Changes in xylem morphology and activity of defense-related enzymes are associated with bean resistance during Fusarium oxysporum colonization.

Genetic resistance is the main strategy to control Fusarium wilt in common bean. Despite this, few studies have focused on defense mechanisms involved in bean resistance to Fusarium oxysporum f. sp. phaseoli (Fop). Thus, the present study aimed to investigate the changes in xylem morphology and involvement of phenylpropanoid compounds and their biosynthetic enzymes in bean resistance against Fop. Uirapuru and UFSC-01 genotypes characterized, respectively, as susceptible and resistant were used. In roots and hypocotyls, guaiacol peroxidase (GPX), phenylalanine ammonia-lyase (PAL), and polyphenol oxidase (PPO) activities were determined at 0, 1, 2, 3, 4, 5, and 6 days after inoculation (dai), and flavonoids, total phenolics, and lignin content were quantified at 0, 3, and 6 dai. Cross sections of taproots and hypocotyls were examined under epifluorescence (at 1, 3, and 6 dai) and transmission electron (at 6 dai) microscopic to analyze the morphology of xylem cell walls. Overall, there was an increase in the activity of all studied enzymes in resistant bean plants, mainly during advanced colonization stages. Modifications in xylem morphology were more intense in roots of resistant genotype resulting in an increase of occluded cells, organelles, and cell wall strengthening. This study provides evidence that bean resistance is associated with increased phenylpropanoid enzymatic activity and cell wall reinforcement of some xylem cells.

Updating embryonic ontogenesis in Araucaria angustifolia: from Burlingame (1915) to the present.

This study addresses gaps in our understanding of pre-fertilization and archegonia development and reinterprets embryonic ontogenesis from Burlingame (Bot Gaz 59:1-39, 1915) to the present based on timescale and structural features allowing us to determine functionally and developmentally accurate terminology for all these stages in A. angustifolia. Different from previous reports, only after pollination, pre-fertilization tissue development occurs (0-13 months after pollination (MAP)) and gives rise to a mature megagametophyte. During all this period, pollen is in a dormant state at the microphyla, and pollen tube germination in nucellus tissue is only observed at the stage of archegonia formation (13 MAP) and not at the free nuclei stage as reported before. For the first time, 14 months after pollination, a fertilization window was indicated, and at 15 MAP, the polyzygotic polyembryony from different archegonia was also seen. After that, subordinated proembryo regression occurs and at least three embryonic developmental stages of dominant embryo were characterized: proembryogenic, early embryogenic, and late embryogenic (15-23 MAP). Along these stages, histochemical and ultrastructural analyses suggest the occurrence of cell death in suspensor and in cap cells of dominant embryo that was not previously reported. The differentiation of meristems, procambium, pith, and cortex tissues in late embryogenic stage was detailed. The morphohistological characterization of pre-fertilization and embryonic stages, together with the timescale of megastrobili development, warranted a referential map of female reproductive structure in this species.

Cellular Responses of Gelidium floridanum (Gelidiales, Rhodophyta) Tetraspores Under Heat Wave and Copper Pollution.

Spore settlement and development are bottlenecks for resilience of habitat-forming macroalgal species. These processes are directly related to temperature, a global stressor protagonist of ocean warming. The toxic effects of local pollutants such as copper may be worsened under a global warming scenario. Therefore, in this paper, we investigated the effects of increased temperature combined with elevated concentrations of copper on the viability, photosynthetic pigments, and ultrastructure of Gelidium floridanum tetraspores. Tetraspores were cultivated on slides with sterilized seawater or seawater enriched with CuCl2 , and incubated under 24°C or 30°C for 24 h. Tetraspores cultivated with copper 3.0 µM under 30°C had lower viability. Both temperature and copper had a significant effect on phycocyanin and phycoerythrin concentrations. Samples cultivated with copper under 30°C presented a heavily altered cellular structure, with vesicles throughout the cytoplasm, chloroplasts with altered structure and cells with degenerated cytoplasm and cell walls. Our findings show that temperature and copper significantly affect the viability, photosynthetic pigments, and ultrastructure of G. floridanum tetraspores, presenting an additive interaction for the physiology of this seaweed's early stages.

Effects of Ultraviolet Radiation (UV-A+UV-B) on the Antioxidant Metabolism of the Red Macroalga Species Acanthophora spicifera (Rhodophyta, Ceramiales) From Different Salinity and Nutrient Conditions.

