Kinetic characteristics of photoassimilate translocation in Alaria esculenta (Laminariales,Phaeophyceae)

The kinetics of translocation of ¹⁴C-labeled photoassimilate were studied in the kelp, Alaria esculenta (L.) Grev., using a Geiger-Müller detector-probe to measure radioactivity in the source and sink regions of dumbbell-shaped explants cut from blades. Rapid tracer efflux from the source occurred for 4 days following a pulse of [¹⁴C]bicarbonate, with 40–60% of the initial activity remaining in the source after 10–14 days. Portions of source and sink tissue were analysed for distribution of radioactivity in mannitol, amino-acid, organic-acid and insoluble fractions. About 75% of the radioactivity in both source and sink at the end of the experiments was in soluble organic matter. The translocation velocity of the moving solute front (1.0-1.6 cm·h^-1) was derived from time-course profiles of tracer arriving in Alaria sinks. Relative rates of translocation, calculated from these profiles, yielded skewed curves, with maximum rates of import by the sink occurring 72–96 h after the source was pulsed.     

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.     

Streblonema (Ectocarpales,Phaeophyceae) infection in the kelp Laminaria saccharina (Laminariales,Phaeophyceae) in the western Baltic

The brown alga Laminaria saccharina is the dominant subtidal macroalga in Kiel Bay, western Baltic. It is infected by the microscopic brown alga, Streblonema aecidioides. Infected thalli may show symptoms of Streblonema disease, i.e. alterations of blade and stipe, ranging from dark spots to heavy deformations and completely crippled thalli. Samples taken from a single locality all year round show that (i) the host population is infected at a high rate of 87±13% (SD), but that (ii) a considerable proportion of thalli containing Streblonema does not show disease symptoms, and that (iii) juvenile hosts, which mainly appear in autumn, are infected at almost the same rate. Thus the infection seems to occur early in the host's life. Juveniles in nature show fewer symptoms of the disease than adults. Two months after infection, oxygen production and growth in laboratory-raised experimentally infected juvenile hosts was not different from uninfected controls. Experimental thalli showed more severe morphological alterations than uninfected controls only four months after infection. Both field and laboratory observations indicate that a lag phase exists between infection and outbreak of the disease.     

Cultivation of Macrocystis integrifolia (Laminariales,Phaeophyta) in southeastern Alaskan waters

The artificial culture of Macrocystis integrifolia in southeastern Alaskan waters has been initiated as a first step in a project to augment the existing herring roe-on-kelp fishery in the state. The growing of Macrocystis in Prince William Sound has the potential of considerably enhancing this fishery by eliminating the costly importation of this kelp from southeast Alaska. In an ongoing feasibility study, Macrocystis has been cultured under laboratory conditions through the embryonic sporophyte stage and outplanted in waters near Sitka, Alaska (57° N). Growth of the outplanted kelps has been monitored as a function of the time and depth of the outplanting. Preliminary results suggest that light is limiting for growth in winter and that the optimal depth for outplanting will vary with the season.     

Undaria pinnatifida (Laminariales,Phaeophyta) 12 years after its introduction into the Atlantic Ocean

Since its first introduction into the Atlantic for farming purposes in 1983, the brown alga Undaria pinnatifida has been found at several sites along the European coasts. The present study deals with an ecological experiment that was performed at the island of Ushant (Brittany, France) in order to check the ability of Undaria to recruit to a rocky substratum in situ. On the one hand, the authors were unsuccessful in getting Undaria to colonize a previously denuded area of shore, which was subsequently colonized by other native species, a result that may speak for a competition between Undaria and the local kelps. On the other hand, evidence is presented that Undaria pinnatifida has become a member of the Atlantic flora for good. The sporophytes can be found growing from low water mark of neap tide (+1.5 m) down to at least –15 m below lower water mark of spring tide. Its propagation is thought to occur in at least two ways: either step by step from cultivation sites along the coasts, or from the hulls of ships sailing from harbour to harbour. The preference of Undaria for settlement is on artificial structures.     

