In Vitro and In Vivo Effects of Palmaria palmata Derived Peptides on Glucose Metabolism

International Journal of Peptide Research and Therapeutics - Three synthetic peptides, ILAP, LLAP and MAGVDHI, derived from a Palmaria palmata protein hydrolysate were assessed for their...     

In vitro antioxidant and anti-diabetic analysis of Andrographis echioides and Andrographis paniculata ethanol extract

It is of interest to analyse and compare the antioxidant and anti-diabetic activity of ethanolic extracts of Andrographis echioides and Andrographis paniculata. Andrographis echioides and Andrographis paniculata were collected from a local farm. In vitro antioxidant activity was assessed by the potential of Piperine, Lupeol, beta sitosterol; DPPH free radical scavenging assay was performed by Liyana Pathirana and Shahidi method. In vitro anti-diabetic activity was assessed by alpha amylase inhibitory activity and alpha glucosidase inhibitory activity. The data were analysed by one-way-ANOVA to check the statistical significance among the groups and considered at the levels of p<0.05. Both the ethanolic extracts of Andrographis echioides and Andrographis paniculata showed significant antioxidant and anti-diabetic potential in a dose-dependent manner (100-500µg) and can be used as potential antidiabetic agents. Similar to antioxidant potential, Andrographis paniculata exhibited an increased anti-diabetic potential compared to Andrographis echioides. Data shows that the ethanolic extracts of Andrographis echioides and Andrographis paniculata possessed antioxidant and anti-diabetic activity and hence our present findings conclude that both plants can be considered for the development of natural drugs for the management of diabetes.     

加拿大-西北大西洋地区掌形藻的种群遗传结构与动态变化

探讨古气候波动(如更新世末期冰期)对典型生物的时空分布和有效种群大小变动的影响是生物地理学和进化遗传学的重要研究课题.本文利用线粒体cox2-3序列和RAPD两种分子标记,对分布于加拿大-西北大西洋地区8个地点(共138个个体)的掌形藻(Palmaria palmata)进行谱系地理学研究,试图阐明当更新世冰期来临时掌形藻如何衍生出适应性的进化机制,并形成当前的地理分布格局.结果表明,线粒体cox2-3间区序列共检测出11个单倍型,其中1个单倍型(C3)在所有种群中都有分布,并位于星状基因谱系的中心位置,可认为是祖先单倍型.St.Lawrence湾内北部的两个种群多样性最高,与其他地理种群分化最明显,这与基于RAPD数据的STRUCTURE聚类分析结果相一致.根据掌形藻遗传多样性及其单倍型谱系结构特征,推测掌形藻在加拿大-西北大西洋沿岸存在多个冰期避难所.分子多态性分析(AMOVA)显示掌形藻的遗传变异主要来自种群内,而St.Lawrence湾和Fundy湾群组间的遗传变异较小.cox2-3序列的Bayesian skyline plots分析结果反映出掌形藻种群在加拿大-西北大西洋沿岸经历了轻微的种群扩张,时间大概在0.18-0.13百万年前.St.Lawrence湾和Fundy湾群组间的K2P遗传距离为0.2％,相应的分化时间大约在0.36百万年前.由此推测,更新世末期的冰期及间冰期是影响掌形藻种群结构及变动的重要古气候环境因子.     

Phyto-constituents profiling of Luffa echinata and in vitro assessment of antioxidant,anti-diabetic,anticancer and anti-acetylcholine esterase activities

