Arbuscular mycorrhizal associations in Lycopodiaceae

This study characterizes the molecular and phylogenetic identity of fungi involved in arbuscular mycorrhizal (AM) associations in extant Huperzia and Lycopodium (Lycopodiaceae). Huperzia and Lycopodium are characterized by a life cycle with long-lived autotrophic sporophytes and long-lived mycoheterotrophic (obtain all organic carbon from fungal symbionts) gametophytes. 18S ribosomal DNA was isolated and sequenced from Glomus symbionts in autotrophic sporophytes of seven species of Huperzia and Lycopodium and mycoheterotrophic Huperzia gametophytes collected from the Páramos of Ecuador. Phylogenetic analyses recovered four Glomus A phylotypes in a single clade (MH3) that form AM associations with Huperzia and Lycopodium. In addition, phylogenetic analyses of Glomus symbionts from other nonphotosynthetic plants demonstrate that most AM fungi that form mycoheterotrophic associations belong to at least four specific clades of Glomus A. These results suggest that most mycoheterotrophic plants that form AM associations do so with restricted clades of Glomus A. Moreover, the correspondence of identity of AM symbionts in Huperzia sporophytes and gametophytes raises the possibility that photosynthetic sporophytes are a source of carbon to conspecific mycoheterotrophic gametophytes via shared fungal networks.     

GAMETOPHYTES AND SUBGENERIC CONCEPTS IN LYCOPODIUM

A critique of the Freeberg and Wetmore work on cultured Lycopodium gametophytes of L. selago, L. flabelliforme, and L. cernuum is presented. All three gametophytes are shown actually to be L. cernuum based on morphological and anatomical features of their sporophytes. A reassessment of characters in the genus demonstrates the taxonomic validity of the three groups proposed as subgenera within Lycopodium.     

Ultrastructure of salivary glands of Ornithodoros (Ornithodoros) moubata (Ixodoidea: Argasidae)

The paired salivary glands of unfed adult Ornithodoros (Ornithodoros) moubata are composed of type I (agranular) and type II (granular) alveoli. Type I alveoli consis of one large central cell surrounded by peripheral cells having the morphology of fluid-transporting epithelia. Type II alveoli contain granular and agranular cells; the former are comprised of morphologically distinct types of cells (a, b, and c) containing granules of different structures and chemical composition with respect to polysaccharide and protein. The agranular cells are the interstitial and cap cells. Golgi bodies and rough endoplasmic reticulum (RER) are found in all granular cells and apparently are involved in granule formation. No appreciable structural changes were observed in type I alveoli during or after feeding. Type c cell granules are released before granules from types a and b cells and may contain anticoagulant substances that promote the blood flow of the host during the tick feeding. Although the cap cells are not structurally affected by feeding, interstitial cells are developed into transporting epithelia.     

Morphology of the petal inAconitum

The petals ofAconitum were classified into six types. Type I: the labium tubular at the base and no appendage inside. Type II: a lambda (A)-shaped enation present inside the limb. The upper part of the enation is situated at the lower edge of the spur mouth and both wings of the enation extend to margins of the labium. Type III resembles type II but both wings do not extend to the margins. Type IV: a small flap attached at the lower edge of the spur mouth. Type V: two auriculate appendages present on both lateral walls of the labium. Type VI: without inside appendage. Most species of sect.Lycoctonum have type I petal and those of sect.Aconitum have type V petal. Type I is distinctly cup-shaped or peltate with a well developed cross zone or adaxial wall and type II is a modification of type I. Type VI is distinctly flat or epeltate without the cross zone. Others are intermediate between cup-shaped and flat or peltate and epeltate types. Based on the observation of petal ontogeny onA. pterocaule var.glabrescens, A. vulparia andA. japonicum var.eizanense, the relation among these types was explained by the partial or total reduction of the adaxial meristematic regions.     

Studies on interaction of oligopeptides with sodium dodecyl sulfate: Stopped-flow kinetics of chemical modification of tryptophan residues withN-bromosuccinimide

The stopped-flow kinetics of the reaction between oligopeptides containing tryptophan residues andN-bromosuccinimide (NBS) were studied in 50 mM sodium phosphate buffer (pH 7.0) containing sodium dodecyl sulfate (SDS). Decreases in the reaction rates attributable to the interaction between oligopeptides and SDS were observed, and oligopeptides studied were classified into types I and II on the basis of the interaction modes. Type I oligopeptides were dissolved in SDS micelles; type II oligopeptides interacted cooperatively with SDS monomers. The manner of interaction between SDS and oligopeptides of type II could be interpreted by a simple equilibrium relation: oligopeptide+n·(SDS)=oligopeptide·(SDS) _n .     

