bluuebunny/crossref_metadata_2025 huggingface dataset:
Viability of the epizoic lichen flora carried and dispersed by green lacewing (Nodita pavida) larvae
Authors: Slocum Robert D. , Lawrey James D.
Published: September 2008

Specimens of green lacewing (Nodita pavida) larvae were collected in oak–hickory stands in southern Ohio. Lacewing larvae construct and carry 'packets' of cryptogamic vegetation upon their backs, a habit which camouflages them from predators and prey. Light and scanning electron microscopy were used to elucidate the attachment and composition of the packets, which consist of lichen soredia and thallus fragments, pieces of bark, moss gametophyte fragments, angiosperm pollen grains, fungal spores, and other plant and insect debris. Rates of net photosynthesis and respiration of lichen diaspores removed from lacewing packets were found to be similar to those of independent lichen thalli growing on trees where the larvae were collected. Viability of lichen propagules on lacewing cocoons attached to the bark substrate was further demonstrated. A discussion is presented in which this unique dispersal mechanism for viable lichen propagules is considered together with the adaptive value of insect camouflage.
The seed banks of prairie glacial marshes
Authors: Valk A. G. van der , Davis C. B.
Published: September 2008

There was very little similarity in the floristic composition of seed banks from the same or different vegetation types in different marshes: the average Sørensen's similarity index values ranged from 24 to 28%. The floristic composition of seed banks from different vegetation types within a given marsh was more similar: the average Sørensen's similarity index value was 41%. The results also suggested that allelopathic interactions in substrate samples with high amounts of organic matter resulted in either the inhibition of seed germination or the death of seedlings of several species.
Sporogens, sterols, and sporulation of Leptosphaerulina briosiana
Authors: Moyer B. G. , Leath K. T.
Published: September 2008

The role of sporogenic compounds and sterols in the light-induced sporulation of Leptosphaerulina briosiana was investigated. Substances similar to P310 sporogens were extracted in greater amounts from light-grown L. briosiana than from dark-grown cultures. Sporulation was not induced in dark-grown L. briosiana treated with P310 substances extracted from light-grown L. briosiana or Ascochyta pisi. P310 substances in L. briosiana occurred primarily in dark-grown stromata or ascostromata from light-grown cultures. Ergosterol was present in L. briosiana, but ascospores were not produced by dark-grown L. briosiana treated with ergosterol or cholesterol. Sterol inhibitors delayed ascospore production and inhibited mycelial growth of L. briosiana. Autoclaved ergosterol counteracted the inhibitor; fatty acids, other sterols, and nonautoclaved ergosterol did not. Three sterol inhibitors prevented ascospore development in detached ascostromata. Neither P310 substances nor sterols could be substituted for the near-ultraviolet (near-UV) light required by L. briosiana for sporulation. P310 substances were more closely associated with stromatal formation than with spore differentiation and were fungal metabolites rather than photochemical degradation products. Near-UV light was required by L. briosiana for ascostromata maturation and ascospore differentiation rather than for ascostromata formation.
Lambertella berberidis n.sp. from India
Authors: Elliott Mary E. , Sharma M. P.
Published: September 2008

Apothecia of a Lambertella species were collected in August from stromatized leaves of Berberis. They are similar to L. pruni in their broadly lunate-shaped ascospores; they differ in their larger ascospores.
Controlled-environment studies on net assimilation and water relations of Dryas integrifolia
Authors: Hartgerink Antoinette P. , Mayo James M.
Published: September 2008

Net CO2 assimilation and water relations of Dryas integrifolia from Devon Island, N. W. T., were studied under controlled-environment conditions. Maximum net CO2 assimilation rate for single leaves was 18.7 mg g−1h−1. The optimum leaf temperature for net CO2 assimilation was between 9 and 14 °C. Positive net CO2 assimilation occurred at −5 °C. Respiration and net CO2 assimilation decreased with the onset of dormancy. Dark respiration was generally equal to or greater than that of other arctic and alpine species. The mean leaf water potential of actively growing plants was −11.4 bars. Values higher than −7 bars were found only infrequently. Turgor pressure was maintained at high values (+6 to +10 bars) over a wide range of water potentials, suggesting osmotic adjustment to soil moisture deficit.
The Galium trifidum group (Galium sect. Aparinoides, Rubiaceae)
Authors: Puff C.
Published: September 2008

By using morphology, karyology, pollen size, leaf flavonoids, ecological observations, and modification experiments, a new classification of the Galium trifidum group is proposed. Nine taxa in five species are recognized: (1) G. tinctorium, with ssp. tinctorium and sap. floridanum (new comb.) in eastern North America; (2) G. brevipes, a rare species centered in the Great Lakes region; (3) G. trifidum, with ssp. trifidum in northern North America. Asia, and Europe, ssp. columbianum (new comb.) in (north)western North America and (north)eastern Asia, and ssp. subbiflorum (new comb.) and ssp. halophilum (new comb.) in northern North America; (4) G. innocuum in southeastern Asia; (5) G. karakulense in central Asia.New chromosome counts of n = 12 and 2n = 24 are reported for G. tinctorium ssp. tinctorium and ssp. floridanum; and G. trifidum ssp. trifidum, ssp. columbianum, and ssp. subbiflorum.
Further observations on the fine structure of marine collared flagellates (Choanoflagellata) from arctic Canada and west Greenland: species of Parvicorbicula and Pleurasiga
Authors: Manton I. , Sutherland J. , Leadbeater B. S. C.
Published: September 2008

