Adventitious Bud Formation from Bulb-scale Explants of Lilium speciosum Thunb. in vitro Effects of aminoethoxyvinyl-glycine, 1-aminocyclopropane-1-carboxylic acid,and ethylene

Several representatives of marine brown macroalgae (Phaeophyceae) including Fucus serratus L., Fucus spiralis L. and Fucus vesiculosus L. as well as Laminaria digitata (Huds.) Lamour., Laminaria hyperborea (Gunn.) Foslie and Laminaria saccharina (L.) Lamour. were investigated with particular regard to features of biosynthesis of the storage product mannitol. The respective catalytic system involved in the last step of mannitol formation, mannitol-1-phosphate dehydrogenase, appears to be a cytoplasmic enzyme as may be judged from the degree of correlation with the chloroplast key enzyme ribulose-1,5-bisphosphate carboxylase in different tissues of Laminaria digitata and Laminaria saccharina. Activity of mannitol-1-phosphate dehydrogenase in vitro is not affected by mannitol-l-phosphate or free mannitol, suggesting that mannitol biosynthesis in vivo) is mainly controlled by the environment and/or developmental stage. Certain inorganic ions such as NO₃^- (including K⁺) exert a strong influence on the activity of mannitol1-phosphate dehydrogenase thus suggesting that the intracellular pools of stored NO₃^- and mannitol are confined to spatially separated cellular compartments.     

Active carbon uptake in Laminaria digitata and L. saccharina (Phaeophyta) is driven by a proton pump in the plasma membrane

Mechanisms for inorganic carbon acquisition in Laminaria digitata (Hudson) Lamour and L. saccharina (L.) Lamour from the Swedish west coast were studied in pH-drift experiments, using several inhibitors for different types of carbon uptake across the cell membrane. Throughout the experiments total carbon decreased in concert with a pH increase while alkalinity stayed relatively stable. Addition of acetazolamide had a strong inhibitory effect on the carbon uptake rate in L. digitata and the anion exchange protein inhibitor DIDS had a small inhibitory effect above pH 9.5. These results indicate that carbon uptake in L. digitata depends on the presence of an external carbonic anhydrase while direct bicarbonate uptake may contribute at high pH. These two mechanisms have previously been shown to occur in L. saccharina. We show that two inhibitors of H⁺-ATPases, vanadate and erythrosin B, also decreased carbon uptake rates in both Laminaria species. The effect of erythrosin B was immediate and it probably acts on the outside of the cell membrane. Contrarily, vanadate needs to be transported into the cell, where it competes with the phosphate from ATP for the aspartic acid phosphorylation site on the plasma membrane P-type H⁺-ATPase. Therefore, 1–2 h of pH drift were usually required before an inhibitory effect became apparent. Additional experiments with P-enriched and P-starved L. saccharina corroborated this process. Based on these results we suggest that the investigated Laminaria species, besides external carbonic anhydrase and DIDS-sensitive anion exchange, also possess a mechanism for the active uptake of carbon, which is dependent on plasma membrane P-type H⁺-ATPase activity. This paper also reports on the buffering capacity of the inhibitors when used in natural seawater, an aspect that has been neglected in previous studies.     

Longitudinal profiles of carbon dioxide fixation capacities in marine macroalgae

Fucus serratus L., Fucus spiralis L., and Fucus vesiculosus L. (Fucales, Phaeophyceae) as well as Laminaria digitata (Huds.) Lamour., Laminaria hyperborea (Gunn.) Fosl., and Laminaria saccharina (L.) Lamour. (Laminariales, Phaeophyceae) have been investigated for the distribution of enzymic CO₂ fixation capacities via phosphoenolpyruvate carboxykinase (EC 4.1.1.32) (PEP-CK) and via ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) (RubP-C) in different regions of the thalli. The maximum of PEP-CK activity is found to be confined to the growing regions of the algae, while the activity of RubP-C achieves its highest values in the entirely differentiated parts of the fronds. These findings are confirmed by the results of photosynthetic and light-independent (dark) carbon assimilation as determined by in vivo ¹⁴CO₂ fixation. The physiological significance of these differential patterns of carboxylation patterns is discussed with respect to the ontogenetic stage and the chemical constitution of the different thallus parts.     

TRANSLOCATION OF IODINE IN LAMINARIA SACCHARINA(PHAEOPHYTA)1

Long-distance translocation of ¹²⁵I in Laminaria saccharina (L.) Lamour. followed a “source to sink” pattern. When the source of ¹²⁵I was placed on the distal mature part of the blade, the translocation was unidirectional, basipetal and directed towards the meristematic region at the blade-stipe junction. When the source was placed directly at the meristem there was no movement of label distal to the meristem. The velocity of¹²⁵I transport ranged from 2 to 3.5 cm · h^?1. The anion I^? seemed to be the only species of¹²⁵I transported. An assay of iodine content in different parts of L. saccharina plant showed much higher levels of iodine in the meristem, stipe and holdfast than in the blade. This distribution concurs well with the pattern of I^? translocation.     

Cytological Observations on Three British Species of Laminaria : a Preliminary Report

Mitotic divisions in male and female gametophytes and in youngsporelings of Laminaria digitata, L. ochroleuca, and L. saccharinafrom Plymouth follow a normal course and do not show the ‘endomitoticmultiplication’ of chromosomes described by Walker inL. digitata from Scotland. Chromosome counts on all three speciesalmost invariably give a value for n between 27 and 31, anda definite count of this order will probably emerge.     

Haloperoxidase activities in Arctic macroalgae

Haloperoxidase activities were assayed in 21 species of Arctic green, red and brown macroalgae collected in the Kongsfjord at Ny-Ålesund (Svalbard). The enzymes were specific for bromide and/or iodide, but not for chloride. Highest bromoperoxidase activities were found in the brown seaweads Laminaria saccharina and L. digitata, whereas highest iodoperoxidase activities were measured in the green species Acrosiphonia sonderi and Enteromorpha compressa. Optimum pH for bromination ranged between pH 4 and 7.     

RESTRICTION ENDONUCLEASE ANALYSIS OF RIBOSOMAL DNA SEQUENCE VARIATION IN LAMINARIA (PHAEOPHYTA)1

The taxonomy and evolutionary relationships of species in the genus Laminaria are poorly understood. Previous studies have demonstrated significant plasticity of morphological characters used to describe taxa, and interfertility has been reported among putative species. We analyzed nuclear ribosomal DNA (rDNA) sequence variation in eight species of Laminaria (L. agardhii Kjell., L. digitata (Huds.) Lamour., L. groenlandica Rosenv. [sensu Druehl 1968], L. longicruris De la Pyl., L. longipes Bory, L. saccharina (L.) Lamour., L. setchellii Silva, and L. yezoensis Miyabe) to elucidate evolutionary relationships in this genus. Restriction maps were constructed using a small subunit rDNA probe from Costaria costata (Turn.) Saunders, an rDNA repeat from the nematode Caenorhabditis elegans, and 11 hexameric restriction endonucleases in an annealing analysis of genomic DNA. Laminaria rDNA restriction maps were compared to each other and to that of the outgroup taxon, C. costata. rDNA restriction maps of Laminaria species and C. costata were similar. Restriction fragment length polymorphisms mapped to both the coding regions and the nontranscribed spacer of rDNA. Laminaria species were distinguished with this method. The restriction maps of L. agardhii, L. saccharina, and L. longicruris were identical, supporting a previous hypothesis that these species are conspecific. Comparison of restriction maps of Laminaria species suggested that the generic subdivision of Sections Simplices and Digitatae may be invalid.     

Protoplast regeneration from gametophytes and sporophytes of some species in the order Laminariales (Phaeophyceae)

Summary Protoplasts were isolated from sporophytes and from gametophyte cultures of several species in the order Laminariales. For each example, the isolation and culture procedures were investigated systematically, to identify conditions leading to plant regeneration. After dedifferentiation through a filamentous stage, protoplasts isolated from adultLaminaria saccharina sporophytes regenerated polystichous bladelets. In contrast, cells isolated fromLaminaria digitata sporophytes proved recalcitrant in culture, except when the donor plants were undifferentiated sporelings. The most critical factors for protoplast development were the origin of explants, the osmoticum used for cell isolation, cultivation in plain seawater, and the absence of stress during the first two weeks of culture. We also found that protoplast isolation from the sporophytes of members of the Laminariales results in the release of hydrogen peroxide, up to 5–120 μM final concentration in the macerating medium, a characteristic which may be related to protoplast recalcitrance. Protoplasts isolated from the gametophytic phase readily regenerated into normal gametophytes, capable of gametogenesis and producing sporophytes by fertilization.     

Isolated, distal blade discs of the brown alga Laminaria digitata form sorus, but not discs, near to the meristematic transition zone

Blade discs of vegetative thalli of Laminaria digitata (Huds.) Lamour. from Helgoland (North Sea) cut at 5–15 cm distance from the blade/stipe transition, formed sorus in the laboratory after 7–12weeks, 5 months earlier than whole fronds in the field. Sorus formation occurred in a broad range of daylength regimes or temperatures, at 8–16 h light pe rday and 6–12 ^°C. No sorus was developed during three months by meristematic blade discs cut from the lowermost 3 cm portion of the blade, nor from whole thalli cultured in parallel to isolated blade discs. These findings point to the possible existence of sporulation inhibitors produced by the laminarian meristem. This revised version was published online in August 2006 with corrections to the Cover Date.     

Microchemical imaging of iodine distribution in the brown alga Laminaria digitata suggests a new mechanism for its accumulation

Brown algal kelp species are the most efficient iodine accumulators among all living systems, with an average content of 1.0% of dry weight in Laminaria digitata. The iodine distributions in stipe and blade sections from L. digitata were investigated at tissue and subcellular levels. The quantitative tissue mapping of iodine and other trace elements (Cl, K, Ca, Fe, Zn, As and Br) was provided by the proton microprobe with spatial resolutions down to 2 μm. Chemical imaging at a subcellular resolution (below 100 nm) was performed using the secondary ion mass spectrometry microprobe. Sets of samples were prepared by both chemical fixation and cryofixation procedures. The latter prevented the diffusion and the leaching of labile inorganic iodine species, which were estimated at around 95% of the total content by neutron activation analysis. The distribution of iodine clearly shows a huge, decreasing gradient from the meristoderm to the medulla. The contents of iodine reach very high levels in the more external cell layers, up to 191 ± 5 mg g⁻¹ of dry weight in stipe sections. The peripheral tissue is consequently the main storage compartment of iodine. At the subcellular level, iodine is mainly stored in the apoplasm and not in an intracellular compartment as previously proposed. This unexpected distribution may provide an abundant and accessible source of labile iodine species which can be easily remobilized for potential chemical defense and antioxidative activities. According to these imaging data, we proposed new hypotheses for the mechanism of iodine storage in L. digitata tissues. In memory of Dr. Charles Mioskowski, “Miko,” who died on 2 June 2007.     

SOME FINE STRUCTURAL OBSERVATIONS ON DEVELOPING AND MATURE SIEVE ELEMENTS IN THE BROWN ALGA LAMINARIA SACCHARINA

The differentiation of sieve elements from inner cortical cells of the stipe of Laminaria saccharina (L.) Lamour. involves the development of a well-structured protoplast and an end wall possessing evenly spaced pores which are visualized by electron microscopy. The protoplast consists of organelles which are commonly found in brown algal cells, including nuclei, cup- or horseshoe-shaped chloroplasts, dictyosomes, mitochondria, and ER. Mitochondria and clusters of small vacuoles, presumably redistributed by the surging effect which occurs in sieve elements, were routinely observed in the vicinity of the end wall. Chloroplasts were seen in progressively degenerated states in older sieve elements, yet nuclei were determined to be non-necrotic. Numerous pores along the end walls interconnect adjacent sieve elements. Each pore is traversed by a strand of cytoplasm and surrounded by plasmalemma. The pores are open and possess no callose. In this paper the sieve element ultrastructures of L. saccharina are compared to those in L. groenlandica, Alaria marginata, Nereocystis lutkeana and Macrocystis pyrifera, and a possible phylogenetic specialization of sieve elements is presented in table form and discussed.     

Distinct patterns of nitrate reductase activity in brown algae: light and ammonium sensitivity in Laminaria digitata is absent in Fucus species1

Fucus and Laminaria species, dominant seaweeds in the intertidal and subtidal zones of the temperate North Atlantic, experience tidal cycles that are not synchronized with light:dark (L:D) cycles. To investigate how nutrient assimilation is affected by light cycles, the activity of nitrate reductase (NR) was examined in thalli incubated in outdoor tanks with flowing seawater and natural L:D cycles. NR activity in Laminaria digitata (Huds.) Lamour. showed strong diel patterns with low activities in darkness and peak activities near midday. This diel pattern was controlled by light but not by a circadian rhythm. In contrast, there was no diel variation in NR activity in Fucus serratus L., F. vesiculosus (L.) Lamour., and F. spiralis L. either collected directly from the shore or maintained in the outdoor tanks. In laboratory cultures, transfer to continuous darkness suppressed NR activity in L. digitata, but not in F. vesiculosus; continuous light increased NR activity in L. digitata but decreased activity in F. vesiculosus. Furthermore, 4 d enrichment with ammonium (50 μmol · L^?1 pulses), resulted in NR activity declining by >80% in L. digitata, but no significant changes in F. serratus. Seasonal differences in maximum NR activity were present in both genera with activities highest in late winter and lowest in summer. This is the first report of NR activity in any alga that is not strongly regulated by light and ammonium. Because light and tidal emersion do not always coincide, Fucus species may have lost the regulation of NR by light that has been observed in other algae and higher plants.     

OSMOTIC ADJUSTMENT IN LAMINARIA DIGITATA (PHAEOPHYTA) WITH PARTICULAR REFERENCE TO SEASONAL CHANGES IN INTERNAL SOLUTE CONCENTRATIONS1

Laboratory studies have indicated that Na⁺, K⁺ (together with Cl^? the presumed counter-ion to these cations), NO₃^? and mannitol represent the major cellular osmotica in Laminaria digitata (Huds.) Lamour. The cellular content of NO₃^? (together with a fraction of the K⁺ pool which acts as the counter-ion to NO₃^?) was found to be inversely proportional to that of mannitol, suggesting that L. digitata maintains a constant turgor by means of an isotonic substitution between these compounds. An analysis of the seasonal changes in solute content in an Arbroath (Scotland) population of L. digitata confirmed this hypothesis and indicated that the total pool of stored photosynthate was partitioned between the interconvertible carbohydrates mannitol and laminaran (which has a much lower osmotic potential than mannitol) depending on the size of the cellular pool of NO₃^?.     

Tauchuntersuchungen zur Vertikalverteilung der sublitoralen Helgoländer Algenvegetation

Zusammenfassung 1. Die Vertikalverteilung der makroskopischen Algen im Helgoländer Sublitoral wurde an fünf Tauchprofilen von insgesamt 7200 m Länge untersucht. Weitere Tauchgänge wurden durchgeführt, um auch seltenere Arten zu erfassen.2. Zwischen 0,5 und 1,5 m Tiefe bildenLaminaria digitata undL. saccharina eine geschlossene Vegetation, zwischen 1,5 und 4 mL. hyperborea. Mehrjährige Exemplare vonL. digitata undL. saccharina kommen nicht unterhalb von 3 m Tiefe vor,L. hyperborea wurde bis 8 m Tiefe gefunden.3. Insgesamt wurden von 1965 bis 1970 im Helgoländer Sublitoral 66 Algenarten bzw. nicht weiter identifizierte Gattungen gefunden (Tab. 2). 38 Arten kamen in mehr als acht der untersuchten 1232 Quadrate (25×25 cm) vor (Tiefenverteilung in Abb. 10). Die sublitorale Algenvegetation erstreckt sich bei Helgoland bis 15 m Tiefe. Durch Vergleich mit Daten von anderen Küsten wurden zwei Artengruppen herausgestellt, deren untere Tiefengrenzen einerseits im oberen, andererseits im unteren Drittel des Sublitorals zu finden sind (Tab. 5).

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Diving investigations on the vertical distribution of sublittoral algal vegetation near Helgoland

The vertical distribution of macroscopic sublittoral algae near the island of Helgoland (North Sea) has been investigated using theScuba diving technique.Laminaria digitata andL. saccharina occupy the depth range between 0.5 and 1.5 m (below mean low water of spring tides). TheL. hyperborea forest extends between 1.5 and 4 m depth. The deepest-growing specimens ofL. hyperborea have been recorded at 8 m depth, the deepest algae (encrusting forms) at 15 m. Some species are confined to the upper part of the sublittoral zone (e. g.Chondrus crispus, Dumontia incrassata, Ahnfeltia plicata, Polyides rotundus, Furcellaria fastigiata), while others penetrate to the lower part (e. g.Phycodrys rubens, Delesseria sanguinea, Brongniartella byssoides, Phyllophora crispa, Bryopsis plumosa).

     

Hydrogen Peroxide-Dependent Uptake of Iodine by Marine Flavobacteriaceae Bacterium Strain C-21

The cells of the marine bacterium strain C-21, which is phylogenetically closely related to Arenibacter troitsensis, accumulate iodine in the presence of glucose and iodide (I⁻). In this study, the detailed mechanism of iodine uptake by C-21 was determined using a radioactive iodide tracer, ¹²⁵I⁻. In addition to glucose, oxygen and calcium ions were also required for the uptake of iodine. The uptake was not inhibited or was only partially inhibited by various metabolic inhibitors, whereas reducing agents and catalase strongly inhibited the uptake. When exogenous glucose oxidase was added to the cell suspension, enhanced uptake of iodine was observed. The uptake occurred even in the absence of glucose and oxygen if hydrogen peroxide was added to the cell suspension. Significant activity of glucose oxidase was found in the crude extracts of C-21, and it was located mainly in the membrane fraction. These findings indicate that hydrogen peroxide produced by glucose oxidase plays a key role in the uptake of iodine. Furthermore, enzymatic oxidation of iodide strongly stimulated iodine uptake in the absence of glucose. Based on these results, the mechanism was considered to consist of oxidation of iodide to hypoiodous acid by hydrogen peroxide, followed by passive translocation of this uncharged iodine species across the cell membrane. Interestingly, such a mechanism of iodine uptake is similar to that observed in iodine-accumulating marine algae.     

RESPONSE OF LAMINARIA SACCHARINA (PHAEOPHYTA) GROWTH AND PHOTOSYNTHESIS TO SIMULTANEOUS ULTRAVIOLET RADIATION AND NITROGEN LIMITATION1

The brown macroalga Laminaria saccharina (L.) J. V. Lamour. was grown in large outdoor tanks at 50% ambient solar radiation for 3–4 weeks in July and August of 2000, 2001, and 2002, in either ambient or nitrogen (N)–enriched seawater and in either ambient light [PAR + ultraviolet radiation (UVR)] or ambient light minus UVR. Growth, N‐content, photosynthetic pigments, and RUBISCO content increased in N‐enriched seawater, indicating N‐limitation. UVR inhibited growth, but this inhibition was ameliorated by N‐enrichment. The response of growth to UVR could not be explained by changes in respiration and photosynthesis. Gross light‐saturated photosynthesis (P_max) remained unaffected by UVR but was significantly higher under N‐enrichment, as was dark respiration (R_d). UVR had no effect on pigments or N content. However, RUBISCO contents were low in the presence of UVR, reflecting the overall change in soluble cellular protein. Overall, our data indicate that the response to UVR in L. saccharina depends on other environmental factors, such as N, and these effects need to be considered when evaluating the response of macroalgae to increased UVR.     

Comparative studies on the nutrition of two species of abalone,Haliotis tuberculata Linnaeus and Haliotis discus hannai Ino I. Effects of algal diets on growth and biochemical composition

Summary

This study was conducted to examine the nutritional value of eight algal diets for two species of abalone, Haliotis tuberculata and Haliotis discus hannai, by measuring biochemical composition of the algae and relating this to feeding rate, growth and biochemical composition of the animals. Nutritional value of algal diets can be divided into three categories for each species of abalone. For H. tuberculata the best performance was on the mixed diet and Palmaria palmata intermediate was Alaria esculenta, Ulva lactuca and Laminaria digitata, and lowest growth was on Laminaria saccharina and Chondrus crispus. For H. discus hannai, best performance was on A. esculenta, P. palmata and the mixed diet; intermediate was on L. saccharina and L. digitata and lowest was on U. lactuca. It is generally accepted that high “balanced” levels of protein (>15%), lipid (3–5%) and carbohydrate (20–30%), with no detrimental substances in natural algae are essential for optimal growth performance of these abalone. The fact that A. esculenta, L. saccharina and U. lactuca had different dietary values for the two abalone species indicates specific nutritive requirements and/or digestive physiology. Overall, H. tuberculata grew faster, had higher food conversion efficiencies and muscle yield than H. discus hannai. Generally abalone fed on the highest category diets, had higher muscle yields and levels of protein, visceral lipids and muscle carbohydrate. Viscera and foot muscle are reservoirs for lipid and carbohydrate, respectively. The effect of algal diet on sexual maturation is similar to that on somatic growth.     

Peroxidase activity in the brown alga Laminaria digitata

Cell-free extracts of the brown alga Laminaria digitata catalyse the oxidation of o-dianisidine and of iodide, as well as the formation of iodoamino acids. The enzyme(s) requires hydrogen peroxide for these activities, which are strongly inhibited by cyanide and azide. It is suggested that the activity may be due to a haem-containing peroxidase which, in extracts, is strongly bound, possibly to alginate.     

Research note: Salinity tolerance of Arctic kelps from Spitsbergen

The effect of hypo‐ and hypersaline treatments on the effective quantum yield of photosystem II was comparatively studied with a pulse amplitude modulated fluorometer (PAM) in the brown algal species Alaria esculenta, Fucus distichus, Laminaria digitata, Laminaria solidungula, Saccharina latissima (formerly Laminaria saccharina) and Saccorhiza dermatodea collected in the Arctic Kongsfjorden (Spitsbergen). While the euryhaline F. distichus was not affected at all by salinities ranging from 5 to 60 psu, A. esculenta, S. latissima and L. solidungula exhibited under hyposaline conditions strong loss of pigments (bleaching) or even high mortality reflecting stenohaline features. In contrast to the latter species, L. digitata and S. dermatodea survived all salinities, but showed reduced photosynthetic activities at the lowest and highest salt treatments and hence, can be characterized as stenohaline‐euryhaline organisms. The data are discussed in terms of vertical zonation (eulittoral versus sublittoral habitat), in terms of interactive effects with other abiotic factors such as temperature and in terms of the species‐specific acclimation potential.