Genetic diversity in Taro (Colocasia esculenta Schott, Araceae) in China: An ethnobotanical and genetic approach

Taro,Colocasia esculenta (Araceae), is a widely distributed and important food crop in the humid tropics and subtropics. Relatively neglected by science, much knowledge of genetic diversity in taro is with farmers. Taro genetic resources managed by five ethnic communities and Han farming villages in diverse ecosystems were sampled and characterized in Yunnan Province, southwest China. This study documented a new type of flowering taro selected by farmers which is widely and intensively cultivated for its edible flower. Samples representing 20 traditional cultivars were grouped into five major morphotypes according to ethnobotanical, agro-morphological, and preliminary genetic characterization. Folk taxonomy and uses tended to confirm the five morphotypes recognized by peoples of Yunnan for their distinctive properties and uses. These major taro morphotypes are key units for assessing how patterns of use maintain genetic diversity and to monitor potential genetic erosion. The morphotype groups also suggest possible evolutionary relationships in cultivated taros.     

A comparison between two populations of Lessonia trabeculata (Phaeophyta: Laminariales) microscopic stages

Lessonia trabeculata is the most important brown seaweed in northern Chilean subtidal environments. It usually grows in areas with high to moderately high water movement, and only occasionally in sheltered habitats. These different hydrodynamic environments produce morphologically and physiologically distinct plants. The purpose of this study was to determine probable differences in reproductive features between two L. trabeculata populations exposed to different water movement intensities. The zoospore production, settlement, germination, gametophyte fertility and survival were studied.Zoospore release and spore attachment capacity were higher from blades from El Francés Beach, the locality with higher water movement energy. Germination at 24 hours was higher in the germlings from El Francés Beach than those from La Herradura Bay. However, after 4 days of culture germination rates were similar. Average survival rates of gametophytes were similar for both populations. After 20 days culturing gametophytes from El Francés Beach fertilization was observed, while in samples from La Herradura Bay the sporophytes were seen at 27d.The results suggest a higher reproductive vitality in plants of Lessonia trabeculata living in an environment with an active water movement, than plants growing in a sheltered environment.     

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.     

The Invasive Kelp Undaria Pinnatifida (Phaeophyceae, Laminariales) Reduces Native Seaweed Diversity in Nuevo Gulf (Patagonia, Argentina)

The kelp Undaria pinnatifida(Phaeophyceae) is a seaweed native to northeast Asia, but during the last two decades, it has been accidentally or intentionally introduced in several temperate coasts worldwide. In central Patagonia (Argentina), this species was first detected in late 1992, and it is progressively spreading from the point of introduction. Through a manipulative experiment involving Undaria removal in 2001, we found that its presence is associated with a dramatic decrease in species richness and diversity of native seaweeds in Nuevo Gulf. Future prospects are worrisome, as, in addition to the negative impact from a biodiversity viewpoint, native commercial macroalgae and invertebrates might also be affected.     

Temperature requirements for the growth of young sporophytes of Undaria pinnatifida and Undaria undarioides (Laminariales, Phaeophyceae)

The relative growth rate of young sporophytes of Undaria pinnatifida (Harvey) Suringar and Undaria undarioides (Yendo) Okamura was examined in order to understand the difference in distribution of these two species around the coast of Japan. The optimal temperature for growth of both species was similar at 20°C and the upper critical temperature for growth was also similar, at 27°C for U. pinnatifida and 26°C for U. undarioides. Therefore, the optimal and upper critical temperatures for growth of the young sporophytes are not the main factors determining the distribution of each species. Next, the lower critical temperatures for growth were examined. For the young sporophytes of U. pinnatifida, the lower limit was less than 5°C while for those of U. undarioides it was 15°C. Thus, the difference in the lower critical temperature for growth between the two species was approximately 10°C. During the period of young sporophyte growth in the field, the temperature at the mouth of Ise Bay, Japan, where U. pinnatifida occurs, ranges from 12.7°C in December to 13.1°C in April, with a minimum of 7.9°C in February. Our experiments indicate that young sporophytes are able to grow throughout this period. The temperature off Hamajima, Japan, where U. undarioides occurs, ranges from 19.1°C to 14.8°C during the same time period. Again, young sporophytes are able to growth throughout this period, although minimum winter temperatures are only just high enough for growth. These natural temperature ranges during the growth season of the sporophytes agree well with the experimentally determined temperature requirements for growth of each species. Therefore, the difference between the two species in the critical temperature required for growth of the young sporophytes, especially in the low temperature range, is one of the major factors determining the distribution pattern of each species.     