Luffa echinata Roxb. is one of the neglected medicinal plants. It is an important source of bioactive metabolites and used in several Ayurvedic formulations. In the present analysis, mature leaves and fruits were extracted with acetone, ethanol, acetonitrile, methanol and water. Phytochemicals like total phenolic (TPC), flavonoid (TFC), tannin (TTC), alkaloid (TAC) and terpenoid (TTEC) content were analysed. Further, antioxidant (AOX) activities like 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, 2,2′-azino-bis-(3-ethyl) benzothiazoline-6-sulfonic acid (ABTS) radical scavenging, metal chelating activity (MC), ferric reducing antioxidant power (FRAP) and phosphomolybdenum assay (PMA) were studied. Highest TPC and TFC (189.57 ± 1.9 mg TAE/g extract, 30.48 ± 0.7 mg CE/g extract, respectively) were reported from acetone extract of the leaves. Ethanolic fruit extract showed the highest TTC (13.79 ± 0.2 mg CE/g extract). Acetone and acetonitrile fruit extract revealed maximum TTEC (602.79 ± 3.5 mg UAE/g extract) and moderate TAC (19.96 ± 0.9 mg GE/g extract), respectively. In AOX, highest DPPH (50.52 ± 0.03 mg AAE/g extract) and ABTS (26.78 ± 0.03 mg TE/g extract) radical scavenging reported in methanolic extract of fruit; however, acetone extract of leaf showed highest FRAP (376.89 ± 1.95 mg Fe(II)/g extract) and PMA (326.54 ± 4.73 mg AAE/g extract). In contrast, aqueous extract of leaf and fruit revealed highest metal chelating activity (41.67 ± 0.49 mg EDTA/g extract). In anti-diabetic studies, acetonitrile extract of leaves and fruits exhibited appreciable inhibition of α-amylase (83.33%) and α-glycosidase (77.42%) enzymes. Similarly, acetyl cholinesterase (AChE) inhibition was highest in water (88.91%) and acetone (81.87%) extracts of leaf and fruits. Fruit extracts showed potent anticancer activity against breast (MCF-7) and colon (HT-29) cancer cell lines (LC₅₀ 329.36 and 385.17 µg/mL, respectively). RP-HPLC analysis revealed highest cucurbitacin B (CuB) (196.24 ± 1.4 mg/g DW), followed by cucurbitacin I (CuI) and cucurbitacin E (CuE) in the fruits (57.14 ± 4.9 and 2.03 ± 0.03 mg/g DW, respectively). RP-HPLC analysis of extracts revealed presence of gallic acid (GA), catechin (CA), vanillic acid (VA), chlorogenic acid (CHLA) and coumaric acid (COA), in which highest GA found in the fruits (1.26 ± 0.07 mg/g DW). Liquid chromatography and mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC–MS) analysis revealed presence of bioactive compounds from various groups. Based on the present findings, it was revealed that the fruit and leaf of L. echinata can be used as potent bioresource for natural antioxidants, anti-diabetic, and anticancer drug.     

Use of enzymatic cell wall degradation for improvement of protein extraction from Chondrus crispus,Gracilaria verrucosa and Palmaria palmata

The effect of polysaccharidases (κ-carrageenase, β-agarase, xylanase, cellulase) on the protein extraction from three rhodophytes has been studied. The kinetic parameters (apparent V _m, apparent K _m) and the optimum activity conditions (pH, temperature) of each enzyme were determined by using pure substrates. All the tested enzymes possess Michaelis Menten mechanism with estimated substrate saturating concentrations of 8 000 mg l⁻¹(carrageenan) for κ-carrageenase, 8 000 mg l⁻¹ (agar) for β-agarase, 5000 mg l⁻¹ (xylane) for β-xylanase and 6 000 mg l⁻¹ (carboxymethylcellulose) for cellulase. The optimum activity conditions are pH 6.5–6.8 at 45°C for carrageenase, pH 6–6.5 at 55°C for agarase, pH 5 at 55°C for xylanase and pH 3.8 at 50°C for cellulose. Different alga/enzymes couples (κ-carrageenase/Chondrus crispus, β-agarase/Gracilaria verrucosa, β-xylanase/Palmaria palmata) were tested under the optimum activity conditions. Alga/cellulase + specific enzyme (e.g. Chondrus crispus/carrageenase + cellulase) systems were also studied at the optimum activity conditions of a specific enzyme (e.g. carageenase). The use of the only cellulose was also tested on each alga. Except for Palmaria palmata, the highest protein yields were observed with the procedures using cellulase coupled with carrageenase or agarase for an incubation period limited to 2 h. The Chondrus crispus/carrageenase + cellulose and Gracilaria verrucosa/agarase + cellulase systems gave ten-fold and three-fold improvements, respectively, in protein extraction yield as compared to the enzyme-free blank procedure. The combined action of xylanase and cellulose on protein extraction from Palmaria palmata does not significantly improve protein yield. The best overall protein yield for P. palmata is for P. palmata/xylanase with a 14-h incubation time. This study shows the interest in the use of a polysaccharidase mixture for improving protein extractibility from certain rhodophytes. This biotechnology approach, adapted from procedures for protoplast production or enzymatic liquefaction of higher plants, could be tested as an alternative method to obtain proteins from seaweeds of nutritional interest.     