Dynamic apical surface rings in superficial layer cells of koi Cyprinus carpio scale epidermis

This study examined the novel ring‐shaped structures found in the apical surface of individual cells of the scale epidermis of koi Cyprinus carpio. These apical rings are highly dynamic structures with lifetimes ranging from a few to several minutes. While several ring forms were observed, the predominant ring morphology is circular or oval. Two distinct ring forms were identified and designated type I and type II. Type I rings have a well‐defined outer border that encircles the surface microridges. Type II rings are smooth‐surfaced, dinner‐plate‐like structures with membranous folds or compressed microridges in the centre. Type II rings appear less frequently than type I rings. Type I rings form spontaneously, arising from swollen or physically interrupted microridges but without initially perturbing the encircled microridges. After persisting for up to several minutes the ring closes in a centripetal movement to form a circular or irregular‐shaped structure, the terminal disc. The terminal disc eventually disappears, leaving behind a submembranous vesicle‐like structure, the terminal body. Type I rings can undergo multiple cycles of formation and closing. Recycling epidermal apical rings form through centrifugal expansion from the terminal disc followed by apparent contraction back to the disc structure, whereupon the cycle may repeat or cease. The findings demonstrate a novel skin surface structure in fishes and are discussed with respect to communication with the external aqueous environment.     

Selection of Type I and Type II methanotrophic proteobacteria in a fluidized bed reactor under non-sterile conditions

Type II methanotrophs produce polyhydroxybutyrate (PHB), while Type I methanotrophs do not. A laboratory-scale fluidized bed reactor was initially inoculated with a Type II Methylocystis-like dominated culture. At elevated levels of dissolved oxygen (DO, 9 mg/L), pH of 6.2–6.5 with nitrate as the N-source, a Methylobacter-like Type I methanotroph became dominant within the biofilms which did not produce PHB. A shift to biofilms capable of PHB production was achieved by re-inoculating with Type II Methylosinus culture, providing dissolved N₂ as the N-source, and maintaining a low influent DO (2.0 mg/L). The resulting biofilms contained both Types I and II methanotrophs. Batch tests indicated that biofilm samples grown with N₂ became dominated by Type II methanotrophs and produced PHB. Enrichments with nitrate or ammonium were dominated by Type I methanotrophs without PHB production capability. The key selection factors favoring Type II were N₂ as N-source and low DO.     

ESTIMATED RATES OF INTRAGAMETOPHYTIC SELFING IN LYCOPODS

Homosporous pteridophytes are characterized by the production of free-living, potentially bisexual gametophytes. Because of the close proximity of archegonia and antheridia on the same thallus, it has been assumed that high rates of intragametophytic self-fertilization would predominate in natural populations of homosporous pteridophytes. Using enzyme electrophoresis we determined sporophytic genotype frequencies for natural populations of three lycopod species, Lycopodium clavatum, L. annotinum, and Huperzia miyoshiana. Based on these genotype frequencies and the estimation procedures of Holsinger (1987), the estimated rates of intragametophytic selfing in these species are extremely low. Estimated selfing rates were greater than 0.000 in only two of 13 populations of L. clavatum, one of six populations of L. annotinum, and one of four populations of H. miyoshiana. Despite the potential for intragametophytic self-fertilization, the gametophytes of these three lycopod species predominantly cross-fertilize, although the mechanism(s) promoting intergametophytic matings are unknown. These results are similar to those obtained for homosporous ferns and Equisetum arvense. It is therefore clear that most homosporous pteridophyte species investigated do not exhibit high rates of intragametophytic self-fertilization; in contrast, intergametophytic matings predominate.     

