bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil-borne propagule populations of isolates of Phytophthora cryptogea and P. parasitica in relation to inhibition of growth of tobacco plants
Authors: Orlikowski Leszek B. , Hendrix James W.
Published: September 2008

The relationship between populations of soil-borne propagules and inhibition of growth of tobacco plants by isolates of Phytophthora cryptogea and P. parasitica incapable of killing tobacco plants was investigated. Although plants usually were severely stunted, they had no effect on populations of the two fungi. This relationship supports the concept that growth inhibition of tobacco plants by these fungi is due to nonparasitic pathogenesis.
Multiple infections of subcrown internodes of wheat (Triticum aestivum) by common root rot fungi
Authors: Tinline R. D.
Published: September 2008

In the greenhouse, subcrown internodes of wheat plants were inoculated with Cochliobolus sativus (Ito & Kurib.) Drechsler ex Dastur, Fusarium culmorum (W. G. Smith) Sacc., F. acuminatum Ell. & Ev., or F. sulplureum Schlecht. and at various times subsequently with C. sativus; or the internodes were inoculated with C. sativus and subsequently with it or a Fusarium sp. Using isolation of the fungi as the criterion for infection, it was found that prepossession of the internode by C. sativus did not prevent later invasion by it or by the fusaria; however, C. sativus was a relatively unsuccessful challenger to F. culmorum and F. acuminatum. The results suggest that when C. sativus and one of these two Fusarium spp. appear together in isolations from common root rot diseased plants that the initial invader was C. sativus.
Structural organization of the rhizobial root nodule of alfalfa
Authors: Tu J.C.
Published: September 2008

The structural organization of mature root nodules of Medicago saliva L. is studied by thin-sectioning, scanning, and freeze-fracturing techniques. The nodules are club-shaped, with their meristematic tissue near the tip of each nodule. The bacteroidal cells situated closer to the tip area are young, whereas those located closer to the neck where the nodule and root join are older. The shape of the bacteroids changes as they grow older. The bacteroids evolve gradually from uniform long-rod or long-club shapes into short-club, short-rod. pear-shaped, ellipsoid, spherical, and Y-shapes, which in turn evolve into pear and spherical shapes. During the early part of the bacteroid's life, the bacteroid is enclosed in a membrane envelope. In older bacteroidal cells, it was observed that a few membrane envelopes contained more than one bacteroid. In senescent bacteroidal cells, the membrane envelopes have disintegrated and dissolved. The plasma membranes of mature bacteroidal cells have high endo- and exo-cytotic activities relative to nonrhizobial-infected root nodule cells or newly infected bacteroidal cells. Endo- and exo-cytotic activities are also evident on the membrane envelopes of bacteroids. The plasma membrane of the bacteroids appears to have no endo- and exo-cytotic activity, for the vesicle-like structures observed on the plasma membrane in thin-sectioning and freeze-fracturing preparations are in fact constricted invaginations of the plasma membrane of the bacteroids, somewhat resembling the cristae of mitochondria.
Growth of Pythium graminicola in barley roots
Authors: McKeen W. E.
Published: September 2008

Pythium graminicola Subrm. entered barley roots within 2 h after inoculation, and sporangial development began immediately. By 10-14 h after infection most root cells were filled with sporangia. For the first 2-3 days the fungal thallus was mostly sporangial and in the cortex; later it consisted of sexual bodies mainly in the stele. Host cell walls were penetrated rapidly, and chemical breakdown at the place of penetration was obvious. A rim of distorted wall material, caused by lateral expansion of infection hyphae, occurred around the penetration hole on the side of the wall approached by the fungus.
The influence of fixation procedure on the ultrastructure of the host–endophyte interface of vesicular-arbuscular mycorrhizae
Authors: Carling D. E. , White J. A. , Brown M. F.
Published: September 2008

The ultrastructure of the interfacial zone which separates the intracellular structures of vesicular-arbuscular mycorrhizal fungi from host cytoplasm has been described in a variety of ways by recent investigators. Evidence is presented here which suggests that previous interpretations of the ultrastructure of the interfacial zone have been based on an artifact of fixation. Using an improved procedure, a dense, granular material was found in the interfacial zone. This material was preserved by simultaneous glutaraldehyde-osmium fixation but not by conventional prefixation and postfixation in glutaraldehyde and osmium, respectively.
A new dasycladacean alga associated with the 'Arctic Ordovician' fauna on Cornwallis Island
Authors: Lee D. G. , Caldwell W. G. E.
Published: September 2008

A new species of dasycladacean alga is present in the upper Thumb Mountain and in the overlying Irene Bay Formations of the Cornwallis Group on Cornwallis Island, Northwest Territories. The alga is associated with the 'Arctic Ordovician' fauna, which is of considerable biogeographical and biostratigraphical importance. This fauna is believed to be of early Late Ordovician (Caradocian) age.The new alga is a member of the cyclocrinitid tribe and clearly is to be referred to the genus Cyclocrinites. It is distinguished from all other cyclocrinitid species by the exceptionally small size, the unusual bilobate form, and the mode of calcification of its thallus. It is believed to have lived in tropical waters which were quiet and shallow, to have been anchored to the seabed by means of rhizoids. and to have grown only in areas in which fine-grained carbonate sediment was accumulating.
Ammonium and urea uptake by some freshwater algae
Authors: Healey F. P.
Published: September 2008

Nitrogen deficiency increases the initial saturated rate of ammonium and urea uptake by three green and three blue-green algae. The increase caused by N deficiency is greater in darkness than in the light. Nitrogen deficiency also increases the size of the N debt in these algae. The green alga Scenedesmus quadricauda and the blue-green alga Pseudoanabaena catenata were selected for more detailed study of some factors affecting the rate of ammonium and urea uptake. The uptake of both ammonium and urea by these algae is light-stimulated; that of urea is sensitive to an uncoupler but not to the urease inhibitor acetohydroxamic acid. Ammonium and urea uptake resemble each other in being dependent on the presence of a chelator, but they differ in their pH dependence. They also differ in their dependence on substrate concentration, ammonium uptake showing half-saturation values of 0.1 to 0.3 μg atom N l−1, and urea uptake, 0.4 to 1.4 μg atom N l−1. While ammonium depresses the uptake of urea and urea depresses that of ammonium, the two substrates do not appear to compete for the same site.
Le mouvement géotropique des feuilles chez la Sensitive (Mimosa pudica) soumise à l'influence d'un agent anesthésique
Authors: Gaillochet Jacky , Fleurat-Lessard Pierrette
Published: September 2008

In Mimosa pudica L., the geotropic movement (a slow variety of leaf movement) induced by inverting plants in the gravific field is reversibly inhibited by diethyloxide used in a range of concentrations producing, reversibly, in the same plant, inhibition of the seismonastic leaf movement (a quick variety of leaf movement) and in other organisms, inhibition of various cellular functions such as photosynthesis, caryocinesis, and bacterial luminescence.The degree of inhibition of geotropic leaf movement is dependent upon the concentration of ether, the duration of etherization, the time of anaesthetic admission, and the sequence of the motor organs. Results led to the following conclusions: preliminary etherization of plants, in vertical position, decreases rate of the geotropic movement; etherization occurring during the course of this movement can stop it in certain conditions; geotropic movement is more inhibitedin primary than in secondary motor organs, whereas the opposite occurs in seismonastic movement.The discussion deals with the contribution of these results to the knowledge of leaf geotropism.
New records and new species of Arnium
Authors: Jeng R. S. , Krug J. C.
Published: September 2008

Three new species of Arnium are described and illustrated. These are A. calymmatosporum found on burro dung from Venezuela; A. ditremum on cow and horse dung from U.S.A. and Venezuela; and A. sexdecimsporum on horse dung from Venezuela. Additional records are provided for a number of other species. In several instances additions or corrections are made to previously published information.
Influence of temperature and photoperiod on growth and yield components in oats (Avena sativa)
Authors: Klinck H. R. , Sim S. L.
Published: September 2008

Two oat cultivars, Clintland 60 and Garry, were grown to maturity in controlled environments under two temperature regimes with daylength held constant and under two daylengths with a constant temperature pattern. Plants were moved between environments at panicle initiation and at anthesis, dividing the growth period into three phases.Growth and development were hastened by warm temperature and by long days. Temperature treatments caused greater variation in the duration of growth phases in Garry than in Clintland 60, but Clintland 60 was affected more by daylength. Higher plant dry weights were obtained from cool temperature treatments; response to daylength was inconsistent.Grain yield was not closely associated with duration of growth phases. The effect of temperature and daylength on yield components was markedly different in the two cultivars. The greatest grain yield response in Clintland 60 resulted from cool temperature during panicle initiation to anthesis, attributable to increased fertile tiller development. Daylength had limited effect on components. In Garry the greatest yield response was from cool temperatures during anthesis to maturity, with increases in all components. Short days before anthesis increased grain size and number.Implications of observed responses relative to cultivar performance in the field are discussed.
Regeneration of protoplasts of Entomophthora egressa, a fungal pathogen of the eastern hemlock looper
Authors: Dunphy Gary B. , Nolan Richard A.
Published: September 2008

The regeneration patterns for protoplasts of Entomophthora egressa MacLeod and Tyrrell grown on modified Grace's insect tissue culture medium supplemented with fetal calf serum (a highly modified version of Grace's medium lacking serum and more closely approximating the hemolymph of the eastern hemlock looper), Müller-Kögler's coagulated egg yolk medium supplemented with Tristearin, and water agar are documented. Protoplasts on liquid and egg yolk media had varying degrees of common developmental patterns. On liquid media, development involving prophyphal spheres and fusion spheres predominated. Hyphae emerged from the prohyphal spheres; however, the fusion spheres did not develop further. On the coagulated egg yolk medium, the individual, non-chain, cells coalesced and developed into pleomorphs which later developed into osmotic shock-resistant postprotoplasts. A postprotoplast gave rise to a hypha which produced a terminal conidium. Later resting spores were detected. Water agar supported scant mycelial growth as compared with that on coagulated egg yolk but more than that on the liquid media. Solid substrates appeared to favor mycelial development. Regeneration could be avoided by the addition of fresh Grace's modified medium to either coagulated egg yolk plates or to cultures with Grace's modified medium. Obtaining protoplasts from hyphae and the reversion of these protoplasts to form hyphae appeared to be a fixed property of E. egressa.This report is believed to be the first for reversion of protoplasts initially produced by non-enzymic means.
The primary productivity of submerged macrophytes in West Blue Lake, Manitoba
Authors: Love R. J. R. , Robinson G. G. C.
Published: September 2008

The productivity of Potamogeton Richardsonii, P. pectinatus, Myriophyllum alterniflorum, Megalodonta Beckii, and Chara vulgaris in West Blue Lake, Manitoba, is reported. Measurements of changes in biomass and assimilation of 14CO2 in random and non-random samples throughout the growing season of 1973 were used. Changes in biomass of P. Richardsonii, M. alterniflorum, M. Beckii, and C. vulgaris determined from random samples compared favourably with those determined from non-random samples. This was not the case for P. pectinatus because of its restricted occurrence. Similarly, measurements of 14CO2 assimilation in random samples of P. Richardsonii, M. alterniflorum, and M. Beckii compared well with non-random samples. Productivity values derived from 14CO2 uptake were far in excess of those attained from biomass changes. Seasonal trends of production and the depth distribution of production are discussed, and macrophyte production is compared with phytoplankton production.
Preliminary report of outer wall helices in trichomes of certain dicots
Authors: Lersten Nels R. , Curtis John D.
Published: September 2008

Unicellular or uniseriate trichomes with helical outer wall bands were found in several taxa of Rosaceae, Betulaceae, and Rubiaceae during a survey of cleared and stained leaves of 93 species in 86 genera of 52 families. Outer wall bands were most common in Rosaceae, especially Rubus. Previously, only bands on the inner wall of trichomes had been described. Trichomes with outer wall bands may provide excellent material for basic cell wall studies, and in certain families they may be a useful taxonomic character.
Latent floret primordia in the glume axils of inflorescences in the subtribe Triticinae
Authors: Fisher John E.
Published: September 2008

Swellings were consistently observed in the glume axils of young differentiating inflorescences of 22 taxa of the subtribe Triticinae. The swellings arose from cell divisions in the tunica (surface and subsurface) and outer cortex (underlying) layers, indicating that they were floret primordia, but since further development was arrested, they are termed latent floret primordia. Occasional floret development in the glume axils has been reported by others. The primordia were present in axils of both glumes in apical spikelets, but only in the second glume of lateral spikelets. They were rapidly obscured by developing glumes, and in lateral spikelets were more easily viewed from the abaxial (inner) side. Because of the ubiquity of the characteristic, it is proposed to be of ancient origin, and possibly can be exploited to increase the grain number and yield of wheats.
Peronospora manshurica on a nonhost and on resistant, susceptible, and intermediate soybeans
Authors: Riggle John H.
Published: September 2008

Soybeans with mature plant resistance and a nonhost, string bean, were inoculated with Peronospora manshurica. Soybeans resistant, susceptible, and intermediate in reaction were inoculated for comparison. Leaves were fixed, cleared, and stained, and whole mounts were made daily. Individual infection sites were examined, and hyphae were measured microscopically. Spore germination varied as a result of self-inhibitory factors. Where it occurred, entrance by the fungus appeared identical on each plant at 12 h. Hyphal growth became rapid in susceptible tissue 36 h after inoculation; growth slowed, starting at 72 h in mature tissue, and was uniformly slow in tissue intermediate in resistance. Hyphal growth after 36 h was essentially zero in resistant tissue, but paradoxically it was sometimes rapid on nonhost tissue. Haustoria occurred in all plants inoculated. The number of haustoria per lesion increased in proportion to the length of hyphae, except on resistant tissue, where the number of haustoria per millimetre of hyphae was very low.
Contribution à l'étude écologique des dunes mobiles. I. Les éléments phytosociologiques
Authors: Lamoureux Gisèle , Grandtner Miroslav M.
Published: September 2008

Using systematical as well as stratified sampling, the authors discussed the phytosociological organization of a 10-km-long by 150-m-wide system of mobile dunes in the Magdalen Islands. They recognized a marked toposequence from the shoreline toward the interior, including nine phytosociological elements, for the most part found in parallel zones. In this paper, they discuss the aerial and underground vertical stratification, the plant composition, and the ecological distribution of those elements.
Paleoecological aspects of the Red Lake Peatland, northern Minnesota
Authors: Griffin Kerstin O.
Published: September 2008