New observations amplifying and sometimes correcting existing descriptions have been compiled for Parvicorbicula socialis (Meunier) Deflandre, Parvicorbicula quadricostata Throndsen, Pleurasiga minima Throndsen, and P. reynoldsii Throndsen from arctic material prepared as whole mounts at the time of gathering. Introductory details on localities, techniques, terminology, etc. relevant to these and other organisms to be considered later are recorded here. Special attention has been paid in each case to previously unrecorded details of lorica construction and, where material has been abundant (P. socialis and P. quadricostata), also to the range of variability in wild populations which, in these two taxa, is shown to be greater at the hind end of the lorica than elsewhere. Some differences from the type descriptions, notably up to 50% larger lorica size in three species and other differences which are interpreted as seasonal in one species (P. socialis), are thought to be ecologically but not taxonomically significant. Other details such as the shapes of costal tips, the nature of the junctions, and the mode of suspension of the protoplast within the lorica, most fully explored in P. quadricostata, are thought to be of possible phyletic significance though full discussion is deferred pending availability of additional taxa. The only nomenclatural recommendation given here is to confer specific rank on Pleurasiga minima var. minuta Leadbeater (as P. minuta Leadbeater) to separate it from P. minima Throndsen itself, which is recorded electron microscopically here for the first time and is shown to be a clearly defined and different taxon. This work is continuing.
Host–parasite interfaces in a resistant and a susceptible cultivar of Solanum tuberosum inoculated with Phytophthora infestans: leaf tissue
Authors: Hohl Hans R. , Suter Elisabeth
Published: September 2008

Host–parasite interfaces in leaves from a resistant (Eba) and a susceptible (Bintje) potato cultivar inoculated with Phytophthora infestans were studied using light and electron microscopy. Host penetration occurs similarly in both cultivars either through stomata or directly through the epidermis. In the susceptible host the fungus spreads throughout the tissue intercellularly and transcellularly, whereas in the resistant host it remains confined to the focus of infection. Yet in both cases live, normal-appearing hyphae can be observed even after 5 days. The appearance of haustoria in both cultivars is similar: they are either surrounded by an extrahaustorial matrix alone or in combination with wall appositions (collars or encasements). Structures with cytological features between those of haustoria and transcellular hyphae were also recorded, indicating a variety of host–parasite interactions within leaf tissue. Sporulation has been observed on the susceptible cultivar but not on the resistant one. The results suggest that cellular reactions against the intruding fungal hypha are qualitatively similar in both cultivars but that at the tissue level the intercellular spread of the pathogen and its sporulation are prevented in the resistant host but not in the susceptible host.
Emblemospora, a new genus of the Sordariaceae
Authors: Jeng R. S. , Krug J. C.
Published: September 2008

Emblemospora is described as a new genus of the Sordariaceae. It is characterized by clavate asci each provided with a small apical ring and dark, one-celled ascospores possessing numerous small plate-like markings and a germ pore at one or both ends of the spore. This genus is established for two new species, E. ditrema and E. monotrema, both found on burro dung collected in Venezuela. Descriptions and illustrations are provided and a key to the species is included.
Différenciation de boutons floraux, de bourgeons végétatifs, de racines et de cal à partir de l'assise sous-épidermique des ramifications florales de Nicotiana tabacum Wisc. 38. Etude infrastructurale
Authors: Van M. Tran Thanh , Chlyah A.
Published: September 2008

Ultrastructural studies of different types of differentiation, organogenetic (formation of flower buds, vegetative buds, or roots) or nonorganogenetic (callus formation), show important modifications at the subepidermal cell level. Besides the changes showing general activation leading to the first mitosis such as an increase of the ribosomes density, a more laboured endoplasmic reticulum, and a denser nucleus located near the centre, other changes seem to be related to a particular differentiation: for the flower program, an early starch accumulation and a higher mitochondrial activity in the cells take place and for the callus program important pinocytosis phenomena occur at the plasmalemma level.
Water potentials of seeds of Bromus inermis and Medicago sativa imbibed on media of various osmotic potentials
Authors: McDonough W. T.
Published: September 2008

Seeds of smooth brome grass (Bromus inermis Leyss.) and alfalfa (Medicago sativa L. cultivar Ladak) were allowed to imbibe in water or solutions of polyethylene glycol (Carbowax 1540), mannitol, or sodium chloride. Seed water potentials were determined over a 72-h period after transfer of seeds to thermocouple psychrometer chambers. Seed water potentials were lower than osmotic potentials of the media, but these two potentials were not clearly related to each other. Possible reasons for the lack of gradation in response are discussed.
Molybdenum and sulfur nutrition effects on nitrate reduction in Burley tobacco
Authors: Pal U. R. , Gossett D. R. , Sims J. L. , Leggett J. E.
Published: September 2008

