Filamentous Gametophytes Research Articles

Discovery of a novel brown algal genus and species Setoutiphycus delamareoides (Phaeophyceae, Ectocarpales) from the Seto Inland Sea, Japan

We describe a new genus and species of brown algae from the Seto Inland Sea, Japan. This species is similar to Delamarea in gross morphology and anatomy, but distinctive in having longer thalli with rare branching and shorter cortical cells. In culture, pluri-zoids derived from plurilocular zoidangia on the erect thalli developed into filamentous gametophytes bearing ectocarpoid plurilocular zoidangia, but also formed parenchymatous erect thalli of sub-sympodial growth similar to Trachynema often having branches, and formed lateral and terminal plurilocular zoidangia. Molecular phylogenies using concatenated chloroplast and mitochondrial gene sequences showed the new alga nested in the clade composed of ectocarpalean genera with diffuse growth, parenchymatous thalli, and multiple chloroplasts, but this species is distinctive. Therefore, we propose Setoutiphycus delamareoides gen. & sp. nov. for this new alga, and provisionally place it in Chordariaceae, Ectocarpales. The Seto Inland Sea repeatedly dried during sea level regressions during glacial periods, and the present sea level recovered after the last glacial maximums (LGM), ca. 10,000 years ago. Therefore, it is unlikely that the species evolved within this area. Its distribution in the area may be explained as a remnant population that survived in refugia in southern Japan during the LGM.

Fase gametofítica de tres taxones de Anemia (Anemiaceae)

Antecedentes y Objetivos: Anemiaceae presenta un único género, Anemia, con 115 especies que se distribuyen en el Neotrópico, África, India e islas en el Océano Índico. El objetivo de este trabajo es caracterizar las esporas vivas y la fase gametofítica de tres taxones de Anemia sudamericanas, poco estudiadas o con estudios fragmentados, A. herzogii, A. tomentosa var. anthriscifolia y A. tomentosa var. tomentosa.Métodos: Los gametofitos de los tres taxones han sido obtenidos a través de cultivos in vitro de las esporas. Las esporas y los gametofitos fueron estudiados a través del microscopio de luz y electrónico de barrido. Se describió el patrón de germinación de las esporas, evolución del desarrollo gametofítico y expresión sexual.Resultados clave: Los gametofitos filamentosos estaban formados por 4-20 células, los adultos fueron cordados simétricos o asimétricos, bisexuales y protándricos, en sus superficies y márgenes se observaron tricomas clavados. Los gametangios corresponden al tipo leptosporangiado. La dehiscencia de los anteridios se produjo mediante una perforación en la célula opercular. Los arquegonios tenían cuellos con cuatro a siete células y cuatro células triangulares en el extremo distal del cuello. Anemia herzogii mostró tricomas ramificados sobre los gametofitos y más tarde desarrolló esporofitos.Conclusiones: La germinación en todos los taxones corresponde al tipo Anemia y el desarrollo gametofítico al tipo Ceratopteris. Anemia herzogii se distingue de las dos variedades por la presencia de tricomas ramificados exclusivos de la fase gametofítica. Los taxones estudiados se caracterizan por la morfología del gametofito, tipo de tricomas y sexualidad.

Early stage growth responses of Saccharina latissima spores and gametophytes. Part 1: inclusion of different phosphorus regimes

Cultivation of Laminariales is an expanding industry and intensive investigations have been conducted in order to optimize the entire production chain from spore to sporophyte. However, despite intense research within the field, literature on the very early development of kelp microstages is scarce. In that perspective, the aim of the present study was to clarify the role of different phosphorus (P) regimes on the very early development of Saccharina latissima microstages using spores with different seasonal origin and thereby contribute to the optimization of cultivation conditions for the early life stages of the species. Results indicated that spores of S. latissima had to obtain a given size before developing into multicellular filamentous gametophytes, and this size was reached at least 2 weeks earlier in spores originating from April than in spores originating from February. Nutrient enrichment (P1–P5) had a profound positive effect on spore and gametophyte growth and development, when compared to natural nutrients levels (C), whereas increasing P levels within the range 23–69 μM phosphate-P did not induce any effect on growth of neither the spores nor the gametophytes with spores originating from April. Filamentous gametophytes appeared after 3 weeks cultivation of spores originating from April and although female gametophytes were recognizable approximately 1 week prior to male gametophytes, the female and males were found in the relation 1:1 in all nutrient treatments after 5 weeks cultivation.

