摘要:

ABSTRACTFour morphologically indistinguishable isolates of monoeciousGelidium vagumOkamura were crossed reciprocally to obtain hybrids for a study on heterosis in this alga. Approximately 50% outcrossing was achieved by adding a small fragment of the designated female parent to a much larger quantity of designated male thallus in the crossing dish. Hybrids in the mixed population of isomorphic hybrid and inbred sporelings were identified by the presence of male‐specific random amplified polymorphic DNA markers. Growth performance of hybrid tetrasporophytes was compared to that of their gametophytic parents and with inbred tetrasporophytes at near‐optimum and sub‐optimum temperature and density. In general, the hybrids showed growth superiority over inbred lines, particularly under sub‐optimum conditions. In these experiments, the hybrid plants from cross 129 × 130 exhibited a 9.5–130% higher growth rate as compared to the mid‐value of the related inbred tetrasporophytes, strongly suggesting the presence

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00091.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTTwo Atlantic species found in the Mediterranean Sea were ascribed to the family Solieriaceae on the basis of morphological features. In the extensive drifting beds of the Mar Piccolo basin (Taranto, Ionian Sea),Agardhiella subulata(C. Agardh) Kraft et Wynne andSolieria filiformis(Kützing) Gabrielson were the dominant species in summer. There were no attached populations, and perennation was ensured only by vegetative propagation. Characteristics of the outer cortex and chromatophores were useful for distinguishing the taxa at the species level and are recommended for recognition of sterile specimens

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00098.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThirty‐nine populations ofBatrachospermumsectionVirescentiafrom North America were compared to eight type specimens and two historically important specimens using multivariate morphometrics and image analysis. From this analysis, two species are recognized: B. helminthosumBory de Saint‐Vincent (syn.B. bruzienseSirodot,B. graibussonienseSirodot,B. sirodotiiSkuja ex Flint,B. testaleSirodot,B. virgatumSirodot nom. illeg., andB. virideSirodot) andB. elegansSirodot (syn.B. coerulescensSirodot nom. illeg.). InB. helminthosumtrichogynes are cylindrical to slightly club‐shaped with few to no protuberances, whereas inB. eleganshalf to all of the trichogynes have one to three basal knobs or branches. None of the qualitative features previously used to separate species in this section were found to be of taxonomic value due to their universal presence; quantitative characteristics were highly variable and overlapped among specimens examined. Emended descriptions of both species are provided.Batrachospermum eleganswas collected in northeastern U.S.A. and central Costa Rica, whereasB. helminthosumranged from Nova Scotia to Louisiana and was collected in central Mexico, Costa Rica, and northwestern U.S.A.Batrachospermum julianumArcangeli andB. transtaganumReis, previously classified in sectionVirescentia, were observed to have twisted carpogonial branches and, therefore, should be placed in sectionContorta.SectionsSetaceaandVirescentiaofBatrachospermumdiffer in whorl size, ratio of carposporophyte height to whorl diameter, and trichogyne stalking; hence, we continue to recognize them as being distinct taxonomic entities as originally desc

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00108.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTVegetative cells and zoospores ofHormotilopsis gelatinosaTrainor&Bold,H. tetravacuolarisArce&Bold,Planophila terrestrisGroover&Hofstetter, andPhyllogloea fimbriata(Korchikov) Silva were examined by transmission electron microscopy. All cells had pyrenoids traversed by cytoplasmic channels. Zoospores were quadriflagellate and had essentially cruciate flagellar apparatuses. Scales were present on free‐swimming zoospores. These features are essentially identical to those ofChaetopeltissp. and are dissimilar to those of other described green algae. The new order Chaetopeltidales is created to accommodate the generaChaetopeltis, Hormotilopsis, Planophilasensu Groover&Hofstetter,Phyllogloea, Dicranochaete, andSchizochlamys, organisms previously scattered among the orders Tetrasporales, Chloro‐coccales, Chlorosarcinales, and Chaetophorales. Members of the order are closely related to the ancestral chlorophycean flagellate genusHafniomonas, may be ancestral with respect to other Chlorophyceae, and may also be closely related to the ulvophycean order Ulotricha