Acanthophora spicifera (M.Vahl) Børgesen is a macroalga of great economic importance. This study evaluated the antioxidant responses of two algal populations of A. spicifera adapted to different abiotic conditions when exposed to ultraviolet-A+ultraviolet-B radiation (UV-A+UV-B). Experiments were performed using the water at two collection points for 7 days of acclimatization and 7 days of exposure to UVR (3 h per day), followed by metabolic analyses. At point 1, water of 30 ± 1 practical salinity unit (psu) had concentrations of 1.06 ± 0.27 mm NH 4 + , 8.47 ± 0.01 mm NO 3 - , 0.17 ± 0.01 mm PO 4 - 3 and pH 7.88. At point 2, water of 35 ± 1 psu had concentrations of 1.13 ± 0.05 mm NH 4 + , 3.73 ± 0.01 mm NO 3 - , 0.52 ± 0.01 mm PO 4 - 3 and pH 8.55. Chlorophyll a, phycobiliproteins, carotenoids, mycosporins, polyphenolics and antioxidant enzymes (catalase, superoxide dismutase and guaiacol peroxidase) were evaluated. The present study demonstrates that ultraviolet radiation triggers antioxidant activity in the A. spicifera. However, such activation resulted in greater responses in samples of the point 1, with lower salinity and highest concentration of nutrients.

Anatomical and biochemical changes associated with thedevelopment and germination of Araucaria angustifolia seeds

This study aimed at assessing the cell cycle, and anatomical and biochemical changes that the embryonic axis of Araucaria angustifolia undergoes during development, focusing on the maturation stage. During all development, cells exhibited intense metabolic activity with an abundance of mitochondria, lipid bodies, and vacuolated cells. The continued accumulation of starch and protein was observed by LM and TEM and indicated by spectra of FTIR. Cell differentiation of the procambium was observed with a thickening of the cell wall and the formation of resiniferous ducts. At Stage III and IV, cells exhibited structural changes such as altered or elongated mitochondria and presence of plastoglobules. These results suggest that there is a gradual transition from developmental metabolism to germination metabolism. Such changes can contribute to the rapid germination of seeds right after their dispersion, making it an ecological strategy to reduce post-dispersal exposure to predators and to avoid damage from reduced moisture.

Effects of Ultraviolet Radiation (UVA + UVB) on Germination of Carpospores of the Red Macroalga Pyropia acanthophora var. brasiliensis (Rhodophyta, Bangiales): Morphological Changes.

Carpospores of Pyropia acanthophora var. brasiliensis are dispersion and reproduction units responsible for giving rise to the diploid filamentous structure of this alga's life cycle. The present study assesses the anthropogenic impact of ultraviolet radiation (UVR) on morphology and ultrastructure, spore viability, autofluorescence of chloroplasts and the amount of intensity of ROS during the germination of carpospores. Carpospores were cultivated at 24 ± 1°C, 40 ± 10 µmol photons m-2  s-1 with photoperiod of 12 h and exposed to UVAR + UVBR for 3 h a day for 2 days with a daily dose of 5.05 J cm-2 for UVAR and 0.095 J cm-2 for UVBR. Samples were cultured for another five days exposed only to PAR in order to confirm their viability after the initial 2-day exposure. Carpospores showed significant sensitivity to UVR exposure after only 48 h, including changes in developmental rate, overall morphology, cell organization and chloroplast autofluorescence. UVR exposure inhibited germ tube formation in carpospores, which were mostly nonviable and/or altered, showing retracted cytoplasm and disorganized cytoplasmic content. Even in the absence of UVR exposure, carpospores remained collapsed, indicating irreversible damage. It can be concluded that UVR is a limiting factor for the development of P. acanthophora.

Ocean warming and copper pollution: implications for metabolic compounds of the agarophyte Gelidium floridanum (Gelidiales, Rhodophyta).

Ocean warming is increasing and scientific predictions suggest a rise of up to 4°C in sea water temperatures. The combination of a polluted and warmer environment may be detrimental for aquatic species, especially for primary producers such as seaweeds. This study investigated the potential for interactive effects of an increased seawater temperature in a copper-rich environment on the photosynthetic pigments and metabolic compounds of the red seaweed Gelidium floridanum. Seaweed samples were cultivated in a factorial design with temperature (24°C and 30°C), copper (0 and 3 µM), and time (7 and 14 d). The exposure of G. floridanum to copper and 30°C for 7 d resulted in a lower concentration of chlorophyll a, smaller phycobiliprotein rods and lower concentration of soluble sugars. After 14 d of cultivation, a higher concentration of chlorophyll a and soluble sugars could be observed on seaweeds cultivated under 30°C. The accumulation of carotenoids and the release of phenolic compounds indicated specific protective mechanisms against temperature and copper, respectively. Overall, seaweeds grew less when exposed to copper 3 µM at 30°C.

