MAAs in all the crust samples. The highest amount of MAAs was found in the crust of Borassus flabellifer (15,729 nmol g dry wt−1 of bark) followed by crust of roof top (14,543 nmol g dry wt−1 of crust). MAAs were separated and partially purified employing HPLC, the most common MAA present in all the crusts was identified as mycosporine-glycine. Presence of mycosporine-glycine (M-Gly) was further confirmed by FTIR and NMR. Test of in vitro colonization on the bark of Mangifera indica and Azadirachta indica by three isolates namely Hapalosiphon, Oscillatoria and Scytonema sp. showed sign of active colonization. It is felt that identification of all the MAAs other than M-Gly may prove useful in future studies especially for assessing their significance in the protection mechanism of cyanobacteria/algae against various types of abiotic stresses.

Variations in photoprotective potential along gradients of leaf development and plant succession in subtropical forests under contrasting irradiances

The successful development of photosynthetic organs is the basis of plant growth and community development. To reveal photo-acclimation to high irradiance in tree species during the course of leaf development and plant succession of subtropical forests, photosynthetic efficiency and photoprotective compounds were analyzed in young and mature leaves of three mid-successional tree species (Castanopsis fissa, Castanopsis chinensis and Schima superba) and three late-successional tree species (Machilus chinensis, Cryptocarya chinensis and Cryptocarya concinna), grown in 100% full sunlight (FL) or 30% of FL (low light, LL). Young leaves of the two species groups exhibited lower chlorophyll (Chl) content, Rubisco content, net photosynthetic rate (Pn), carboxylation efficiency (CE), effective photochemical yield (ΦPSII), photorespiratory electron flow (JO), but higher dark respiration (Rd), and ratios of carotenoids/chlorophylls (Car/Chl), anthocyanins/chlorophylls (Anth/Chl), flavonoids/chlorophylls (Flav/Chl), phenols/chlorophylls (Phen/Chl) and total antioxidant capacity/chlorophylls (TAC/Chl) than those of mature leaves, regardless of growth irradiance. Young leaves of both species groups demonstrated a higher flexibility of Anth/Chl, Flav/Chl, Phen/Chl and TAC/Chl in response to different light conditions than mature leaves. Flav/Chl in young leaves of late-successional group was remarkably higher than that of mid-successional group under the same light conditions. There was a negative correlation between antioxidant-dependent photoprotective potential and photosynthetic efficiency in young and mature leaves of the six tree species grown under either FL or LL. Our results explain partial mechanisms that lie behind the replacement of communities in subtropical forests: highly integrated photoprotective potential allows young leaves of shade-tolerant late-successional species to develop smoothly into mature organs under high irradiance.

The Transcriptional Responses and Metabolic Consequences of Acclimation to Elevated Light Exposure in Grapevine Berries.

An increasing number of field studies that focus on grapevine berry development and ripening implement systems biology approaches; the results are highlighting not only the intricacies of the developmental programming/reprogramming that occurs, but also the complexity of how profoundly the microclimate influences the metabolism of the berry throughout the different stages of development. In a previous study we confirmed that a leaf removal treatment to Sauvignon Blanc grapes, grown in a highly characterized vineyard, primarily affected the level of light exposure to the berries throughout their development. A full transcriptomic analysis of berries from this model vineyard details the underlying molecular responses of the berries in reaction to the exposure and show how the berries acclimated to the imposing light stress. Gene expression involved in the protection of the photosynthetic machinery through rapid protein-turnover and the expression of photoprotective flavonoid compounds were most significantly affected in green berries. Overall, the transcriptome analysis showed that the berries implemented multiple stress-mitigation strategies in parallel and metabolite analysis was used to support the main findings. Combining the transcriptome data and amino acid profiling provided evidence that amino acid catabolism probably contributed to the mitigation of a likely energetic deficit created by the upregulation of (energetically) costly stress defense mechanisms. Furthermore, the rapid turnover of essential proteins involved in the maintenance of primary metabolism and growth in the photosynthetically active grapes appeared to provide precursors for the production of protective secondary metabolites such as apocarotenoids and flavonols in the ripening stages of the berries. Taken together, these results confirmed that the green grape berries responded to light stress much like other vegetative organs and were able to acclimate to the increased exposure, managing their metabolism and energy requirements to sustain the developmental cycle toward ripening. The typical metabolic consequences of leaf removal on grape berries can therefore now be linked to increased light exposure through mechanisms of photoprotection in green berries that leads toward acclimation responses that remain intact until ripening.