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00118.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTTwo morphotypes,fusiformandoval, were isolated from a single clone of the diatomPhaeodactylum tricornutumBohlin and maintained as subclones by culturing in liquid and solid substrates, respectively. Salinity of the medium, from brackish to marine, had no effect on expression of the phenotypes. Theovalcell is generated endogenously within a “transformed”fusiformcell upon transfer from liquid medium to agar plates. With the light microscope, normal and “transformed”fusiformcells, prior to giving rise toovalcells, can be discriminated by means of their staining response to toluidine blue.Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of protein extracts from lysed cells revealed slight differences in polypeptide composition betweenfusiformandovaltypes. A phenotype‐restoration experiment fromovaltofusiformdemonstrated that theovaltype readily reestablished not onlyfusiformmorphology but also the protein pattern characteristic for thefusiformtype. Immunochemical analyses(western blots)using antisera raised against whole and lysed cells of both morphotypes revealed antigenic alterations of theovalmorphotype. Several antigenic determinants restricted mainly to the surface ofovalcells were detected. Results indicate that environmentally induced phenotypes ofPhaeodactylummay be not only the consequence of specific gene expression but also the result of significant, general post‐translational

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00129.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe development of two red algal parasites was examined in laboratory culture. The red algal parasiteBostrychiocolax australisgen. et sp. nov., from Australia, originally misidentified asDawsoniocolax bostrychiae(Joly et Yamaguishi‐Tomita) Joly et Yamaguishi‐Tomita, completes its life history in 6 weeks on its hostBostrychia radicans(Montagne) Montagne. Initially the spores divide to form a small lenticular cell, and then a germ tube grows from the opposite pole. Upon contact with the host cuticle, the germ tube penetrates the host cell wall. The tip of the germ tube expands, and the spore cytoplasm moves into this expanded tip. The expanded germ tube tip becomes the first endophytic cell from which a parasite cell is cut off that fuses with a host tier cell. The nuclei of this infected host cell enlarge. As parasite development continues, other host‐parasite cell fusions are formed, transferring more parasite nuclei into host cells. The erumpent colorless multicellular parasite develops externally on the host, and reproductive structures are visible within 2 weeks. Tetrasporangia are superficial and cruciately or tetra‐hedrally divided. Spermatia are formed in clusters. The carpogonial branches are four‐celled, and the carpogonium fuses directly with the auxiliary (support) cell. The mature carposporophyte has a large central fusion cell and sympodially branched gonimoblast filaments.Early stages of development differ markedly inDawsoniocolax bostrychiaefrom Brazil. Upon contact with the host, the spore undergoes a nearly equal division, and a germ tube elongates from the more basal of the two spore cells, penetrates the host cell wall, and fuses with a host tier cell. Subsequent development involves enlargement of the original spore body and division to form a multicellular cushion, from which descending rhizoidal filaments form that fuse with underlying host cells. This radically different development is in marked contrast to the final reproductive morphology, which is similar toB. australisand has lead to taxonomic confusion between these two entities. The different spore germination patterns and early germ‐ling development ofB. australisandD. bostrychiaewarrant the formation of a new genus for the Australi

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00137.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe discovery in the early 1980s that meiosis occurs during germination of conchospores ofPorphyra yezoensisUeda suggested that the sexually divided fronds ofPorphyra purpurea(Roth) C. Agardh might similarly originate from meiotic segregation of a pair of sex‐determining alleles during early sporeling development. After establishing conditions suitable for propagatingP. purpureain culture, observations on developing sporelings demonstrated that meiosis takes place during the first two divisions of the germinating conchospores. In the first division, the spore is split into an upper and lower cell. In the second, an anticlinal division in the upper cell yields two daughter cells situated one beside the other, and a periclinal division in the bottom cell gives two cells arranged one above the other. Thus, during normal development, the first four cells of the sporeling constitute a meiotic tetrad whose cells are arranged in a characteristic fashion. Stable color mutants ofP. purpureawere isolated, genetically characterized, and used as genetic markers to follow the fate of individual cells of the tetrad during subsequent frond development. Nearly the entire blade of the mature thallus is derived from the two upper cells of the tetrad, with the two lower cells mostly giving rise to the rhizoidal holdfast region. Cell lineage boundaries laid down by the segregation of color alleles at meiosis corresponded perfectly with those later defined by sexual differentiation on the same fronds, strongly supporting the hypothesis that sex determination inP. purpureais controlled by alleles at a segregating chromosomal locu

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00147.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY