bluuebunny/crossref_metadata_2025 huggingface dataset:
Leaf anatomy and ultrastructure of the North American marine angiospermPhyllospadix(Zosteraceae)
Authors: Kuo John , Stewart Joan G.
Published: April 2011

The leaf anatomy and ultrastructure of the North American Phyllospadix species P. serrulatus Rupt. ex Aschers., P. scouleri Hook, and P. torreyi Watson are described. The unique anatomical and ultrastructural features of these species are compared with those of other seagrasses and their possible functional significance is discussed. All three species have ultrastructures similar to those in other members of the family Zosteracae. Subcuticular cavities, wall ingrowths, and numerous mitochondria and chloroplasts with well-developed grana are present in the blade epidermal cells and the adaxial sheath epidermal cells, indicating that these cells may play a major role in photosynthesis, osmoregulation, and absorption. Plasmodesmata are present occasionally between adjacent epidermal cells, and also between epidermal and mesophyll cells, suggesting that solutes can be transferred symplastically between these tissues. The vascular bundle sheath cells are not easy to recognize, as cell walls are thin and not suberized. The phloem contains both normal and nacreous-walled sieve tubes that may be functional. The walls of the phloem parenchyma cells facing nacreous-walled sieve tubes possess weak wall ingrowths, leading to speculation that these parenchyma cells may play an important role in solute translocation. The absence of suberin lamella in bundle sheath cells and the presence of a small xylem element in each vascular bundle suggest that the water flow in xylem elements in these seagrasses may be limited and that water is taken directly from the water column by leaf epidermal cells and is transported apoplastically along cell walls. The three North American Phyllospadix species can be separated by anatomical characters such as number of vascular bundles, the shape of epidermal cells in both transverse sectional and surface views, and the distribution of fibre bundles. It is proposed that P. serrulatus is taxonomically more closely related to the Japanese P. iwatensis Makino than to P. scouleri and P. torreyi and that there is no detectable hybrid species occurring between P. scouleri and P. torreyi. Key words: anatomy, ultrastructure, seagrasses, Phyllospadix, North America.
Old-growth, disturbance, and ecosystem management
Authors: Johnson E. A. , Miyanishi K. , Weir J. M. H.
Published: April 2011

The forested landscape consists of a mosaic of patches of different times since the last disturbance (i.e., different stand ages). Therefore, we can form a distribution of forest ages for the entire landscape (landscape age distribution). Studies of disturbance by fire in boreal and subalpine conifer forests have shown that the cumulative age distribution (landscape survivorship distribution) is best fit by a negative exponential model for which the parameter, the disturbance cycle, gives the time required to disturb an area equal in size to the study area. This distribution describes the rate at which parts of the landscape will survive disturbance, and consequently it tells us the percentage of the landscape that will survive to be old-growth forest. Empirical studies show that old forests make up a small proportion of the boreal and subalpine landscape. We introduce the concept of characteristic oldest age, which is a function of disturbance cycle and size of the study area. This landscape approach to old growth allows one to estimate the minimum area required to ensure the continued existence of some user-defined old-growth forest for any given disturbance cycle. Key words: old growth, disturbance cycle, ecosystem management, landscape age distribution, boreal forest, landscape ecology.
The regulation of flowering in Arabidopsis thaliana: meristems, morphogenesis, and mutants
Authors: Haughn George W. , Schultz Elizabeth A. , Martinez-Zapater Jose M.
Published: April 2011

In the last decade, the study of mutants defective in floral development has contributed significantly to our understanding of floral evocation and morphogenesis. Genes in Arabidopsis thaliana and Antirrhinum majus that play key roles in (i) the transition from the vegetative to reproductive phase, (ii) the activation of floral development in specific shoots, and (iii) the unique arrangement of floral organs have been identified genetically and in many cases cloned. Many of the genes appear to encode transcription factors that act to select specific developmental programs of division and differentiation for groups of primordial cells. Other genes may be involved in detecting environmental conditions and transducing the signal to the developing meristems. Key questions remaining include how the regulatory proteins are produced in specific temporal and spatial patterns, interact with each other and initiate specific morphological programs. Although current research on floral morphogenesis has been limited to only a few species there is growing evidence that the basic processes are common to all flowering plants.Thus the information and tools currently being generated should be useful for studying a wide variety of flowering species. It seems reasonable to predict that within the next decade, we should have a fairly complete understanding of the basic mechanisms underlying floral morphogenesis and its evolution among the angiosperms. Key words: Arabidopsis thaliana, floral morphogenesis, molecular genetics.
Light and electron microscopy of a host–fungus interaction in the roots of some epiphytic ferns from Costa Rica
Authors: Schmid E. , Oberwinkler F. , Gómez L. D.
Published: April 2011

The roots of 11 epiphytic fern species from the genera Elaphaglossum, Peltapteris, Hymenophyllum, Grammitis, and Lellingeria were studied by means of light and electron microscopy. All species showed a similar association with an ascomycete that traversed the root hairs and formed intracellular hyphal coils within cytoplasmic epidermal and outer cortical cells. The unbranched fungal hyphae were of a uniform diameter. They were surrounded by a flocculent matrix material and by the host plasmalemma. Cytoplasmic hyphae also occurred within degenerated host cells. The host–fungus interaction showed similarities to Ericoid mycorrhizae. Key words: ferns, mycorrhiza, ascomycete, ultrastructure, Costa Rica.
Trichocintractia, a new genus for Cintractia utriculicola (Ustilaginales)
Authors: Piepenbring Meike
Published: April 2011