Epi-endophytic symbiosis between Laminariocolax aecidioides (Ectocarpales, Phaeophyceae) and Undaria pinnatifida (Laminariales, Phaeophyceae) growing on Argentinian coasts

The present is the first study on epi-endophytic algae on thalli of Undaria pinnatifida growing along Argentinian coasts. The main goal is to describe the nature and the morphology of this symbiosis. Individuals of Laminariocolax aecidioides were detected in both June and December 2004, growing on U. pinnatifida sporophytes. In nature, the epi-endophyte were macroscopically observed as dark zones that partially covered the hosts’ fronds. L. aecidioides vegetative thalli were irregularly branched uniseriate filaments. The life cycle is described from laboratory cultures started from Patagonian populations. Caryology revealed that the sporophytic diploid phase presented 16 chromosomes whereas the gametophytic haploid phase presented 8 chromosomes. Isolates made from thalli growing in the interior of infected hosts developed into filamentous, branched sporophytes that reproduced by both unispores and plurispores that were produced in unilocular and plurilocular sporangia, respectively. The results of this paper also allowed us to conclude that L. aecidioides uses the thalli of U. pinnatifida as a proper substrate. The penetration of endophitic filaments among the host′s cortical cells produced a lateral compression and, finally, their thalli development generated perforations in the host tissues. The effects of the epi-endophytic infection of L. aecidioides on U. pinnatifida are neither severe nor deleterious.     

Development of the intercalary meristem in Chorda filum (Laminariales, Phaeophyceae) and other primitive Laminariales

Development of the intercalary meristem in the terete laminarialean species Chorda filum (L.) Stackhouse was studied in culture using light and transmission electron microscopy as well as by tracing elongation and cell divisions in various parts of the sporophyte. Growth of C. filum sporophytes could be classified into three developmental stages: (i) diffuse growth; (ii) basal meristematic growth; and (iii) intercalary meristematic growth. In the diffuse growth stage, elongation and cell division frequency were almost the same in each cell. In the basal meristematic growth stage, elongation and division of cells became localized in the tissues derived from the meristematic initial cell. Cells of the basal meristematic region contained smaller chloroplasts and many small opaque vesicles. In the intercalary meristematic growth stage, there was further elongation and differentiation of cells originating from the meristematic region, and this became more active in adjacent regions below the meristem than in regions above the meristem, causing the relative position of the intercalary meristem to shift towards the tip of the sporophyte. Meristematic cells of C. filum contained well-developed Golgi vesicles around the nucleus (perinuclear Golgi), many secretion vesicles and many small disk-shaped chloroplasts whose thylakoids were not well developed. Sporophytes of three other terete members of Laminariales, Chorda tomentosa Lyngbye, Pseudochorda nagaii (Tokida) Kawai et Kurogi, and Pseudochorda gracilis Kawai et Nabata, show diffuse growth and basal meristematic growth, but no intercalary meristematic growth. This suggests that the common ancestor of the Pseudochordaceae and Chordaceae had basal meristematic growth, and intercalary meristematic growth evolved more recently in C. filum.     

Tissue culture of Ecklonia radiata (Phaeophyceae,Laminariales): effects on growth of light,organic carbon source and vitamins

The effects of light quality and irradiance, and supply of organic carbon and vitamins on the growth of two forms of Ecklonia radiata in tissue culture were examined. A callus of unpigmented cells developed over the cut surface of newly excised explants of stipe. This growth was best in the dark but stopped after 10 weeks. Pigmented, mainly filamentous clumps of cells developed from explants after several weeks in culture. These required light for growth, with growth being enhanced by increasing photon flux density up to 30 μmol photon m^-2 s^-1, with the active spectral component being red light (> 600 nm). The addition to the medium of a range of organic carbon sources or vitamins did not stimulate growth of either culture type in the dark. author for correspondence     

Temperature requirements for the growth and maturation of the gametophytes of Undaria pinnatifida and U. undarioides (Laminariales, Phaeophyceae)

