A comparison of tapetal structure and function in pteridophytes and angiosperms

This article is based on a survey of literature with particular reference to the structure and functioning of the tapetum during sporogenesis in angiosperms and pteridophytes. Some original observations onSchizaea pectinata andSelaginella japonica are also included. In the past, superficial similarities in the structure and function of pollen grains and spores have dominated the research approach, but patterns of development and the functioning of the tapetum during sporogenesis in angiosperms and pteridophytes are shown to differ quite significantly and raises questions relating to homologies. It is suggested that direct comparisons may no longer be appropriate.     

Euduboscquella costata n. sp. (Dinoflagellata,Syndinea), an Intracellular Parasite of the Ciliate Schmidingerella arcuata: Morphology,Molecular Phylogeny,Life Cycle,Prevalence, and Infection Intensity

The syndinean dinoflagellate Euduboscquella costata n. sp., an intracellular parasite of the tintinnid ciliate Schmidingerella arcuata, was discovered from Korean coastal water in November of 2013. Euduboscquella costata parasitized in about 62% of the host population, with infection intensity (= number of trophonts in a single host cell) ranging from 1 to 8. Based on morphology and nuclear 18S ribosomal RNA gene sequences, the parasite is new to science. Euduboscquella costata n. sp. had an infection cycle typical of the genus, but had morphological and developmental features that distinguished it from congeneric species. These features include: (1) episome of the trophont with 25–40 grooves converging toward the center of the shield; (2) a narrow, funnel‐shaped lamina pharyngea extending from the margin of the episomal shield to the nucleus; (3) persistence of grooves during extracellular development (sporogenesis); (4) a single food vacuole during sporogenesis; (5) separation of sporocytes early in sporogenesis, regardless of type of spore formed; and (6) dinospore size (ca. 14 μm in length) and shape (bulbous episome with narrower, tapering hyposome). After sporogenesis, E. costata produced four different types of spore that showed completely identical 18S rRNA gene sequences. The gene sequence was completely identical with a previously reported population, Euduboscquella sp. ex S. arcuata, from Assawoman Bay, USA, indicating that the two populations are likely conspecific. Favella ehrenbergii, a widely recorded tintinnid known to host Euduboscquella spp., co‐occurred with S. arcuata, but was not infected by E. costata in field samples or during short‐term, cross‐infection experiments.     

INCIPIENT POLYPLOID SPECIATION IN THE MAIDENHAIR FERN (ADIANTUM PEDATUM; ADIANTACEAE)?

Despite the widespread occurrence of polyploids in plant taxa and the many advantages attributed to polyploidy, very little is known about the specific processes that lead to the establishment of polyploids in nature. Classical models suggested that polyploids arise following somatic chromosome doubling in hybrids. However, the production of polyploids from unreduced meiotic products has been receiving greater attention. During an enzyme electrophoretic study of a local population of Adiantum pedatum, a mutant producing viable unreduced spores along with abortive spores was discovered. Studies of sporogenesis showed that a synaptic mutation caused the paired chromosomes to disassociate, with mostly univalents remaining at metaphase I. In such aberrant spore mother cells, one of two pathways was followed in the remaining stages of meiosis. Cells attempting both meiotic divisions formed abortive spores. However, in spore mother cells that bypassed meiosis I and formed a restitution nucleus, meiosis II and subsequent stages of sporogenesis proceeded normally. Unreduced diploid spores resulted from this second pathway. When sown on either agar or sterile soil, these diplospores germinated and produced diploid gametophytes. Tetraploid sporophytes were produced by the gametophytes growing on sterile soil. The discovery of diploid sporophytes producing unreduced spores provided the opportunity to characterize the first step of one possible route to polyploid formation. Continued observations of the natural population may provide insights into the earliest stages of natural polyploid formation.     