Cintractia utriculicola, which produces sori in the spikelets of Rhynchospora spp., differs from typical Cintractia species by long sterile cells at the base of the sorus instead of a mycelial stroma with sporogenous pockets and by a persistent peridium of spherical cells. While in other Cintractia species the ornamentation of the teliospores originates at an undulated plasmalemma as an irregular surface of the exosporium, in Cintractia utriculicola warts develop on a smooth cell surface and are loosely connected to the exosporium. A new genus, Trichocintractia, is proposed for Cintractia utriculicola. Key words: Ustilaginales, Cintractia, Cintractia utriculicola, Trichocintractia utriculicola, soral morphology, spore wall ultrastructure.
Multiple branching stems in a hybrid between bread wheat (Triticum aestivum) and lymegrass Leymus mollis
Authors: Koebner R. M. D. , Martin P. K. , Anamthawat-Jónsson K.
Published: April 2011

Hybrids have been produced between bread wheat (Triticum aestivum L. em. Thell.) and lymegrass (Leymus mollis (Trin.) Pilger), and these are vegetatively highly vigorous but sexually sterile. The plants are unusual for Triticeae in having both extensive intravaginal branching along the length of the stem and the ability to spontaneously develop aerial roots from the stem nodes. These morphological changes are probably genetically determined, since the phenotype was expressed in a number of independent hybrids grown in widely differing environments. It may, however, be an epigenetic effect, arising from the tissue culture period necessary for embryo rescue. As the hybrids are self-sterile, the character is useful as it allows for ready vegetative reproduction. Key words: wheat, Leymus, wide hybrid, branching stem, aerial roots.
Plant size effects on allocation to male and female functions in pearl millet, a hermaphroditic wind-pollinated species
Authors: Dajoz Isabelle , Sandmeier Michel
Published: April 2011

In hermaphroditic higher plants, reproductive fitness can be achieved through male and female functions. The relative allocations to reproduction by maternal and paternal investments define the gender of each individual. In wind-pollinated species, the theory predicts that gender should evolve with plant size, the largest plants investing the most in male function. More specifically, the tallest plants should exhibit the highest degree of maleness, because pollen dispersal is most effective when the release point is high. We searched for potential variation in gender with plant size in pearl millet (Pennisetum typhoides), where each plant produces several shoots. Size was estimated by using four parameters, namely height, stem diameter, total leaf area, and vegetative weight, for shoots and for plants. Gender was estimated as the pollen to ovule (P:O) ratio for each shoot or plant. We found that allocation to male function is very variable, both between shoots within a plant and between plants. Most of the difference observed is correlated with differences in the weight of the shoots or plants, the heaviest ones having the highest P:O ratios. The theoretical prediction that maleness should increase with plant height was not fulfilled. The parameter used to estimate plant size seems to have a great influence on the ability to detect gender variation with size. The allocation to reproduction (defined as the weight of seeds, stamens, floral parts, and rachis of the spike) represented a decreasing proportion of total plant weight; also, the heavier the plant, the higher the proportion of this allocation devoted to male function. Since pearl millet is a cultivated species, this may be due to the fact that the domestication process, by selecting for larger plants, involuntarily selected for maleness by favoring the largest plants. Key words: pearl millet, resource allocation, sexual function, plant size.
The taxonomy and distribution of rare or uncommon species of Albatrellus in western North America
Authors: Ginns J.
Published: April 2011

Habitat data, although sparse, and occurrence are summarized for nine rare or uncommon species of Albatrellus. Significant range extensions are Albatrellus avellaneus in British Columbia, Oregon, and Washington, Albatrellus caeruleoporus in California, British Columbia, Oregon, and Washington, Albatrellus dispansus in Washington, Albatrellus ellisii in Colorado, Oregon, Washington, and Wyoming, Albatrellus flettii in Alaska, Alberta, northern British Columbia, Idaho, New Mexico, and Wyoming, Albatrellus subrubescens in Alberta, California, Northwest Territories, and Washington, Albatrellus syringae in North America (Alaska, Alberta, British Columbia, and Yukon Territory). Three additional collections of Albatrellus skamanius bring the total known collections of the species to four; all are from the same general locality. A key to the western species, emphasizing features of fresh basidiomes, is included. The basidiome features of these species are supplemented with data from additional collections. Spore sizes in several species are more critically defined. Amyloidity occurred in basidiospores and (or) hyphae of A. avellaneus, Albatrellus affin. cristatus, A. ellisii, A. flettii, A. skamanius, and A. subrubescens. Key words: systematics, ecology, Basidiomycetes, conservation, biodiversity, fungi.
Ophiostoma protearum sp.nov. associated with Protea caffra infructescences
Authors: Marais G. J. , Wingfield M. J.
Published: April 2011

A new ophiostomatoid fungus, Ophiostoma protearum, and its Sporothrix anamorph, is described based on isolations from infructescences of Protea caffra. The species is compared with ophiostomatoid fungi previously described from Protea infructescences in the Western Cape Province of South Africa. Based on differences in their anamorphs, there appear to be two evolutionary lines among these fungi in this niche. Key words: Ceratocystis, Ceratocystiopsis, Ophiostoma protearum, Sporothrix, Knoxdaviesia, biogeography.
Microsporogenesis and pollen sulcus type in Asparagales (Lilianae)
Authors: Rudall Paula J. , Furness Carol A. , Chase Mark W. , Fay Michael F.
Published: April 2011

