Temperature requirements for growth and maturation of the warm temperate kelp Eckloniopsis radicosa (Laminariales,Phaeophyta)

The annual kelp Eckloniopsis radicosa is distributed along Japanese coasts and occurs within the area with a February isotherm ranging 15–18°C and August isotherm ranging 25–28°C. In this study, the effects of temperature on the gametophyte growth and maturation, and the young sporophyte growth of E. radicosa were examined and the results are discussed in relation to the distribution of other warm‐adapted kelp species and the potential effects of climate change. The optimal temperature ranges for growth of male and female gametophytes were 23–27°C and 20–26°C, respectively. The upper survival temperature for gametophyte growth was 31°C for males and 30°C for females, respectively. The optimal temperature range for maturation of female gametophytes was ≤23°C. The optimal temperature range for growth of young sporophytes was 14–22°C. It was clarified that E. radicosa has the most warm‐adapted characteristics for growth and maturation of gametophytes among members of the Laminariales studied so far. The natural seawater temperature ranges during the growth and maturation seasons for gametophytes of E. radicosa, as well as the growth season for young sporophytes near to the northern and southern distribution limits (Izu‐Oshima: 14.9–24.5°C, Ichiki‐kushikino: 17.1–29.6°C), agreed with the experimentally determined temperature requirements. The warm‐adapted gametophyte stage and annual lifecycle are major factors enabling survival of E. radicosa in warm waters near tropical regions along the Japanese coast.     

Callus formation in Ecklonia cava Kjellman (Laminariales,Phaeophyta)

Explants from stipes and meristems of Ecklonia cava were incubated on six media under several culture conditions. Both stipe and meristem explants developed calluses three to six weeks after inoculation onto all media except AS PC-1. Calluses developed on stipe explants but did not develop on meristem explants at a temperature of 23 °C. Temperatures from 8 to 13 °C were favorable for callus development. Callus development on meristem explants required light but callus development on stipe explants did not.     

Dark respiration of the stipe of Ecklonia cava (Laminariales, Phaeophyta) in relation to temperature

Sporophytes of Ecklonia cava Kjellman (Laminariales, Phaeophyta) with a stipe length of 22–102 cm were collected at 6–9 m depth in Nabeta Bay, Shimoda, central Japan by scuba diving in February (winter) and in August (summer) 1998. Dark respiration of the intact stipe of E. cava was measured at various water temperatures ranging from 15 to 27.5°C in winter and 15–30°C in summer in a closed system by using a dissolved oxygen meter. The stipe respiration was compared on whole stipe, length, surface area, volume, wet weight and dry weight bases. On each basis, the stipe respiration always increased with a rise in water temperature within the temperature range investigated. The stipes showed similar respiration rates on each basis of length, surface area, volume, wet weight and dry weight at each temperature, irrespective of the stipe length. The mean respiration rates in winter (at 15–27.5°C) were: length, 16.7–32.5 μL O₂ cm^?1 h^?1; surface area, 3.2–6.2 μL O₂ cm^?2 h^?1; volume, 7.6–15.0 μL O₂ cm^?3 h^?1; wet weight, 6.2–12.2 μL O₂ g (wet weight)^?1 h^?1; and dry weight, 43.8–88.0 μL O₂ g (dry weight)^?1 h^?1. Those for summer (at 15–30°C) were: length, 17.1–32.0 μL O₂ cm^?1 h^?1; surface area, 3.6–6.8 μL O₂ cm^?2 h^?1; volume, 9.7–18.7 μL O₂ cm^?3 h^?1; wet weight, 7.6–14.6 μL O₂ g (wet weight)^?1 h^?1; and dry weight, 49.4–95.8 μL O₂ g (dry weight)^?1 h^?1. This is the first report of the intact stipe respiration of E. cava at various temperatures.     