Halimeda jolyana (Bryopsidales, Chlorophyta) presents higher vulnerability to metal pollution at its lower temperature limits of distribution.

Seaweeds living at their temperature limits of distribution are naturally exposed to physiological stressors, facing additional stress when exposed to coastal pollution. The physiological responses of seaweeds to environmental conditions combining natural and anthropogenic stressors provide important information on their vulnerability. We assessed the physiological effects and ultrastructural alterations of trace metals enrichment at concentrations observed in polluted regions within the temperature ranges of distribution of the endemic seaweed Halimeda jolyana, an important component of tropical southwestern Atlantic reefs. Biomass yield and photosynthetic performance declined substantially in samples exposed to metal, although photosynthesis recovered partially at the highest temperature when metal enrichment was ceased. Metal enrichment caused substantial ultrastructural alterations to chloroplasts regardless of temperatures. The lack of photosynthetic recovery at the lower temperatures indicates a higher vulnerability of the species at its temperature limits of distribution in the southwestern Atlantic.

Morphological and functional characterization of the hemocytes from the pearl oyster Pteria hirundo and their immune responses against Vibrio infections.

Hemocyte populations of the pearl oyster Pteria hirundo were characterized at morphological, ultrastructural and functional levels. Three main hemocyte populations were identified: hyalinocytes, granulocytes and blast-like cells. Hyalinocytes were the most abundant population (88.2%) characterized by the presence of few or no granules in the cytoplasm and composed by two subpopulations, large and small hyalinocytes. Comparatively, granulocytes represented 2.2% of the hemocyte population and were characterized by the presence of numerous large electron-lucid granules in the cytoplasm. Finally, the blast-like cells (9.5%) were the smallest hemocytes, showing spherical shape and a high nucleus/cytoplasm ratio. Hemocytes exhibited a significant phagocytic capacity for inert particles (38.5%) and showed to be able to produce microbicidal molecules, such as reactive oxygen species (ROS) (ex vivo assays). The immune role of hemocytes was further investigated in the P. hirundo defense against the Gram-negative Vibrio alginolyticus. A significant decrease in the total number of hemocytes was observed at 24 h following injection of V. alginolyticus or sterile seawater (injury control) when compared to naïve (unchallenged) animals, indicating the migration of circulating hemocytes to the sites of infection and tissue damage. Bacterial agglutination was only observed against Gram-negative bacteria (Vibrio) but not against to marine Gram-positive-bacteria. Besides, an increase in the agglutination titer was observed against V. alginolyticus only in animals previously infected with this same bacterial strain. These results suggest that agglutinins or lectin-like molecules may have been produced in response to this particular microorganism promoting a specific recognition. The ultrastructural and functional characterization of P. hirundo hemocytes constitutes a new important piece of the molluscan immunity puzzle that can also contribute for the improvement of bivalve production sustainability.

Effects of phenanthrene on early development of the Pacific oyster Crassostrea gigas (Thunberg, 1789).

Phenanthnere (PHE) is a polycyclic aromatic hydrocarbon continuously discarded in the marine environment and bioavailable to many aquatic species. Although studies about PHE toxicity have been documented for adult oysters, the effects on early developmental stages are poorly characterized in bivalves. In this study, the effects of PHE (0.02 and 2.0µg.L-1) were evaluated on the embryogenesis and larval development of Crassostrea gigas. Toxicity bioassays, growth and deformities assessment, analysis of shell calcium abundance and transcript levels of genes related to xenobiotic biotransformation (CYP2AU2, CYP30C1), immune system (Cg-Tal) and tissue growth and shell formation (Ferritin, Insulin-like, Cg-Try, Calmodulin and Nacrein) were assayed in D-shape larvae after 24h of PHE exposure. At the highest concentration (2.0µg.L-1), PHE decreased the frequency of normal development (19.7±2.9%) and shell size (53.5±2.8mm). Developmental deformities were mostly related to abnormal mantle and shell formation. Lower calcium levels in oyster shells exposed to PHE 2.0µg.L-1 were observed, suggesting effects on shell structure. At this same PHE concentration, CYP30C1, Cg-Tal, Cg-Tyr, Calmodulin were upregulated and CYP2AU2, Ferritin, Nacrein, and Insulin-Like were downregulated compared to control larvae. At the lowest PHE concentration (0.02µg.L-1), it was observed a minor decrease in normal larval development (89,6±6%) and the remaining parameters were not affected. This is the first study to provide evidences that exposure to PHE can affect early oyster development at the molecular and morphological levels, possibly threatening this bivalve species.