Cladistic analysis of molecular data (plastid rbcL sequences) supports the interpretation of simultaneous microsporogenesis as an apomorphy for Asparagales (Lilianae), with a reversal in the most derived 'higher' asparagoid clade, which is entirely successive. 'Lower' asparagoids are mainly simultaneous, with occasional reversals to the successive state, such as in Xanthorrhoea, Hypoxidaceae, and a few Orchidaceae and Iridaceae (including Geosiris). Trichotomosulcate pollen, a characteristic feature of one of the lower asparagoid clades, is associated with simultaneous microsporogenesis. Some lower asparagoids, such as Doryanthes and a few Iridaceae, are recorded as having both successive and simultaneous microsporogenesis. Irregular tetrads occur frequently in Asphodelaceae and sometimes in higher asparagoids, although not in the group with trichotomosulcate pollen. We relate the distributions of these characters to the positions of the same taxa in the rbcL tree, expanded to include more taxa sampled for pollen characters. The pollen data are highly congruent with the rbcL tree, although when viewed from the perspective of all previous classifications, trichotomosulcate pollen would be interpreted to have evolved several times. We interpret distribution of both simultaneous microsporogenesis and trichotomosulcate pollen with the DNA tree to be an indication of the reliability of both for taxonomic revision of family limits. Key words: tetrads, trichotomosulcate pollen, Phormiaceae.
Intensification de la régénération du pois (Pisum sativum L.), par le thidiazuron, via la formation de structures caulinaires organogènes
Authors: Popiers Delphine , Flandre Frédéric , Sangwan-Norreel Brigitte S.
Published: April 2011

In vitro regeneration of pea (Pisum sativum L.), a regeneration recalcitrant legume, was optimised using thidiazuron. Buds were initiated from the meristems of the cotyledonary nodes of embryo axes, isolated from mature seeds, and subcultured on Murashige and Skoog medium supplemented with 13.3 μM 6-benzylaminopurine, 16.1 μM α-naphthaleneacetic acid, and 0.2 μM 2,3,5-triiodobenzoic acid. Proliferation of buds was preceded by the formation of white nodular-like protrusions. These structures were cut transversally in fine slices and subcultured on the same medium or in presence of thidiazuron that produces a second wave of secondary budding. The best results (90–110 buds per expiant) were obtained with 10 μM thidiazuron. The capacity of regeneration was genotype independent and reproducible. Buds elongated on the initial medium, then formed roots in presence of 5.37 μM α-naphthaleneacetic acid. and developed into viable plants. Key words: Pisum sativum L., regeneration, meristems, embryo axes, thidiazuron.
Les symbioses mycorhiziennes des arbres de la forêt tropicale humide de Guyane française
Authors: Béreau M. , Gazel M. , Garbaye J.
Published: April 2011

Roots of 75 tree species, belonging to 28 families, were sampled on different types of soil in the forest of French Guiana. Both seedlings and mature trees of each species were studied. The roots were first observed for ectomycorrhizas, then thinned and stained to observe and quantify endomycorrhizal associations. Ectomycorrhizas were found only on two genera: Coccoloba (Polygonaceae) and Neea (Nyctaginaceae). All the species studied had zygomycetous endomycorrhizas with hyphal coils and vesicles. It is remarkable that some families (Caesalpiniaceae, Myrtaceae, Tiliaceae, Euphorbiaceae, Lauraceae), considered as frequently ectomycorrhizal in other regions of the world, were not so in our sample. In addition, the results contradict the theory that ectomycorrhizal species are dominant in the poorest soils in tropical rainforests (tropical podzols). Key words: tropical rainforest, symbioses, mycorrhizas, French Guiana.
Genetic and temporal variation in wound healing after abscission of peach leaves in relation to peach canker disease
Authors: Biggs A. R.
Published: April 2011

Leaf scars from 13 peach cultivars and clones with varying susceptibility to peach canker disease were collected during the period November 1986 through May 1987 and were examined histologically. Leaf scar sections were examined with light and fluorescence microscopy for tissue changes related to wound healing, including depth and width of the polysaccharide-impregnated zone, the timing and tissue depth at which the ligno-suberized layer occurred, the thickness and numbers of cells in the ligno-suberized layer, the longitudinal length of the ligno-suberized layer and whether or not the tissue was complete in longitudinal section through the leaf scar, and the presence and numbers of phellem cells in the wound periderm and whether or not the periderm was complete across the longitudinal section of the leaf scar. The percentage of leaf scars with a complete polysaccharide-impregnated zone varied by date with 94–96% of the leaf scars exhibiting the zone in January and April. The thickness of the polysaccharide-impregnated zone also varied by date, reaching its thickest in January and April. Percentages of lignified leaf scars were mostly similar among cultivars on four of the five dates; however on 1 May, there was considerable variation among cultivars with percent lignification ranging from 0 to 100%. The proportion of leaf scars with lignification was not significantly correlated with the field susceptibility rankings for peach canker disease at any of the five dates. The proportion of leaf scars with complete ligno-suberized layers varied by date only, with the highest values observed on 12 January and 14 May. The lowest values was observed on 1 May, and this was significantly less than that observed on 7 November and 10 April. The highest percentage of leaf scars possessing periderm occurred on 12 January (74%), with all the other dates not significantly different from each other (ranging from 29 to 40%). Analysis of cultivar across all dates combined indicated that Candor generally showed the highest percentages of leaf scars with periderm (64%), and this was significantly higher than Sunhaven (24%), Earlired (14%), and V68101 (13%), which were not different from each other. The proportion of leaf scars with periderm was not significantly correlated with the field susceptibility rankings for peach canker disease at any of the five dates. Key words: Prunus, wounding, Leucostoma.
Breeding system in an alpine species: Rhododendron ferrugineum L. (Ericaceae) in the French northern Alps
Authors: Escaravage Nathalie , Pornon André , Doche Bernard , Till-Bottraud Irene
Published: April 2011