Nicotiana tabacum L. cv. Ky-14 plants were grown in an intermittently irrigated gravel culture system in a greenhouse. The nutrient variables were either Mo (0 to 0.66 μeq/l) or Mo (0 and 0.33 μeq/l) plus SO42− (0 to 0.50 meq/l). About 45 days after initiating the treatments, the plants were harvested and separated into leaves, midribs, stalk epidermis, stalk xylem–phloem, and stalk pith for Mo, S, NO3−, total N, and nitrate reductase (NR) (EC 1.6.6.1) activity assay. Other plants were grown in complete Hoagland's solution (i.e., 0.66 μeq Mo/l and 0.50 meq SO42−/l) for all nutrient elements and used for determinations of canopy and seasonal profiles of NR activity.Molybdenum concentration in all plant parts increased with increasing solution Mo concentration. Sulfate drastically reduced the concentration of Mo, and the inhibition was essentially equal in all plant parts. Greatest reduction of Mo occurred with the first increment of SO42− (0.05 meq/l), with little effects from further additions of SO42−. The data suggest that the inhibitory effects of SO42− on Mo content occur primarily during the absorption process, with some antagonistic mechanism involved during translocation from roots to leaves. Molybdenum was not inhibitory to S accumulation. Contents of Mo and S in leaves were greater than in any other plant part.NR activity generally increased from bottom to top leaves. About 60% of the NR in the plant occurred in the leaves. The canopy profiles suggest that the recent, completely open leaf (7–9 in. long) and the second and third leaves below it could be sampled for maximum NR activity for NO3− reduction experiments. Sulfate nutrition increased NR activity, as a result of increased NR synthesis, while Mo nutrition was without effect on NR in these experiments. The NO3− content was not affected by SO42−, but NO3− increased in the absence of Mo.
Geographical distribution and taxonomy of fungi from salt marsh Spartina
Authors: Gessner R. V. , Kohlmeyer J.
Published: September 2008

Collections were made of filamentous fungi on Spartina alterniflora, S. patens, and Spartina sp. from tidal salt marshes along the east coasts of North and South America. Buergenerula spartinae, Phaeosphaeria typharum, Phoma sp., and Stagonospora sp. were found at most of the sites sampled. All the species collected in Florida have also been reported from Rhode Island, indicating that a characteristic mycota is possibly associated with Spartina alterniflora along the east coast of the U.S.A. A compilation of all the higher filamentous fungi reported from Spartina spp. from marine habitats is included. The list has been compiled from the literature and our collections and includes 66 Ascomycetes, 5 Basidiomycetes, 29 Fungi Imperfecti, and 1 Mycelium Sterilium. Ellisiodothis inquinans and Leptosphaeria typhicola are reported for the first time from Spartina. The new name Leptosphaeria neomaritima Gessner et Kohlmeyer nom. nov. (basionym Sphaeria maritima Cooke et Plowright 1877, non S. maritima Crouan et Crouan 1867) is proposed. Leptosphaeria discors Sacc. et Ellis 1882 is made a synonym of L. obiones (Crouan et Crouan) Sacc. (basionym Pleospora obiones Crouan et Crouan 1867).
Studies on lichen-dominated systems. XVIII. Morphological control of evaporation in lichens
Authors: Larson D. W. , Kershaw K. A.
Published: September 2008

The current belief that lichens are incapable of controlling their water relations is based largely on evidence collected from experiments testing for active metabolic controls only. In this study, controlled wind tunnel experiments designed to test for any passive morphological control of evaporation in four lichen species show that such mechanisms are important to the water relations of the plants and thus suggest that the observed morphological variability in lichens is of great ecological significance.Time-dependent and moisture-content-dependent changes in evaporation rate were examined using samples of lichen thalli from a number of different arctic and subarctic populations of Alectoria ochroleuca (Hoffm.) Massal., Alectoria nitidula (Th.Fr) Vain, Cetraria nivalis (L.) Ach., and Cladina alpestris (L.) Harm. The work has shown that the observed interspecific and intraspecific variability in evaporative resistance found in these plants is influenced by three separate morphological characteristics: variability in surface area to weight ratio; variability in thallus shape; and variability in the degree of clumping of thalli. When other aspects of the ecology and physiology of the test lichens were considered, it became clear that these lichens exhibited a potential to modify their morphological characteristics over long periods of time in such a way that greater photosynthetic productivity was assured.It was concluded that although the control of water relations in lichens is of a different nature from higher plants, the control is present nonetheless.
The specific activities of peroxidase and aminolevulinic acid dehydratase during the growth cycle of peanut suspension culture
Authors: Kossatz V. C. , Huystee R. B. van
Published: September 2008

Peroxidase (EC 1.11.1.7) enzyme units that were recovered by sequential extraction at low and high ionic strength buffer pH 7 from a peanut suspension culture at various intervals of cell growth appeared to increase with culture time. In particular, at the end of a 14-day growth cycle, peroxidase specific activity rose while protein content and the specific activity of porphobilinogen synthase (aminolevulinic acid, dehydratase EC 4.2.1.24) declined. The decrease of the protein content could probably be accounted for by the 95% decrease of protein synthesis at the end of the growth phase. The highest specific activity of aminolevulinic acid dehydratase (ALA dehydratase) appeared to be associated with organelles which could be precipitated at 500 × g and this specific activity appeared to be unaffected by the stage of growth of these cells. It is suggested that the ALA dehydratase activity in nonchlorophyllous peanut cells, which is as high as that found in green tissue, may play a function in the biosynthesis of the hemoprotein peroxidase.
Histochemistry and identification of disease-induced terpenoid aldehydes in Verticillium-wilt-resistant and -susceptible cottons
Authors: Mace M. E. , Bell A. A. , Beckman C. H.
Published: September 2008