Gametophytic phase of Alsophila odonelliana (Cyatheaceae)

The gametophytic morphology and development of Alsophila odonelliana (Alston) Lehnert, have been studied through in vitro cultures. This species grows in southern Bolivia and northwestern Argentina. The spores are uniform in structure, but not in size; a certain percentage being smaller than the average. 16 spores per sporangium were found. The germination is of the Cyathea type. It was found that spores stored at 4°C can maintain their viability for over two years. The maximum value of germination depends on spore age. The filamentous gametophytes are 4–16 cells long. Young gametophytes have 1–2 branches that give rise to new gametophytes. Male, female, bisexual and neuter gametophytes were found. Propagules were frequently found in neuter gametophytes, and female and bisexual gametophytes were found to have chlorophyll containing scales. The antheridia are made up of five cells and produce non‐viable spermatozoids. The archegonia have necks formed by four columns with four cells each. Most of the gametophytic phase is documented with photomicrographs.

Novel means for variety breeding and sporeling production in the brown seaweed Undaria pinnatifida (Phaeophyceae): Crossing female gametophytes from parthenosporophytes with male gametophyte clones

SummaryThe unialgal haploid gametophyte clones are frequently used for variety breeding and sporeling production in the brown seaweed Undaria pinnatifida because a single crossing of a pair of the selected male and female gametophyte clones can generate sporophytic offspring with identical genotype and phenotype. As the seeds to be sprayed on the collectors, the detachment rate of the filamentous gametophytes is high in comparison to the seeded spores. In this investigation, we report the use of parthenogenesis to achieve the same goal in variety selection and sporeling production but with higher efficiency. The selected female unialgal gametophyte clone (Code: 06‐8‐1F) was induced to produce parthenosporophytes. These sporophytes were grown up in a controlled system and used to release zoospores. All zoospores generated into female gametophytes. These female gametophytes were allowed to go through parthenogenesis for the second year to confirm the applicability of this means. In the third year, the zoospores released from the parthenosporophytes were seeded on collectors over summer in female gametophyte form. In the early autumn, a selected male unialgal gametophyte clone (code: 5#F1‐2‐5M) was used to cross the seeded female gametophytes on the collectors. When the sporelings reached a mean length of 780 μm, they were transplanted to open sea on longlines for growing up. At harvest, the average length, width and wet weight of the adult sporophytes were 211 cm, 48.8 cm and 373 g, respectively. The sporophytic blades were uniformly smooth without wrinkles on both sides of the midrib, indicating top quality of the products. Amplified fragment length polymorphism analyses confirmed the identical genotypes of sporophytic offspring. These results suggested that this novel variety breeding and sporeling production method could serve as an efficient alternative to the traditional breeding technique for U. pinnatifida and possibly other commercial kelps that have identical life cycles.

Spore germination of Gleichenella pectinata (Willd.) Ching (Polypodiopsida-Gleicheniaceae) at different temperatures, levels of light and pH

This study investigated the effects of different temperatures (25 and 30 ± 2 ºC), light levels (62, 42, 22 and 5% of natural light), and pH (4.0, 4.5, 5.0, 5.5, 6.0 and 6.7) on the spore germination of Gleichenella pectinata. To accomplish this, the spores were surface sterilized and sown in bottles containing mineral medium. The spores of G. pectinata are monolets and the perispore surface can show large and irregular deposits. During germination, filamentous gametophytes with and without developing rhizoids were observed. Only gametophytes which presented developed rhizoids were able to reach the heart-shaped developmental stage. Based on the collection, the rate of and gametophyte development were generally very low. The relative germination rates were higher at 25 ºC than at 30 °C. Moreover, the highest percentages of gametophytes with developed rhizoids were observed at 22 and 5% of natural light (8.8 ± 2.3% and 11.3 ± 2.2% respectively) and the highest percentage of heart-shaped gametophytes were observed at pH 4.5 and 5.0 (1.2 ± 0.8% and 2.2 ± 0.8%, respectively).