The breeding system of the alpine shrub Rhododendron ferrugineum was studied at two sites of a population (site L and site H) in the French Alps. The aims were to estimate the degree of selling and (or) outcrossing and to determine if floral traits (including floral morphology, pollen to ovule ratio, stigma receptivity) may be related to the breeding system of the shrub. First, floral traits (corolla length and anther, and style heights) were measured, the number of pollen tetrads and ovules were counted, and the date of stigma receptivity and anther dehiscence were recorded. Second, five pollinations treatments (unmanipulated flowers, natural selfing, hand selfing, natural outcrossing, and hand outcrossing) were performed on 35 randomly chosen individuals in each site, and after each treatment the number of seeds per fruit was recorded. The results demonstrate that Rhododendron ferrugineum is self-compatible (self-compatibility index = 0.95 and 0.97; auto-fertility index = 0.92 and 0.98; selfing rate = 0.24 and 0.11 at sites L and H, respectively). Indices values are not significantly different between the two sites and facultatively xenogamous (pollen to ovule ratio = 669.5 ± 280.5 and 845.2 ± 246.9 at sites L and H, respectively). Key words: breeding system, Rhododendron ferrugineum, floral morphology, phenology, P:O ratio.
Riparian bryophyte vegetation in the Cascade mountain range, Northwest U.S.A.: patterns at different spatial scales
Authors: Jonsson Bengt Gunnar
Published: April 2011

Riparian forests are productive and species rich ecosystems where the vegetation is structured by sharp environmental gradients. The study describes community patterns of bryophytes in stream-side forests, relates these patterns to major environmental gradients, and compares within-site factors with site level variables. Samples were collected from 360 plots 2 × 4 m in size distributed among 42 sites in old-growth Pseudotsuga–Tsuga forests. The sites ranged from 420 to 1250 m asl and stream size from 1st to 5th order streams. There were significant changes in species richness and composition along several environmental gradients. Richness within sites varied among different geomorphic surfaces with the highest number of species on areas periodically flooded. Richness was also higher in plots with high abundance of woody debris. No site level factors influenced richness at the sample plot level, while the highest species number at the site level was for large streams. The main gradients in the species composition within sites were changes with increasing distance from the stream and amount of woody debris. Both elevation and stream size significantly influenced species composition. The complex set of factors that influenced species richness and composition implies that management of riparian vegetation must be based on both coarse scale considerations such as regional distribution of different stream types and fine scale factors such as spatial availability of different substrate types. Key words: old-growth forest; CCA analysis; fluvial disturbance; bryophytes; elevation effects; coarse woody debris.
New and interesting Laboulbeniales (Ascomycetes) from New Zealand
Authors: Weir Alex , Rossi Walter
Published: April 2011

Four new species of Laboulbeniales collected on insects in New Zealand are described and illustrated: Cucujomyces phycophilus sp.nov. parasitic on Macralymma brevipenne Cameron and Omaliomimus conicus (Fauvel) (Coleoptera: Staphylinidae: Omaliinae), Diaphoromyces kuschelii sp.nov. parasitic on Menimus spp. (Coleoptera: Tenebrionidae), Diphymyces penicillifer sp.nov. parasitic on Stenomalium helmsii (Cameron) (Coleoptera: Staphylinidae: Omaliinae), and Stigmatomyces novozelandicus sp.nov. parasitic on Sapromyza neozealandica Tonnoir & Malloch (Diptera: Lauxanidae). All of the new species are compared with exiting taxa. In addition, Smeringomyces trinitatis Thaxt., Stigmatomyces purpureas Thaxt., and S. spiralis Thaxt. are recorded from New Zealand for the first time, and a review of the known species of Laboulbeniales from New Zealand is presented. Key words: Laboulbeniales, taxonomy, New Zealand.
Systematic value of tapetal orbicules: a preliminary survey of the Cinchonoideae (Rubiaceae)
Authors: Huysmans Suzy , Smets Erik , El-Ghazaly Gamal , Nilsson Siwert
Published: April 2011