Revision of the kelp family Alariaceae and the taxonomic affinities of Lessoniopsis Reinke (Laminariales,Phaeophyta)

The morphologically diverse members of the Laminariales are separated into three families, the Alariaceae, Laminariaceae and Lessoniaceae, on the basis of developmental features exhibited at the stipeblade transition zone. We have investigated the relationships of lessoniacean taxa with those of alariacean and laminariacean affinity. This was done by completing phylogenetic analyses of 3 small-subunit (SSU) rRNA gene (113 bp), first internal transcribed spacer (ITS 1), 5.8S rRNA gene and second internal transcribed spacer (ITS2)(12 bp) sequence data from a variety of taxa. In summary, the Alariaceae and Lessoniaceae are polyphyletic. We present a restricted view of the Alariaceae, including only Alaria and Pterygophora of the genera usually placed in this family, and transfer the monotypic genus Lessoniopsis to this group. Current theories of kelp evolution and biogeography must be reconsidered in view of our data.     

Relation between size and age of holdfasts of Ecklonia stolonifera Okamura (Laminariales,Phaeophyta) in northern Honshu,Japan

Ecklonia stolonifera is distributed along the coast facing the Sea of Japan. The size of various parts of the shoot (blade length and width and stipe length and diameter) and the age were determined at Ooma, Aomori Prefecture. The smaller the holdfast, the higher the percentage of one-year-old shoots. Holdfasts 10 cm in diameter seemed to be three years old, whereas holdfasts 40 cm in diameter seemed to be five or more years old. Zoosporangial sori were observed on blades three or more years old. Ecklonia stolonifera holdfast diameter expands only vegetatively by stoloniferous rhizoids. Zoospores, formed on shoots three or more years old, serve for the formation of new populations.     

Regeneration from callus of Undaria pinnatifida (Harvey) Suringar (Laminariales,Phaeophyta)

Calli were formed on the explants of midrib, meristem and immature stipe parts from freshly collected Undaria pinnatifida sporophytes. Each part was sterilized by Betadine and ethanol, and was cut into explants. The explants were incubated on an agar medium at 10 hours light and 14 hours dark photoperiod under a photon flux density of 80 µmol m^–2 s^–1. Callus was formed best on the explants of meristem parts at a temperature of 13 °C on PESI medium. Calli were cut off from the explants and were transferred into a sterile liquid PESI medium in flasks. Callus was dark brown in colour and was composed of well-pigmented cells. The cells were loosely bound and were separated by low power sonication, and were easy to attach to vinylon strings. From the calli formed on the explants of meristem parts, entire fronds were regenerated, but from the calli formed on the explants of midrib parts, only thin layered laminae were regenerated. The calli formed on the explants of immature stipe parts did not exhibit any regeneration at all.     

A morphometric comparison of Ecklonia kurome (Laminariales,Phaeophyta) from Japan*

A morphological comparison was made of Ecklonia kurome Okamura collected from seven localities, including a lectotype locality (Shirahama), in Japan. Morphometric characters and their size ranges were recorded as follows: the central lamina width (5.1–67.8 cm), the median fascia thickness (0.9–3.3 mm), the primary pinna width (2.2–24.0 cm), the ratio of width to length of the primary pinna (0.07–0.56) and the primary pinna number index (PPNI; 0.24–2.21). The results suggested that the morphological variations observed within this species were related to their habitat. A thick and distinct median fascia and an undulate central lamina margin were found on plants from moderate wave-exposed locations. Plants having narrow primary pinnae with indistinct ruga were observed on shores facing open sea. Wide and thin plants grew in wave-sheltered habitats. Flat plants were found on a shore exposed to a continuous strong current throughout the year. There were noticeable differences in morphology among the Tateyama, Tsuno, Aburatsubo and Tonoshima populations. The yellow and crisp primary pinna edge was a major characteristic of the Tateyama population. Narrow plants in which the central lamina and primary pinnae were half as wide as those of the Shirahama population were found in Tsuno. Wide and thin plants were observed in Aburatsubo. In this locality, the central lamina and primary pinnae were nearly three times wider but half the thickness of those of the Shirahama population. Flat plants grew in Tonoshima. The Muroto and Oki populations exhibited morphologically similar characteristics to the Shirahama population. A hollow stipe and slightly high PPNI value were found in the Muroto population, and a slightly low PPNI value was found on the Oki population.     