Life-cycle of Scinaia interrupta (Nemaliales, Rhodophyta)

The life-cycle of Scinaia interrupta (A.P. de Candolle) M. J. Wynne was investigated in vitro using four irradiance regimes: 4, 8, 12 and 16 μmol photons m �2 s �1 . A triphasic heteromorphic life-cycle was observed. Carpo- spores released by cystocarps of gametophytes collected in the field developed into filamentous tetrasporophytes, which produced tetrahedral tetrasporangia. Tetrasporangial development was accelerated under higher irradiance levels. Tetraspores germinated into filamentous protonemal gametophytes, initially identical to the tetrasporophyte. Filamentous gametophytes developed apical utricles and gave rise directly to the fleshy gametophyte. Further development of the fleshy gametophyte was not observed at the lowest irradiance regime (4 μmol photons m �2 s �1 ). The present study reports for the first time the influence of the irradiance regime on the initial tetrasporangial devel- opment and in the development of the fleshy gametophyte, and reinforces the importance of light intensity on Scinaia life-cycle. Production of apical utricles by the filamentous gametophyte is newly reported for the genus.

Aspects of Gametophyte Development of Dicksonia sellowiana Hook (Dicksoniaceae): an Endangered Tree Fern Indigenous to South and Central America

Abstract With the purpose of providing a basis for programs of sustainable management in the conservation of this endangered species, this paper presents morphological aspects on the gametophyte development of Dicksonia sellowiana (Dicksoniaceae) by light microscopy and scanning electron microscopy. Dicksonia sellowiana spores were germinated in Morh's nutrient solution modified by Dyer (1979) under a 16-hour photoperiod at 23 ± 2°C. To determine the best substrate for gametophyte and sporophyte development, 30 days after spore sowing filamentous gametophytes were transferred to different substrates: soil rich in organic matter; coxim (coconut fiber); sterilized typic hapludult soil (distroferric red nitosoil); and sterilized typic hapludult soil (distroferric red nitosoil) with the addition of organic compost. The best system for D. sellowiana growth was the red soil with the addition of compost. Fifteen days after spore sowing in mineral solution, gametophytes were filamentous. Some had attained laminar...

Characterization of rbcS genes in the fern Pteris vittata and their photoregulation.

The fern Pteris vittata L. belongs to the evolutionarily highest group of vascular plants that still maintains a free-living gametophytic stage. The two-dimensional gametophytes developed under blue light exhibit higher CO2 fixation efficiency and different ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit (SSU) composition when compared to the red-induced filamentous gametophytes (H. Eilenberg et al., 1991, Plant Physiol 95: 298-304). To unravel the correlation between SSU structural differences and light regulation, two rbcS genes and two additional partial cDNAs were characterized. Fern rbcS genes resemble those of higher plants in their promoter light-regulatory elements (LREs) and intron number and positions. However, the primary structure of the fern mature SSUs displays much higher divergency within the gene family. This structural variability was correlated with differential steady-state mRNA levels under red and blue light. Genes rbcS-1 and-4 and 4-to 6-fold higher transcript levels in red light while rbcS-2 and-3 contribute relatively more to the blue rbcS mRNA levels. Five of the 12 amino acids that differ between rbcS-2 and-4 affect hydrophobicity and might play a crucial role in determining the efficiency of CO2 fixation. Dendrograms of Rubisco SSUs and LSUs indicate early divergence of the fern types from the rest of the vascular plants. However, prominent higher-plant-like Rubisco features such as high carboxylation efficiency, promoter LREs and exon-intron structure, suggest that molecular specialization of the higher-plant Rubisco prototype occurred earlier than the emergence of ferns.