The brown seaweed Sargassum cymosum: changes in metabolism and cellular organization after long-term exposure to cadmium.

Sargassum cymosum was exposed to cadmium (Cd) to determine any physiological and ultrastructural effects. To accomplish this, S. cymosum samples were cultivated under photosynthetic active radiation (PAR) and Cd (0, 0.1, 0.2, 0.4 and 0.8 mg L-1) during 7 and 14 days in laboratory-controlled conditions (0 mg L-1 Cd at both exposure times as control). Seaweeds had high retention capacity (over 90 %) for both exposure times. Growth rates showed significant increases by 14 days, especially for 0.1 and 0.4 mg L-1 Cd. Photosynthetic parameters were unaffected by Cd treatments. Chlorophyll contents were present in higher concentrations for all Cd treatments compared to respective control. Carotenoid profile showed significant differences in total composition and proportion of fucoxanthin and ß-carotene, and no lutein was detected at 14 days. Phenolic and flavonoid compounds showed major accumulation at 14 days. Transmission electron microscopy (TEM) analyses presented major alterations in Cd-treated samples, when compared with respective control, in particular disorganization of cell wall fibrils. When compared to respective control samples, multivariate analyses showed disparate and complex interactions among metabolites in Cd-exposed seaweeds, giving evidence of physiological defence response. Thus, it can be concluded that Cd is a stressor for S. cymosum, resulting in physiological and structural alterations related to defence mechanisms against oxidative stress and toxicological effects resulting from long-term metal exposure. However, in the present paper, some observed changes also appear to result from acclimation mechanisms under lower concentration of Cd relative to the tolerance of S. cymosum to experimental conditions.

Morphological and ultrastructural characterization of the acidophilic and lipid-producer strain Chlamydomonas acidophila LAFIC-004 (Chlorophyta) under different culture conditions.

Chlamydomonas acidophila LAFIC-004 is an acidophilic strain of green microalgae isolated from coal mining drainage. In the present work, this strain was cultivated in acidic medium (pH 3.6) under phototrophic, mixotrophic, and heterotrophic regimes to determine the best condition for growth and lipid production, simultaneously assessing possible morphological and ultrastructural alterations in the cells. For heterotrophic and mixotrophic treatments, two organic carbon sources were tested: 1 % glucose and 1 % sodium acetate. Lipid content and fatty acid profiles were only determined in phototrophic condition. The higher growth rates were achieved in phototrophic conditions, varying from 0.18 to 0.82 day-1. Glucose did not result in significant growth increase in either mixotrophic or heterotrophic conditions, and acetate proved to be toxic to the strain in both conditions. Oil content under phototrophic condition was 15.9 % at exponential growth phase and increased to 54.63 % at stationary phase. Based on cell morphology (flow cytometry and light microscopy) and ultrastructure (transmission electron microscopy), similar characteristics were observed between phototrophic and mixotrophic conditions with glucose evidencing many lipid bodies, starch granules, and intense fluorescence. Under the tested conditions, mixotrophic and heterotrophic modes did not result in increased neutral lipid fluorescence. It can be concluded that the strain is a promising lipid producer when grown until stationary phase in acidic medium and under a phototrophic regime, presenting a fatty acid profile suitable for biodiesel production. The ability to grow this strain in acidic mining residues suggests a potential for bioremediation with production of useful biomass.

The influence of salinity on growth, morphology, leaf ultrastructure, and cell viability of the seagrass Halodule wrightii Ascherson.

Halodule wrightii is an ecologically important seagrass; however, little is known about the adaptation of this species in the context of environmental change, particularly changes arising from alterations in salinity of coastal ecosystems. This study aimed to determine the effects of different salinities on growth, morphology, leaf ultrastructure, and cell viability of H. wrightii. To accomplish this, plants were cultivated for 21 days in salinities of 25, 35, and 45. More hydropotens were observed in samples exposed to salinity of 45 with increased invagination of the plasma membrane and cell wall. These invaginations were also observed in other epidermal cells of the leaf blade. In particular, a significant retraction of plasma membrane was seen in samples exposed to salinity of 45, with possible deposition of compounds between the membrane and cell wall. Osmotic stress in samples exposed to salinity of 45 affected the chloroplasts through an increase in plastoglobules and thylakoids by granum in the epidermal chloroplasts of the leaf and decrease in the number of chloroplasts. Overall, this study showed that H. wrightii can survive within salinities that range between 25 and 45 without changing growth rate. However, the plant did have higher cell viability at salinity of 35. Salt stress in mesocosms, at both salinity of 25 and 45, decreased cell viability in this species. H . wrightii had greater changes in salinity of 45; this showed that the species is more tolerant of salinities below this value.