Photosynthesis and respiration in bladelets of Ecklonia cava Kjellman (Laminariales, Phaeophyta) in two localities with different temperature conditions

Characteristics of photosynthesis and respiration of bladelets were compared between Ecklonia cava Kjellman sporophytes growing in a warmer temperate locality (Tei, Kochi Pref., southern Japan) and in a cooler temperate locality (Nabeta, Shizuoka Pref., central Japan). Photosynthesis and respiration were measured with a differential gas-volumeter (Productmeter). In photosynthesis-light curves at 20°C, the rate of net photosynthesis was almost the same at light intensities lower than 25 μmol m⁻² s⁻¹ and the light-saturation occurred at 200–400 μmol m⁻²s⁻¹ in plants of both localities. The light-saturated net photosynthetic rates were higher in winter and spring than in summer and autumn in both plants. The optimum temperature for net photosynthesis at 400 μmol m⁻²s⁻¹ was 27°C throughout the year in the Tei plant and 25–27°C in the Nabeta plant. The decrease of net photosynthetic rates in the supraoptimal temperature range up to 29°C was sharper in winter and spring than in summer and autumn in both plants, being smaller in the Tei plant than in the Nabeta plant in all seasons. The dark respiration rate always increased with water temperature rise in both plants. No clear differences were found in the dark respiration rate between Tei and Nabeta plants except that when measured against dry weight, the Tei plant showed a slightly lower rate as compared with the Nabeta plant.     

Artificial induction of sporulation in Lessonia (Phaeophyta, Laminariales)

The effects of three physical variables on sporulation, germination and gametophyte survival were evaluated on two species of Laminariales at Coquimbo, Chile (30° S). Parameters were evaluated using reproductive fronds of Lessonia nigrescens Bory and Lessonia trabeculata Villouta and Santelices with treatment variables including type of pre-rinse, dehydration, and temperature. Although the response was slightly different in the two species, it was found that pre-rinsing the blades with tap water produced marked sporulation without affecting germination and survival. Minor effects were observed with other variables, including positive effects of lower temperature and negative effects of longer dehydration periods. The high commercial value of these two species has promoted much interest in their artificial propagation in Chile. This revised version was published online in June 2006 with corrections to the Cover Date.     

Morphometric study of Ecklonia cava (Laminariales, Phaeophyta) sporophytes in two localities with different temperature conditions

Sporophytes of Ecklonia cava Kjellman (Laminariales, Phaeophyta) were collected seasonally from within 3–4 replicate, 1‐m² quadrates, haphazardly placed in dense assemblages at 6–9 m depth in Tei, Tosa Bay (southern Japan; water temperature 15–29°C) from 1995 to 1996, and in Nabeta Bay, Shimoda (central Japan; water temperature 13–25°C) from 1996 to 1997. Growth rings were checked for all samples and mean values of each biometric parameter of sporophytes 1‐year‐old and over were compared. The plant length (stipe length + primary blade length) was always shorter in Tei sporophytes (24–52 cm) than Nabeta sporophytes (70–100 cm), the difference being mainly owing to the shorter stipe length in Tei sporophytes (7–14 cm) than in Nabeta sporophytes (54–83 cm). However, the primary blade length was sometimes longer in Tei sporophytes (12–38 cm) than in Nabeta sporophytes (14–21 cm). Stipe diameter, longest bladelet length and primary blade width were mostly less in Tei sporophytes (8.6–12.4 mm, 5.5–7.0 cm and 23.4–38.0 cm, respectively) than Nabeta sporophytes (16.4–20.2 mm, 9.2–12.0 cm and 43.0–52.6 cm, respectively). Nevertheless, the number of bladelets of sporophytes from Tei (15–28) and Nabeta (18–29) were within the same range. At Tei, 32–43% of the sporophytes had wrinkled blades in summer and autumn, whereas wrinkled primary blades or bladelets were not observed in Nabeta sporophytes throughout the experimental period. These morphometric differences of E. cava between the two localities are suggested to be dependent on environmental factors, especially seawater temperature.     