Distribution and UV protection strategies of zooplankton in clear and glacier-fed alpine lakes

Zooplankton, a group of aquatic animals important as trophic link in the food web, are exposed to high levels of UV radiation (UVR) in clear alpine lakes, while in turbid glacier-fed lakes they are more protected. To study the interplay between behavioral and physiological protection responses in zooplankton from those lakes, we sampled six lakes of different UVR transparency and glacial turbidity. Copepods were absent in the upper water layers of the clearest lake, while in glacier-fed lakes they were more evenly distributed in the water column. Across all lakes, the weighted copepod mean depth was strongly related to food resources (chlorophyll a and rotifers), whereas in the fishless lakes, glacial turbidity largely explained the vertical daytime distribution of these organisms. Up to ~11-times (mean 3.5) higher concentrations of photo-protective compounds (mycosporine-like amino acids, MAAs) were found in the copepods from the clear than from the glacier-fed lakes. In contrast to carotenoid concentrations and antioxidant capacities, MAA levels were strongly related to the lake transparency. Copepods from alpine lakes rely on a combination of behavioral and physiological strategies adapted to the change in environmental conditions taking place when lakes shift from glacially turbid to clear conditions, as glacier retreat proceeds.

Effect of UV-B Radiation and Desiccation Stress on Photoprotective Compounds Accumulation in Marine Leptolyngbya sp.

Increased awareness regarding the harmful effects of ultraviolet (UV)-B radiation has led to the search for new sources of natural UV-B protecting compounds. Mycosporine-like amino acids are one of such promising compounds found in several organisms. Cyanobacteria are ideal organisms for isolation of these compounds due to their compatibility and adaptability to thrive under harsh environmental conditions. In the following investigation, we report the production of shinorine in Leptolyngbya sp. isolated from the intertidal region. Based on the spectral characteristics and liquid chromatography-mass spectrometry analysis, the UV-absorbing compound was identified as shinorine. To the best of our knowledge, this is the first report on the occurrence of shinorine in Leptolyngbya sp. We also investigated the effect of artificial UV-B radiation and periodic desiccation on chlorophyll-a, total carotenoids, and mycosporine-like amino acids (MAAs) production. The UV-B radiation had a negative effect on growth and chlorophyll concentration, whereas it showed an inductive effect on the production of total carotenoids and MAAs. Desiccation along with UV-B radiation led to an increase in the concentration of photoprotective compounds. These results indicate that carotenoids and MAAs thus facilitate cyanobacteria to avoid and protect themselves from the deleterious effects of UV-B and desiccation.

Near-infrared reflectance spectroscopy allows rapid and simultaneous evaluation of chloroplast pigments and antioxidants, carbon isotope discrimination and nitrogen content in Populus spp. leaves

Poplar species are economically important sources of timber and bioenergy and they also have a valuable application in phytoremediation and in forest restoration programmes. The characterization of their responses in the face of environmental constraints is essential to ascertain their adaptation capacity. Quantification of chloroplast pigments and antioxidant compounds, nutrients and carbon isotope discrimination (Δ13C) of a large set of samples in ecophysiological studies is important for determining the plant’s physiological responses. Δ13C and nitrogen are parameters of special interest for providing information on photosynthesis, water relations and nutritional characteristics in forest stands. Photoprotective and antioxidant compounds participate in the physiological defence of plants subjected to stressful environmental conditions. The measurement of these leaf components by traditional techniques is laborious and expensive. To evaluate them, a calibration model was obtained using Near-Infrared Reflectance Spectroscopy (NIRS) and chemical analyses of Populus spp. leaves sampled from different clones in different years under different physiological conditions. Predictive calibration equations for the concentration of chloroplast pigments (Chlorophylls a and b, lutein, neoxanthin, β-carotene (β-Car), VAZ (violaxanthin+antheraxanthin+zeaxanthin), epoxidation index (EI=(0.5·antheraxanthin+violaxanthin)/VAZ)), antioxidants (total phenolics (TPhe), ascorbate and α-tocopherol), Δ13C and N content were established using a partial least squares regression algorithm. Results showed a remarkable accuracy of the calibration equations for quantifying several antioxidative and photoprotective defence compounds such as neoxanthin (R2=0.844), β-Car (R2=0.827), VAZ (R2=0.846), EI (R2=0.831) and excellent accuracy for TPhe (R2=0.957), N (R2=0.963) and Δ13C (R2=0.922). As shown, results can be obtained on multiple physiological attributes with a single measurement, saving time and money and demonstrating the suitability of NIRS for ecophysiological purposes and bioremediation programs.