The life history of a Santa Catalina Island population of Liagora californica (Nemaliales, Rhodophyta) in the field and in laboratory culture

The gametangial phase of Liagora californica Zeh has a life span rarely exceeding 10 mo at Santa Catalina Island, California. Gametophytes reached maximal cover during late summer and autumn, periods of longer photoperiods and warmer sea temperatures, before declining sharply in abundance by late winter. Field-collected gametophytes were both dioecious and monoecious. Carpospores developed in culture into filamentous tetrasporophytes that produced irregular, cruciate tetrasporangia within 45 d. No monosporangia were detected in either gametophytes or tetrasporophytes. 4′,6-diamidino-2-phenylindole (DAPI) fluorescence of the nuclei of gametophyte vegetative cells was half that of vegetative sporophyte cells, suggesting that meiosis occurs during tetrasporogenesis. The magnitude of tetrasporangial production varied between two clones but occurred under all nine photoperiod (14: 10, 12: 12, and 10: 14 h L: D) and temperature combinations (13, 17, and 21°C); best tetraspore production occurred in both clones under ‘summer’ conditions (14: 10 h L:D; 21°C). Germination of tetraspores into uniseriate, filamentous gametophytes and the production of erect gametophyte axes from bud-like initials also occurred under all photoperiod-temperature conditions. Greatest production of young, uniseriate gametophytes occurred under 13 and 17°C; best growth and development of erect, multiaxial gametophyte fronds occurred under the combination of longer day and warmer temperature conditions. On the basis of field and laboratory data, we hypothesize that small, prostrate, uniseriate gametophytes are the overwintering stage of L. californica at Santa Catalina Island. Enhanced tetrasporogenesis and the growth and development of erect gametophyte axes under longer days and warmer temperatures may be adaptations that evolved at lower latitudes and not ones optimally suited for year-round maintenance of L. californica gametophytes at temperate Santa Catalina Island, the northern distributional limit of this species in the eastern North Pacific.

Effects of ultrasonic treatment on female gametophytes ofLaminaria japonica (Phaeophyta)

This study on the effects of ultrasonic treatment on female gametophytes ofLaminaria japonica showed that: 1. Ultrasonic treatment had shortening effect on filaments of female gametophytes. Within certain period of time, the average length of filamentous female gametophytes was shortened. 2. Ultrasonic treatment had emptying effect on cells. The number of empty cells increased with time of treatment. Ultrasonic treatment had harmful effect on cells. 3. Ultrasonic treatment could break down cell walls. The combination of frequency of 20 kHz, output of 15 W, 40 s and 60 s of treatment was best for this purpose. After ultrasonic treatment, the regeneration of female gametophytes into sporophytes was effected. Female ganetophytes could not recover after too long period of treatment.

Life History, Reproductive Morphology and Development of the Antarctic Brown Alga Desmarestia menziesii J. Agardh*

AbstractThe life history, reproduction and development of Desmarestia menziesii J. Agardh from Antarctica is described. Unilocular sporangia occur singly or in small groups in the outermost cortical layer of the sporophyte. They are formed by periclinal division of cortex cells into a stalk cell and the sporangium initial. Meiospores germinate into dioecious microscopic filamentous gametophytes. As in other perennial Antarctic species of the Desmarestiales, gametangia are formed in culture under short‐day conditions or in darkness. In nature, juvenile sporophytes should therefore be formed in winter. They develop only attached to the oogonium. At first they are uniseriate and elongate by means of an intercalary meristem located in their middle part. Laterals are formed predominantly in this region, and they subsequently give rise to secondary laterals. The branching pattern is opposite to alternate in both young and adult plants. Cortication of the main axis is initiated by filaments growing out from the lowermost cells of the primary laterals. In sporophytes of this developmental stage the meristem of the main axis is confined to a small region where cortication starts and above. Lateral branches elongate and become corticated in the same way as the main axis. In mature plants, cells of the inner cortex can become meristematic again and form a meristoderm which contributes to axis thickness by periclinal and anticlinal divisions. The observations are discussed in relation to possible evolutionary relationships in the genus Desmarestia and in the order Desmarestiales.

A Technique for the Investigation of Genetic Variation in Filamentous Gametophytes of Trichomanes (Hymenophyllaceae)

