The growth,reproductive phenology,and longevity of non-tide-pool Fucus distichus (L.) powell in New England

The growth, reproductive phenology, and longevity of in situ populations of Fucus distichus L. ssp. edentatus (De la Pylaie) Powell and F. distichus L. ssp. evanescens (C. Agardh) Powell were evaluated in New England. Both subspecies exhibited maximum growth during early summer, a slight decline in late summer, and a brief resurgence in the early fall. The maximum growth rates (in terms of elongation) for F. distichus ssp. edentatus and ssp. evanescens were 3.5 and 3.7 cm/28 days, respectively. Populations of both subspecies showed a distinct bimodal reproductive periodicity, with maxima in the spring and fall. Even so, individuals were either reproductive in the spring or fall but never in both seasons. After reproduction, receptacles dehisced and plants either became vegetative or died. Higher rates of plant attrition were observed during periods of reproduction than during non-reproductive periods.     

MORPHOLOGICAL VARIATION WITHIN AND BETWEEN NATURAL POPULATIONS OF NON-TIDE POOL FUCUS DISTICHUS (PHAEOPHYTA) IN NEW ENGLAND1,2

The sources of morphological variation in natural populations of Fucus distichus L. ssp. edentatus (De la Pyiaie) Powell and F. distichus L. ssp, evanescens (C. Agardh) Powell from New England were evaluated. Individuals from different populations were morphologically distinct as judged by population means and analysis of variance. A correlation between the plant's form and its habitat was established by field observation. The broadest material grows in calm estuarine habitats, while the narrowest plants occur in exposed, open coastal areas. Major differences in morphology also appear seasonally. In addition, microhabitat factors such as exposure to wave action and elevation explain some morphological variation. Cultured germlings from distinct populations of “evanescens” and “edentatus” type plants were outplanted to an experimental garden in order to ascertain whether the variation was heritable or environmentally induced. The latter experiments indicate that major differences in morphology are genetically determined.     

EFFECTS OF WOUNDING BY THE HERBIVOROUS SNAILS LITTORINA SITKANA AND L. SCUTULATA (MOLLUSCA) ON GROWTH AND REPRODUCTION OF THE INTERTIDAL ALGA FUCUS DISTICHUS (PHAEOPHYTA)1

Small (3–7 cm long) Fucus distichus ssp. edentatus (de la Pyl.) Pow. Plants were tagged at three sites in which densities of the herbivorous snails Littorina sitkana and L. scutulata ranged from 367–4690 animals · M^-2. From April–August 1986, the growth rate, degree of wounding, and reproductive status of individual thalli were monitored at 2–4 week intervals. Grazer-inflicted damage to the thalli varied within and among sites. Mean growth rates at the site with low densities of littorines were about twice those at the site with intermediate densities and about four times those at the high density site. At the site with high densities of littorines, F. distichus growth rates were negatively correlated with the degree to which the plants were wounded. There appeared to be no correlation of grazer density with F. distichus survivorship. Thalli at the site with few herbivores tended to reproduce earlier and at a larger size than did those at the other two sites. In all three areas, only thalli that had received little damage from herbivores became reproductive. By lowering growth rates and delaying reproduction in F. distichus, grazing by littorine snails can potentially cause variation in reproductive output among individual thalli.     

Annual variation in growth rate of perennial littoral fucoid algae from the west coast of Norway

The growth of apical segments of six perennial fucoid littoral algae (Pelvetia canaliculata (L.) Dec. et Thur., Ascophyllum nodosum (L.) Le Jol., Fucus spiralis L., F. vesiculosus L., F. serratus L. and F. distichus L. subsp. edentatus (Pyl.) Powell) was measured at approximately monthly intervals during 1 year.In winter, elongation was limited by temperature and light. Maximum growth in May–June coincided with minimum N concentration in the seawater, but with high N concentration in the apical tissue. Throughout summer, both growth and tissue N concentration decreased, indicating that the growth was nutrient limited.A close linear correlation is indicated between elongation and weight increase in apices of A. nodosum.     