Sixteen species of 14 genera of 7 different tribes of the Cinchonoideae (Rubiaceae) were investigated with a scanning electron microscope to examine orbicule presence and morphological diversity. Orbicules are lacking only in Gouldia terminalis (Hook, et Arn.) Hbd. and Simira rubescens (Benth.) Bremek. ex Steyerm. Four orbicule types could be distinguished mainly on the basis of shape and ornamentation characteristics. Spiny orbicules (type I) we found only in the Catesbaeeae (sensu Delprete). Augusta longifolia (Spreng.) Rehd. has microrugulate orbicules (type II). Smooth and spherical orbicules smaller than 0.5 μm (type III) are most widespread in our sample of the Cinchonoideae. In Burttdavya nyasica Hoyle, they are irregular and folded (type IV). For each species a description is given of the orbicule and of the sexine morphology, to allow comparison. Species with spiny orbicules always have microspines on the pollen sexine. For the other orbicule types no such resemblance could be observed. Transmission electron microscope observations of four species are included to comment on ultrastructural differences between orbicule types. From this preliminary survey, we suggest that orbicule features in Cinchonoideae may be systematically useful on generic and tribal levels. Key words: Ubisch bodies, Rubiaceae, Cinchonoideae, orbicule ultrastructure, tapetum.
Effects of light, salinity, and thermoperiod on the seed germination of halophytes
Authors: Khan M. Ajmal , Ungar Irwin A.
Published: April 2011

Seed germination of desert shrubs (Atriplex griffithii Moq., Haloxylon recurvum (Moq.) Bunge ex Boiss, Suaeda fruticosa (L.) Forssk., Triglochin maritima L.), and a forb (Zygophyllum simplex L.) was studied under various light, temperature, and salinity regimes. Seed germination of Atriplex griffithii, Z. simplex, and Suaeda fruticosa was least affected by light, whereas, seeds of H. recurvum and T. maritima had a light requirement for germination. Haloxylon recurvum seeds did not germinate at 10–20 °C in the dark, and no T. maritima seeds germinated in dark at all thermoperiod and salinity regimes studied. Seed germination was inhibited in all species with an increase in salinity, and this inhibition was more substantial in dark than in light. Key words: Atriplex griffithii, halophyte, Haloxylon recurvum, light, seed germination, Suaeda fruticosa, Triglochin maritima, thermoperiod, Zygophyllum simplex.
Puccinia deosaiensis sp.nov. on Epipactis helleborine (L.) Crantz.
Authors: Khalid A. N. , Iqbal S. H.
Published: April 2011

Puccinia deosaiensis sp.nov. is described and illustrated from Deosai Plains, northern Pakistan. Key words: Epipactis, northern Pakistan, Puccinia deosaiensis, a new rust.
Phylogenetic implications of chloroplast DNA restriction site variation in subtribes Raphaninae and Cakilinae (Brassicaceae, tribe Brassiceae)
Authors: Warwick S. I. , Black L. D.
Published: April 2011

Chloroplast DNA restriction site data was used to assess relationships among 41 taxa of the subtribes Raphaninae and Cakilinae (tribe Brassiceae, Brassicaceae). A total of 456 restriction site mutations was observed, with 237 (52%) being phylogenetically informative. Cladistic analysis, based on Wagner parsimony analysis, indicated four major clades: (i) CAKILE, (ii) CRAMBE, (iii) NIGRA lineage, and (iv) RAPA-OLERACEA lineage. The CAKILE clade was divided into two lineages: (i) Cakile, Erucaria (including Reboudia), and Didesmus (previously assigned by Schulz to the Raphaninae) and (ii) Crambella (previously assigned by Schulz to the Raphaninae). The Raphaninae as currently circumscribed is polyphyletic in origin. The cpDNA data supported separate subtribal status for Crambe (Raphaninae) and indicated two major lineages corresponding to sect. Dendrocrambe and the combined sections Crambe and Leptocrambe. Enarthrocarpus arcuatus, Enarthrocarpus lyratus, Morisia monanthos, Raphanus raphanistrum, Raphanus sativus, and Rapistrum perenne were included in the RAPA-OLERACEA lineage of subtribe Brassicinae. Ceratocnemum rapistroides, Cordylocarpus muricatus, Guiraoa arvensis, Hemicrambe fruticulosa, Kremeriella cordylocarpus, Muricaria prostrata, Otocarpus virgatus, Raffenaldia primuloides, and Rapistrum rugosum were included in the NIGRA lineage of subtribe Brassicinae. Key words: Brassicinae, Raphaninae, Cakilinae, chloroplast DNA restriction site variation, molecular systematics.
Relationship of mycorrhizal activity to time following reclamation of surface mine land in western Kentucky. II. Mycorrhizal fungal communities
Authors: Gould Ann B , Hendrix James W
Published: April 2011

Over a period of 2.5 years, mycorrhizal fungal communities in soils of five abandoned surface coal mine sites in western Kentucky were studied in relation to time following reclamation. These sites were reclaimed at different times and were in varying stages of revegetation. At the seeding stage of reclamation, low populations of mycorrhizal fungal spores of only a few species, notably Glomus microcarpum Tul. & Tul., Glomus aggregatum Schenck & Smith emend. Koske, and Glomus fasciculatum (Thaxter) Gerdemann & Trappe emend. Walker & Koske, were present. Populations of spores of these species increased rapidly during the first 1 or 2 years after reclamation. Other species, notably those with larger spores, appeared with time. Spores of one group of species were a high proportion of the total early after reclamation, then declined in relation to populations of other species. A second group appeared soon after reclamation and maintained a relatively constant proportion of the total population. A third group was inconspicuous for a few years after reclamation but increased in proportion to the total population of spores with time. Species richness was low soon after reclamation, rose slowly and erratically over 5 years, then stabilized at about 10 species. Species dominance, diversity, and evenness were relatively constant after the first 2 years of reclamation.Key words: Glomales mycorrhizal fungi, arbuscular mycorrhizal fungi, abandoned minespoil, succession, community relations.
Systematics of North American Petasites (Asteraceae: Senecioneae). I. Morphometric analyses
Authors: Cherniawsky Donna M , Bayer Randall J
Published: April 2011

Petasites Mill. (Asteraceae: Senecioneae) is a taxonomically difficult genus of polygamodioecious, perennial clonal herbs distributed across Canada, Alaska, and the northern contiguous United States. The taxonomic confusion surrounding the genus is reflected in the ambiguity of the various classification systems currently used. As many as ten species and as few as two species have been recognized (Petasites sagittatus (Banks ex Pursh) Gray and Petasites frigidus (L.) Fries with three varieties), in addition to one hybrid taxon. To determine if discrete groups could be recognized according to a combination of vegetative and (or) reproductive characters and thereby clarify the phenetic relationships among the taxa of Petasites, morphological data were subjected to principal components and discriminant analyses. Particular emphasis was placed on P. frigidus var. frigidus, P. frigidus var. nivalis sensu Bogle, and the purported hybrid between these taxa, which exhibits an intermediate morphology (the frigidus complex). Additionally, the specific status of P. sagittatus was investigated. Evidence obtained from multivariate morphometric analyses indicates that North American Petasites is comprised of four closely related polymorphic entities. While morphological variation among different taxa of Petasites is continuous for most reproductive characters, leaf characters were determined to be the most taxonomically discriminating. The entities of the frigidus complex form a cohesive group somewhat distinct from the other taxa. The morphological differentiation between P. sagittatus and other taxa of Petasites is not considered sufficient to warrant recognition of specific status. Therefore, we recommend that only one polymorphic species of Petasites in North America be recognized (P. frigidus with three varieties) in addition to one hybrid taxon originating from a cross between two of the varieties. Key words: Petasites, Asteraceae, North America, systematics, principal components analysis, discriminant analysis.
Nuclear DNA amount in pure species and hybrid willows (Salix): a flow cytometric investigation
Authors: Thibault Jérôme
Published: April 2011

Flow cytometry (FCM) has been used to estimate the nuclear DNA content of 11 Salix species and 5 hybrids. One hundred and sixty nine individuals were studied including 159 individuals from a sequence of 32 communities along a stretch of river in France and 10 individuals from French and English collections for comparison. Isolated nuclei were stained with propidium iodide. FCM was a significantly more practical and rapid technique than that of establishing the karyotype to survey many samples of Salix for variation in ploidy. The 2C DNA amounts for diploid species ranged from 0.76 to 0.98 pg, and tetraploid values ranged from 1.62 to 1.80 pg. The DNA values were consistent with the known ploidy levels. With the exception of a doubtful Salix xquercifolia, ploidy levels and DNA amounts of hybrids were intermediate compared with those of their parents. Intraspecific variation of nuclear DNA values including instrumental variation was low (i.e., 6-11% at the same ploidy level). FCM appeared to be an accurate tool for determination of Salix triploid hybrids. However, it remains limited concerning hybrids from crosses between species of the same ploidy level. Results suggest that natural hybridization might not be frequent in the communities studied, although they have been subject to disturbance. Previous overestimates of hybridization frequency in willows were probably due to misinterpretation of the effects of the environment on Salix spp. morphology; however, the extent and mechanisms of introgression in the genus remain to be further investigated. Key words: flow cytometry, Salix, hybridization, nuclear DNA content, riparian vegetation, disturbance.
Aquatic hyphomycetes in three rivers of southwestern France. II. Spatial and temporal differences between species
Authors: Fabre Eric
Published: April 2011

Spatial and temporal changes in conidial concentration of species of aquatic hyphomycetes were studied in three southwestern French rivers (Adour, Nive, and Tech). The survey was conducted from source to mouth for a year by water filtration. Fifty-two species were identified. Alatospora acuminata and Clavariopsis aquatica were the most abundant species in all three rivers. Most other species made small contributions to the total amount of conidia, but species such as Heliscella stellata or Lemonniera aquatica occasionally may be important in a particular river. The timing of seasonal peaks of conidia concentration of some species was studied. Species were classified into three groups according to the similarity or differences among rivers. Peak conidial concentration could appear at the same season on the three rivers (e.g., Alatospora acuminata, Articulospora tetracladia, Heliscella stellata, Lemonniera aquatica, Lunulospora curvula) or in different seasons on the three rivers (e.g., Pyricularia submersa, Tetrachaetum elegans). No peak was found for Clavariopsis aquatica or Clavatospora longibrachiata on any river. Changes in conidial concentration along the three rivers were analysed. Patterns of individual species varied among rivers and seasons. During summer on the Tech River, conidial concentration of Heliscella stellata increased abruptly to the highest values of this study after having remained close to zero in the uppermost 20 km. This coincided with a drastic decrease in community diversity in these reaches. Both altitude and downstream distance influence conidial concentrations in a complex manner. Key words: Ingoldian fungi, conidia concentration, season, elevation.
Population genetic structure in a bird-dispersed pine,Pinus albicaulis(Pinaceae)
Authors: Bruederle Leo P , Tomback Diana F , Kelly Kathleen K , Hardwick Renea C
Published: April 2011

Whitebark pine (Pinus albicaulis) is the sole North American representative of Pinus subgenus Strobus section Strobi subsection Cembrae, a group of five species characterized by bird-dispersed seeds. Whereas population genetic structure has been described for several Eurasian Cembrae pines, the purpose of the present research was to quantify genetic diversity in whitebark pine and assess the distribution of genetic variation within and among populations interpreted within the context of this species' unique life history. Allozyme analyses were conducted on nine populations from the Greater Yellowstone Area. Genetic diversity, as measured by population means for percentage of loci polymorphic, number of alleles per locus, and expected heterozygosity was relatively low (i.e., 38.57, 1.66, 0.152) when compared with means reported for pines with wind-dispersed seeds. Genetic differentiation was also low (i.e., 0.025) relative to means reported for other gymnosperms including wind-dispersed pines. These populations are poorly differentiated, with the majority of all observed variation due to differences among individuals within populations. The data reported herein for whitebark pine populations are similar to those reported for other Cembrae pines and may reflect their recent evolutionary history, as well as life history, including documented bird dispersal of seeds.Key words: population genetic structure, plant evolutionary biology, bird dispersal, Pinus albicaulis, Pinaceae.
New records and species of Canalisporium (Hyphomycetes), with a revision of the genus
Authors: Goh T K , Ho W H , Hyde K D , Whitton S R , Umali T E
Published: April 2011

Three new species of Canalisporium, namely Canalisporium exiguum Goh & K.D. Hyde, Canalisporium kenyense Goh, W.H. Ho & K.D. Hyde, and Canalisporium pallidum Goh, W.H. Ho & K.D. Hyde, are described and illustrated. New records of Canalisporium caribense, Canalisporium pulchrum, and Canalisporium elegans, are given. They are also illustrated from fresh material and briefly discussed. Comparisons of conidial morphology of all species from different localities are made and a key to the species of the genus is provided.Key words: Berkleasmium, dematiaceous hyphomycetes, freshwater fungi, lignicolous fungi, systematics.
Photoassimilate allocation and photosynthetic and biochemical characteristics of two alfalfa (Medicago sativa) cultivars of different ozone sensitivities
Authors: Renaud J P , Laitat E , Mauffette Y , Allard G.
Published: April 2011

Ozone (O3) is a major air pollutant that has been reported to affect growth of alfalfa (Medicago sativa L.). In the present study, an O3-sensitive cultivar, 'Apica', and an O3-tolerant cultivar, 'Team', of alfalfa were exposed to multiple levels of ambient O3 concentrations (i.e., 0x, 1x, 1.5x, and 3x) using open-top chambers. The objectives were to characterize O3 sensitivities at the leaf level and to determine whether stomatal or mesophyll conductance could account for the differences in O3 sensitivity. Differences in photoassimilate allocation were also determined using 14CO2. Effects of O3 exposures on leaf characteristics such as leaf area and dry matter; leaf concentrations of chlorophyll, starch, proteins, amino acids, and nutrients; and stomatal density were evaluated. Gas exchange measurements were also performed. Results showed that O3 exposures produced a greater decline in leaf biomass, chlorophyll concentration, and net assimilation rate for 'Apica' compared with 'Team'. For O3 concentrations of 20-40 nL ·L-1, a 7-15% reduction in net assimilation rate was observed for 'Apica' only. With an increase in O3 concentrations, stomatal limitation did not increase correspondingly, and a strong correlation between net assimilation rate, stomatal conductance, and carboxylation efficiency was observed, suggesting a physiological coordination of the O3 stress response at the leaf level. Possibly the decrease in assimilation rate induced by O3 could be associated with the O3 effects at the mesophyll level. For both cultivars, O3 increased the CO2 compensation point of the leaves, and some effects were also noted in terms of leaf mineral concentrations. O3 did not alter photoassimilate allocation between shoots and roots but stimulated their retention in leaves compared with stems. These results suggest that O3 has a major impact on the carbon metabolism of leaves, which could explain differences in O3 sensitivities.Key words: gas exchange, ozone tolerance, alfalfa cultivars, stomata, photoassimilate allocation.
Genetics of Cronartium ribicola. IV. Population structure in western North America
Authors: Kinloch, Jr. Bohun B , Westfall Robert D , White Eleanor E , Gitzendanner Matthew A , Dupper Gayle E , Foord Brett M , Hodgskiss Paul D
Published: April 2011

Population genetic parameters were estimated for six populations of Cronartium ribicola in western North America from British Columbia to the southern Sierra Nevada, and two outgroups from eastern North America, using isozyme, random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers on cultured haploid clones. Diversity was low, with only 8% polymorphism in the 212 markers identified. Each polymorphic locus had only two alleles, except for an RFLP marker in the ribosomal DNA complex with multiple alleles, that resulted from variable numbers of tandem repeats. Expected heterozygosity within populations, estimated from diploid teliospores, was only 0.025. The three types of markers were highly consistent with each other for these parameters. Yet, populations were highly differentiated; the proportion of the total variation attributable to differences among populations was 0.205. Multivariate statistical analysis as well as different clustering algorithms based on contrasting evolutionary assumptions (drift, mutation) all showed similar relationships and differences among populations. Genetic distances were not associated with geographic distances; western populations within a few kilometres of each other were often more distant from each other genetically than they were from eastern populations across the continent. The lack of pattern over the landscape of this metapopulation is consistent with aspects of the life cycle and epidemiological behavior of the pathogen, in which genetic drift appears to play a major role.Key words: white pine blister rust, isozymes, RAPDs, RFLPs, multivariate analysis, genetic drift.
Étude cytologique de l'effet de l'éthéphon sur la texture des cerises Bigarreau-Napoléon
Authors: Batisse Cyrille , Coulomb Claude , Coulomb Philippe Jean , Buret Michel
Published: April 2011

This study presents a comparison between tissues of treated and nontreated Bigarreau-Napoléon cherries using physiochemical and cytological tests. Ethephon provokes a cell wall destructuration greater in the mesocarp tissue than in the under-peduncular area. It consists of breakage or an enlargement of some cell walls with the formation of a hydrated pectin network. Ethephon induces a cell wall catabolism characteristic of a fast cell wall senescence.Key words: Ethephon, ethylene, Bigarreau-Napoléon cherries, cell wall alterations, mechanical harvest.
Unusual polyamines in aquatic plants: the occurrence of homospermidine, norspermidine, thermospermine, norspermine, aminopropylhomospermidine, bis(aminopropyl)ethanediamine, and methylspermidine
Authors: Hamana Koei , Niitsu Masaru , Samejima Keijiro
Published: April 2011

Four aquatic plants were tested for the occurrence of unusual polyamines. The leaves of the aquatic plants tested ubiquitously contained homospermidine in addition to usual polyamines such as diaminopropane, putrescine, cadaverine, spermidine, spermine, and agmatine. Brasenia schreberi and Nuphar japonicum belonging to the family Nymphaeaceae contained aminopropylhomospermidine. Norspermidine and norspermine were detected in the blackweed Hydrilla verticillata belonging to Hydrocharitaceae. Thermospermine was detected in Brasenia schreberi. A novel tetraamine, N,N'-bis(3-aminopropyl)-1,2-ethanediamine (NH2(CH2)3NH(CH2)2NH(CH2)3NH2), was discovered in the aquatic plant Nuphar japonicum. This is the first report of the occurrence of N4-methylspermidine (NH2(CH2)3N(CH3)(CH2)4NH2) in the water chestnut Trapa natas belonging to the family Hydrocaryaceae. Key words: aquatic plants, polyamine, bis(aminopropyl)ethandiamine, methylspermidine.
Seasonal and needle age-dependent changes of the endophytic mycobiota in Pinus thunbergii and Pinus densiflora needles
Authors: Hata Kunihiko , Futai Kazuyoshi , Tsuda Mitsuya
Published: April 2011

Monthly changes in the endophytic mycobiota in Pinus thunbergii Parl. and Pinus densiflora Sieb. et Zucc. needles were detected by tissue culture. Endophytic mycobiota of these pine needles were dominated by four taxa: the Leptostroma anamorph of the Lophodermium pinastri (Schrad. ex Hook.) Chev. complex, Phialocephala sp., Cenangium ferruginosum Fr.:Fr., and an unidentified hyphomycete species (BrS). The mycobiota differed with host pine species, position on the needle, and needle age. Virtually no endophytes were detected in needles just after emergence, but most segments of the older needles harbored endophytes. The endophytic mycobiota changed slowly with needle aging, except for the periods of rapid increase in the detection frequency of Leptostroma and Phialocephala sp. Detection frequency of Leptostroma, the most frequently detected endophyte taxon in the needles of the two pine species, continuously increased with needle aging, while that of Phialocephala sp., the endophyte mainly detected from the basal segments of Pinus densiflora, slowly decreased with needle aging after a massive emergence in current-year needles.Key words: Pinus thunbergii, Pinus densiflora, pine needle, endophytic fungi.
Hybridization and the origin of the arctic grass Poa hartzii (Poaceae): evidence from morphology and chloroplast DNA restriction site data
Authors: Gillespie Lynn J. , Consaul Laurie L. , Aiken Susan G.
Published: April 2011

The hypothesized hybrid origin of Poa hartzii Gand. (Poaceae) was investigated by analysis of morphological and molecular data. This endemic nearctic caespitose grass has been considered to be a hybrid between two of the three sympatric arctic species, Poa glauca M. Vahl, Poa arctica R. Br., and Poa abbreviata R. Br. Field observations and morphological studies indicate that Poa hartzii is a morphologically distinct apomictic species that reproduces and disperses by seed. Restriction enzyme analysis of polymerase chain reaction amplified chloroplast DNA revealed the presence in Poa hartzii of two very different haplotypes. One haplotype is identical to the dominant type found in Poa glauca, while the second is identical to the haplotype of Poa secunda J. Presl., located south of the arctic region. These results are consistent with an hypothesis of ancient hybrid origin involving Poa glauca and Poa secunda, but not Poa arclica nor Poa abbreviata. They are also consistent with an hypothesis of cytoplasmic transfer via hybridization and introgression from Poa glauca to an ancestral Poa hartzii in the Poa secunda complex. Direction of transfer is suggested by the widespread occurrence of the Poa secunda haplotype in Poa hartzii and by closer morphological similarity with Poa secunda than Poa glauca. The origin of Poa hartzii provides an excellent example of reticulate evolution and the importance of hybridization in the speciation of arctic grasses. Key words: Poa hartzii, arctic Poa, chloroplast DNA, restriction enzyme analysis, hybridization, introgression.