Hemigossypol (HG) and 6-methoxyhemigossypol (MHG) were the major terpenoid aldehydes isolated from stem stele tissue of 6-week-old verticillium-wilt-susceptible Rowden and verticillium-wilt-resistant Seabrook Sea Island 12B2 (SBSI) cotton plants infected for 14 days with Verticillium dahliae. HG constituted 90 and 45 mol % and MHG 6 and 41 mol % of the induced terpenoid in the steles of Rowden and SBSI, respectively. No terpenoids were detected in extracts of noninfected steles.The cellular localization of terpenoids in infected and noninfected stems was studied histochemically with a SbCl3 reagent. Terpenoids first occurred in both SBSI and Rowden in scattered, usually solitary, paratracheal parenchyma cells appressed to infected xylem vessels. After extensive fungal colonization, diffusion of induced terpenoids obscured the initial, discrete sites of localization.
Leaf development in Begonia hispida var. cucullifera with special reference to vascular organization
Authors: Lieu S. M. , Sattler R.
Published: September 2008

The leaf is initiated by periclinal divisions in the second cell layer of the apex. Early in development, it assumes an asymmetrical shape as a result of the non-median position of the apical meristematic region that forms the leaf tip. The other main lobes of the leaf are formed by two additional regions of growth to the side of the tip. In the second plastochron, primordia are initiated on the upper surface of the main ribs of the leaf and these often develop into large, leaf-like appendages. During the third plastochron, the leaf becomes covered by a dense layer of trichomes. Vascular development is well correlated with regions of growth. The median procambial strand extends diagonally into the skewed apical growth region and another strand branches from this and develops on the other side. Lateral procambial strands usually form in an abaxial to adaxial sequence in the petiole: one strand of the first pair to develop forms part of the median rib and the other forms a third main rib on the opposite side. After the initiation of primordia on the leaf surface, a 'ventral system' of procambia is developed supplying mainly the ventral rib surface and consequently the epiphyllous appendages. This consists of branches from the adaxial-most peripheral bundles in the petiole as well as a bundle in the centre. The vascular anatomy of the stem and nodal region is also described in relation to that of the leaf.
The ultrastructure of sexual reproduction in Pythium acanthicum
Authors: Haskins R. H. , Brushaber J. A. , Child J. J. , Holtby L. B.
Published: September 2008

The young oogonium and young antheridium in Pythium acanthicum Drechsler are densely and randomly packed with numerous mitochondria, dictyosomes, nuclei, interlocking vacuoles of several types, some of which contain a dense storage body, a variety of vesicles, endoplasmic reticulum, and cytoplasmic ribosomes. Wall vesicles, evenly distributed next to the plasma-lemma in rapidly growing oogonia, become localized in groups at points where they appear to initiate the hyphal tip-like development of the oogonial spines. They are also found on both sides of the antheridium−oogonium contact zone. Spine development starts shortly after antheridium−oogonial contact is made and ceases with entry of antheridial material into the oogonium. Excess nuclei, mitochondria, and various organelles are abandoned in the periplasmic space, where they normally quickly disintegrate when the oospore is formed. The periplasmic space is invaded frequently by vegetative hyphae originating outside of the oogonium.
Cycling of leaf conductance in citrus exposed to natural and controlled environments
Authors: Levy Yoseph , Kaufmann Merrill R.
Published: September 2008

Three types of evidence indicate that stomatal cycling occurs in citrus under field conditions. First, dendrograph records collected from 1963 to 1965 on 30-year-old trees revealed daytime oscillations in trunk diameter, with a period of about 1 h. These oscillations occurred during winter and summer months at two southern California locations. Second, leaf conductance measurements were made on 12-year-old citrus in southern California during clear, mild days in March and April, 1975. Oscillations having a period of shorter than 1 h were observed. Third, oscillations in photosynthesis measured with a Shimshi apparatus were observed on 17-year-old citrus in Israel during clear days in November 1975. In controlled greenhouse experiments on 4-year-old citrus in large pots, cycling in leaf conductance, leaf water stress, and trunk diameter were observed, but the patterns differed with root temperatures of 5 and 25 °C. At 5 °C, cycling began early and decreased later in the day, and water stress and trunk diameter changes lagged behind conductance changes. At 25 °C, cycling became more prominent as the day progressed, and no lag was observed.
Apothecium morphogenesis in Peziza quelepidotia: scanning electron and light microscopy
Authors: O'Donnell K. L. , Hooper G. R. , Fields W. G. , Ackerson Arthur O.
Published: September 2008

This study on Peziza quelepidotia Korf & O'Donnell, a homothallic operculate Discomycete (Pezizales, Pezizaceae), presents the first detailed correlative light microscopic and scanning ultrastructural observations of any species in this genus. This investigation was possible because P. quelepidotia. unlike other Peziza spp., produces fertile ascomata in pure culture. A complete structural and functional image of apothecium morphogenesis was obtained by combining scanning electron micrographs of the initial stages with light micrographs of whole mounts and thick sections of apothecia embedded in plastic at all stages of development. The temporal–spatial relationship between the ascogonia and the Botrytis-like imperfect state suggests that the ascogonial coils may be under chemotrophic control of the conidiophores. Although functional ascogonia are present, sexuality is apparently parthenogenetic since antheridia were never observed. A unique feature of paragymnohymenial apothecium development in this species is the elevation of the ascogonial coil as the stipe develops. Scanning electron microscopic observations on longitudinally cryofractured ascocarps are presented.
Studies on Gracilaria. 2. Growth under greenhouse conditions
Authors: Edelstein T. , Bird C. J. , McLachlan J.
Published: September 2008