Depth-dependent reproductive output of the green sea urchin, Strongylocentrotus droebachiensis (O.F. Müller), in relation to the nature and availability of food

Reproductive output of green sea urchins (Strongylocentrotus droebachiensis O.F. Müller) in the field was highest at depths where preferred macro-algae were abundant, and lowest at depths where preferred macro-algae were overgrazed or replaced by non-preferred species (Agarum and Ptilota). Feeding rate and gonad indices of sea urchins in the laboratory were highest on a diet of preferred algae (Fucusdistichus L. subsp. edentatus (Pyl.) Powell, Laminaria longicruris Pyl., Desmarestia spp. and Saccorhizadermatodea (Pyl.) J. Ag.), and lowest on the less preferred Agarum cribrosum (Mert.) Bory, Ptilota serrata Kütz., and crustose corallines. Gamete production/unit area in overgrazed habitats was as great or greater than in kelp beds because of the higher biomass of urchins in overgrazed areas. Gonad weight and reproductive output of urchins from habitats poor in food can be increased by providing preferred foods.     

Monoclonal antibodies as molecular probes for cell wall antigens of the brown alga,Fucus

Monoclonal antibodies to cell wall carbohydrates were produced against carbohydrates extracted from the brown alga, Fucus distichus ssp. edentatus (de la Pyl.) Powell. Mouse spleen cells were immunized in vitro with alginate and fucans, and hybridoma cultures were screened by enzyme immunoassay. Most antibodies were immunoglobulin (Ig)M and one was IgA. Antigens were localized on methacrylate sections of Fucus tissues by indirect immunofluorescence. Each antibody labelled tissues with a distinctive distribution pattern in cell walls and extracellular matrix regions, demonstrating that each antibody was specific for a different extracellular epitope (i.e., antigenic determinant). Most antibodies also labelled intracellularly on at least one cell type. Punctate, fibrous or clumped labelling was characteristic of individual antibodies and provided information related to carbohydrate structure and solubility. These antibodies are molecular probes for small regions on cell wall polymers and should be valuable in studies of cell wall synthesis, secretion, assembly and modification as well as carbohydrate fine structure and function.Abbreviations EDTA ethylenediaminetetraacetic acid - EIA enzyme immunoassay - Ig immunoglobulin (IgG, IgM and IgA are immunoglobulin types)     

EFFECTS OF MICROTUBULE INHIBITORS ON PRONUCLEAR MIGRATION AND EMBRYOGENESIS IN FUCUS DISTICHUS(PHAEOPHYTA)1

Pronuclear migration in Fucus distichus spp. edentatus (de la Pyl.) Powell is blocked by incubation of fertilized eggs in colchicine (1 mg/ml) and Nocodazole (2 μg/ ml). Rhizoids form prior to decondensation of the sperm chromatin in eggs in which pronuclear fusion is blocked. This occurs during continuous colchicine incubation as well as in eggs recovering from a short treatment with either drug following fertilization. During recovery of the cells, the sperm and egg chromosomes condense, and the sperm chromosomes migrate toward the egg pronucleus. The delay in migration following removal of colchicine is as much as 24 h and is even slower following removal of Nocodazole. The egg chromosomes form a metaphase plate in treated cells while the sperm chromosomes are still distant in the cytoplasm. This suggests that egg centrioles are important in the mitotic division of the zygote, not sperm centrioles. The effect of colchicine treatment on the mitotic plane and cytokinesis is also discussed.     

An ecological study of fucus spiralis L.

An ecological study of Fucus spiralis L. has been made at Jaffrey Point, Newcastle, New Hampshire and the adjacent Great Bay Estuary System from 1972–1975. The distribution, growth, reproductive periodicity, attrition and longevity of the plants are described in relation to a variety of environmental factors. F. spiralis shows a broad but discontinuous estuarine distribution within the Great Bay Estuary System. The presence or absence of appropriate substrata is considered to be a factor determining its discontinuous distribution, since it is usually associated with metasedimentary or metavolcanic rock outcrops. The maximum growth and reproduction of F. spiralis are during the summer. The summer growth rates ranged from 1.9 to 2.8 cm/month while the average growth rate throughout the year was 1.2 cm/month.F. spiralis populations showed two periods of major attrition, namely, during the winter and summer. The average longevity of F. spiralis plants is ≈ 2 yr. The F. spiralis zone lies in the uppermost intertidal area between +2.12 and +2.31 m above M.L.W. There is a micro-stratification of biomass, stature, and reproductive activity within this zone. Average plant weight, length, and fertility tend to decrease with increasing elevation.     