In vitro propagation of Caralluma tuberculata and evaluation of antioxidant potential

Present study describes rapid in vitro propagation of Caralluma tuberculata, a traditional medicinal plant, and antioxidant potential of calli and plants extracts. The highest callus induction rate (93.3%) with maximum weight of calli 5.2 g was achieved from shoot tip explants on MS medium supplemented with 9.04 μM 2,4-D and 4.44 μM BA. The maximum shoot induction rate (71.1%) with mean number of shoots 3.66 ± 1.53 and 4.6 cm average shoot length was observed on 13.32 μM BA, 4.52 μM 2,4-D and 2.89 μM GA3 appended in MS medium. The developed shoots were best rooted in the presence of 5.07 μM IAA with 3.0 ± 0.15 roots per plantlet. The plants were successfully acclimatized under in vivo conditions. The plants and calli extracts exhibited good antioxidant activities, however, plant extract activities were more pronounced. The phenolic compounds in plant and calli extracts were 0.16% and 0.057%, respectively. While the flavonoids were 0.092% in plant and 0.039% in calli extract. Total Phenolics, flavonoids; DPPH radical scavenging activity and reducing power potential distributed among different fractions depending upon polarity of the solvent. The highest DPPH scavenging activity and reducing power was exhibited by water fractions; 4.95 mg/mL and 0.729 OD at 10 mg/mL, respectively. The micropropagation protocol can be successfully used for large-scale multiplication and conservation of germplasm of this threatened plant. Furthermore, antioxidant value describes importance of this valuable plant as food and medicine.     

Impact of temperature and cooking time on the physicochemical properties and sensory potential of seaweed water extracts of Palmaria palmata and Saccharina longicruris

Journal of Applied Phycology - The growing world population, global ecological awareness, and the desire to have alternatives to animal proteins, as well as the need for a diet that is tasty,...     

Bioremediation potential of Chondrus crispus (Basin Head) and Palmaria palmata: effect of temperature and high nitrate on nutrient removal

To evaluate the nutrient removal capabilities of two red macroalgae, apical blades were cultured in the lab for 4?weeks at either 6, 10, or 17°C and nitrate at either 30 or 300?μM, typical of the seasonal range of conditions at a land-based Atlantic halibut farm. Stocking density was 2.0?g?L^?1, irradiance 125?μmol?photons?m^?2?s^?1, photoperiod 16:8 (L:D), and nitrogen to phosphorus ratio 10:1. For both species, the highest growth rate was at 300?μM NO ₃ ^? with Palmaria palmata growing fastest at 6°C, 5.8%?day^?1, and Chondrus crispus growing best at 17°C, 5.5%?day^?1. Nitrogen and carbon removal by P. palmata was inversely related to temperature, the highest rate at 6°C and 300?μM NO ₃ ^? of 0.47?mg N and 6.3?mg C per gram dry weight per day. In contrast, C. crispus removal of N was independent of temperature, with mean removal of 0.49?mgN?gDW^?1?day^?1 at 300?μM NO ₃ ^? . The highest carbon removal by C. crispus was 4.4?mgC?gDW^?1?day^?1 at 10°C and 300?μM nitrate, though not significantly different from either 6 or 17°C and 300?μM nitrate. Tissue carbon:nitrogen ratios were >20 in both species at 30?μM nitrate, and all temperatures indicating nitrogen limitation in these treatments. Phycoerythrin content of P. palmata was independent of temperature, with means of 23.6?mg?gFW^?1 at 300?μM nitrate. In C. crispus, phycoerythrin was different only between 6°C and 17°C at 300?μM nitrate, with the highest phycoerythrin content of 12.6?mg?gFW^?1 at 17°C. Morphological changes were observed in P. palmata at high NO ₃ ^? concentration as curling of the fronds, whilst C. crispus exhibited the formation of bladelets as an effect of high temperature.     

Meristem clusters in cortical layer of thallus cells of the cultured red alga Palmaria palmata

For the first time somatic spotlike formations of 1.5 mm in diameter and height up to 0.5 mm were revealed in thalli of the red alga Palmaria palmata reared in an aerated stirred culture. It was determined that some cortical cells of the thallus are able to divide in the periclinal and anticlinal directions forming spots. Deep freezing and subsequent thawing of thalli showed that the cortical cells of spots were meristematic cells. In certain conditions they enabled the formation of prolifications, which germinated plantlets. These clusters of meristem tissue in the cortical layer of cells of the thallus of P. palmata, which were formed in the culture as in nature, function as growth cells facilitating growth of thalli in thick and natural “planting material” formed upon thalli fragmenting after their freezing in the winter season.     

Environmental conditions influence on the physicochemical properties of wild and cultivated Palmaria palmata in the Canadian Atlantic shore

Seaweeds are a promising biomass resource that contain proteins with high potential for sustainable exploration. Palmaria palmata, one of the main red seaweeds of the Canadian coast, has a high protein content and much interest as an ingredient. Understanding the associations between environmental conditions and P. palmata color and chemical composition is of paramount importance to predict optimum harvesting conditions and thus increase its value. This study investigated the influence of environmental conditions on the composition and color of wild and cultivated P. palmata. Important changes in these parameters were found for P. palmata harvested in the subarctic Canadian transition zone, depending on the harvesting site/month. A marked increase in carbohydrates and decrease in ashes content (up to 2-fold) were observed from June to October, while photosynthetically active radiation (PAR) values have decreased. These associations suggest that wild P. palmata is shade acclimated to the Gulf of Saint Lawrence region. Maximum protein content was found for samples in June and was especially higher for samples from Grande-Rivière. Samples were intensely colored in June, possibly related to the higher protein content found in this month. Although several intricate factors seem to influence color development in this species, data from this study assist harvesting sites and period to maximise dark red color and avoid pigmentation degradation and paleness. In sum, these results may help indicate the best site/period to take commercial advantage of this species and orient future research on the multifactored relationships between environmental factors and macroalgae chemical composition and color.

     

用膨化柱填料的方法从红藻中规模分离纯化R-藻红蛋白

以Phenyl-sepharose作为柱填料,用streamline柱层析技术从红藻(Palmaria palmata (Lannaeus) Kuntze)中规模分离捕光色素蛋白--R-藻红蛋白.由于不是传统的从层析柱上方进样,而是用泵将样品从streamline层析柱的下方加样(从下至上),因而解决了用一般层析柱分离R-藻红蛋白时海藻抽提液中大量的粘性多糖堵塞层析柱的难题.用P.palmata粗提液上样后,分别用0.2 mol/L、 0.1 mol/L和0.05 mol/L的(NH4)2SO4溶液从相反的方向(即从上到下)洗脱层析柱,发现这些洗脱液中的藻红蛋白纯度已经较高.然后将洗脱液透析去盐,用阴离子交换柱层析(Q-sepharose)进一步纯化.经过这两次柱层析后,R-藻红蛋白的纯度(OD565/OD280)超过3.5,高于一般认可的R-藻红蛋白的纯度标准3.2;产率为每克冷冻P.palmata可纯化0.122 mg高纯度的R-藻红蛋白,比使用一般分离方法的产率要高10倍.这些结果表明,使用本文报道的方法纯化藻红蛋白,将会使作为生化检测试剂的藻红蛋白市场价格大幅度下降.     