Various conditions for growth of Gracilaria sp. in tanks with running seawater were studied. An increase in weight of 389% in 4 weeks was obtained at 25 °C with natural daylight. With artificial light a somewhat larger increase was obtained under slightly different conditions. Maximum growth occurred in undiluted seawater, with deterioration of plants at 10%n salinity.
Effects of translocation and assimilate demand on photosynthesis
Authors: Geiger Donald R.
Published: September 2008

Net carbon dioxide uptake by a photosynthesizing primary leaf of bean plants, Phaseolus vulgaris cv. Black Valentine, was measured during treatments designed to alter export from the leaf. Removal of shoot apices lessened sink demand while removal of all source leaves except the one being observed increased sink demand. Export from the leaf under study was lessened by chilling the primary leaf petiole and node to 2 °C. No adjustments in the rate of net photosynthesis were observed during the 33-h period after any of the treatments.The results of this study are in general agreement with previous reports in the literature. After modification of sink demand or of export by experimental manipulation of plants, a period of 2 or 3 days is usually required for adjustment of net photosynthesis rate. Rapid changes in net photosynthesis rate are generally the result of concomitant changes in morphology or metabolism during the course of plant development. The results of this work, and of others in the literature, indicate an indirect mechanism possibly involving hormonal control in some instances rather than direct feedback control of photosynthesis by product inhibition.
Development of trichospores and their appendages in Genistellospora homothallica and other Harpellales and fine-structural evidence for the sporangial nature of trichospores
Authors: Moss S. T. , Lichtwardt R. W.
Published: September 2008

Stages in the formation of trichospores and their appendages and released and germinated trichospores of Genistellospora homothallica and other Harpellales (Trichomycetes) were studied by light and electron microscopy. The trichospore is shown to be a dehiscent, monosporous sporangium with the appendages contiguous with the sporangial wall. In G. homothallica the five–seven appendages develop within the generative cell at an early stage in trichospore formation after the fusion of vesicles containing appendage precursor material with specific sites on the plasmalemma. Each formed appendage is contained within an invagination of the plasmalemma, the appendage sac, and is surrounded by a matrix. Comparative studies with other genera of Harpellales indicate a similar mechanism of appendage formation but differences in their substructure, time of formation, and location within the generative cell. The significance of apical spore bodies and associated canals which penetrate the sporangiospore walls of mature trichospores is discussed in relation to spore germination and holdfast secretion.A hypothesis is presented for appendage formation, and two basic types of appendage arrangement within the generative cell are recognized. A comparison is made between the trichospore–generative cell complex of the Harpellales and the merosporangium–pseudophialide complex of the Kickxellales.
Canadian and some extralimital Ophiobolus species
Authors: Shoemaker R. A.
Published: September 2008

Descriptions and illustrations are given for 31 species of Ophiobolus. Two allied species of Lulworthia, and Gaeumannomyces graminis are briefly contrasted. Ophiobolus species now recorded in Canada are O. acuminatus (Sow. ex Fries) Duby in Rab., O. anguillidus (Cooke in Cooke & Ellis) Sacc., O. cesatianus (Mont, ex Ces. & De Not.) Sacc., O. collapsus Ellis &Sacc., O. drechsleri n.sp., O. erythrosporus (Riess in Rab.) Winter in Rab., O. fulgidus (Clinton & Peck in Peck) Sacc., O. galii Richon, O. herpotrichus (Fries) Sacc., O. mathieui (West.) Sacc., O. minor Bubak, O. niesslii Bäumler, O. prunellae (Ellis& Ev.) n. comb., O. rubellus (Pers. ex Fries) Sacc., and O. tanaceti (Fuckel) Sacc. Extralimital species include from U.S.A., O. anthrisci (L. Holm) L. Holm, O. castellejae Tracy & Earl in Greene, O. crassus n.sp., O. filiformis (Wehmeyer) n. comb., O. lonicerae Fabre, O. ophioboloides (Sacc.) L. Holm, O. robustus (Strasser) n. comb., and O. vermisporus (Ellis) n. comb.; and from Europe, O. cirsii (Karsten) Sacc., O. compressus Rehm, O. dictamni (Fuckel) Sacc., O. fruticum (Rob. ex Desm.) Sacc., O. megalosporus (Auersw. & Niessl in Niessl) n. comb., O. ponticus Petrak, O. pseudoaffinis Petrak, and O. rudis (Riess) Rehm.
In vitro plant regeneration from leaf expiants of Lycopersicon esculentum (tomato)
Authors: Behki R. M. , Lesley S. M.
Published: September 2008