Metabolomics of Ulva lactuca Linnaeus (Chlorophyta) exposed to oil fuels: Fourier transform infrared spectroscopy and multivariate analysis as tools for metabolic fingerprint.

Fossil fuels, e.g. gasoline and diesel oil, account for substantial share of the pollution that affects marine ecosystems. Environmental metabolomics is an emerging field that may help unravel the effect of these xenobiotics on seaweeds and provide methodologies for biomonitoring coastal ecosystems. In the present study, FTIR and multivariate analysis were used to discriminate metabolic profiles of Ulva lactuca after in vitro exposure to diesel oil and gasoline, in combinations of concentrations (0.001%, 0.01%, 0.1%, and 1.0% - v/v) and times of exposure (30min, 1h, 12h, and 24h). PCA and HCA performed on entire mid-infrared spectral window were able to discriminate diesel oil-exposed thalli from the gasoline-exposed ones. HCA performed on spectral window related to the protein absorbance (1700-1500cm-1) enabled the best discrimination between gasoline-exposed samples regarding the time of exposure, and between diesel oil-exposed samples according to the concentration. The results indicate that the combination of FTIR with multivariate analysis is a simple and efficient methodology for metabolic profiling with potential use for biomonitoring strategies.

In vitro exposure of Ulva lactuca Linnaeus (Chlorophyta) to gasoline - Biochemical and morphological alterations.

Refined fuels have considerable share of pollution of marine ecosystems. Gasoline is one of the most consumed fuel worldwide, but its effects on marine benthic primary producers are poorly investigated. In this study, Ulva lactuca was chosen as a biological model due to its cosmopolitan nature and tolerance to high levels and wide range of xenobiotics and our goal was to evaluate the effects of gasoline on ultrastructure and metabolism of that seaweed. The experimental design consisted of in vitro exposure of U. lactuca to four concentrations of gasoline (0.001%, 0.01%, 0.1%, and 1.0%, v/v) over 30 min, 1 h, 12 h, and 24 h, followed by cytochemical, SEM, and biochemical analysis. Increase in the number of cytoplasmic granules, loss of cell turgor, cytoplasmic shrinkage, and alterations in the mucilage were some of the ultrastructural alterations observed in thalli exposed to gasoline. Decrease in carotenoid and polyphenol contents, as well as increase of soluble sugars and starch contents were associated with the time of exposure to the xenobiotic. In combination, the results revealed important morphological and biochemical alterations in the phenotype of U. lactuca upon acute exposure to gasoline. This seaweed contain certain metabolites assigned as candidates to biomarkers of the environmental stress investigated and it is thought to be a promise species for usage in coastal ecosystems perturbation monitoring system. In addition, the findings suggest that U. lactuca is able to metabolize gasoline hydrocarbons and use them as energy source, acting as bioremediator of marine waters contaminated by petroleum derivatives.

Triterpene derivative: A potential signaling pathway for the fern-9(11)-ene-2α,3ß-diol on insulin secretion in pancreatic islet.

AIM: Triterpenes and their derivatives influence on carbohydrate metabolism. In vivo and in vitro treatment investigated the effect of the natural triterpene fern-9(11)-ene-2α,3ß-diol (1), isolated from Croton heterodoxus, and a derivative triterpene (2) on glucose homeostasis. MAIN METHODS: The antidiabetic effect of the crude extract from C. heterodoxus leaves, the natural triterpene (1) as well as the derivative triterpene (2) were assayed on glucose tolerance. The effect and the mechanism of action on in vivo treatment with triterpene 2 on glycaemia and insulin secretion were studied. In addition, in vitro studies investigated the mechanism of triterpene 2 on glucose uptake and calcium influx on insulin secretion in pancreatic islets. KEY FINDINGS: The results show the extract slightly reduced the glycaemia when compared with hyperglycemic group. However, the presence of the substituent electron-withdrawing 4-nitrobenzoyl group in the A-ring of triterpene 2 powered the serum glucose lowering compared to triterpene 1. In addition, in vivo treatment with triterpene 2 significantly increased the insulin secretion induced by glucose and stimulated the glucose uptake and calcium influx in pancreatic islet. The effect of triterpene on calcium influx was completely inhibited by diazoxide, nifedipine and stearoylcarnitine treatment. SIGNIFICANCE: The stimulatory effect of triterpene 2 on glucose uptake, calcium influx, regulation of potassium (K(+)-ATP) and calcium (L-VDCCs) channels activity as well as the pathway of PKC highlights the mechanism of action of the compound in pancreatic islets on insulin secretion and glucose homeostasis. In addition, this compound did not induce toxicity in this experimental condition.