Interspecific differences in the response of juvenile stages to physical stress: fluorometric responses of fucoid embryos to variation in meteorological conditions1

Chl fluorescence during and immediately after low tide under four meteorological conditions was measured in embryos of three fucoid algae [Ascophyllum nodosum (L.) Le Jol., Fucus vesiculosus L., and Fucus distichus subsp. edentatus Bach. (Pyl.) H. T. Powell] vertically distributed in the intertidal zone in Québec, Canada. Artificial substrata with attached embryos of each species were outplanted into each zone and into two different microhabitats: under and outside an adult canopy. Several fluorescence measurements were made using pulse‐amplitude‐modulated (PAM) fluorometry, from which maximum quantum yield (F_v/F_m), effective quantum yield (φ_PSII), relative electron transport rate (rETR), and nonphotochemical quenching (NPQ) were calculated. F_v/F_m, φ_PSII, and rETR decreased, and NPQ increased during low tide, most rapidly under the most desiccating meteorological conditions (i.e., sunny‐windy weather). The species occurring lowest in the vertical distribution, F. distichus subsp. edentatus, was the most affected, and the two highest species, A. nodosum and F. vesiculosus, only rarely differed. Tidal height itself also influenced the decline in fluorescence parameters, with more gradual declines in lower zones, except under the least desiccating conditions (i.e., cloudy‐calm weather). Recovery upon reimmersion was rapid in all circumstances. Under a canopy, decreases in maximum and effective quantum yields were more gradual than in exposed locations. Although the young stages of these species were affected by physical conditions experienced during low tide and their exact response depended on the precise meteorological conditions, differences in responses among species were surprisingly small. The abilities of young stages to withstand aerial conditions were, however, consistent with the zonation patterns of adults, and conditions under an adult canopy offered some protection.     

Three sympatric forms of Arctic charr Salvelinus alpinus complex (Salmoniformes,Salmonidae) from Lake Kamkanda,Northern Transbaikalia

We studied morphology, size and age structure, growth, feeding, and variation at microsatellite loci of three forms of Arctic charr Salvelinus alpinus complex (dwarf, small, large) from mountain Lake Kamkanda in River Olekma basin, northern Transbaikalia. The forms differ in meristic and morphometric characters, external appearance and size. The small form distinctly differs from the dwarf and large forms in higher number and length of gill rakers. The forms differ in growth rate; however, differences in growth between the dwarf and the small forms are not as large as between sympatric dwarf and small charr from other Transbaikalian lakes. The large form is heterogeneous in growth rate. The small form matures one year earlier than the dwarf form and has a shorter life span. The dwarf form is a benthophage, the small form is a planktophage, and the large form is a predator. The dwarf form spawns in September, while the small form spawns in November-December, and there is no overlap in their spawning time. The three forms have clear genetic differences, which support their reproductive isolation. It is assumed that the three forms of Arctic charr originated within Lake Kamkanda on the basis of trophic polymorphism and spawning time displacement and attained a high degree of morphological and genetic divergence.     

Combined effects of temperature and salinity on growth rates of germlings of threeFucus species from iceland,helgoland and the north adriatic sea

The growth rate of germlings of threeFucus species (F. distichus subsp.edentatus from Iceland,F. vesiculosus from Helgoland, North Sea, andF. virsoides from the North Adriatic Sea) has been investigated under different temperature and salinity conditions. The highest growth rate and the maximum elongation factor were found at 9° C forF. distichus; in the other two species growth increased with increasing temperature. Growth decreases with dilution in the three species under consideration. A rather low tolerance to dilution was observed inF. vesiculosus germlings. In view of the overall distribution of the latter species the opposite was expected. It seems likely, however, that susceptible strains have developed at Helgoland, where salinity rarely drops below 30.     

Dwarfism in Brassica napus L. induced by the over-expression of a gibberellin 2-oxidase gene from Arabidopsis thaliana

Gibberellins (GAs) are endogenous hormones that play an important role in regulating plant stature by increasing cell division and elongation in stem internodes. The GA2-oxidase gene from Arabidopsis thaliana (AtGA2ox8) was introduced into Brassica napus L. by Agrobacterium-mediated floral-dip transformation with the aim of decreasing the amount of bioactive GA and hence reducing plant stature. As anticipated, the transgenic plants exhibited dwarf phenotype. Compared with the wild type, the transgenic plants had increased primary branches (by 14.1?C15.3%) and siliques (by 10.8?C15.2%), which resulted in a significant increase in the seed yield (by 9.6?C12.4%). Moreover, the contents of anthocyanin in leaves of 60-day-old transgenic plants was about 9.4-fold higher in winter and about 6.8-fold higher in summer than the wild type. These excellent agronomic traits of the transgenic plants could not only improve the lodging resistance and seed yields, but also protect them against stress. Therefore, the over-expression of AtGA2ox8 might be used to produce dwarf varieties and increase seed yield in Brassica napus L.     