Tank cultivation of the red alga Palmaria palmata: Effects of intermittent light on growth rate, yield and growth kinetics

Tank cultivation of marine macroalgaeinvolves air-agitation of the algal biomassand intermittent light conditions,i.e.periodic, short light exposure of thethalli in the range of 10 s at the watersurface followed by plunging to low lightor darkness at the tank bottom andrecirculation back to the surface in therange of 1–2 min. Open questions relate toeffects of surface irradiance on growthrate and yield in such tumble cultures andthe possibility of chronic photoinhibitionin full sunlight. A specially constructedshallow-depth tank combined with a darktank allowed fast circulation times ofapproximately 5 s, at a density of 4.2 kgfresh weight (FW) m^-2s^-1. Growthrate and yield of the red alga Palmaria palmata increased over a widerange of irradiances, with no signs ofchronic photoinhibition, up to agrowth-saturating irradiance ofapproximately 1600 mol m^-2s^-1 in yellowish light supplied by asodium high pressure lamp at 16 h light perday. Maximum growth rate ranged at 12% FWd^-1, and maximum yield at 609 gFW m^-2 d^-1. This shows that highgrowth rates of individual thalli may bereached in a dense tumble culture, if highsurface irradiances and short circulationtimes are supplied. Another aspect ofintermittent light relates to possiblechanges of basic growth kinetics, ascompared to continuous light. For thispurpose on-line measurements of growth ratewere performed with a daily light reductionby 50% in light-dark cycles of 1, 2 or 3min duration during the daily light period.Growth rates at 10 °C and 50 molphoton m^-2 s^-1 dropped in allthree intermittent light regimes duringboth the main light and dark periods andreached with all three periodicitiesapproximately 50% of the control , with noapparent changes in basic growth kinetics,as compared to continuous light.     

用膨化柱填料的方法从红藻中规模分离纯化R-藻红蛋白(英)

以Phenyl_sepharose作为柱填料 ,用streamline柱层析技术从红藻 (Palmariapalmata (Lannaeus)Kuntze)中规模分离捕光色素蛋白———R_藻红蛋白。由于不是传统的从层析柱上方进样 ,而是用泵将样品从streamline层析柱的下方加样 (从下至上 ) ,因而解决了用一般层析柱分离R_藻红蛋白时海藻抽提液中大量的粘性多糖堵塞层析柱的难题。用P .palmata粗提液上样后 ,分别用 0 .2mol/L、0 .1mol/L和 0 .0 5mol/L的 (NH4) 2 SO4溶液从相反的方向 (即从上到下 )洗脱层析柱 ,发现这些洗脱液中的藻红蛋白纯度已经较高。然后将洗脱液透析去盐 ,用阴离子交换柱层析 (Q_sepharose)进一步纯化。经过这两次柱层析后 ,R_藻红蛋白的纯度 (OD565/OD2 80 )超过 3.5 ,高于一般认可的R_藻红蛋白的纯度标准 3.2 ;产率为每克冷冻P .palmata可纯化 0 .12 2mg高纯度的R_藻红蛋白 ,比使用一般分离方法的产率要高 10倍。这些结果表明 ,使用本文报道的方法纯化藻红蛋白 ,将会使作为生化检测试剂的藻红蛋白市场价格大幅度下降。     

In vitro cell-based assays for evaluation of antioxidant potential of plant-derived products

Several plant-derived compounds have been screened by antioxidant assays, but many of these results are questionable, since they do not evaluate the pharmacologic parameters. In fact, the development of better antioxidants stills a great challenge. In vitro cell-based assays have been employed to assess the antioxidant effect of various compounds at subcellular level. Cell-based assays can also reveal compounds able to enhance the antioxidant pathways, but without direct radical scavenging action (which could not be detected by traditional assays). These methodologies are general of easy implementation and reproducible making them suitable for the early stages of drug discovery. Hydrogen peroxide, a nonradical derivative of oxygen, can be employed as an oxidative agent in these assays due its biochemical properties (presence of all biological systems, solubility) and capacity to induce cell death. Truthfully, if their limitations are understood (such as difference on cell metabolism when in in vitro conditions), these cell-based assays can provide useful information about the pathways involved in the protective effects of phytochemicals against cell death induced by oxidative stress, which can be exploited to develop new therapeutic approaches.     

Effects of temperature on the photoreactivation of ultraviolet-b–induced dna damage in Palmaria palmata (Rhodophyta)

The accumulation of DNA damage (thymine dimers and 6-4 photoproducts) induced by ultraviolet-B radiation was studied in Palmaria palmata (L.) O. Kuntze under different light and temperature conditions, using specific monoclonal antibodies and subsequent chemiluminescent detection. Both types of damage were repaired much faster under ultraviolet-A radiation (UVAR) plus photosynthetically active radiation (PAR) than in darkness, which indicates photoreactivating activity. At 12° C, all thymine dimers were repaired after 2 h irradiation with UVAR plus PAR, whereas 6-4 photoproducts were almost completely repaired after 4 h. After 19 h of darkness, almost complete repair of 6-4 photoproducts was found, and 67% of the thymine dimers were repaired. In a second set of experiments, repair of DNA damage under UVAR plus PAR was compared at three different temperatures (0, 12, and 25° C). Again, thymine dimers were repaired faster than 6-4 photoproducts at all three temperatures. At 0° C, significant repair of thymine dimers was found but not of 6-4 photoproducts. Significant repair of both thymine dimers and 6-4 photoproducts occurred at 12 and 25° C. Optimal repair efficiency was found at 25° C for thymine dimers but at 12° C for 6-4 photoproducts, which suggests that the two photorepair processes have different temperature characteristics.     

Bioremediation potential of Palmaria palmata and Chondrus crispus (Basin Head): effect of nitrate and ammonium ratio as nitrogen source on nutrient removal

Palmaria palmata and Chondrus crispus were grown for 4 weeks in 1-L flasks at 10 °C to evaluate nutrient uptake and their potential application as nutrient biofilters in effluent from finfish culture. For greatest bioremediation benefit within an integrated system, we conclude that a seaweed biofilter using these species should be placed prior to bacterial biofiltration for exposure to greater proportions of ammonium than nitrate, though it is apparent that the productivity of both species is not influenced by the nitrogen source. Five combinations of ammonium– and nitrate–nitrogen were compared, each with a total N concentration of 300 μM (300:0, 270:30, 150:150, 30:270, 0:300). Molar nitrogen/phosphorus ratio was 10:1. The maximum growth rates were 8.9 and 6.0 % per day for P. palmata and C. crispus, respectively. For both species, the total nitrogen uptake was highest at 300 μM ammonium, 4.46 mgN gDW^?1 day^?1 for P. palmata and 3.40 mg?N? g?DW^?1?day^?1 for C. crispus. Over a 24-h period, 23–37 % of the available nitrate and 91–100 % of the available ammonium were taken up by P. palmata. In the same period, C. crispus took up 55–87 % of available nitrate and 89–100 % of ammonium. Tissue N in P. palmata was highest (4.1 %) at 270 and 300 μM ammonium, while the nitrogen source did not have a significant effect on the tissue N of C. crispus (mean of 4.6 %).     

In vitro and in vivo assessment of the antioxidant activity of melatonin and related indole derivatives

Effects of melatonin and some structurally related indole compounds were studied by in vitro methods such as (i) an inhibition of the hyaluronic acid degradation and (ii) a standard lipid peroxidation assay. In vivo approach was based on the alloxan model of hyperglycaemia. Reduction of the viscosity of a hyaluronic acid solution in the reaction mixture was inhibited by tryptamine (91% inhibition), as well as by indole-3-carboxylic acid and indomethacin (80% and 77% inhibition, respectively). Lipid peroxidation with tert-butyl hydroperoxide as a source of radicals was followed by the formation of thiobarbituric acid reactive substances. Tested drugs inhibited lipid peroxidation in the order: tryptamine (59%) > indole-2-carboxylic acid (38%) > indomethacin (26%) > melatonin and indole-3-carboxylic acid (13%). In vivo, alloxan-induced hyperglycaemia was reduced in mice pretreated with drugs tested. The highest protective effect was observed with indomethacin (52% inhibition), followed by tryptamine and melatonin (18% and 16% inhibition, respectively).     

Phylogeographic analysis of the red seaweed Palmaria palmata reveals a Pleistocene marine glacial refugium in the English Channel

Phylogeography has provided a new approach to the analysis of the postglacial history of a wide range of taxa but, to date, little is known about the effect of glacial periods on the marine biota of Europe. We have utilized a combination of nuclear, plastid and mitochondrial genetic markers to study the biogeographic history of the red seaweed Palmaria palmata in the North Atlantic. Analysis of the nuclear rDNA operon (ITS1-5.8S-ITS2), the plastid 16S-trnI-trnA-23S-5S, rbcL-rbcS and rpl12-rps31-rpl9 regions and the mitochondrial cox2-3 spacer has revealed the existence of a previously unidentified marine refugium in the English Channel, along with possible secondary refugia off the southwest coast of Ireland and in northeast North America and/or Iceland. Coalescent and mismatch analyses date the expansion of European populations from approximately 128,000 BP and suggest a continued period of exponential growth since then. Consequently, we postulate that the penultimate (Saale) glacial maximum was the main event in shaping the biogeographic history of European P. palmata populations which persisted throughout the last (Weichselian) glacial maximum (c. 20,000 BP) in the Hurd Deep, an enigmatic trench in the English Channel.     

The effect of ultraviolet radiation on ultrastructure and photosynthesis in the red macroalgae Palmaria palmata and Odonthalia dentata from Arctic waters

In radiation exposure experiments, the effects of mild artificial UV conditions (4.7 W m(-2) UV-A and 0.20 W m(-2) UV-B) plus PAR (25 - 30 micromol photons m(-2) s(-1)) on photosynthesis and ultrastructure of two red algal species from the Arctic have been investigated. While Palmaria palmata was collected from the upper sublittoral of the Kongsfjord (Spitsbergen, Norway), Odonthalia dentata represents a typical deepwater species at this high latitude. After 6 h and 24 h exposure to UV, chlorophyll fluorescence of photosystem II (PS II efficiency, F(v)/F(m)) was determined as an indicator for photosynthetic performance, and the relative electron transport rates in response to increasing photon fluence rates were recorded. In parallel, tissue samples were prepared for the transmission electron microscope (TEM). The presented data clearly demonstrate a significant influence of experimental UV on photosynthetic performance. Photochemical efficiency of PS II of both red algal species decreased to about one third of the initial value under UV. While the PI (photosynthesis-irradiance) curve parameter alpha (positive slope at limiting photon fluence rates) strongly decreased in both plants, the I(k) values (initial value of light-saturated photosynthetic rate) increased 3 - 5-fold. Palmaria palmata does not appear to become photoinhibited under these conditions, but O. dentata showed strong photoinhibition. The TEM results demonstrated that the photosynthetic apparatus was severely influenced by UV in both species, because thylakoid membranes appeared wrinkled, lumen dilatations occurred, and the outer membranes were altered. Moreover, mitochondria were damaged, and numerous plasma vesicles were observed. In conclusion, both red algal species are negatively affected by UV on the physiological and ultrastructural level. However, the differences in photoinhibitory responses correlate well with the vertical depth zonation of P. palmata and O. dentata in the Arctic Kongsfjord.