The gametophyte of most ferns is a small, thalloid, heart-shaped, short-lived structure. In some species of Trichomanes (Hymenophyllaceae), the gametophytes are filamentous and consist of a weft of inter-twining branched filaments. Such gametophytes are perennial and can reproduce asexually by means of gemmae. Independent colonies of gametophytes have been reported from North America (Farrar, 1967, 1992), Britain (Rumsey et al., 1990) and Central Europe (Vogel et al., 1993, Jerome and Rasbach, 1994). These colonies of filamentous gametophytes can exist as very small patches (<10mm2) or can cover huge areas (20m2). Such a colony, whether large or small, may have arisen from a single spore, from several spores or, asexually, by establishment from one or more gemmae. A colony of filaments may represent either a single individual, or consist of many individuals interwoven. This presents a problem for the study of genetic variation of individuals in these independent colonies when using conventional methods, eg. allozyme analysis (Hamrick, 1990). Since the maximum length of a continuous individual filament that can be isolated from a colony is only about 60-100 cells, conventional allozyme analysis and DNA extraction methods are inapplicable. To extract DNA from a single gametophyte filament, ultrasonication was used directly to provide a crude DNA extract for DNA amplification. To establish the extraction and amplification techniques, gametophytes of four taxa of Trichomanes were compared using a large single-copy region of chloroplast DNA. Taberlet et al. (1991) have shown that the use of their universal primers for DNA amplification of the chloroplast intergenic spacers between the trnT and trnF genes is informative for a wide range of plant species. MATERIALS & METHODS

Sexual reproduction and the life history ofSplachnidium rugosum(Phaeophyceae)

Sexual reproduction in Splachnidium rugosum is anisogamous. Sporophytes produce unilocular sporangia in conceptacles. In culture, zoospores developed into filamentous gametophytes which remained sterile but occasionally gave rise to sporophytes directly. Wild gametophytes become fertile during spring and summer. They are dioecious and bear conical plurilocular gametangia. Male gametangia are distinguished from females by their orange colour and smaller loculi. Male gametes are smaller than female gametes and possess a smaller chloroplast with a more conspicuous eyespot. Plasmogamy occurs rapidly after female gametes have settled and withdrawn their flagella. Female gametes are capable of parthenogenesis and develop into more female gametophytes. Male gametes germinate but fail to develop beyond a few cells. Chromosome counts gave 20–24 for wild sporophytes and eight-10 for wild gametophytes, and it is inferred that meiosis occurs in unilocular sporangia. During sporogenesis, the characteristic stellate ch...

The anatomy, life history and development of the Antarctic brown alga Phaeurus antarcticus (Desmarestiales, Phaeophyceae)

Abstract Most aspects of the anatomy, life history and development of Phaeurus antarcticus Skottsberg are typical of the Desmarestiales. Branching is opposite, and the thallus is essentially filamentous in construction. The central axial filament, which comprises cells with thin end walls, and is surrounded by a sheath of narrow filaments, resembles the trumpet hyphae of Desmarestia. The outer surface is covered with assimilatory filaments that arise from cortical cells. Meiosporangia are unusual in that they are catenate, and zoospores develop into dioecious filamentous gametophytes. Female gametophytes consist of very few, relatively large cells, while male gametophytes form more extensive growths of narrower filaments. The oogonia and antheridia are typical of the order. Eggs are released, and in culture frequently remain attached to the oogonial wall. Sporophytes develop from eggs, and also arise apogamously from vegetative cells of female gametophytes. The main axis and primary laterals of sporophyte...

On the sexual reproduction ofDictyosiphon foeniculaceus (Phaeophyceae, Dictyosiphonales)

Dictyosiphon foeniculaceus from Sweden and Newfoundland was studied in laboratory culture. Zoids from unilocular sporangia developed into dioecious microscopic filamentous gametophytes which produced uniseriate plurilocular gametangia in low temperatures (0 to 8 °C). Zygotes and unfused isogametes gave rise to filamentous protonemata on which parenchymatous macroscopic sporophytes were formed. Isolates from Sweden and Newfoundland were interfertile. Although formed in culture, genetically unisexual sporophytes were not detected in nature. Female gametes ofD. foeniculaceus produced a sexual pheromone. It was identified as finavarrene, which is also known as the sperm attractant inAscophyllum nodosum.

Interactions of nitrate and phosphate on the development of microscopic stages of Lessonianigrescens Bory (Phaeophyta)

The effects of different concentrations of nitrate and phosphate on the microscopic stages of development of Lessonia nigrescens Bory were studied. Meiospores were cultivated under different concentrations of nutrients (0 to 100 μmol N·l −1, and 0 to 1.00 μmol P·l −1) and optimal light and temperature conditions. The successive stages of development have different nutrient demands. Meiospore germination occurred in all the nitrate and phosphate concentrations tested, the germination percentage was not significantly modified by the different nutrient amounts. Although gametophytes developed in all conditions, their patterns of development and fertility varied. When no nutrients were added, gametophytes remained unicellular and sterile. Depending on the interacting effects of the amounts of nitrate and phosphate added to the culture media, few-celled or multicellular gametophytes developed. The highest gametogenesis was found in the conditions favouring few-celled gametophytes. In the conditions inducing filamentous gametophytes, gametogenesis was delayed or inhibited. Sporophytes developed only in very precise and restricted conditions. The results, however, suggested that fertilization was the process requiring the most precise conditions; once sporophytes developed, even when only in small numbers, most of them showed normal patterns of growth.

Culture studies on the life history of Adenocystis utricularis (Phaeophyceae, Dictyosiphonales)

Adenocystis is endemic to southern circumpolar coasts. Diploid macroscopic thalli are sporophytes forming unilocular sporangia. Meiospores develop into filamentous or discoid microthalli which are dioecious gametophytes. Morphological isogametes are formed in nodular multicellular structures on filamentous gametophytes or singly in disc cells. Zygotes reconstitute the diploid Adenocystis phase. Unfertilized gametes develop into gametophytes of the same sex. Adenocystis plants also originate directly on discoid or filamentous gametophytes and are genetically unisexual and presumably haploid. Chromosome counts gave 23 ± 4 and 47 ± 5 for haplo- and diplo-phases, respectively.

Initial events in the tip-swelling response of the filamentous gametophyte of Onoclea sensibilis L. to blue light

Several inhibitors were applied to filamentous gametophytes of the fern Onoclea sensibilis in the attempt to characterize how electrical phenomena might be involved in the tip-swelling response to blue light (BL). The membrane potential of the apical cell in the typical fern filament rests near-120 mV in darkness, but irradiation with blue light causes the membrane to hyperpolarize at a steady rate of 2.6 mV min(-1) until it reaches a new stable value between-130 and-135 mV. In darkness, 10(-4)M salicylhydroxamic acid (SHAM), an inhibitor of BL-mediated absorbance changes in putative plasma-membrane fractions from maize coleoptiles, has no observable effects on the membrane potential or on filamentous growth. A SHAM pretreatment before BL irradiation causes approx. 70% inhibition of the membrane hyperpolarization as well as a comparable reduction in the growth response; however, SHAM has no effect in experiments where its application follows the onset of the electrical response. Exposing the filaments to 10(-5)M Na3VO4, an inhibitor of the plasma-membrane ATPase, depresses the membrane potential in darkness. Depending on the timing of application, Na3VO4 prevents the initiation of or blocks further increases in the BL-mediated hyperpolarization. Application of Na3VO4 causes an immediate cessation of growth in both darkness and BL. These findings implicate the involvement of a plasmalemma-bound flavin-cytochrome complex and ATP-driven proton pump in the initial events of this growth response to blue light.

Cell expansion in the filamentous gametophyte of the fernOnoclea sensibilis L.

Filamentous gametophytes of the fernO. sensibilis were exposed to paired combinations of light of different qualities, hormones and cations in the attempt to elucidate the underlying processes that regulate cell expansion. Simultaneous treatments with high-pH buffers or the auxin antagonistp-chlorophenoxyisobutyric acid abolished blue-light-mediated expansion but did not influence growth in red light. In contrast, the red-light response was preferentially altered by the ethylene absorbant KMnO4 or the Ca(2+) chelator ethyleneglycol-bis(β-aminoethyl ether) N,N'-tetraacetic acid. The Ca(2+) ionophore A23187 caused a significant reduction in cell expansion under both blue and red irradiation. A marked promotion of expansion was mediated by high concentrations of indole-3-acetic acid, but this effect was dependent on the presence of low-pH buffers. The ethylene-generating agent 2-chloroethylphosphonic acid decreased the magnitudes of both photoresponses; this inhibition was further enhanced by high Ca(2+) concentrations. These findings and those with other plants are interpreted in terms of two independent control mechanisms for cell expansion: 1) a blue light photoreceptor-auxin-hydrogen ion system, and 2) a phytochrome-ethylene-calcium ion system.