Leaf discs from 15 mutant clones of tomato were tested for their morphogenetic response in Murashige and Skoog medium supplemented with 12 combinations of the growth regulators napthaleneacetic acid (NAA) and benzylaminopurine (BA) and 4 combinations of NAA and zeatin. The results show that either callus, shoots, roots, or shoots and roots can be produced depending upon the hormone concentrations and ratios. Plants were regenerated from 12 of the 15 varieties tested.
The transport of 3H and 14C in phloem strands of Heracleum lanatum and polyester threads
Authors: Hoddinott John , Gorham Paul R.
Published: September 2008

Experiments are described which show a great similarity in the profiles of rapid movement of tritium after external application of 3H2O to a small segment of a phloem strand of Heracleum lanatum and a water-soaked polyester thread. Efflux of rapidly transported tritium from phloem strands and polyester threads was also similar. No rapid movement of radioisotope from [U-14C]sucrose, [6,6′-3H]sucrose, or [6-3H]glucose along phloem strands was observed. A possible explanation for the rapid movement of tritium in terms of proton transfer is offered. It is concluded that the rapid movement of tritium in a phloem strand which occurs when 3H2O is applied externally to a segment is an artifact and that no normal translocation is occurring.
The growth and development of the leaf in tomato (Lycopersicon esculentum). I. The plastochron index, a suitable basis for description
Authors: Coleman Warren K. , Greyson Richard I.
Published: September 2008

Growth analysis indicates that the plastochron index (PI) is consistently applicable for describing the morphological status of the vegetative tomato shoot in quantitative terms, and pronounced seasonal variability in the growth habit is minimized. However, the PI is not applicable to tomato shoots after flower buds are produced at the vegetative apex. True leaf no. 3 goes through four growth stages which can be characterized in terms of the leaf plastochron index (LPI3). A basipetal trend in leaf growth and development is evident.
Collematospora, a new genus of the Trichosphaeriaceae
Authors: Jeng R. S. , Cain R. F.
Published: September 2008

Collematospora is described as a new genus of the Trichosphaeriaceae. It is characterized by having dark setaceous ascocarps, cylindrical and persistent asci provided with distinct apical rings, and light-colored ascospores, which normally are fused vertically in groups of two to four and are enclosed by a pinkish to light yellowish brown, dextrinoid, membrane-like structure. A single species, C. venezuelensis sp. nov., is described and photographed from horse dung collected in Venezuela.
A study of Avena macrostachya
Authors: Baum B. R. , Rajhathy Tibor
Published: September 2008

The morphology, distribution, developmental and reproductive behaviour, cytology, and glumes' epicuticular waxes of Avena macrostachya, a long overlooked species, have been studied and described. In addition, a few interspecific crosses have been attempted but were unsuccessful. Based on unique traits, such as perenniality, cross-fertilization, and quadrivalent-forming autotetraploidy (2n = 4x = 28), it was found to have an isolated position in Avena. It was concluded, however, that at present there is no strong reason to exclude it from the genus. Because of its unique traits, this species may be particularly important in breeding programs when the nature of its reproductive isolation barriers is understood.
Phytoene photoinduction in a carotenoid mutant of Neurospora crassa
Authors: Lansbergen J. C. , Renaud R. L. , Subden R. E.
Published: September 2008

The dynamics of carotenoid photoinduction in N. crassa have been studied by comparing a wild type and a mutant strain lacking the second step (phytoene dehydrogenation) in the carotene biosynthetic pathway. The data indicate that dark-grown cultures contain 113 to 150 μg carotenoid per gram dry weight and that light induction can double the carotenoid content. Phytoene synthesis and phytoene dehydrogenations are photoregulated independently.
Differential effects of water stress on respiration in the light in woody plants from wet and dry habitats
Authors: Bunce James A. , Miller Lee N.
Published: September 2008

Respiration in the light, dark respiration, and leaf water status were monitored once a day in leaves of woody plants as seedlings dried during 7- to 10-day periods. Light respiration was estimated from an electrical analogue model of the response of net photosynthesis to ambient CO2 concentration and also by the rate of CO2 evolution into CO2-free air. Respiration in the light was found to increase with water stress in four dry-habitat species and to decrease with stress in four wet-habitat species. Dark respiration changes could not account for the different trends observed. When light respiration in dry-habitat plants under water stress was temporarily inhibited, net photosynthesis during recovery from water stress was reduced compared with controls for at least a week. This may indicate a protective role of light respiration in these plants when under water stress.
Compositional changes in cotyledons of woody angiosperms
Authors: Marshall P. E. , Kozlowski T. T.
Published: September 2008

The nature and rate of breakdown of food reserves in cotyledons varied markedly among species. Embryonic cotyledons of Acer negundo L. stored mostly proteins, whereas those of Ailanthus altissima (Mill.) Swingle were fat-storing. Fraxinus pennsylvanica Marsh, cotyledons contained nearly equal quantities of lipids and proteins (45% of dry weight for each) as did those of Robinia pseudoacacia L. (25% dry weight for each). Total nonstructural carbohydrate contents of embryonic cotyledons of Acer and Robinia (exalbuminous species) were considerably higher than those of Ailanthus or Fraxinus (albuminous species). Carbohydrate contents of Acer and Robinia cotyledons initially decreased, but carbohydrate contents of all four species increased rapidly as cotyledons became chlorophyllous and photosynthetic. Synthesis of cotyledonary chlorophyll and emergence of cotyledons occurred faster for seedlings of Acer and Robinia than for those of Ailanthus and Fraxinus. Protein and lipid contents of cotyledons of all four species declined as cotyledons matured after germination.
The distribution of ribosomes in the vegetative and floral apices of Adonis aestivalis
Authors: Lin Joseph , Gifford Jr. Ernest M.
Published: September 2008