THE LIFE CYCLE OF BANGIA FUSCOPURPUREA IN CULTURE. I. EFFECTS OF TEMPERATURE AND PHOTOPERIOD ON THE MORPHOLOGY AND REPRODUCTION OF THE BANGIA PHASE12

The Bangia phase of Bangia fuscopurpurea was grown in laboratory culture in a variety of photoperiod and temperature regimes. Plants of the Bangia phase grown from 2 types of asexual spores, monospores and conchospores, exhibited growth differences under similar growing conditions. Plants derived from monospores grew more rapidly and matured earlier than those derived from carpospores. Day length and temperature were found to significantly influence growth rule, maturation, and plant size. Long day lengths resulted in more rapid growth in filament length and diameter and earlier spore formation and spore release. Maximum filament length was observed in a 12/12 hr light-dark cycle at 15 C. Spore formation and release were delayed by decreasing day length or temperature. Temperature and photoperiod were also found to influence the type of spores produced by the Bangia phase. When grown at 22 C, the Bangia phase produced only monospores, which reproduced the Bangia phase. At 9 C, with photoperiods of 11 hr or more of light, the Bangia phase produced carpospores which gave rise to the alternating Conchocelis phase. The conditions under which sporogenesis occurred determined the spore type differentiated.     

REPRODUCTION IN ZONARIA FARLOWII. I. GAMETOGENESIS,SPOROGENESIS, AND EMBRYOLOGY1

The brown alga Zonaria farlowii which exhibits an alternation of isomorphic generations has been found to be a particularly suitable organism for a comparative study of game to gene sis, sporogenesis, and embryonic development. The germinations of the zygote and spore have been compared and found to be similar. The development of the oogonium and sporangium has been studied with the light and electron microscopes, in an attempt to discern ontogcnetical similarities or differences. The timing and periodicity of oogenesis and sporogenesis were found to differ: oogonial development requires a lunar month from the time of its initiation to the time of egg release which occurs around the first quarter of the moon, whereas the sporangium does not follow this periodicity. The development of the spore embryos and zygotic embryos is essentially the same. It appears that the difference between the 2 phases of the life cycle exists only in the later stages of oogenesis and sporogenesis. These differences continue in the egg until fertilization, after which the zygote has the same cytoplasmic configuration as the spore. It is also notable that during release of the spore it must increase in size considerably since before germination begins it has attained the size of the egg.     

SEASONAL LIGHT AND TEMPERATURE INTERACTION EFFECTS ON DEVELOPMENT OF LAMINARIA SACCHARINA (PHAEOPHYTA) GAMETOPHYTES AND JUVENILE SPOROPHYTES1

In previous studies, Laminaria saccharina L. (Lamour.) sporophytes were found to exhibit two major peaks of sporogenesis and an annual life cycle in Long Island Sound, New York. Young sporophytes were observed shortly after the sporogenesis peaks in early autumn and spring, but most of the mature sporophytes decayed during summer. A new study was conducted to determine if the spring sporogenesis activity contributed to the recruitment observed in autumn through oversummering of gametophytic and juvenile sporophytic stages, as previously suggested. Reproduction and growth in gametophytes and growth in juvenile sporophytes were studied under crossed gradients of light and temperature. Periodic outplantings of substrata seeded with gametophytic and sporophytic stages to the field were conducted to assess actual survival. The optimum temperature and light conditions for gametophyte development, growth and reproduction varied with the time of year meiospores were obtained. Most of this variation was attributable to temperature. A seasonal adaptation to temperature in most developmental stages was observed. Higher temperatures resulted in greater numbers of male gametophytes. Gametophytic stages could develop at all times, suggesting that oversummering in this stage was possible. Juvenile sporophytes had a narrower optimum temperature range and again photon fluence rate contributed little to observed variances. Out planting of sporophytic stages at various times during the year indicated only sporophytes prepared from autumn and winter could survive summer conditions. The thalli of these plants grew rapidly in spring and eroded back to the meristematic region in summer. Most of these plants then quickly became reproductive, resulting in another autumn sporogenesis peak. Gametophytic and sporophytic outplantings prepared from spring meiospores did not survive the summer. Thus, the recruitment observed in autumn can only be the result of the previous autumn's sporogenesis activity. The sporogenous activities of spring and early summer appear to be unimportant, despite the fact that all reproductive indices are superior at those times.     