The Red Lake Peatland, situated on the eastern arm of the Lake Agassiz plain in north central Minnesota, is made up of large black spruce raised bogs separated by sedge-covered water tracks marked by string patterns and teardrop-shaped forested islands. About 3 m of peat overlie a prairie soil; the basal peat is 3170 ± 100 years old (14C date). Stratigraphic distribution of pollen, macrofossils, and peat components in a series of cores along a small forested island was used to study the development of the peatland.In pollen zone RLB-1 (lowest) the upland pollen types suggest an oak savanna with a developing mesic deciduous forest. The local pollen indicates a succession from a Typha marsh to a sedge meadow. Zone 2 shows a small rise in Pinus pollen; Ericaceae pollen and Sphagnum spores indicate the development of a bog–heath vegetation type at the coring site. An increase in pollen of spruce and larch reflects the establishment of the island forest. Zone 3 is marked by a rise in Ambrosia pollen, recording agricultural land clearance in northwestern Minnesota in about 1890.The Salix–herb macrofossil assemblage occurs at the base of some cores; it is succeeded stratigraphically by the Typha–Scirpus assemblage, which also makes up the base of the remaining cores. There follows the Carex diandra – Carex aquatilis assemblage, suggesting a sedge meadow. The overlying Menyanthes–Larix assemblage continues to the surface under the sedge fen; under the island, seeds of Chamaedaphne and needles of Picea occur in this assemblage. The incoming of the Menyanthes–Larix assemblage is believed to reflect the first development of the patterned wetland.Reed peat comprises the bottom 20–50 cm of all cores; it corresponds with the lower part of pollen zone 1 and contains the Typha–Scirpus macrofossil assemblage. Pure sedge peat or sedge peat with Bryales corresponds with zone 2 and upper zone 1 of the pollen diagram and contains the Carex diandra –C. aquatilis macrofossil assemblage. Ericaceous peat occurs only under the island, and it contains the Menyanthes–Larix macrofossil assemblage. Laterally under the present sedge fen it grades into sedge peat with ericaceous components.The general upward succession of communities observed in these peat cores can be duplicated along a west-to-east surface traverse across the present prairie–forest transition. The stratigraphic succession thus records the westward movement of the prairie–forest transition across Beltrami County about 4000–2000 years ago.The area was covered by prairie more than 3100 years ago. Development of a cooler, moister climate led to a Typha marsh in the poorly drained lowland; oak savanna occupied the surrounding upland. As the water level rose in the lowland, peat started to accumulate as sedge meadow developed, and aspen parkland and conifer–hardwood forest moved into the upland. About 2000 years ago the growth of Sphagnum moss increased, accompanied by the development of patterned wetland and bog forest, with conifer–hardwood forest on the upland.
Effects of ambient ozone pretreatment on transpiration and susceptibility to ozone injury
Authors: Runeckles V. C. , Rosen P. M.
Published: September 2008

The effects of daily pretreatment with low levels of ozone (0.02 μl litre−1) on the susceptibility of primary bean leaves to acute ozone injury involve several stages. Plants subjected daily to low ozone from the time of sowing exhibit an early resistance to acute injury which decreases with time. When the low ozone pretreatments begin about 10 days after sowing, there is no change in susceptibility for 2–3 days, then it increases to a level which remains constant. At the start of this period of greater susceptibility, such pretreated plants are more susceptible than controls in filtered air; after about 8 days, they are less susceptible because of the marked increase insusceptibility of the controls with time. In contrast, daily pretreatments with higher (0.05 μl litre−1) levels, beginning 8 days after sowing, cause an initial decrease in susceptibility followed by a marked increase, leading to predisposition to acute injury.The early increase in susceptibility of plants transferred from filtered air to 0.02 μl ozone litre−1appears to be the result of the decreased ability of stomates to close in response to high ozone levels. The later stage of decreased relative susceptibility is associated with a dampening of stomatal activity, which is independent of the presence of high ozone levels.
Changes in structure and function of epigeous cotyledons of woody angiosperms during early seedling growth
Authors: Marshall P. E. , Kozlowski T. T.
Published: September 2008

Variations in anatomy and stomatal characteristics of cotyledons were studied with light microscopy and scanning electron microscopy during postgermination development. Species investigated were Acer negundo L., Ailanthus altissima (Mill.) Swingle, Fraxinus pennsylvanica Marsh., and Robinia pseudoacacia L. During their development, cotyledons of all species progressed through storage, transition, photosynthetic, and senescent stages. When germination was initiated, most cells of embryonic cotyledons were filled with reserve materials (lipids, proteins, and carbohydrates). Embryonic cotyledons lacked functional stomata, and those of very few species had developing guard-cell mother cells. In embryonic cotyledons, the mesophyll was differentiated into palisade and spongy parenchyma. Amounts of cotyledon expansion varied greatly among species, and cotyledon expansion was due primarily to increased cell size. Emergence of cotyledons from seed coats occurred over a range of seedling ages, depending on species. After cotyledons emerged, chlorophyll was rapidly synthesized and stomata became functional. Anatomical characteristics of cotyledons were much different from those of foliage leaves. Leaves were much thinner and had smaller parenchyma cells than did cotyledons. Cotyledons of Acer negundo and Robinia pseudoacacia were relatively short-lived (less than 30days), while those of the other species were more persistent.
Influence of irrigation on survival of Poa pratensis infected by Ustilago striiformis and Urocystis agropyri
Authors: Hodges Clinton F.
Published: September 2008

Irrigation increased the number of surviving plants of Poa pratensis 'Merion' infected with Ustilago striiformis (stripe smut) and Urocystis agropyri (flag smut) and stimulated the production of healthy shoots from infected plants. These effects were more pronounced with plants infected by U. striiformis. Nonirrigated plants infected by U. agropyri had died by the end of the second growing season: irrigation increased the survival of some U. agropyri infected plants to a third growing season and increased the survival of many U. striiformis infected plants for the same period. The number of healthy plants established from irrigated plants infected by U. striiformis also was much greater than those established from plants infected by U. agropyri. The pattern of development for healthy shoot production from infected plants differed for the respective pathogens. The reaction of U. striiformis and U. agropyri to irrigation suggests that U. agropyri is the more destructive of the two pathogens. The production of healthy shoots from infected plants may provide a means for evaluation of P. pratensis for resistance to U. striiformis.
Stabilizing effect of benzimidazole on 6-phosphofructokinase activity in wheat leaves
Authors: Williams Bolanle A. A. , Godavari H. R. , Waygood E. R.
Published: September 2008

Primary leaves of Triticum aestivum L. var Selkirk were excised when 7–9 days old. 6-Phosphofructokinase (PFK) (EC 2.7.1.11) activity was determined in extracts from freshly excised leaves and those floated for 1, 3, or 5 days on a solution of benzimidazole (50 mg/litre) or water.PFK activity in extracts from detached leaves treated with benzimidazole was essentially the same as that in extracts from freshly excised leaves. However, the activity of the enzyme from leaves floated on water declined rapidly after 24 h floatation.
Effets de la carence en biotine sur la composition des parois cellulaires d'Hypomyces chlorinus
Authors: Touzé-Soulet J. M. , Dargent R.
Published: September 2008

A deficiency of biotin for Hypomyces chlorinus Tul. does not change the nature of major components of walls but alters their proportions. The mean percentage of neutral sugars decreased from 48.97% for the biotin-rich walls to 40.98% for the biotin-deficient walls. The molar proportions for glucose, galactose, and mannose are respectively 10:5.5:9 and 10:3:8; glucosamine, incorporated in the form of N-acetylglucosamine in chitin, increased from 19.17% to 26.75%. Variations of proteins and lipids are not significant. The results indicate occurrence of a peptide–polysaccharide complex and a glucan having essentially a β configuration. All walls treated by β-D-glucosidase have fibrillar structure. This structure disappears when the walls are treated with chitinase.
Beejasamuha and Sutravarana, two new genera of coprophilous hyphomycetes
Authors: Subramanian C. V. , Chandrashekara K. V.
Published: September 2008

Two hyphomycetes, Beejasamuha samala gen. et sp. nov. and Sutravarana samala gen. et sp. nov., isolated from goat and rabbit dung samples, respectively, are described from India. The taxonomy of these two fungi is discussed.
Inheritance of virulence of loose smut of wheat, Ustilago tritici, on the differential cultivars Renfrew, Florence × Aurore, Kota, and Little Club
Authors: Nielsen J.
Published: September 2008

Inheritance of virulence of Ustilago tritici on four cultivars of wheat was studied, using a cross between races T 1 and T 2. Two recessive genes for virulence were identified: Utv1 conditioned virulence on the cultivars Renfrew and Florence × Aurore; Utv2 conditioned virulence on Kota and Little Club.
The structure of the epiphyllous appendages of Begonia hispida var. cucullifera
Authors: Maier Uta , Sattler Rolf
Published: September 2008

The upper side of the leaves of Begonia hispida Schott. var. cucullifera Irmsch. Bears appendages that may be classified as hair-like and leaf-like appendages. In addition, trichomes occur. Externally, the two classes of epiphyllous appendages and the trichomes are continuous. Anatomically, a discontinuity exists between the trichomes and the most hair-like appendages. The former lack vascular tissue and other tissues such as chlorenchyma, a hypodermis, and typical epidermis. The hair-like appendages, the leaf-like appendages, and the intermediates between them share the following common element of construction: they terminate in an attenuation at whose base a hump is situated. A vascular bundle supplies this hump and ends in two hydathodes. The smallest hair-like appendages consist only of one attenuation-hump element. In the leaf-like appendages the tip as well as each tooth ends in an attenuation-hump element. The same applies to the main leaves, i.e. the teeth of the main leaves are built in a similar fashion. The anatomy of the epiphyllous appendages, especially the leaf-like appendages, is strikingly similar to that of the main leaf. The leaf-like appendages as well as the main leaves have an upper epidermis with a large-celled hypodermis, palisade and spongy tissue, a lower hypodermis, and epidermis with stomata.
The taxonomic status of Vaccinium boreale
Authors: Kloet S. P. Vander
Published: September 2008

Two hundred and fourteen specimens of Vaccinium subgen. Cyanococcns were collected from 40 sites in northeastern North America for taxonomic studies. Data collected using various techniques indicate that V. boreale Hall & Aalders should be recognized as a species. Three characters, viz. dimension, pubescence, and leaf margin, separate V. boreale from V. angustifolium and V. myrtilloides. Although the three species are sympatric, only a few natural hybrids between V. boreale and V. myrtilloides have been found among the collected material. Crossing trials between V. boreale and V. pallidum suggest that the two are probable ancestors of V. angustifolium.
Importance of Coniothyrium minitans in survival of sclerotia of Sclerotinia sclerotiorum in wilted sunflower
Authors: Huang H. C.
Published: September 2008

The relationship between Sclerotinia sclerotiorum, causal agent of wilt or basal stem rot of sunflower (Helianthus annuus L.), and its hyperparasite Coniothyrium minitans was investigated in a sunflower field naturally infested with the two organisms. Sclerotia of S. sclerotiorum were collected biweekly from roots and basal stems of wilted plants and analyzed for infection by the hyperparasite. The results showed that C. minitans parasitized and killed the sclerotia produced on the root surface. This hyperparasite continued to parasitize the pathogen inside the root and upwards into the base of the stem, thus infecting the sclerotia produced at these sites. By the end of the growing season, 59%, 76%, and 29% of sclerotia on the root surface, inside the root, and inside the stem, respectively, had been killed by the hyperparasite, while 4%, 9%, and 68% of the sclerotia at these locations were healthy. Death of the rest of the sclerotia was due to organisms other than C. minitans. The data also indicate that C. minitans is more effective in parasitizing sclerotia produced on or inside the root than those produced in the basal stem.
Cytology and breeding behavior of some Impatiens hybrids and their backcross progeny
Authors: Pasutti David W. , Weigle Jack L. , Beck Allen R.
Published: September 2008

Impatiens crosses were made between Plant Introduction (P.I.) 349629 (2n = 16) and cultivar Tangerine (2n = 8), producing a hybrid (2n = 12) that seemed sterile. A large number of pollinations of the hybrid with 'Tangerine' pollen, however, produced only three progeny with 2n numbers of 8, 9, and 12. The backcross with hybrid pollen on P.I. 349629 produced five progeny, all of which were 2n = 20. None of these backcross progeny has shown fertility at present. Backcrosses involving the hybrids between 32 chromosome P.I. accessions and 'Tangerine' have been unproductive. Eleven of the hybrids (2n = 24) between P.I. 349629 and several of the 32-chromosome P.I. accessions occasionally produced viable pollen. When used on a 'Tange-glow' female, which is a 24-chromosome amphidiploid, numerous progeny resulted, some of which proved to be fertile in subsequent crosses.
The genus Neolecta (Neolectaceae fam. nov., Lecanorales, Ascomycetes) in Canada
Authors: Redhead Scott A.
Published: September 2008

Descriptions and illustrations of Neolecta irregularis and N. vitelline from Canada are given. Amyloid ascus walls are reported for both species and conidia from N. vitelline. The Neolectaceae fam. nov. is created for Neolecta and is tentatively placed in the Lecanorales.
The genus Mitrula in North America
Authors: Redhead Scott A.
Published: September 2008

The genus Mitrula is monographed for North America. Endemic to North America are M. elegans, M. lunulatospora sp.nov., and M. borealis sp. nov. The last-named species also occurs in Europe, as does M. paludosa. Each species has a distinctive geographic range, sporulating period, and ascospore morphology.A neotype is chosen for Mitrula paludosa and both M. norvegica and M. omphalostoma are placed in synonymy with that species. Mitrula morchelloides is transferred to the genus Verpatinia. Mitrula gracilis is transferred to the genus Bryoglossum gen. nov.Each of the accepted species of Mitrula is illustrated and described, and a key to the species is given.
Tunicago uniolae gen. et sp. nov., a pycnidial fungus with unusual conidia
Authors: Sutton B. C. , Pollack Flora G.
Published: September 2008

Tunicago uniolae gen. et sp. nov. is introduced for a fungus with simple pycnidia, septate, branched conidiophores, phialidic conidiogenous cells, and brown, smooth, single-euseptate, guttulate conidia which are enclosed in a thick, brown, rigid sheath at maturity. The relationships of the genus are discussed by reference to several pycnidial genera with single-septate conidia.
Fungal exudates. I. Characteristics of hyphal exudates in Fusarium culmorum
Authors: McPhee W. J. , Colotelo N.
Published: September 2008

Exudates have been observed on a number of fungi as liquid droplets adhering to the hyphae, and detailed investigation with Fusarium culmorum shows a definite pattern to the distribution of the droplets in relation to colony morphology. This suggests that the process of exudation is of physiological significance and specific properties of the droplets, absorption, and reexudation, their apparent role in spore formation, and their biochemical contents support this premise. Droplets appear to be closely associated with colony aging and their properties change as this process occurs. Initially they are transparent and water-like but become granular and opaque, and in some instances packed with spores as the colony develops. The sequence of droplet development and a mechanism for the release of these droplets and their function in normal physiological functioning of the organism is discussed.
A new species of Selaginella in the S. apoda complex
Authors: Buck William R.
Published: September 2008

A new species of Selaginella (Subg. Stachygynandrum), S. eclipes Buck, is described from the mid western United States and the Great Lakes area. It is similar to S. apoda but is characterized by dorsal leaves which have long, attenuate apices. The apices are usually hyaline, fragile, and unkeeled; the midrib extends into the apex. The strobilus is typically longer than that of S. apoda and the sporophylls are generally broader. The megaspores are laxly reticulate with broad muri and a pitted surface. Evolution within the S. apoda complex is discussed and a key to the species is given.
A new Hypoxylon species with appendaged, ornamented ascospores
Authors: Rogers Jack D.
Published: September 2008

A new Hypoxylon species with a cellular appendage on the ascospore, H. weldenii, is described. The fungus, collected in Louisiana, differs from other described Hypoxylon species in having ascospores with longitudinal valley-like depressions in the wall.
Cytokinin levels in healthy and Verticillium-infected tomato plants
Authors: Patrick T. W. , Hall R. , Fletcher R. A.
Published: September 2008

Yellowing of leaves is often an early and persistent symptom of plants infected with vascular wilt fungi. This symptom is also characteristic of senescence and hence the cytokinin levels in healthy and Verticillium-infected tomato plants were investigated. Tomato plants (Lyeopersicon esculentum L. cv. Bonny Best) were inoculated with the fungus Verticillium dahliae Kleb. 49 days after seeding. At intervals after inoculation, cytokinin levels in root xylem exudate were determined in healthy and infected plants. Cytokinin concentrations (per plant and per millilitre of exudate) were similar in healthy and infected plants at days 50 and 55 but were lower in infected plants at days 61 and 65 owing to reduced concentrations of both free and bound forms of cytokinin. Infected plants first showed visible symptoms of chlorosis on older leaves at day 56. By day 61 the lower three to five leaves were obviously wilted and chlorotic and by day 65 wilt and chlorosis were apparent on most leaves on the lower half of the shoot. Whether the first chlorotic symptoms in infected plants were due to the concomitant reduction in cytokinin concentrations was not resolved. However, the consistently lower concentrations of cytokinin in infected plants after the onset of symptoms are presumed to contribute significantly to the continued rapid loss of chlorophyll measured in older leaves and the progressive development of visible chlorosis in younger leaves. Reduced water potentials in leaves and fungal activity in infected roots are likely to be among factors responsible for the reduction in cytokinin concentration in infected plants.
The effect of lead, cadmium, arsenate, and fluoride ions on the growth and fine structure of Sphagnum nemoreum in aseptic culture
Authors: Simola Liisa Kaarina
Published: September 2008

The growth of Sphagnum nemoreum Scop, and the fine structure of its leaf cells were studied in aseptic cultures to which were added lead, cadmium, arsenate, and fluoride (0.001, 0.01, 0.1, and 1 mM solutions). The highest concentration having no or almost no effect on the dry weight was 0.1 mM for lead, 0.01 mM for fluoride and cadmium, and 0.001 mM for arsenate. The 1 mM solution of Na2HAsO4 and 0.1 mM solution of CdSO4 were toxic and the inocules died rapidly. The 1 mM solutions of KF and Pb(NO3)2 were growth-retarding. The chloroplasts tended to accumulate starch when arsenate (0.1 mM) was added to the medium. Fluoride promoted the development of plastoglobuli, and lead (0.1 mM) promoted lipid accumulation in the cytoplasm. High concentrations of arsenate and fluoride inhibited the differentiation of hyaline cells. The physiological and ecological effects of these substances have been discussed with special reference to the problem of pollution.
Electron microscopy of early gametangial interaction in Phytophthora megasperma var. sojae
Authors: Hemmes Don E. , Ribeiro Olaf K.
Published: September 2008

The ultrastructure of gametangial development and oospore formation was studied in Phytophthora megasperma var. sojae, a species with the paragynous antheridium. Except for the early gametangial interaction, the developmental stages of oogonial expansion, fertilization tube formation, oosphere and oospore formation were very similar to those reported for amphigynous species. The initial contact differs in the two types of gametangial interaction in that in amphigyny the oogonial hypha contacts and penetrates the antheridial initial from the side, whereas in paragyny the antheridial hypha touches and fuses with the oogonial initial from the side without penetrating it. In both cases the end result seems to be the same: the establishment of a firm adhesion zone between the gametangia. Dictyosome-derived vesicles were active in the formation of the contact zone, during oogonial expansion and wall thickening, and during extension of the fertilization tube. An extensive conversion of cytoplasm occurred during differentiation within the oogonium from a largely 'functional' cytoplasm rich in mitochondria, ribosomes, rough endoplasmic reticulum, and dictyosomes to a largely 'storage' cytoplasm within the oospore consisting of an ooplast and surrounding lipid layer.
Anatomy and ultrastructure of the haustorium in Comandra (Santalaceae)
Authors: Toth Ronald , Kuijt Job
Published: September 2008

The endophyte of the haustorium in Comandra and the tissues of the upper haustorium have a complex developmental and structural relationship with each other. Glands may be found near the tip of a young endophyte, providing evidence that the gland and surrounding tissues have been moved into the host as a unit. A distinct interrupted zone is present, traversed by a small number of unbranched vessels. Additionally, some apparently blind vessels in the more central portion of this zone are occluded with fibrous material which seems to be secreted by vesicles in the adjacent parenchyma. Advance into the host seems to involve crushing host cells and subsequent absorption of cell contents. It is suggested that superficial digitate cells are also crushed and that the lytic enzymes thus liberated play a role in the attack on host cells. The dark-staining non-cellular layer delimiting many parts of the endophyte seems to be made up of crushed cell walls from both partners. No cytoplasmic connections between host and parasite have been observed. Mature xylem contacts may be abutments in pit areas of host vessels or actual invasions of the latter, often with cell divisions within such invaded tracheary members. The function of the gland remains obscure.
Cytochemical localization of acid phosphatase in endophyte cells of the semiparasitic angiosperm Comandra umbellata (Santalaceae)
Authors: Toth Ronald , Kuijt Job
Published: September 2008

Acid phosphatase (orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.2) has been localized in cells at the growing tips of the endophyte in the semiparasitic angiosperm Comandra umbellata. Lysosomes in tip cells release their contents into the apoplast at the host–parasite interface before any possible release of enzyme from disrupted host lysosomes. However, a large-scale digestion of host cells does not occur. Parasite cells release acid phosphatase and probably other lysosomal enzymes which appear to disrupt host cell membranes causing a loss in turgor pressure followed by the eventual crushing of host cells by the invading endophyte.
A study of the flavonoids of the Potentilla pensylvanica complex in North America
Authors: Kohli B. L. , Denford K. E.
Published: September 2008

The major flavonoid complement of leaves of the polyploid series Potentilla finitima Kohli & Packer (2n = 14), P. pensylvanica L. (2n = 28), and P. bipinnatifida Hook. (2n = 56) has been determined. Eleven flavonoid glycosides have been identified and their distribution within the polyploid series plotted and discussed. Evidence is presented for the occurrence of a 'recombinant' flavonoid in the species P. pensylvanica L.
Acid phosphatase and protease release by the insectivorous plant Drosera rotundifolia
Authors: Clancy Finbarr G. , Coffey Michael D.
Published: September 2008

The leaves of the insectivorous plant Drosera rotundifolia L. produced extracellular hydrolytic enzymes in response to feeding with gelatin. Enzyme release was first detected 1 to 2 days after feeding, reached a maximum on day 4, and then gradually declined. Optimal activity of both acid phosphatase (orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.2) and protease enzymes was in the acidic range of pH. The acid phosphatase attacked a range of phosphorylated compounds but its p-nitrophenylphosphatase (PNPPase) and ribonucleoside triphosphatase activities were highest. It displayed relatively low phosphomonoesterase (EC 3.1.3.1, 3.1.3.2) activity. Both acid phosphatase and protease enzymes were insensitive to the sulphydryl inhibitor N-ethylmaleimide. The acid phosphatase was strongly inhibited by fluoride and orthophosphate. The nature of the apparent induction of hydrolase enzyme activity is briefly discussed.
Low K+ in Paphiopedilum leeanum leaf epidermis: implications for stomatal functioning
Authors: Nelson Sherman D. , Mayo James M.
Published: September 2008

Abaxial epidermal strips from leaves of Paphiopedilum leeanum were analyzed via sodium cobaltinitrite staining and atomic absorption spectrophotometry for the presence and location of potassium. On a dry weight basis K content of the abaxial epidermis was found to be 103 times less than has been reported in other species, and unlike other species no localization of K+ in guard cells of open stomata could be detected via the sodium cobaltinitrite stain for potassium.Flame photometric analysis of the mesophyll indicated that it contained normal amounts of K+ (about 1.87% on a dry weight basis). Analysis showed that the K+ content of the abaxial epidermis (0.032%) was considerably less than that of the mesophyll, a situation unlike previous reports for other species in which the epidermal concentration was found to be greater than the mesophyll. A process for exclusion of K+ from the abaxial epidermis is suggested, as is the lack of involvement of K+ as the major osmoticum in the stomatal mechanism of this species.
Le gynécée du Begonia tuberhybrida et ses variations
Authors: Lecocq Michèle
Published: September 2008

The gynoecium of the Begonia tuberhybrida Voss is characterized by the inferior position of its three ovaries, which are united between themselves and with the four or five parts of the perianth. The modifications of this gynoecium are highly diversified, but the most frequent are the variation of number of carpels giving rise to meiomerous or pleiomerous gynoecia and the variation in the position of ovaries which results in the formation of gynoecia of the pattern of another genus of the same family, Hillebrandia (semiinferior ovaries), or of the pattern of the hypothetic flower of Begoniaceae (superior ovaries).The study of the morphology and of the vascularization of these normal or abnormal gynoecia leads to an understanding of the constitution of the carpel and of the ovarian wall in this genus.
Gametophytes of Lycopodium obscurum as grown in axenic culture
Authors: Whittier Dean P.
Published: September 2008

Gametophytes of Lycopodium obscurum were grown from spores in axenic culture on a medium containing inorganic nutrients and sucrose. The prothalli developed into thick, disk-shaped gametophytes which bore antheridia. No archegonia were observed on these 1-year-old gametophytes. The morphology of the prothalli in culture was essentially that described for prothalli of L. obscurum from nature. However, these Lycopodium gametophytes in culture developed without the endophytic fungus which is necessary for the growth of prothalli of L. obscurum in nature.
Effect of blasticidin S, ethionine, and polyoxin D on stem rust development and host-cell necrosis in wheat near-isogenic for gene Sr6
Authors: Kim W. K. , Rohringer R. , Samborski D. J. , Howes N. K.
Published: September 2008

Seedlings of resistant (Sr6) and susceptible (sr6) near-isogenic lines of wheat (Triticum aestivum L.) were inoculated with an avirulent (P6) race of stem rust (Puccinia graminis (Pers.) f.sp. tritici Eriks. & Henn.) and kept for 2 days at 26 °C where the Sr6 gene is ineffective, treated with blasticidin S, ethionine, polyoxin D, or buffer, and transferred to 19 °C where the Sr6 gene is normally effective. One and 2 days later, leaves were stained with Calcofluor and examined by fluorescence microscopy to detect autofluorescing necrotic host cells and Calcofluor-stained stem rust colonies.Blasticidin S was phytotoxic to wheat leaves at concentrations that had no effect on fungal growth during the first 2 days after treatment. At later stages, extensive host necrosis, resulting from the phytotoxicity of this antibiotic, inhibited rust development.Ethionine and polyoxin D strongly inhibited rust development at concentrations that were not phytotoxic. In genotypically resistant leaves treated with ethionine and polyoxin D there were fewer necrotic cells associated with stem rust colonies than in leaves treated with buffer. The spacial distribution of necrotic cells was consistent with the view that necrosis occurs only in cells newly invaded after the temperature was lowered to 19 °C.The observations do not support the concept that host-cell necrosis in the hypersensitive reaction conditioned by this gene results from the death of the fungus.