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The morphology and reproduction of the red alga Acrochaetium pectinatum
Abstract
The life history of the marine red alga Acrochaetium pectinatum (Kylin) Hamel was studied in unialgal culture using supplemented natural seawater media. The tetrasporophytes are larger than the gametophytes, have a compact filamentous basal system, and produce monosporangia and tetrasporangia. Mono-spores give rise to tetrasporophytes. Tetraspores develop into small gametophytes with unicellular bases. The gametophytes are heterothallic when small (usually less than 500 μ) but as some females become larger (2-3 mm) they produce spermatangia as well as carpogonia. Gametophytes may bear mono-sporangia in addition to carpogonia or spermatangia. These monospores give rise to gametophytes. Fertilization of the carpogonia has not been observed. The tetrasporophytes produce only monosporangia in day-lengths of 12-16 hr, but both tetrasporangia and monosporangia are formed in daylengths of 6–10 hr. Tetrasporangial production is reduced at 15 C compared with 10 C. Light intensity in the range of 5-200 ft-c (cool white fluorescent lighting) has no apparent influence on induction of tetrasporangia. Induction of tetrasporangia is not a photoperiodic response because their development is not inhibited by a brief light break in the middle of the dark period in short daylengths.
Plastid morphology, origin, and frequency of sporangia and vegetative branching are variable during the ontogeny, and consequently are somewhat unreliable as taxonomic criteria. Differences in basal systems between gametophytes and tetrasporophytes also indicate that this feature, which is used to distinguish major subgeneric groupings in Acrochaetium, may not be as useful as previously thought.
... The taxonomical systems most usually applied to this family are those of KYLIN (1944) and of PAPENFuss (1945) and are based primarily on the morphologies of the basal parts of the plants and of the chloroplast, respectively. KYLIN's system has proved to be more or less insufficient as shown by recent culture studies by WEST (1968), who demonstrated the presence in Acrochaetium pectinatum (KYLIN) HAMEL of gametophytes and tetrasporophytes with unicellular and multicellular bases, respectively. Chloroplast morphology is somewhat variable also, depending upon developmental stage. ...
... Until rather recently the gametophytes of this species were unknown, but culture studies by KNAGGS (1968) and by WEsT (1969) have demonstrated reduced gametophytes in certain clones. It seems likely that the specimens from Greenland correspond with those from Alaska (Amchitka Island) (WEsT, 1969) and show a one-generation life history. ...
... Until rather recently the gametophytes of this species were unknown, but culture studies by KNAGGS (1968) and by WEsT (1969) have demonstrated reduced gametophytes in certain clones. It seems likely that the specimens from Greenland correspond with those from Alaska (Amchitka Island) (WEsT, 1969) and show a one-generation life history. Culture experiments with material from Greenland may further elucidate this. ...
One hundred and twenty-four species of marine algae from South Greenland are dealt with, of which 11 belong in the Cyanophyceae, 28 in the Rhodophyceae, and 1 each in the Chrysophyceae, Dinophyceae, and Xanthophyceae, respectively, 49 in the Phaeophyceae and 33 in the Chlorophyceae. Of the 11 Cyanophyceae 4 have not previously been reported from Greenland: Aphanothece sp., Nostoc minutum, Hydrocoleum lyngbyaceum and Lyngbya infixa. Further, new observations are presented concerning cell divisions, which resulted in daughter cells of uneven size, in Pleurocapsa amethystea, and two new host plants, Rhodochorton purpureum and Ulothrix speciosa, are reported for Sarcinastrum urosporae in Greenland. All the red algaeare well known from literature, but additional information are given especially with regard to reproductive structures. Antheridia-like cells were observed in Rhodochorton spetsbergense and in Audouinella membranacea in plants that also bore tetrasporangia.The present data support the combining of Rhodochorton penicilliforme with Rhodochorton spetsbergense. For Rhodophysema elegans some details concerning the formation of tetrasporangia and the presence of branched paraphyses are reported. Female gametophytes as well as a presumed male gametophyte of Antithamnion boreale have been