Separation of processes associated with differentiation of two-celled Fucus embryos

Various inhibitors were used to separate the overlapping processes of polar axis fixation, intracellular localizations forming a polar cell, and cell division, all of which are essential for cellular differentiation in two-celled embryos of Fucus distichus L. Powell. Cycloheximide and sucrose delayed the appearance of a polar cell (rhizoid formation) without inhibiting the fixation of a polar axis. Cytochalasin B, at 10 μg/ml, reversibly inhibited rhizoid formation without altering cell division. At higher concentrations (50–100 μg/ml) given in short pulses, cytochalasin affected the orientation and delayed the fixation of a light-induced polar axis with no qualitative effect on cell division. Disruption of the mitotic apparatus and prevention of cell division by colchicine had no influence on rhizoid formation or on the photopolarization of the developmental axis.     

Nutrient uptake and growth kinetics in brown seaweeds: Response to continuous and single additions of ammonium

The brown seaweeds Fucus distichus Linnaeus subsp. edentatus (de la Pylaie) Powell, a perennial, and Chordaria flagelliformis (O.F. Mueller) C. Agardh, a summer annual, were grown in continuous-flow greenhouse cultures. In winter, the growth of Fucus distichus ( μ = 0.01 · day^?1 ) in culture was not stimulated by added ammonium. Nitrogen in excess of the growth requirement was accumulated in the thallus ( 1.34–2.18 % N by dry wt, depending on the N-loading). In summer, the growth of both species in continuous cultures was stimulated by added ammonium. Chordaria flagelliformis showed higher rates of both growth (μ_max = 0.109 · day^?1) and ammonium uptake $\text{(V}{}_{\max }\text{= 23.2 μmol NH}{}_4{}^{\mathrm{+}}\text{· h}{}^{\mathrm{?1}}\text{· g dry wt}{}^{\mathrm{?1}}\text{)}$ than Fucus distichus (μ_max = 0.074 · day^?1, V_max = 13.9 μmolNH₄⁺ · h^?1 · gdrywt^?1). Calculated nitrogen subsistence quotas were similar in the two species (0.7% N in Chordaria, 0.6% N in Fucus). In those continuous cultures which did not receive added ammonium, Chordaria stored less nitrogen in excess of the subsistence quota than Fucus, although both species accumulated nitrogen at increased N-loading. Transient uptake rates were measured in response to single additions of ammonium. At any given initial concentration, short-term (30 min) uptake rates were a decreasing function of the thallus nitrogen quota and were higher for Chordaria than for Fucus. In N-depleted plants, short-term ammonium uptake rates exceeded both the uptake rates predicted from continuous cultures and the nitrogen requirements for growth. Chordaria flagelliformis, in particular, is able to scavenge efficiently low ambient N-nutrient concentrations and to sequester rapidly transient ammonium pulses. In comparison with Fucus distichus, Chordaria flagelliformis appears to be better adapted to short-term fluctuations in nutrient availability (on a scale of minutes to hours). Their N-storage capability allows both of these seaweeds to buffer the effect of fluctuations in external N-nutrient concentrations on their growth rates over periods of days to several weeks.     

A diploid form ofPhragmites communis,as a possible result of cytogenetical response to ecological stress

Phragmites communis Trin., a highly polymorphous and widely spread species has been described by several authors by the series of polyploidy ranging from triploid to octoploid forms (2n=36 to 96). The original spontaneous diploid form was not known. The present communication describes the experimental transplantation of a dwarf saline form into freshwater substrate conditions, including a new and extremely changed habitus of a sterile plant, the chromosome number of which has been determined as 2n=24.     

VARIABILITY IN TEMPERATURE AND HISTORICAL PATTERNS IN REPRODUCTION IN THE FUCUS DISTICHUS COMPLEX (HETEROKONTOPHYTA; PHAEOPHYCEAE): IMPLICATIONS FOR SPECIATION AND THE COLLECTION OF HERBARIUM SPECIMENS1

Natural and anthropogenic‐induced fluctuations in temperature can have profound effects on an organism's reproduction. The potential of herbarium collections for detecting changes in the timing of reproduction associated with interannual fluctuations in temperature from 1905 to 2003 was assessed in several taxa in the Fucus distichus (L.) emend. Powell complex from northern New England. Data were also used to evaluate whether air and/or sea temperature and North Atlantic Oscillation indices can cause overlap in the reproductive seasonalities of these taxa, a potential mechanism that prevents speciation. For all taxa, there was much variability in reproductive seasonalities among years. Discerning potential correlations with air or sea temperature was difficult because of a suspected bias to collect reproductive specimens at times when most of the population was nonreproductive. Nevertheless, there was a trend for seawater temperature to explain aseasonal reproduction for some taxa. Moreover, the existing archive (1895–2003) shows that the reproductive seasons of these taxa often overlap, and we suggest that interannual variability in temperature may often inhibit speciation. Suggestions also include archive of both reproductive and vegetative materials as well as coordinated sampling in critical biogeographic regions. No one investigator or institution can accomplish this, but phycological societies could organize and sustain such efforts.     

Improvement of two traditional Basmati rice varieties for bacterial blight resistance and plant stature through morphological and marker-assisted selection

Bacterial blight (BB) is a major production threat to Basmati, the aromatic rice prized for its unique quality. In order to improve the BB resistance of two elite, traditional BB-susceptible Basmati varieties (Taraori Basmati and Basmati 386), we utilized the strategy of limited marker-assisted backcrossing for introgression of two major BB resistance genes, Xa21 and xa13, coupled with phenotype-based selection for improvement of their plant type and yield. Improved Samba Mahsuri, an elite high-yielding, fine-grain-type BB-resistant rice variety served as donor for BB resistance. Backcross-derived improved Basmati lines at BC1F5 possessing a single resistance gene (i.e. either Xa21 or xa13) displayed moderate resistance to BB, while lines possessing both Xa21 and xa13 showed significantly higher levels of resistance. Two-gene pyramid lines (Xa21 + xa13) possessing good grain and cooking quality similar to their respective traditional Basmati parents, short plant stature (<110 cm plant height) and higher grain yield than the recurrent parent(s) were identified and advanced. This work demonstrates the successful application of marker-assisted selection in conjunction with phenotype-based selection for targeted introgression of multiple resistance genes into traditional Basmati varieties along with improvement of their plant stature and yield.     

Effects of dwarf bamboo, Fargesia nitida (Mitford) Keng f. ex Yi, on bark stripping by ungulates in a subalpine Abies faxoniana Rehder & E. H. Wilson forest, southwest China

Incidence and intensity of bark stripping of trees by ungulates was investigated at no bamboo (Fargesia nitida (Mitford) Keng f. ex Yi) (B-) site and understory bamboo dominant (B+) site of a subalpine Abies faxoniana Rehder & E. H. Wilson forest, southwest China. The percentage of damaged trees in B-site was higher than in B+ site. Bark stripping obviously occurred more frequently on Abies faxoniana compared to other tree species. Appearance of stripped bark and dead stems of the trees in different size-classes of A. faxoniana strongly depended on the density of dwarf bamboo at the site, and also on the size and bark structure of the trees, with highest damage rates occurring on the smaller DBH classes (10–40 cm) in B-site. The bark stripping intensity of A. faxoniana decreased significantly with higher density and coverage of F. nitida around damaged trees. Therefore, there is an indirect negative effect of the distribution of dwarf bamboo, F. nitida, on bark stripping of tree species. We suggest the indirect effects of dwarf bamboo species should be taken into account while considering the succession and regeneration of natural forests.     

Cell wall assembly in Fucus zygotes. II. Cellulose synthesis and deposition is controlled at the post-translational level

An alkali-insoluble cell wall component of Fucus distichus embryos is shown to be cellulose. Cellulose is not found in eggs, but within 20 min following fertilization is present in cell walls of zygotes. Incorporation of [³H]glucose or NaH¹⁴CO₃ confirms that this cellulose in zygotes of F. distichus and F. vesiculosus is newly synthesized, with the highest rate of synthesis occurring within the first 60 min. Use of specific inhibitors indicates that the increase in cellulose does not require protein or RNA synthesis. The evidence is consistent with the hypothesis that the initiation of cellulose synthesis triggered by fertilization is controlled at the post-translational level.