Gametophytes of two Undaria species, U. pinnatifida and U. undarioides (Laminariales, Phaeophyceae), were studied to determine their water temperature requirements in order to understand their different distributions in Mie Prefecture, Japan. The optimal temperature for growth was 20°C for gametophytes of both species, and the upper critical temperature for growth was also the same for both species at 28°C. Therefore, the optimal and critical temperatures for growth of the gametophytes are not the main factors determining distribution. The optimal temperature for maturation of U. pinnatifida was approximately 10–15°C, whereas it was closer to 20–21°C for U. undarioides, a difference between these species of at least 5°C. In autumn and early winter, the seawater temperature at the mouth of Ise Bay, where U. pinnatifida is distributed, ranges from 21.6°C (October) to 12.7°C (December), and off Hamajima, where U. undarioides is found, the range is from 22.7°C (October) to 19.1°C (December). The seawater temperatures from October to December, which is the maturation season for the gametophytes, agreed well with the optimal temperature requirements for maturation of the gametophytes of both species. Thus the difference in the maturation temperature range of the gametophytes is a major factor determining distribution of these Undaria species along the Japanese coast.     

Induction of callus from axillary buds of taro (Colocasia esculenta var. esculenta,Araceae) and subsequent plantlet regeneration

Summary Axillary buds of taro (Colocasia esculenta var. esculenta, Araceae) cultured on half strength Murashige-Skoog medium (HMS) containing taro extract (HMSTE) and 2, 4, 5-trichlorophenoxyacetic acid produce a compact, hard, slow growing callus which is not very active morphogenetically and produces only a few plantlets. When cultured on HMSTE plus 5 mg 1^–1 each of naphthaleneacetic acid and benzyl adenine (HMSNB) the buds produce a fast growing, friable and morphogenetically active callus. Meristematic regions form on the friable callus after 30 days on HMSNB. If transferred to HMSTE at this point the callus gives rise to plantlets. Addition of taro extract to the media is required for the culture of buds, induction of callus and plantlet regeneration.Abbreviations BA benzyl adenine - BNA b-naphthoxyacetic acid - CW coconut water (liquid endosperm) - DW dry weight - FW fresh weight - HMS half strength Murashige-Skoog medium - HMSCW HMSTE plus 100 ml CW 1^–1 - HMSNB HMSTE plus 5 mg 1^–1 each NAA and BA - HMSTE HMS plus 25 ml taro extract 1^–1 - HMSTR HMSTE plus 2 mg 2,4,5-T 1^–1 - MNA methyl-1-naphthaleneacetate - NAA naphthaleneacetic acid - OCPAA ortho-chlorophenoxyacetic acid - TE taro extract - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid     

The introduced alga Undaria pinnatifida (Laminariales,Alariaceae) in the lagoon of Venice

Since its appearance in 1992 in the lagoon of Venice, the brown algae Undaria pinnatifida (kelp) has gradually expanded along the banks of canals both at Chioggia and Venice, becoming the dominant species in the local algal community chiefly from February to July. In Chioggia Island, where another brown seaweed (Sargassum muticum) is present since 1992, the spreading of Undaria reaches a plateau. In Venice Island, instead, the colonisation process is still in progress. During 1999, the kelp has colonised the main canals (e.g. The Grand Canal) and, subsequently, the small inner ones. In order to evaluate the dynamics of substrate re-colonisation by Undaria, two mechanical eradications were carried out during (March) and after the fertile period (July) of the algae. Such experimental manipulations provided evidence of the fast re-colonisation potential of the algae mainly attributable to its efficient reproductive system. Eradication made during the fertile period, in fact, permitted the kelp development during the following year, while re-colonisation has started 2 years later where eradication was performed after the reproductive period. A significant decrease in the surface covered by other species has been observed both in shallow (Ulva rigida, Enteromorpha spp., Antithamnion pectinatum, Chondracanthus acicularis) and deeper areas (Rhodymenia ardissonei) during the period of maximum development of U. pinnatifida. On the basis of the results of this study, the following conclusions can be drawn: (1) the alga U. pinnatifida is continuously expanding in lagoon environments of Venice; (2) in order to limit its spreading, mechanical eradications would be done on a large spatial scale and before the zoospores release; (3) there is suggestive evidence of competition between Undaria and the remaining indigenous algae.     