The distribution of ribosomes and changes in the ratio of polyribosomes to monoribosomes were determined for the vegetative, transitional, and floral apices of Adonis aestivalis L., a day-neutral plant. Ribosomal counts were made with a Quantimet 720 image-analyzing computer. Two methods in the analysis of the shoot apex were compared: (1) ribosomal distribution based upon the average number of ribosomes per unit volume of cytoplasm (concentration) and (2) distribution based upon total number of ribosomes per cell.It was found that the concentration of ribosomes was greater in the peripheral zone than in the central zone. Increase occurred in the latter zone during transition to flowering. On a per cell basis, however, the number of ribosomes was the greatest in the rib meristem, followed by the central and peripheral zones. During transition to flowering, the number of ribosomes per cell increased only in the peripheral zone.It is suggested that consideration of ribosomal data on a per cell basis may be helpful in achieving a better understanding of the interzonal relationships within the shoot apex.
Ultrastructural and functional similarity of the haustorial neckband of rust fungi and the Casparian strip of vascular plants
Authors: Heath Michèle C.
Published: September 2008

In susceptible hosts infected with rust fungi, an osmiophilic band, bridging the interface between host and parasite, is usually observed about midway along the haustorial neck. This neckband bears certain ultrastructural resemblances to the Casparian strip of endodermal cells, and the possible similarity in function as a barrier to apoplastic transport was investigated using 4-acetamido, 4′-isothiocyanostilbene-2, 2′-disulphonic acid (SITS) and uranyl acetate solutions. Both these reagents appeared to travel along host and fungal walls but did not readily penetrate the protoplasts of either organism.When rust-infected cowpea leaves were infiltrated with SITS reagent, haustoria in broken cells fluoresced as brightly as the walls of both intercellular hyphae and host cells. Mature haustoria in intact cells, however, did not fluoresce, suggesting the presence of a barrier to the flow of reagent to the haustorium. When rusted corn leaves were allowed to take up uranyl acetate solution, the ultrastructural distribution of uranyl crystals indicated that this barrier was, indeed, the neckband, and additional circumstantial evidence for the function of this structure was provided by indications from both techniques that the transport barrier was absent from very young haustoria; the latter have previously been shown to lack an ultrastructurally detectable neckband during the early stages of their development.These results appear to confirm the functional, as well as morphological, similarity of the haustorial neckband and the Casparian strip, and these, therefore, present an unusual example of parallel evolution at the structural and functional level. The importance of such a barrier to apoplastic transport in haustoria-producing fungi is discussed.
A cytoembryological study of Agrostis pilosula
Authors: Muniyamma M.
Published: September 2008

A detailed investigation of microsporogenesis, megasporogenesis, female gametophyte development, and embryogeny in Agrostis pilosula Trin. has been made. The chromosome number of 2n = 44 is the first record for this species. Pollen mother cell meiosis reveals normal chromosome behaviour. Microspore tetrads are mostly isobilateral. The bitegmic ovule is initially anatropous and becomes hemianatropous. The inner integument delimits the micropyle. A single archesporial cell, which is hypodermal or, more rarely, deeply seated in origin, directly functions as the megaspore mother cell. Meiosis usually results in the formation of a T-shaped tetrad of megaspores, but occasionally a linear triad of megaspores is seen instead. After three mitotic divisions, the chalazal megaspore gives rise to an eight-nucleate embryo sac. The mature female gametophyte is atypical because of the lateral displacement of antipodals and its triangular shape. It consists of two synergids, a pear-shaped egg slightly pushed aside, fused polar nuclei in close approximation to the egg cell, and three large ballooned laterally displaced coenocytic antipodal cells with hypertrophied nuclei. This antipodal condition might be associated with hormonal imbalance. The endosperm is free nuclear at first and leads to the formation of solid endosperm. Starch grains are observed in older cells of endosperm. The embryo development is regular and conforms to Pooid type.
Cohabitation of three Hieracium species in relation to the spatial heterogeneity in an old pasture
Authors: Thomas A. G. , Dale H.M.
Published: September 2008

Three closely related species, Hieracium floribundum. H. pratense, and H. florentinum, are found in Wellington County and they frequently grow together in old pastures near Guelph, Ontario. In the 60 × 60 m study area, the maximum difference in elevation per metre was 0.5 m. Each species occupied a distinctive but a highly overlapping position in the available niche space as determined by relief exposure and influenced by competition. Although all three species were found on slopes facing in any direction, each was significantly associated with a particular exposure. Hieracium floribundum and H. pratense were positively associated with northwest- and north-facing slopes, respectively. These two vegetatively reproducing species displaced H. florentinum from northern slopes when they came into contact. Hieracium florentinum had the broadest niche over the range of exposures but was positively associated only with south-facing slopes. The small variations in relief resulted in higher maximum temperatures and higher accumulated degree-hours on southwest than on northeast slopes. We concluded that the spatial heterogeneity of the old pasture was sufficiently high and that temperature differences were great enough to account for the cohabitation of the three species. The conclusions drawn from the study area are extrapolated and used to explain the distribution pattern within the county.
Inhibition of conidial germination by Claviceps purpurea honeydew fluid
Authors: Cunfer Barry M.
Published: September 2008