DNA methylation profiles differ between field- andin vitro-grown leaves of apple

A reliable method has been previously developed to detect cytosine methylation at the 5′-CCGG-3′ sequence using isoschizomers (Msp I and Hpa II) and a modified amplified fragment length polymorphism (AFLP) technique. With this method, DNA methylation profiles were investigated in leaf tissues of apple (Malus × domestica cv. Gala) grown under two different growth conditions, field and tissue culture. A total of 1,622 AFLP bands were detected using 32 pairs of primers, and these banding patterns were assembled into three groups. Type I AFLP bands were present in both EcoR I/Hpa II and EcoR I/Msp I lanes. Type II bands were present in the EcoR I/Msp I lanes, but not in EcoR I/Hpa II lanes. Type III bands were present in EcoR I/Hpa II lanes, but not in the EcoR I/Msp I lanes. For leaf tissues of field- and in vitro-grown apples, the ratios of types I, II, and III to the total number of amplified fragments were 70 %, 24 %, and 6 %, and 71 %, 23 %, and 6 %, respectively. Although the ratios of the three types of banding patterns were similar in both leaf tissues, a few bands specific to either field-grown trees or in vitro-grown shoots were observed. This study provided evidence that changes in methylation occurred in apple leaf tissues subjected to tissue culture growth conditions.     

Evolutionary conservation of the chlorophyll a/b-binding proteins: cDNAs encoding type I, II and III LHC I polypeptides from the gymnosperm Scots pine

Summary cDNAs encoding three different LHC I polypeptides (Type I, Type II and Type III) from the gymnosperm Scots pine (Pinus sylvestris L.) were isolated and sequenced. Comparisons of the deduced amino acid sequences with the corresponding tomato sequences showed that all three proteins were highly conserved although less so than the LHC II proteins. The similarities between mature Scots pine and tomato Types I, II and III LHC I proteins were 80%, 87% and 85%, respectively. Two of the five His residues that are found in AXXXH sequences, which have been identified as putative chlorophyll ligands in the Type I and Type II proteins, were not conserved. The same two regions of high homology between the different LHC proteins, which have been identified in tomato, were also found in the Scots pine proteins. Within the conserved regions, the Type I and Type II proteins had the highest similarity; however, the Type II and Type III proteins also showed a similarity in the central region. The results suggest that all flowering plants (gymnosperms and angiosperms) probably have the same set of LHC polypeptides. A new nomenclature for the genes encoding LHC polypeptides (formerly cab genes) is proposed. The names lha and lhb are suggested for genes encoding LHC I and LHC II proteins, respectively, analogous to the nomenclature for the genes encoding other photosynthetic proteins.     

FLEXURAL STIFFNESS ALLOMETRIES OF ANGIOSPERM AND FERN PETIOLES AND RACHISES: EVIDENCE FOR BIOMECHANICAL CONVERGENCE

Evidence for convergence in biomechanical and anatomical features of leaves (elastic modulus E, second moment of area I, taper of petioles, the longitudinal distribution of petiolar and laminar weight, and volumes of tissues) is presented based on a survey of 22 species (distributed among dicots, monocots, and ferns). In general, regardless of taxonomic affinity, petioles were found to be mechanically constructed in one of two ways: Type I petioles—as cantilevered, end-loaded beams with relatively uniform flexural stiffness (EI) (simple and palmate leaves); and Type II petioles—as tapered cantilevered beams whose static loadings (biomass) and EI increase basipetally (pinnate leaves). In general, collenchyma and sclerenchyma were found to be peripherally located in transections through Type I and II petioles, respectively. Statistical analyses within each species and among species with either type of petiole indicated that EI ≈ k₁Lp^2.98 and EI ≈ k₂Lp^2.05 for Type I and II petioles, respectively, where k₁ and k₂ are dimensional constants and Lp is petiolar length. The data are interpreted to indicate that Type I and II petioles mechanically operate to deal with static loadings in two distinct ways, such that Type II petioles function in an analogous manner to branches supporting separate leaves (leaflets). The convergence in mechanical “designs” among taxonomically distinct lineages (angiosperms and ferns) is interpreted as evidence for selection on mechanical attributes of load supporting structures (petioles).     

Indoleacetic acid movement in the root cap

Summary When applied on the root cap of Zea mays L., indol-3yl-acetic acid (IAA) may enter the root tip and move basipetally inside the cap. From the cap to the apex (quiescent centre and meristem) the IAA transport is very slow. Polarity of IAA movement, in relation to growth, is discussed.     