Plant regeneration in vitro of South Pacific taro (Colocasia esculenta var. esculenta cv. Akalomamale,Aracea)

Summary Axillary bud expiants from South Pacific (Solomon Islands) taro, Colocasia esculenta var. esculenta cv. Akalomamale (Araceae) cultured on a modified Murashige-Skoog medium containing 1 mg NAA 1^–1 and TE formed callus and produced multiple plantlets. Explants died if NAA was present at levels lower than 0.1 mg 1^–1. BA was not required and may have been inhibitory. Plantlets developed faster and became larger following transfer to a hormone-free medium two weeks after the start of culture. Fully grown plants were established in a potting mix and are growing well in a greenhouse.Abbreviations BA benzyladenine - BM basal medium - Ca Colocasia esculenta var. antiquorum - Ce Colocasia esculenta var. esculenta - Ck cytokinin(s) - CW coconut water - HSMSM half strength Murashige Skoog macroelements - HSMS half strength Murashige and Skoog medium - IM initial medium(ia) - MS Murashige and Skoog medium - NAA naphthaleneacetic acid - SM second medium - TE taro corm extract - UCI University of California, Irvine     

Compensatory growth of the kelp Macrocystis integrifolia (Phaeophyceae, Laminariales) against grazing of Peramphithoe femorata (Amphipoda, Ampithoidae) in northern-central Chile

Compensation of tissue loss has been considered an alternative strategy for seaweeds that have no or only minor chemical or structural defense against herbivory. Compensatory responses are facilitated by resource transfer among different tissues and have been suggested for large kelps. Macrocystis integrifolia (Bory) is a common kelp species from northern-central Chile, which is characterized by high growth rates and the absence of lipophilic chemical defenses against herbivore grazing. Herein, we used the giant kelp M. integrifolia to test for compensatory growth in response to grazing by the nest-dwelling amphipod Peramphithoe femorata (Krøyer). Amphipods were allowed to graze inside nests on subapical blades of M. integrifolia sporophytes for 14 days. We measured growth and chemical composition (C, N, laminaran and mannitol) of apical and subapical blades of grazed and ungrazed (control) sporophytes. Our results revealed the capability of M. integrifolia to maintain elongation rates in grazed subapical blades, which were similar to those of subapical blades from ungrazed sporophytes. Apical blades grew slower in grazed than in ungrazed sporophytes indicating a trade-off between apical and subapical blades when herbivores were present. Thus, compensation occurs in blades directly attacked by grazers and is probably mediated by vertical resource allocation within sporophytes to subapical blades, a suggestion supported by the fact that stipe internodes in these regions grew more on grazed sporophytes. In general, our study indicates that M. integrifolia exhibits compensatory growth against the herbivore amphipod P. femorata, and we suggest that this could be an important strategy of large kelp species to tolerate moderate grazing intensities.     

Influence of tissue source and growth rates on dry weight and carrageenan composition of Chondrus crispus (Gigartinales,Rhodophyta)

Carrageenan analyses were conducted on vegetative female clones of Chondrus crispus that were cultured to provide tissues with differing growth rates. Tissue dry weights increased from apex to base of fronds. Total carrageenan contents were lower in apical 1 to 2 cm segments than elsewhere in the frond, except when the alga was grown at high photon irradiances. Clone 373A contained more carrageenan than clone G8. The proportion of 0.3 M KCl-soluble polymers in the total native carrageenans varied from 44 to 92%, being highest in older tissues of fronds cultured at high photon irradiances. The apical 1 cm segments contained less KCl-soluble carrageenans than other tissues from the corresponding fronds. The KCl-soluble carrageenans, when alkali-modified and refractionated, afforded the expected kappa-iota carrageenan in > 79% yields. The remainder consisted of a polymer containing 23.1% SO₃Na and 8.4% 3,6-anhydrogalactose. Lambda carrageenan was not detected. Variations in carrageenan distribution between the apical region and other parts of the frond may reflect the increasing influence of medullary tissue developed as the immature cells differentiate.