Data supporting the role of enzymes and polysaccharides during cassava postharvest physiological deterioration.

This data article is referred to the research article entitled The role of ascorbate peroxidase, guaiacol peroxidase, and polysaccharides in cassava (Manihot esculenta Crantz) roots under postharvest physiological deterioration by Uarrota et al. (2015). Food Chemistry 197, Part A, 737-746. The stress duo to PPD of cassava roots leads to the formation of ROS which are extremely harmful and accelerates cassava spoiling. To prevent or alleviate injuries from ROS, plants have evolved antioxidant systems that include non-enzymatic and enzymatic defence systems such as ascorbate peroxidase, guaiacol peroxidase and polysaccharides. In this data article can be found a dataset called "newdata", in RData format, with 60 observations and 06 variables. The first 02 variables (Samples and Cultivars) and the last 04, spectrophotometric data of ascorbate peroxidase, guaiacol peroxidase, tocopherol, total proteins and arcsined data of cassava PPD scoring. For further interpretation and analysis in R software, a report is also provided. Means of all variables and standard deviations are also provided in the Supplementary tables ("data.long3.RData, data.long4.RData and meansEnzymes.RData"), raw data of PPD scoring without transformation (PPDmeans.RData) and days of storage (days.RData) are also provided for data analysis reproducibility in R software.

Synthesis, characterization and toxicological evaluation of Cr2O3 nanoparticles using Daphnia magna and Aliivibrio fischeri.

Chromium III oxide (Cr2O3) nanoparticles (NPs) are used in pigments for ceramics, dyes, paints and cosmetics. However, few studies addressing the toxic potential of these NPs have been reported in the literature. Thus, this research aimed to evaluate the acute and chronic effects of Cr2O3 NPs through acute toxicity tests with Daphnia magna and Aliivibrio fischeri and chronic toxicity tests with Daphnia magna. Cr2O3 NPs were synthesized by the sol-gel method and characterized through TEM, X-Ray diffraction (XRD), zeta potential (ZP) and surface area analysis. In the acute toxicity tests the EC(50,48h) value obtained with D. magna was 6.79 mg L(-1) and for A. fischeri the EC(50,15min) value was 16.10 mg L(-1) and the EC(50,30min) value was 12.91 mg L(-1). Regarding the chronic toxicity tests with D. magna, effects on longevity (OEC=1.00 mg L(-1)), reproduction (OEC=1.00 mg L(-1)) and growth (OEC=0.50 mg L(-1)) were observed. On the SEM and TEM images, ultrastructural alterations in the organelles of exposed organisms were also observed. Thus, toxicological studies with NPs are of great importance in order to reduce the risk of environmental contamination.

Seasonal biochemical and photophysiological responses in the intertidal macroalga Cystoseira tamariscifolia (Ochrophyta).

Seasonal changes in the biochemistry and photophysiology of the brown macroalga Cystoseira tamariscifolia was analyzed in southern Spain. Total carbon and nitrogen contents, phenolic compounds, antioxidant and photosynthetic activities were seasonally determined over two years. Carbon, nitrogen and photoprotective phenolic contents were higher in winter and spring than in summer and autumn. Antioxidant levels were highest in spring and we found a positive correlation between phenolic content and antioxidant activity (EC50). Photosynthetic capacity (ETRmax) and photosynthetic efficiency (αETR) were also highest in spring, and there was a positive correlation between ETRmax and the amount of phenols present. Increased irradiance in spring enhanced algal productivity, antioxidant activity and the production of photoprotective compounds but in summer nutrient depletion due to thermal stratification of coastal waters reduced photosynthetic activity and the photoprotective capacity of C. tamariscifolia. Electron microscopy showed that phenols occurred in the cytoplasm of cortical cells inside physodes. Spring would be the best period to harvest C. tamariscifolia to extract photoprotectors and antioxidants for potential commercial uses, although the environmental impacts would need to be carefully assessed.