Photosynthetic performance of transplanted ecotypes ofEcklonia cava(Laminariales, Phaeophyta)

Young sporophytes of short-stipe ecotype ofEcklonia cavafrom a warmer locality (Tei, Kochi Pref., southern Japan) and those of long-stipe ecotype from a cooler locality (Nabeta, Shizuoka Pref., central Japan) were transplanted in 1995 to artificial reefs immersed at the habitat of long-stipe ecotype in Nabeta Bay, Shizuoka Pref., central Japan. The characteristics of photosynthesis and respiration of bladelets of the transplanted sporophytes of the two ecotypes were compared in winter and summer 1997; the results were assessed per unit area, per unit chlorophyllacontent and per unit dry weight. In photosynthesis-light curves at 10–29 °C, light saturation occurred at 200–400 mol photon m^–2s^–1in sporophytes from both Tei and Nabeta. The maximum photosynthetic rate (P _max) at 10–29 °C and the light-saturation index (I _k) at 25–29 °C in sporophytes from both localities were generally higher in winter than in summer.P _maxat 25–29 °C (per unit area and chlorophylla) were higher in sporophytes from Tei than those from Nabeta in both seasons. The optimum temperature for photosynthesis was 25 °C in winter and 27 °C in summer at high light intensities of 100–400 mol photon m^–2s^–1. However, at lower light intensities of 12.5–50 mol photon m^–2s^–1, it was 20 °C in winter and 25–27 °C in summer for sporophytes from both locations. Dark respiration increased with temperature rise in the range of 10–29 °C in sporophytes from both locations in summer and winter. The sporophytes transplanted from Tei (warmer area) showed higher photosynthetic activities than those from Nabeta (cooler area) at warmer temperatures even under the same environmental conditions. This indicates that these physiological ecotypes have arisen from genetic differentiation.     

Culture and growth of Lessonia trabeculata (Phaeophyta,Laminariales) juvenile sporophytes in La Herradura de Guayacan Bay,northern Chile

Lessonia trabeculata is one of the major kelps found along the northern coast of Chile. In addition to its ecological and economic importance, L. trabeculata may be severely affected by environmental disturbances such as El Níño, which during 1982–1983 cleared wide areas along the coast of Peru and Chile. The main goal of this work was to mass culture L. trabeculata and to observe the growth of sporophytes obtained in the laboratory and cultured in the sea. Juvenile sporophytes obtained in the laboratory were attached between 1 and 6 m in depth. The linear growth rate, as blade elongation, was recorded weekly for seven months. No significant differences (p < 0.05) were found in sporophyte blade linear growth at different depths. The best elongation growth rate was 7.5 ± 1.6 mm d^–1 at 3 m during March. This preliminary work suggests that L. trabeculata follows an annual growth cycle similar to that of other Laminariales with a high rate of blade elongation during the summer and decreasing towards autumn. This species can be considered a potential candidate for aquaculture to increase the availability of raw material and aid in repopulation of overexploited areas.     

Growth of Ecklonia cava (Laminariales, Phaeophyta) sporophytes transplanted to a locality with different temperature conditions

Transplanting experiments were carried out to determine whether the small type sporophytes with short stipe of Ecklonia cava Kjellman (Laminariales, Phaeophyta) growing in a locality with warm temperatures, change into larger type with a long stipe when transplanted to a locality with cooler temperatures. Juvenile E. cava sporophytes, having a stipe shorter than 5 cm long were collected from Tei in Tosa Bay (southern Japan) (seawater temperature 15–29°C) and transplanted to Nabeta Bay (central Japan) (seawater temperature 13–25°C), where larger type E. cava sporophytes characterized by long stipe (ca 1 m) grow. They were attached to artificial reefs at the sea bottom (9 m depth) in Nabeta Bay to monitor their growth. For comparison, juvenile E. cava sporophytes of almost similar size growing in Nabeta Bay were also transplanted in the same way to the same experimental site. Observations of growth of sporophytes from Tei and Nabeta were carried out monthly for 2 years from November 1995 to October 1997. The transplanted Tei and Nabeta sporophytes showed an increase in stipe length and diameter from winter to spring, whereas almost no increase was observed during summer and autumn. At the end of the study period, the stipe of Nabeta sporophytes reached 25.6 cm in length and 17.0 mm in diameter, whereas that of Tei sporophytes reached 11.1 cm in length and 11.2 mm in diameter. The primary blade length was 16.0 cm in Nabeta sporophytes, whereas it was 5.5 cm in Tei sporophytes. Thus, Tei sporophytes still remained smaller than Nabeta sporophytes even under the same environmental conditions.     

The effect of fertilizer application on farming of the seaweed Undaria pinnatifida (Laminariales, Phaeophyta)

A slow-release ammonium phosphate fertilizer coated with porous plastic was tested on Undaria pinnatifida (Harvey) Suringar as a possible solution to the nutrient deficiency in seawater that causes quality and yield deterioration in seaweed farming. The yield of U. pinnatifida within the fertilized area was 17–40% greater than that of the control area (unfertilized area). In addition, two harvests were possible per season and the quality of harvested U. pinnatifida was also better than that outside the fertilizer diffusion area. The released NH₄-N did not increase the concentration of NH₄-N outside the farming area. Therefore, this fertilizer increased yield and improved quality without causing water pollution.     

The life cycle of Laminaria abyssalis (Laminariales,Phaeophyta) in culture

Laminaria abyssalis occurs in deep water in tropical latitudes of the Brazilian coast (19° 23 S, 38° 28 W to 22° 54 S, 42° 13 09 W). Its life cycle has been completed in the laboratory in seven months using different conditions of light and temperature. The gametophytic stage required for growth the low photon flux density of 1.2 ± 0.3 µmol m^–2 s^–1 and 18 °C, while the juvenile and adult sporophytes needed 15 µmol m^–2 s^–1 and 18 °C. The sporophytes became fertile at 23 °C. Our results showed that light and temperature are the main factors regulating the growth and life history of this species under the culture conditions tested.     

Comparative photosynthetic studies of Ecklonia cava (Laminariales,Phaeophyta) bladelets with and without zoosporangial sori

Photosynthetic rates were compared between Ecklonia cava bladelets with and without zoosporangial sori sampled from the subtidal zone (about 5 m deep) in Nabeta Bay, Shimoda, Japan. Photosynthetic rates of bladelets were lower in the sorus portion than in the non-sorus portion on the basis of area, dry weight and chlorophyll a. Respiration rates were higher in the sorus portion than in the non-sorus portion on the basis of area and chlorophyll a, whereas they were almost the same on a dry weight basis. The differences were mainly due to a large difference in dry weight per unit bladelet area between the sorus and the non-sorus portion. Light compensation points were higher in the sorus portion than in the non-sorus portion.     

冬凌草组织培养及其愈伤组织诱导研究

实验采用L9（34）正交试验方法优化冬凌草组织培养快繁培养基,筛选冬凌草增殖、生根和愈伤组织诱导的最佳培养基配方。结果表明：不定芽诱导的最适培养基为MS＋0.2 mg/L IBA＋0.1 mg/L6-BA＋0.2 mg/L NAA;生根培养基为1/2 MS＋1 mg/L IBA＋1 g/L活性炭;以冬凌草茎段为外植体诱导愈伤最佳培养基为MS＋1.5 mg/L6-BA＋2 mg/L2,4-D。     

黄山药愈伤组织的诱导与分化

以黄山药的叶片、茎段和叶柄作外植体,以MS为基本培养基,试验了不同激素组合对愈伤组织诱导的影响,采用正交试验法研究了愈伤组织的分化效果。结果表明,以MS+2,4-D1~2mg/L+6-BA2mg/L培养基对叶片的愈伤组织诱导效果最好,接种12d后初见愈伤组织,20d后可形成大量的愈伤组织,而茎段和叶柄的诱导效果较差。分化试验结果表明,生根率最高可达85.3%,而出芽率最高仅达29.6%。     