A single structural type in the regular surface layer of Aeromonas salmonicida

The surface protein array of Aeromonas salmonicida (or A-layer) appears, in negatively stained preparations, as two distinct patterns, type I and type II. Type I patterns were restricted to, and predominated in, darkly stained areas, whereas lighter staining regions exclusively displayed type II patterns. The type I morphology was faithfully reproduced in computer-simulated superimpositions of type II patterns, as was the intermediate transition zone frequently seen between the two patterns. Variations in the lattice constant of both patterns, presumably due to artifactual flattening, demonstrated that these patterns could not be distinguished on this basis. The conceptual model presented points to the type II pattern as the only single A-layer structural type. We propose the use of the terms type 1/type II to exclusively describe the morphological patterns that appear upon negative staining and the open/closed nomenclature to describe the conformations that a single structural type can adopt.     

Validation of generic names inLycopodiaceae: with a description of a new genusPseudolycopodiella

Four earlier proposed and invalidly published generic names ofLycopodiaceae are validated:Lateristachys (type:Lycopodium laterale R. Br.),Lycopodiastrum (type:Lycopodium casuarinoides Spring),Pseudodiphasium (type:Lycopodium volubile G. Forster) andPseudolycopodium (type:Pseudolycopodium densum (Rothm.) Holub). A new genusPseudolycopodiella (type:Lycopodium carolinianum L.) is described. New nomenclatural combinations are proposed for 17 species of these genera and ofLycopodiella.     

POLLEN ULTRASTRUCTURE OF THE TRIBE INGEAE (MIMOSOIDEAE: LEGUMINOSAE)

All genera within the Ingeae, excluding Wallaceodendron, were examined with the transmission electron microscope. Thin sections reveal two pollen types (Types I and II) distinguished primarily by differences in polyad cohesion and ektexine organization. Type I polyads (only eight-grained species of Calliandra) are calymmate and the ektexine of individual cells is continuous around the grain, organized into a thin, foraminate tectum, irregularly shaped, often basally flared, foraminate columellae and thin, discontinuous foot layer. Type II polyads (16-grained species of Calliandra and remaining Ingeae) are predominantly acalymmate with individual grains typically free from one another or rarely, partially calymmate, i.e., individual grains show limited forms of attachment through small endexinous bridges (Pithecellobium latifolium [Zygia], Lysiloma) or localized appression of adjacent endexines (Pithecellobium daulense [Cathormion]). The adhesion of individual grains through localized fusion of lateral-distal and proximal ektexine in Enterolobium is unique among the partially calymmate Type II polyads. Ektexine in Type II polyads, largely restricted to the distal face, is composed of a thick, channeled tectum, granular interstitium and when present, thin discontinuous foot layer. Lateral-distal and proximal areas exhibit only endexine and, occasionally, a foot layer. The occurrence of nondistal ektexine is restricted to Enterolobium. The pollen data suggest that the acalymmate Ingeae polyads composed of grains with porate apertures, thick, highly channeled tectum, granular interstitium and lack of, or greatly reduced foot layer, are clearly derived within the Mimosoideae. Type I calymmate polyads appear to be independently derived. Ultrastructural data suggest that the Ingeae, excluding the eight-grained Calliandra species, represent a natural grouping with a close affinity to the Acacieae.     

PATTERNS OF GENICULAR DEVELOPMENT IN AMPHIROA (CORALLINACEAE)

Two types of genicular development (designated Types I and II) are present in South African species of Amphiroa. Genicula of both types originate when medullary tissue near branch endings softens by decalcification. In Type I decalcification does not progress to the branch surface and the joint therefore does not become flexible until the cortex, which remains calcified, cracks and partly sloughs. This type occurs in all species of Amphiroa in South Africa except one, and possibly occurs in those in the rest of the world as well. In Type II decalcification continues centrifugally to the surface of the branch; this results in a geniculum comprising medullary and cortical tissue. As far as is known this type occurs only in Amphiroa ephedraea. Type I appears to be more primitive than Type II.     

Comparative investigations on the differentiation of the endodermis and the development of the Hartig net in mycorrhizae of Picea abies and Larix decidua

Summary The differentiation of the endodermis of mycorrhizal roots of Picea abies and Larix decidua was investigated by means of light and transmission electron microscopy and with fluorescence techniques. The initiation and differentiation of the Hartig net were recorded. Differences between the two tree species were found, as were differences between the two tree species and angiosperms. The Casparian band developed immediately after the origin of endodermal cells from the meristem in mycorrhizae of both tree species. In L. decidua only the primary endodermis was present in most mycorrhizal laterals. The secondary structure of the endodermis was restricted to main roots and proximal parts of larch mycorrhizae. In P. abies mycorrhizae, however, the secondary stage of the endodermis developed soon after the primary endodermis and was characterized by regular alternation of short, active passage cells and elongated, rapidly degenerating cells, the inner surface of which was covered by a thick suberin layer. Hartig net development started in P. abies short roots only after the differentiation of endodermis into the secondary stage, whereas in L. decidua, the Hartig net was already initiated at the primary endodermal stage. Differences were specific for tree species.     