Induction of microcycle sporulation in Bacillus brevis spp. AG4 by amethopterin

Addition of amethopterin to medium before inoculation inhibited DNA synthesis and induced microcycle sporogenesis in Bacillus brevis spp. AG4. Synthesis of RNA and proteins occurred at a considerably reduced rate.Abbreviations TVC total viable counts - HSC heat stable counts - CDGS chemically defined medium for growth and sporulation - TCA trichloro acetic acid     

Microcycle sporogenesis in some streptomycetes without shift down treatment

Conditions for microcycle sporogenesis in two streptomycete strains without shifting the culture were found. The sporulation in Streptomyces granaticolor took place after 24 h of cultivation. The dry mass was increasing till 32 h probably due to production of a hydrophobic substance resembling fibrous sheath of aerial hyphae and spores. Ultrathin section of microcycle spores are presented.     

SPORE DEVELOPMENT IN THE LIVERWORT RICCARDIA PINGUIS

The ontogeny of spores of the liverwort Riccardia pinguis was studied at the light and electron microscope levels. Three stages of development were arbitrarily defined: spore mother cell (SMC); early tetrad with nonpigmented and unsculptured walls; and mature tetrad with pigmented and sculptured spore walls. The SMC is quadrilobed with a two-layered SMC wall, containing a central nucleus, many chloroplasts, spherosomes, and other organelles. During and following meiosis cell plates form from coalescing Golgi vesicles. These plates by continued coalescence eventually form a septum, completing the tetrad. This septum comprises middle lamella and primexine; within the latter the exine forms. By continued addition of vesicle contents to the septum and dorsal surfaces of the tetrad, the exine (sexine and nexine) and intine layers of the spore wall are laid down. The contents of the vesicles change successively during wall formation, corresponding to the different wall layers being formed. It is concluded that wall formation is under the exclusive control of the spore protoplast, and that the pattern of the mature exine is determined by the primexine. Rearrangement of organelles and other cellular components during sporogenesis is described.     

The Presence of Keratin-like Substance in Spore Coat of Bacillus subtilis

Unique crystalline structures were found by X-ray diffractometry to be present in spore coats of Bacillus subtilis. By crystallographical and chemical studies of the purified spore coats it was found that these crystalline structures of the spore coats were essentially similar to those of α- and β-keratin, and that the spore coats were composed of keratin-like substance (or keratin). This keratin-like substance was found to be synthesized during sporogenesis from sulfur-containing water-soluble substances in the cells.     

Inhibitory effect of penicillin on spore-specific functions inBacillus polymyxa 2459

Penicillin at concentrations non-inhibitory to the vegetative growth was found to inhibit sporulation inBacillus polymyxa 2459. The effect of penicillin was shown to be at the level of spore-specific mucopeptide synthesis. Penicillin had no effect on the early events such as DNA and protein synthesis in sporogenesis The sensitive period of inhibition was between T₀ to T₂ hours of sporulation.     

鲢疯狂病病原体鲢碘泡虫孢子形成各阶段的观察研究

链碘泡虫是鲢疯狂病的病原体。本文报道鲢碘泡虫营养体细胞的核型、各期有丝分裂相、孢子形成过程的早期、即二个生殖细胞的联合以及孢子的产生。     

Ascopore formation in yeasts during active growth on hydrocarbons

Summary Induction of ascospore formation in hydrocarbon utilizing ascosporogenous yeasts was observed during the growth of the yeasts on gas oil, diesel oil, white kerosene and n-alkanes. Studies of relationships between cell morphology and cell growth showed that ascospores were formed during the active growth phase on gas oil but not on glucose. Contact of yeast cells with hydrocarbons may be the possible reason for sporogenesis on hydrocarbons.     

An unusual method of development and sporulation of Colletotrichum gloeosporioides on castor leaf – an SEM account

Development and sporogenesis of Colletotrichum gloeosporioides on castor leaf differed from that on other known host plants. C. gloeosporioides had three kinds of hyphae on castor leaf: primary infection hyphae (PIH), runner hyphae (RH) and secondary infection hyphae (SIH). The PIH originated from conidia, grew on leaf surface and entered the leaf by direct penetration of the cuticle without forming appressoria. The RH were sub-cuticular hyphae, the track of which was traceable by the bulgings on the leaf surface, and the SIH were the hyphae that emerged to leaf surface from RH through the cuticle or stomata. Conidia were initiated as small protrusions along the lengths of RH and SIH that got differentiated into distinct conidia, each born on a short stumpy conidiophore without forming any congregation. The protrusions from RH emerged to the leaf surface by piercing the cuticle, and they developed into distinct conidia on the leaf surface. The conidia developed from RH and SIH were identical in size and shape. Even though conidia were occasionally found emerged through stomata, that appeared to be random than a preferred route for the discharge of conidia. The penetration and sporogenesis of C. gloeosporioides on castor leaf differed from that reported on mulberry leaf.     

On the nature of sporogenesis in some aerobic bacteria

Washed vegetative cells of various species of aerobic spore-forming bacteria sporulate abundantly when shaken in distilled water in air. The spores thus formed possess the same heat resistance as spores formed in a complete growth medium. Various factors influencing sporogenesis in water are described. Glucose in low concentration completely suppresses sporogenesis under these conditions and the suppression is relieved by the presence of ammonia as an exogenous source of nitrogen. Various amino acid and purine antimetabolite analogues inhibit sporogenesis and their inhibitory effects are completely reversed by much smaller amounts of the corresponding metabolites. Sporogenesis is thus regarded as a de novo synthesis of spore proteins from preexisting endogenous (enzyme) proteins. Cells low in protein fail to sporulate and the capacity of the cell to adaptively attack maltose and trehalose is strongly interfered with after the cell is irreversibly committed to sporulation, but not before that. Evidence is advanced supporting the hypothesis that sporogenesis is an endogenous process which commences when the supply of exogenous energy and carbon is depleted. It utilizes low molecular weight nitrogenous substances liberated by the degradation of preexisting enzyme proteins of the vegetative cell. Sporogenesis and adaptive enzyme formation are regarded as competitive synthetic processes, both utilizing endogenous enzyme proteins. The events of sporogenesis suggest that this process may be an adaptive protein synthesis, analogous to adaptive enzyme synthesis.     

Cellular differentiation of heterospory inSelaginella

Summary Selaginella pilijera consistently displays two rows of microsporangia and two rows of megasporangia. It is therefore possible to detect in longitudinal sections of strobili at least three significant differences in development between both types of sporangia prior to meiosis: size of young sporangia, abortion or development of sporocytes based an RNA staining, and presence or absence of callose walls around sporocytes. The functional significance of these differences is discussed in relation to the heterosporous habit and higher plant sporogenesis.     

A molecular phylogeny of <Emphasis Type="Italic">Haptoglossa</Emphasis> species,terrestrial peronosporomycetes (oomycetes) endoparasitic on nematodes

Phylogenetic relationships of seven Haptoglossa isolates were analyzed by using mitochondrial COII amino acid sequences with a data set of 34 peronosporomycetes. Haptoglossa isolates formed a single clade and appeared to be basal to the clade consisting of all other peronosporomycetes. The Haptoglossa clade was divided into two subclades: one clade consisted of five aplanosporic isolates and the other included one aplanosporic and one zoosporic isolate. These results indicate that the genus Haptoglossa is monophyletic, and patterns of infection cell formation reflect more the phylogenetic relationship between the species than patterns of sporogenesis.     

笔竹大小孢子发生及雌雄配子体发育研究

为探讨笔竹(Pseudosasa viridula)结实率低的原因,该文通过采用石蜡切片的方法结合显微技术对笔竹大小孢子发生及雌雄配子体的发育过程进行研究.结果表明:(1)笔竹的雄蕊多为3枚,极少有6枚,每枚花药具有4个花粉囊.(2)花药壁发育为基本型,由4层细胞构成,由外向内依次为表皮细胞、药室内壁细胞、中层细胞和绒...