found for the first time in nature in Greenland. It is suggested that this species has a typical Polysiphonia-type of life history in this part of its distribution. This suggestion is supported also from observations from cultures recently established. Callocolax neglectus, presently known as a red algal parasite on Callophyllis laciniata, was found and further described growing on Callophyllis cristata, which is a new host for thisparasite. The known distribution for Greenland of H alosacciocolax kjellmanii, previously known from the type locality in Scoresby Sund only, has been considerably extended. The brown algae Myriactula clandestina and Streblonema chordariae are reportedfrom Greenland for the first time, the latter from an old collection by ROSENVINGE. A new find of Phaeostroma parasiticum is reported and the relation to P. pustulosum is discussed. Additional information are given on Porterinema flufliatile, including anew host plant, Delamarea attenuata. In some cases supplementary information have been added from culture studies of algae from the Godthåbsfjord, West Greenland. Thus the development of hairs in Phaeostroma pustulosum has been followed, and the taxonomic reliability of this character confirmed. The presence of a microthallus and hair-like structures in the life his tory of Elachista fueicola has been demonstrated, and it is suggested to give up the combination Myriactula lubrica. The culture studies also support the assumption that Pilayella littoralis and P. paria are conspecific, and suggest a removal of Litosiphon filiformis from the genus Litosiphon. All the green algae found are well known to science. It is suggested to remove Entoderma wittrockii from the flora of Greenland. Culture studies indicate that Chlorochytrium inclusum is connected with Acrosiphonia (possibly A. sonderi) in Greenland, while Chlorochytrium cohnii is an independant species.
... Seven species of red algae form tetraspores under short days. These are Acrochaetium pectinatum (West, 1968), A. asparagopsis (Abdel-Rahman, 1982a and b), Rhodochorton purpureum (West, 1968(West, , 1969Dring and West, 1983) and R. tenue (West, 1968(West, , 1969 and Halymenia latifolia (Maggs and Guiry, 1982), the Hymenoclonium stage of Calosiphonia vermicularis (Mayhoub, 1976) and the Trailliella stage of Bonnemaisonia hamifera (Liining, 19806). ...
... Seven species of red algae form tetraspores under short days. These are Acrochaetium pectinatum (West, 1968), A. asparagopsis (Abdel-Rahman, 1982a and b), Rhodochorton purpureum (West, 1968(West, , 1969Dring and West, 1983) and R. tenue (West, 1968(West, , 1969 and Halymenia latifolia (Maggs and Guiry, 1982), the Hymenoclonium stage of Calosiphonia vermicularis (Mayhoub, 1976) and the Trailliella stage of Bonnemaisonia hamifera (Liining, 19806). ...
... There are several other reported responses which accomplish the same results but seem to be mediated by pigments other than phytochrome and do not respond to a light break in the dark period. West (1968) reported a SD response in Acrochaetium pectinatum which did not respond to a light break. Several of the photoperiodic responses I have cited in this paper have similar responses. ...
SYNOPSIS. Constantinea subulifera, a perennial red alga with a bushy type growth, uses a short day (long night) photoperiodic response to initiate a new blade at the tips of several stipes in September to October. These blades complete the lag phase of their growth during the winter via a food transfer from the old blade.
Under a 9L–15D photoperiod it requires 21–28 days to initiate a new blade. The critical photoperiod is 11–12 hr. This is a phytochrome-mediated response which can be negated by a low quantum dose light break of red or blue light in the middle of a 16-hr dark period. Blades will initiate and grow in complete darkness.
The initiation of new blades in the fall and their slow growth throughout the winter (lag phase) gives Constantinea subulifera an advantage in capture of habitat space.
... The genus with historical precedence is Audouinella Bory (1823:340), and its usage requires some new nomenclatural combinations herein proposed. With the advent of further culture work in this family, it is possible that in the future we will be able to resegregate the species into more than one genus based on more reliable characters, such as life history characteristics (West, 1968(West, , 1969Stegenga, 1978;Stegenga and van Wissen, 1979). ...
... The number of gametophytes that become reproductive is less than the number of tetrasporophytes that do so, indicating that gametophytic reproduction is being inhibited by depth. The specific factors involved in re production of C. chamissoi are still unknown and could be either environmental or endogenous like in other species (West, 1968;Edwards, 1971;Guiry, 1984;McLachlaneM/., 1988). Stud ies upon aspects such as differences in the performance of early stages of development (González & Meneses, 1996) resulted in higher rates of settlement and germination for tetraspores which could explain the higher ratio of haploid plants in the field. ...
Chondracanthus chamissoi (C. Ag.) Kützing is a commercial resource in certain areas oí the Chilean coast and is becoming increasingly important due to its food valué in Asían countries. This species grows only in natural beds that require to be rationally exploited in order to avoid their depletion. Since the first step necessary to develop this exploitation is a knowledge of the dynamics of the populations, the study oí seasonal and spatial variations in abundance and reproduction oí a natural bed in the locality of Puerto Aldea has been carried out. Samples taken bimonthly at four different depths during an entire year resulted in the detection of a sharp seasonality of biomass of sterile as well as reproductive plants with its máximum in summer months due mainly to the increase in growth of plants rather than in density. Reproductive plants only contributed 30% of the total biomass. Reproductive sporophytes were more abundant throughout the year. Reproductive gametophytes and sporophytes behaved differently over depth, with cystocarpic plants being more abundant at shallower depths and tetrasporophytes showing no differences along the bathymetric profile. Nevertheless, phase ratios calculated considering sterile and reproductive plants resulted in a higher proportion of haploid (gametophytes) plants. Differences appear to be due to phase-spedfic behavior at early stages of development or to difieren tial rates of attachment to the sustrate by drifting frond pieces.
Reproduction and life history patterns in culture of five Caloglossa species from Australia and New Zealand are compared. Caloglossa adhaerens King et Puttock and Caloglossa bengalensis (Martens) King et Puttock have a Polysiphonia-type sexual life history (P-type, isomorphic alternation of generations). Caloglossa monosticha Kamiya occurs only in Western Australia (WA) and is a P-type. Caloglossa ogasawaraensis Okamura occurs in WA, Northern Territory (NT), Queensland (QLD), New South Wales (NSW), Victoria (VIC) and South Australia (SA) and is for the most part a P-type in culture. A few isolates have bisexual gametophytes that are self-compatible, while most are unisexual. Caloglossa ogasawaraensis from Adelaide, SA and from Wilsons Promontory, VIC are new records for these States. In Australia, Caloglossa postiae (King et Puttock) Kamiya et King occurs in NSW, NT and QLD. All nine isolates are P-type. Isolates of Caloglossa leprieurii (Montagne) G. Martens from NSW, NT, QLD, Tasmania, VIC and New Zealand are P-type except for the freshwater isolates in which tetraspore germlings do not reproduce. In some isolates mixed-phase reproduction is seen with male gametophytes producing both viable spermatia and tetrasporangia and female gametophytes producing procarps and sori with non-dividing sporangia. All isolates of C. leprieurii from Spencer Gulf and Gulf of St Vincent, SA and one isolate from QLD give rise to successive asexual generations of tetrasporophytes. Based on RuBisCO spacer DNA data an asexual life history has arisen several times in the C. leprieurii complex. The literature on apomixis, mixed-phase reproduction, bisexuality and sexual compatibility in red algae is surveyed.
Rhodachlya hawaiiana Kurihara, J. A. West, Conklin et A.R. Sherwood sp. nov. is described based on cultured material from the island of Hawaii as the second member of the genus Rhodachlya. The pit plug ultrastructure of this alga is characterized by the presence of inner and outer cap layers but lacking a cap membrane between the layers, which is a diagnostic feature of the order Rhodachlyales and the genus Rhodachlya. Morphologically, R. hawaiiana is distinctive from R. madagascarensis in vegetative cell dimensions, frequency of colorless hair cell formation, and spore germination pattern. Rhodachlya hawaiiana and R. madagascarensis are also distinguishable by their nuclear SSU rRNA gene sequence divergence (p-distance = 0.0064), which is comparable to other species-level divergences among members of the Nemaliophycidae.
An examination of the type specimens of two of the most widely distributed species of Acrochaetium growing in Liagora clarifies the status of A. liagorae Børgesen (which includes A. collinsianum) and A. barbadense (Vickers) Børgesen (including A. liagorae of Hamel and A. vanbosseae Papenfuss). Remarks are also made on A. laxum which has been confused with A. liagorae.
Red algal systematics is in a state of flux unparalleled since the early decades of this century. Ultrastructural and biochemical studies are providing features for a revised classification at ordinal and supraordinal ranks, whereas characters of vegetative and reproductive morphology continue to establish discontinuities among taxa at lower ranks. Cytological, biosystematic, and chemotaxonomic contributions are viewed as useful in defining relationships at specific and infraspecific ranks. Chemotaxonomic studies, depending on the properties of the taxa that are being studied, are applicable at all taxonomic levels. The taxonomic importance of life histories and themes of vegetative morphology, including spore germination, heterotrichy, initiation and differentiation of thalli are discussed at length. Homologies of auxiliary cells, carpogonial branches, and connecting filaments are examined in the context of relationships among Corallinales, Cryptonemiales, Gigartinales, and Rhodymeniales, and their included families. Based on a phylogenetic analysis, we provide a synopsis of our classification of Rhodophyta, together with the features that define each order.
The genus Ceramium Roth shows a high degree of morphological variability within some of its species. As reported in several descriptions, this variability has been experimentally examined in only a few cases where it has been shown to be the result of environmental influences or, it has been detected between tetrasporophytic and gametophytic generations. In order to examine the effect of environmental factors upon the morphology of different phases of the life cycle of the genus, three conspicuous species from Hawaii were cultured under controlled conditions and compared with field-grown plants. Ceramium clarionensis Setchell et Gardner, Ceramium flaccidum (Kutzing) Ardisonne and Ceramium sp. 1 showed different results for a number of characters assessed under the same conditions. Ceramium sp. 1 has a uniform morphology between gametophytes and tetrasporophytes while in C. clarionensis the phases are morphologically distinguishable. Ceramium flaccidum retains its self-defining character, the arrangement of cells in the node, in spite of the growing conditions. No comparisons between sexual and asexual phases were done in this species. However, the three cultured species show differences in their morphological characters from plants grown in the field, indicating their susceptibility to environmental factors. These results indicate the variability of responses within the genus and suggest the necessity to treat each species separately.
Although most sexually reproducing strains of Rhodochorton purpureum are dioecious, an isolate from Chile is monoecious. The tetrasporophyte of the monoecious strain differentiates directly from the fertilized carpogonium as in the dioecious strains but it differs slightly in its development.
An isolate of the filamentous red alga Acrochaetium efflorescens from the NE Atlantic was followed in culture through a triphasic sexual life history. Morphology of each phase matched previous descriptions for this alga. However, inclusion of A. efflorescens in the genus Acrochaetium is problematic. In current taxonomic treatments this genus includes acrochaetioid algae with a stellate plastid and a large central pyrenoid. Acrochaetium efflorescens, on the other hand, has consistently been reported to possess spiral to ribbon-shaped plastids. To determine the phylogenetic affinities of A. efflorescens, we sequenced large subunit ribosomal DNA and resolved full support (Bayesian posterior probabilities; maximum likelihood, neighbour joining, and parsimony bootstrap percentages) for inclusion of A. efflorescens within the order Acrochaetiales. However, it does not associate closely with any of the existing genera in this order, showing only a weak affinity to the genus Rhodochorton. The genus Grania, originally established by Kylin, is currently available for this species. Given its distinct anatomy (ribbon-shaped plastids in combination with seriate carposporangia), unique molecular signature, and lack of congruence with other current generic concepts within the Acrochaetiales, we advocate resurrecting the genus Grania for G. efflorescens.
Spermatangial, carposporangial and tetrasporangial plants of Cordylecladia erecta are found sporadically from September to April inclusive. Cultured tetraspores from plants collected on the west coast of Ireland formed dioecious gametangial plants at 15°C, under short day conditions and under an interrupted dark period, while control plants under long day conditions, remained sterile. Carpospores from the carposporophytes of fertilized female plants in culture formed tetrasporangial plants under short day conditions at 15°C and 10°C, as well as under an interrupted dark period at 15°C. Control plants under long day conditions at 15°C, and with interrupted dark period at 10°C remained sterile. C. erecta thus has a Polysiphonia-type life history, with reproduction under photoperiodic control.Procarps are described for the first time from cultured female plants. They are formed in small depressions surrounded by sterile hairs. The carpogonial branch is four-celled, and the carpogonium forms a strongly emergent trichogyne that protrudes amongst the sterile hairs. Carpogonial branches are formed on a supporting cell that also bears a two-celled auxiliary cell branch, which is formed before fertilization. Development of the carposporophyte takes place outwards from a fusion cell. Tetrasporangia are formed in an intercalary position on modified cortical filaments. These reproductive details confirm the current placement of the genus Cordylecladia in the family Rhodymeniaceae (Rhodymeniales), close to Rhodymenia.
Shell-boring microthalli in
Helminthocladia
and
Scinaia
(Nemaliales, Rhodophyta). Spores shed from pink mussel shells were shown to develop into branched monosiphonous thalli, their filaments penetrating into shell fragments. Isolates from four single germlings were cultivated. Two of these produced gametophytes ofHelminthocladia andScinaia; the others have so far only reproduced by tetraspores or monospores. Evidently the microthalli of some genera of the Nemaliales — which are, with the exception ofNemalion multifidum, known only from cultures — are shell-inhabiting and have therefore not been found in nature. The adult algae occur mainly on shells and CaCO3 substrates. Until the beginning of the century,Helminthocladia andScinaia frequently occurred at Helgoland, but they have not been found there for more than 50 years. Their microthalli, however, are still present as shell-boring algae. This study is intended to stimulate similar ones in other genera of the Nemaliales so as to obtain a broader basis for discussion of systematic and phylogenetic relationships.
SUMMARY Reproduction and life history patterns in culture of five Caloglossa species from Australia and New Zealand are compared. Caloglossa adhaerens King et Puttock and Caloglossa bengalensis (Martens) King et Puttock have a Polysiphonia-type sexual life history (P-type, isomor- phic alternation of generations). Caloglossa monosticha Kamiya occurs only in Western Australia (WA) and is a P-type. Caloglossa ogasawaraensis Okamura occurs in WA, Northern Territory (NT), Queensland (QLD), New South Wales (NSW), Victoria (VIC) and South Australia (SA) and is for the most part a P-type in culture. A few isolates have bisexual gametophytes that are self- compatible, while most are unisexual. Caloglossa oga- sawaraensis from Adelaide, SA and from Wilsons Promontory, VIC are new records for these States. In Australia, Caloglossa postiae (King et Puttock) Kamiya et King occurs in NSW, NT and QLD. All nine isolates are P-type. Isolates of Caloglossa leprieurii (Montagne) G. Martens from NSW, NT, QLD, Tasmania, VIC and New Zealand are P-type except for the freshwater iso- lates in which tetraspore germlings do not reproduce. In some isolates mixed-phase reproduction is seen with male gametophytes producing both viable spermatia and tetrasporangia and female gametophytes producing procarps and sori with non-dividing sporangia. All isolates of C. leprieurii from Spencer Gulf and Gulf of St Vincent, SA and one isolate from QLD give rise to successive asexual generations of tetrasporophytes. Based on RuBisCO spacer DNA data an asexual life history has arisen several times in the C. leprieurii complex. The literature on apomixis, mixed-phase reproduction, bisexuality and sexual compatibility in red algae is surveyed.