ASCOCARPIC CENTRUM ONTOGENY OF SPECIES OF HYPODERMATACEAE OF CONIFERS. II

Ascocarpic studies of the ontogeny of Lophodermium nitens disclosed a type of development unlike that of all other species of Hypodermataceae occurring on conifer needles. For this reason the centrum of L. nitens is designated as Type III and is compared with Type I (Gordon, 1966). Because L. nitens produces its ascocarp in several tissues of various species of pine, the ontogeny of ascocarps in different locations is discussed and illustrated. The most significant ontogenetic feature of the ascocarp of L. nitens is a layer of hyaline cells in the primordium; this layer is meristematic and gives rise to all subsequent structures of the centrum.     

Comparative development of heavily asymmetric-cordate gametophytes of <Emphasis Type="Italic">Anemia phyllitidis</Emphasis> (Anemiaceae) focusing on meristem behavior

Development of heavily asymmetric cordate gametophytes of Anemia phyllitidis (Anemiaceae), one of the schizaeoid ferns, was examined using a sequential observation technique; epi-illuminated light micrographs of the same growing gametophytes were taken approximately every 24 h. The apical cell-like wedge-shaped cell was produced once from the terminal cell of a germ filament, but it stopped dividing soon after production of one or two derivative cells. Without a functional apical cell, the gametophyte developed by intercalary growth until the early stage of wing formation, and then the multicellular (pluricellular) meristem arose from the lower lateral side of the gametophyte. This was in sharp contrast to the observation that the multicellular meristem forms in place of the apical cell in typical cordate gametophytes. Loss of the functional apical cell probably caused a site-shift in the multicellular meristem of the Anemia phyllitidis gametophyte during evolution from apical to lateral. The results suggest that apical cell-based and multicellular meristems are primarily independent of each other. The multicellular meristem produced cells equally in the distal and proximal directions to form wings in both directions but proximally produced cells divided much less frequently. As a result, a heavily asymmetric gametophyte was formed.     

Differential ultrastructure of synaptic terminals on ventral longitudinal abdominal muscles in Drosophila larvae

The innervation of ventral longitudinal abdominal muscles (muscles 6, 7, 12, and 13) of third-instar Drosophila larvae was investigated with Nomarski, confocal, and electron microscopy to define the ultrastructural features of synapse-bearing terminals. As shown by previous workers, muscles 6 and 7 receive in most abdominal segments “Type I” endings, which are restricted in distribution and possess relatively prominent periodic terminal enlargements (“boutons”); whereas muscles 12 and 13 have in addition “Type II” terminals, which are more widely distributed and have smaller “boutons.” Serial sectioning of the Type I innervation of muscles 6 and 7 showed that two axons with distinctive endings contribute to it. One axon (termed Axon 1) has somewhat larger boutons, containing numerous synapses and presynaptic dense bodies (putative active zones for transmitter release). This axon also has more numerous intraterminal mitochondria, and a profuse subsynaptic reticulum around or under the synaptic boutons. The second axon (Axon 2) provides somewhat smaller boutons, with fewer synapses and dense bodies per bouton, fewer intraterminal mitochondria, and less-developed subsynaptic reticulum. Both axons contain clear synaptic vesicles, with occasional large dense vesicles. Approximately 800 synapses are provided by Axon 1 to muscles 6 and 7, and approximately 250 synapses are provided by Axon 2. In muscles 12 and 13, endings with predominantly clear synaptic vesicles, generally similar to the Type I endings of muscles 6 and 7, were found, along with another type of ending containing predominantly dense-cored vesicles, with small clusters of clear synaptic vesicles. This second type of ending was found most frequently in muscle 12, and probably corresponds to a subset of the “Type II” endings seen in the light microscope. Type I endings are thought to generate the ?fast’? and ?slow’? junctional potentials seen in electrophysiological recordings, whereas the physiological actions of Type II endings are presently not known. © 1993 John Wiley & Sons, Inc.