Claviceps purpurea honeydew contains a factor(s) which inhibits conidial germination of some fungi. Filters-sterilized honeydew fluid inhibits germination, whereas washed C. purpurea conidia do not. Conidia of Fusarium heterosporum, which colonizes honeydew and prevents the formation of sclerotia on ergot-infected cereals, were not affected by the inhibitor(s). Fungi found unable to colonize the honeydew stage of C. purpurea on barley were sensitive to the inhibitor(s).Honeydew fluid at −30 bar water potential can be diluted 4–8 times without loss of inhibitory activity. The inhibitor(s) was both fungicidal and fungistatic against sensitive test isolates. Honeydew fluid retained its inhibitory activity when heated at 100 °C for 15 min but not after 30 min heating or after autoclaving. The role of the inhibitor(s) in the life of C. purpurea and its possible use for identification of biocontrol agents are discussed.
An assessment of the roles of furanocoumarins in Heracleum lanatum
Authors: Camm Edith L. , Wat Chi-Kit , Towers G. H. N.
Published: September 2008

Several naturally occurring furanocoumarins such as xanthotoxin cause cell damage by complexing with DNA in the presence of long-wave UV light. Heracleum lanatum, an Umbellifer, contains high concentrations of such compounds in the leaves but survives in sunlight and is a food source for insects, fungi, and man. Microscopic investigations and feeding experiments carried out in long-wave UV show that although the compounds are normally isolated in the petiolar oil ducts, the plant can tolerate xanthotoxin uptake in the transpiration stream. Aphids living on Heracleum take up and bind xanthotoxin fed via a cut stem but are unaffected over short term. Such tolerance in plant and aphid may be due to limited cell divisions during the test, but the biochemical basis of tolerance in growing Heracleum is not known. Various fungi, including pathogens of Umbellifers, show differing sensitivities to xanthotoxin plus UV, perhaps because of differing uptake rates and growth habits.
Studies on the genus Apios. I. Chromosome number and distribution of Apios americana and A. priceana
Authors: Seabrook Janet A. E. , Dionne Leo A.
Published: September 2008

Two sonatic chromosome numbers were found for the leguminous plant Apios americana Medikus, i.e., 22 and 33. The former was interpreted as diploid, and the latter, as triploid. The triploid form predominated in the northern range of the species. The diploid was represented in northern material by a single collection (from Medoc, Ontario). A collection of plants produced from seeds obtained from a site in Tennessee was uniformly diploid. A combination of triploidy and self-incompatibility is suggested as the cause of the apparent complete sterility of the species over much of its range. Characterization of individual clones indicated that at least three different triploids were in existence. One of these was distributed over much of the northern range of the species. Chromosome counts of Apios priceana Robinson, a rare and the only other known American species in the genus, showed it to be a diploid with 22 somatic chromosomes.
An experimental study of water dispersal in Polygonum spp.
Authors: Staniforth R. J. , Cavers P. B.
Published: September 2008

The annual smartweeds Polygonum lapathifolium L., P. pensylvanicum L., and P. persicaria L. grow on alluvial river bars during the summer and autumn when their substrate is free of flood waters and physical disturbance. They are dependent upon dispersal for the annual recolonization of this habitat. Achenes are the only diaspores (dispersal units), and hydrochory (water dispersal) appears to be a major dispersal method.An experimental study of water dispersal of these species revealed several adaptive features. The coordination of fruit fall with the availability of the agent (flood water) ensures that the achenes are picked up. The duration of buoyancy is adequate for successful transport downstream. The presence and condition of the perianth, degree of water turbulence, and achene size are factors which determine the duration of buoyancy. Alteration of the degree of dormancy but no loss of viability occurs as a result of water transport. After deposition the achenes may remain dormant or germinate rapidly depending on environmental conditions. The deposition stage (and therefore, hydrochory) is unsuccessful for most achenes of P. persicaria, which rapidly lose viability in sites where deposition is likely to occur. The presence of this species on alluvial bars must be due to other means of dispersal.
Clone size in American aspens
Authors: Kemperman Jerry A. , Barnes Burton V.
Published: September 2008

The area of two clones of Populus tremuloides Michaux in the Fish Lake Basin, Sevier County, Utah, was determined using aerial photographs combined with ground delineation using leaf, bark, and stem characteristics. The clones occupied 24.9 acres (10.1 ha) and 106.8 acres (43.3 ha) and contained about 15 000 and 47 000 ramets, respectively. Other clones up to an estimated 200 acres (81.0 ha) were observed in the vicinity and in other areas of the central and southern Rocky Mountains. In contrast, the largest P. tremuloides clone in eastern North America whose boundary has been verified was 3.8 acres (1.5 ha). Populus tremuloides and P. grandidentata Michaux clones of eastern North America are generally small, typically less than 0.1 acres (0.04 ha) in size. The large size of many western clones is probably due to the establishment of few seedlings, periodic fires promoting suckering, expansion over a long time period, and little competition with conifers or other vegetation. Small size of most eastern North American clones and lack of large clones are probably due to establishment of many seedlings per unit area, competition among clones and with other more shade-tolerant vegetation, and their relatively young age.