Growth of Prasinocladus marinus (Cienk.) Waern was maximal in media of 35‰ salinity, showing a five-fold increase over a 7-day period. At lower salinities (10–27.5‰) growth varied between 55–90% and at 45‰ was 85% of that in ‘normal’ sea water. Yield of extracellular carbohydrate was higher than in ‘normal’ sea water in lowered salinities and at 45‰ over a 42-day period. Larger quantities of extracellular carbohydrate were obtained at all stages of growth in media of 15‰, compared with those of 35‰ and 45‰. Whilst growth forms were markedly different at low salinities, DNA measurements indicated that similar quantities of cell material were present. Mannitol and glucose were the principal carbohydrates identified in intracellular material, and glucose in the extracellular products. Chloroplast pigment synthesis appears unaffected by growth at 15‰, 35‰, and 45‰.
Five phylogenetic schemes are presented for the Acrochaetiaceae based on comparative morphology and ultrastructure. The relationships between the possible phylogenetic relatives of the family and the taxonomic rank at which the group can be recognized are discussed. The most satisfactory schemes derive at least part of the Bangiophyceae from an acrochaetioid ancestor in which pit connections were present. All schemes that recognize the primitive nature of Audouinella in the Florideophyceae suggest the recognition of the Acrochaetiaceae at ordinal level. On this basis, the order Acrochaetiales is again proposed.
The life history of Rhodophysema georgii from the Atlantic coast of Canada is shown to be exclusively asexual, with direct development of tetrasporophytes from mitotically derived tetraspores. Sexual structures are completely absent and the presence of intercalary sporangial stalk cells provides further morphological evidence of the asexual origin of the tetrasporangia. Chromosome numbers of 17 or 18 were found both in vegetative cells and tetrasporocytes. The occurrence of a large-celled medulla, which characterizes globular thalli of R. georgii, is variable within the species, and the mechanism of its formation, by cellular fusion, is not limited to this species within the genus Rhodophysema. Thus, R. georgii is not fundamentally different in vegetative ontogeny and morphology from other, exclusively crustose, species of Rhodophysema. The morphological features related to life history and medullary cell formation were also observed in lectotype material of R. georgii, thus confirming the identity of the Canadian material.
We have determined the conditions which give optimal growth and conchospore release in laboratory cultures of free conchocelis of the red alga Porphyra torta Krishnamurthy. With cool white fluorescent light on a 16L.8D photoregime, the fastest sustained growth (5% volume increase d−1) was observed from 10–15°C and 25–100 μE-m −2.s−1; slightly faster growth was observed at 15°C and 300 μE.m−2.s−1, but such conditions are close to lethal. Conchoporangin will form under a wide range of conditions in conchocelis of this species. However, conchospores will mature and release only when the cultures are exposed to a short day photoperiod. The critical pholoperiod is just shorter than 12 h, The minimum number of photoinductive cycles for complete conchospore release is four for a range of conditions but can be just one depending on pretreatment.
Preliminary evidence is presented which indicates that far-red irradiation promotes and near-red inhibits rapid stipe elongation in Nereocystis luetkeana (Mertens) Postels & Ruprecht. Laboratory results showed afar-red reversal of red inhibition, but a red/far-red reversal was not evident in field experiments. The effects of changing ratios of red and far-red irradiation brought about by selective water absorption are discussed in relation to stipe elongation of Nereocystis.
The life histories of the red algae Rhodochorton purpureum and R. tenue were studied in unialgal culture. Telrasporophytes produced sporangia in short day regimes (8–12 hr) with 50–200 ft-c cool white light at 10 or 15 C. Mature gametophytes were not observed in the Washington and Alaska clones of R. purpureum. Tetraspores from R. tenue and the California clones of R. purpureum give rise to unisexual gametophytes that are reproductive when smaller than the tetrasporophytes. The tetrasporophytes develop directly from the gonimoblast cells. Because of similarities in morphology and life histories, it is proposed that R. tenue be placed in synonomy with R. purpureum.
Over 250 new strains of algae have been added to the Collection since the latest supplementary list was published in 1966. The formulae for additional maintenance media and for useful experimental media are included. Reprints of this supplementary list and both previous listings are available without charge from the Collection.
In the Rhodophyta there are few reports of light-mediated responses. In Bangia fuscopurpurea the formation of the fertile cell rows by the Conchocelis phase meets criteria established for the definition of photoperiodism in higher plants. Throughout the life history of the alga maintained in culture, cell fate and cell function fire under photoperiodic regulation. Maintenance and conversion photoperiods are established. Sequential induction studies suggest the absence of metabolic effects operative in the induction, response of fertile cell row formation. Preliminary studies of non-24-hr photoperiods suggest the absence of short-term endogenous rhythms involved in spore formation. A phytochrome response involved in the formation of the fertile cell rows is demonstrated.
The phases of the life-cycle of the alga are described, from both wild and cultured material. The whole sequence of generations has been found to take place in uni-algal culture. The possible relationship between epiphyte and host is considered. A brief account of the taxonomy of the plant is appended and reasons are given for its inclusion in the genus Rhodochorton.
1. The complete life-cycle of Porphyra tenera was obtained in vitro.2. Chemically defined media or enriched sea water permit good growth of these unialgal (not bacteria-free) cultures.3. Under suitable light and temperature, the complete life-cycle is completed in 5-6 months. Both the Conchocelis and the thallus phases may be grown out of season.4. The Conchocelis phase grows well free in liquid media; a calcareous substrate is unnecessary. Conchocelis colonies grown in liquid media when free-floating, are stellate and round, but mold-like when attached to glass walls. They are brown-black or purple-red, depending on the composition of the medium. Rapid and abundant growth of the free Conchocelis is elicited by high-light intensities. Fluorescent light is a good light source.5. Monosporangia formation and release of fertile monospores are induced by short-day conditions (8-11 hours daily); monosporangia and germinating monospores develop after 1-2 months from the inoculation of the Conchocelis filaments. ...
Chez les Floridées filamenteuses, comme chez les autres Algues, chaque filament possède une vagina, chaque cellule une locula, et les cellules sont séparées par des pièces interloculaires complexes. Après gonflement par l'acide sulfurique, celles-ci se présentent sous la forme de pièces en H compliquées, séparées chez les Céramiacées, et au contraire réunies en un système continu chez les Rhodochortons. En outre, des détails sont donnés sur les appareils synaptiques de ceux-ci, encadrés par des pièces para-synaptiques.
The induction of monospore-development in the Conchocelis stage of Porphyra tenera
Kjellm. was investigated.1.
Experiments with light-breaks during the dark-periods indicate the decisive role of a photoperiodic control.
2.
The critical daylength is approximately 10 hr. Daily light periods longer than 10 hrs inhibit the formation of monospores.
3.
Changes in temperature did not induce monospore formation. However, temperature influences the duration of time from photoperiodic induction until the appearance of monospores.
4.
By experiments with light-interruption in the dark period the effectiveness of different wavelengths was tested. A strong effect is exerted by wavelengths of 674 nm and 446 nm, and a lesser effect by wavelengths of 674 nm, 553 nm and 431 nm.
5.
Light-break experiments with red and far-red light indicate the participation of phytochrome in this photoperiodic control.
they do in nature. The free-living Conchocelis colonies cultured in continuous light produce only otherConchoceliscolonies.Itbecame theninteresting tofindhow new Conchocelis colonies are produced. It was found that new colonies could be obtained from small pieces of Conchocelis filaments. However, the Conchocelis colonies grown in continuouslightproduce sporangiawhich are morphologicallydifferentfrom the normal sporangia produced under short-day conditions. Even though free spores were not found in continuouslight,itwas not excluded that new Conchocelis coloniescouldbe producedby specialsporesproduced under continuouslight. The present work was undertaken to study the type of sporangia formed by free-living Concliocelis colonies under long-day conditions, and the fate of their spores. It was found that spores are indeed formed and that they can originate new Conchocelis colonies, revealing, under these conditions, a new part of the life cycleofP. tenera. MATERIALS AND METHODS The original material derives from mature leafy thalhi collected at Matsukawa ura Inlet located near Sendai in 1960. The Conchocelis colonies used for the presentstudieswere obtainedfrom carposporesproduced by the leafythallus passing through one life-cycle in vitro. This Conchocelis strain was a uni-algal culture, but accompanied by bacteria and yeast. Two treatments with ultraviolet light for 1â€"2minutes, at intervals of one month, eliminated the bacteria but not the yeast. Two types of liquid media, the artificial medium ASP12NTA (Pro vasoli's medium), and the enriched sea water medium SWI, were employed for the experiments (Table I). The cultures were carried on mainly in screw-cap tubes (125 x 20 mm.) with 10 ml. of medium. When necessary, the hanging culture technique was employed. RESULTS I. Types of sporangia produced in long-day conditions a) The “¿�inflated spherical†cells Small pieces of Conchocelis filament were inoculated in culture media and grown under different conditions. Tue first observation was made on the strain cultured at a win(low in subdued natural light (max. 500 ft.c.) from July to
The life history of Pilayella littoralis f. rupincola from Washington was studied in culture using supplemented natural seawater media and various temperature, photoperiod, and light intensity regimes. Plants in nature exhibited characteristics typical for f. rupincola. Plants in culture, however, did not show the same morphological features, although they had a life history presumed typical for f. rupincola. Successive generations of plants in culture formed only unilocular sporangia. On the basis of morphological characters and the life history, Kylin elevated f. rupincola to species rank. Variation in morphology of both field collected and cultured specimens makes such recognition untenable. It is concluded that the type of life history alone is not adequate justification for the recognition of P. rupincola as a species, but the stability of the life history in various culture environments appears to warrant continued recognition of this taxon as a distinct form of P. littoralis, as originally proposed by J. E. Areschoug.
Carpospores of Liagora farinosa from the western Mediterranean in culture gave rise to an Acrochaetium-like phase with filamentous prostrate and sparsely branched erect systems. This phase reproduced readily by tetraspores and monospores. The tetrasporangia were found to go through meiosis and the four haploid spores then gave rise to filamentous protonemal growths on which buds arose that developed into typical (though usually uncalcified) Liagora thalli. The monospores appeared to repeat the Acrochaetium-phase. These observations suggest that Liagora farinosa is another example of those members of the Nemalionales which show a heteromorphic life-history, with the sporophyte generation respresented by a dwarf phase.
Some aspects of the developmental physiology of the species are discussed.
The conchocelis-phase of Porphyra tenera Kjellman has been grown in in vitro culture, and subjected to a variety of daylength treatments.
Details of the culture apparatus designed for these treatments are given, and quantitative techniques, which have been devised for estimating the growth and reproduction of the alga, are described and discussed.
Growth was found to be directly proportional to daylength within the range 8–16 h, but abundant sporangia were only formed in daylengths of 10 h or less. The interruption of a 16 h dark period by 1 h of light completely inhibited the production of sporangia, but exposure to 8 short-day cycles, followed by long days, induced the formation of as many sporangia as were found after 25 short days. These results are discussed with reference to the photoperiodic responses of flowering plants.
The life histories of the red algae Rhodochorton purpureum and R. tenue were studied in unialgal culture. Telrasporophytes produced sporangia in short day regimes (8–12 hr) with 50–200 ft-c cool white light at 10 or 15 C. Mature gametophytes were not observed in the Washington and Alaska clones of R. purpureum. Tetraspores from R. tenue and the California clones of R. purpureum give rise to unisexual gametophytes that are reproductive when smaller than the tetrasporophytes. The tetrasporophytes develop directly from the gonimoblast cells. Because of similarities in morphology and life histories, it is proposed that R. tenue be placed in synonomy with R. purpureum.
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