The role of external carbonic anhydrase in the photosynthetic use of inorganic carbon in the deep-water alga Phyllariopsis purpurascens (Laminariales, Phaeophyta)

Mechanisms of inorganic carbon assimilation were investigated in the deep-water alga Phyllariopsis purpurascens (C. Agardh) Henry et South (Laminariales, Phaeophyta). The gross photosynthetic rate as a function of external pH, at a constant concentration of 2 mM dissolved inorganic carbon (DIC), decreased sharply from pH 7.0 to 9.0, and was not substantially different from 0 above pH 9.0. These data indicate that P. purpurascens is inefficient in the use of external HCO₃ ⁻ as a carbon source in photosynthesis. Moreover, the photosynthetic rate as a function of external DIC and the highest pH (9.01 ± 0.07) that this species can achieve in a closed system were consistent with a low capacity to use HCO₃ ⁻, in comparison to many other species of seaweeds. The role of external carbonic anhydrase (CA; EC 4.2.1.1) on carbon uptake was investigated by measuring both the HCO₃ ⁻-dependent O₂ evolution and the CO₂ uptake, at pH 5.5 and 8.0, and the rate of pH change in the external medium, in the presence of selected inhibitors of extra- and intracellular CA. Photosynthetic DIC-dependent O₂ evolution was higher at pH 5.5 (where CO₂ is the predominant form of DIC) than at pH 8.0 (where the predominant chemical species is HCO₃ ⁻). Both intra- and extracellular CA activity was detected. Dextran-bound sulfonamide (DBS; a specific inhibitor of extracellular CA) reduced the photosynthetic O₂ evolution and CO₂ uptake at pH 8.0, but there was no effect at pH 5.5. The pH-change rate of the medium, under saturating irradiance, was reduced by DBS. Phyllariopsis purpurascens has a low efficiency in the use of HCO₃ ⁻ as carbon source in photosynthesis; nevertheless, the ion can be used after dehydration, in the external medium, catalyzed by extracellular CA. This mechanism could explain why the photosynthetic rate in situ was higher than that supported solely by the diffusion of CO₂ from seawater. Received: 6 March 1998 / Accepted: 22 June 1998     

Revision of the systematics of algae in the order Laminariales (Phaeophyta) from the Far-Eastern Seas of Russia on the basis of molecular-phylogenetic data

An overview of the literature changes in the systematics of algae in the order Laminariales (Phaeophyta) based on molecular phylogentic data is given. In a recent taxonomic revision by Lane et al., [45], the number and status of the families traditionally included in the order have been revised. One family was transferred to the order Tilopteridales; a new family, the Costariaceae, was described; and the genus Laminaria was split into 2 genera, Laminaria and a newly resurrected genus Saccharina. These innovations have necessitated a systematic revision of the Far Eastern species of the Laminariales. Our genetic studies indicate that 2 species of Laminaria and 12 intraspecific taxa (1 subspecies and 11 forms) from the Russian Pacific coasts should be transferred to the genus Saccharina. The following new nomenclatural combinations are proposed: Saccharina bongardiana, comb. nov. (including 4 forms: f. bifurcata, f. subsessilis, f. subsimplex, f. taeniata) and Saccharina gurjanovae, comb. nov. (including f. lanciformis). In addition, new nomenclature combinations are proposed for intraspecific taxa of the Laminaria species (L. angustata, L. cichorioides, L. japonica) that have already been transferred to the genus Saccharina [45]. These include S. angustata subsp. sibirica, comb. nov., 4 new combinations for the forms of S. cichorioides (f. coriacea, f. sacchalinensis, f. sikotanensis, and f. sinuicola), and 2 new combinations for the forms of S. japonica (f. diabolica, and f. longipes). The taxonomic status of the rest of the members of the Laminariales known from the seas of the Russian Far East is discussed. Laminariaceous algae in this area represent 6 of the 8 known families currently included in the Laminariales (Chordaceae, Pseudochordaceae, Alariaceae, Arthrothamnaceae, Laminariaceae, and Costariaceae).