bluuebunny/crossref_metadata_2025 huggingface dataset:
The pathogenicity of Ceratocystis montia to lodgepole pine
Authors: Strobel Gary A. , Sugawara Fumio
Published: April 2011

Ceratocystis montia (Rumb.) Hunt, an ascomycetous fungus, is associated with bark beetle infested lodgepole pine in the intermountain region of United States and portions of western Canada. The organism, when inoculated into lodgepole pine (20 years old) caused necrosis of the inner bark, a blue-stained appearance of the sapwood, and chlorosis and necrosis of the foliage. Koch's postulates were fulfilled in these experiments. Particles of inner bark provided the best support for fungal growth and inhibitors of fungal growth may develop in sapwood during the process of drying.
The distinction between Mallomonas acaroides var. acaroides and Mallomonas acaroides var. muskokana var.nov. (Chrysophyceae)
Authors: Nicholls K. H.
Published: April 2011

A previously undescribed member of the genus Mallomonas (Chrysophyceae) has been found in several Ontario soft-water lakes. Its scale and bristle structure is reminiscent of M. acaroides; however, it has been assigned new variety status (Mallomonas acaroides var. muskokana). There are several features of scale and bristle structure that serve to separate this taxon from its closest relatives, M. acaroides var. acaroides Petty emend. Iwanoff and M. acaroides var. inermis Fott.
A comparison of bryophyte species diversity and niche structure of montane streams and stream banks
Authors: Glime Janice M. , Vitt Dale H.
Published: April 2011

Eleven alkaline western Canadian montane streams were sampled by transects to compare the bryophyte species cover, diversity, frequency, richness, niche width, and niche overlap in three vertical zones (relative to water level) with the same parameters in four acidic streams on Slide Mountain in the Adirondack Mountains of New York. Resources for niche width and overlap include vertical distance from water surface, aspect in stream, substrate size, and percent bare substrate. Species cover, richness, and diversity increase from the submerged zone 1 (< −5 cm) to the terrestrial zone 3 (10–30 cm). Brillouin species diversity increases from 1.98 to 3.03 (means per stream) along the same gradient. All species except one from zone 1 also occur in zone 3. The niche widths for aspect in stream, substrate size, and vertical distance from water surface are all negatively correlated with their chi-square values, indicating that the width values are most reliable for small widths and become increasingly less reliable for large niche widths. Niche overlap is high among most species for at least one resource parameter.
Dualité des corps protéiques du mésophylle adaxial et abaxial des cotylédons de quelques espèces de la tribu des Génistées (Légumineuses)
Authors: Citharel L. , Citharel J.
Published: April 2011

The presence of globoids in cotyledon protein bodies is confirmed in several Genistae. In addition, the duality (homogeneous protein bodies in cells on the adaxial side and heterogeneous protein bodies in cells on the abaxial side), previously reported in Cytisus scoparius cotyledons, has now been established in other Cytisus species, as well as in other genera of the Genistae tribe.
Uptake of phosphate by two cyanophytes: cation effects and energetics
Authors: Budd K. , Kerson G. W.
Published: April 2011

Phosphate uptake in the cyanophytes Synechococcus leopoliensis and Oscillatoria limnetica did not require exogenous metallic cations. In O. limnetica phosphate uptake was described by a single Michaelis–Menten relationship between 0.2 and 10.0 μM phosphate. Calcium increased the maximum velocity and decreased the half-saturation concentration for this system; phosphate uptake was also enhanced by Sr2+ and by Mg2+ but not by Na+, K+, or Zn2+ at up to 1 mM. Calcium appeared to act upon the phosphate transporter and its action is suggested to be ecologically significant. Uptake of phosphate in the light by both cyanophytes was unaffected by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) but was abolished by carbonylcyanide m-chlorophenylhydrazone (CCCP) or dicyclohexylcarbodiimide (DCCD) at concentrations that abolished apparent photosynthesis; however, phosphate uptake was not inhibited by concentrations of CCCP or DCCD that were only slightly inhibitory to apparent photosynthesis. At 5 μM, CCCP abolished light hyperpolarization of the membrane potential but was noninhibitory to phosphate uptake. Phosphate uptake in O. limnetica was accompanied by hyperpolarization of the membrane potential. Gramicidin hyperpolarized the membrane but did not influence phosphate uptake. It is suggested that phosphate uptake in both cyanophytes is independent of the proton motive force.
Ontogeny of Eucalyptus pilularis – Pisolithus tinctorius ectomycorrhizae. I. Light microscopy and scanning electron microscopy
Authors: Massicotte H. B. , Peterson R. L. , Ashford A. E.
Published: April 2011

Eucalyptus pilularis Sm. seedlings were grown in growth pouches and inoculated with the broad host range ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker & Couch. External morphology and internal structure of all stages of ectomycorrhiza formation on first-order and second-order laterals were studied. The morphology of the ectomycorrhiza is dependent on the stage of lateral root development at the time of colonization by fungal hyphae. Emerging lateral roots are colonized by hyphae originating from the inner mantle of the parent root. The Hartig net does not spread internally from the parent root to the lateral root. All primary tissues of mycorrhizal lateral roots are differentiated close to the apical meristem. The epidermal cells undergo a marked increased in radial growth instead of the usual elongation in the axial plane. The hypodermis is a barrier to the penetration of hyphae so that Hartig net formation is paradermal only. Older portions of ectomycorrhizal roots show a degeneration of the epidermis, hypodermis, and cortex excluding the endodermis, and a proliferation of hyphae in these senescing tissues.
Morphological characteristics of the experimental allopolyploid Triticum durum × Haynaldia villosa (2n = 42)
Authors: Stefani Agostino , Meletti Paolo , Onnis Antonino
Published: April 2011

The experimental allopolyploid (2n = 42) Triticum durum Desf. cv. Cappelli (2n = 28) × Haynaldia villosa (L.) Schur. (2n = 14) obtained in 1972 has now reached the 12th generation. In the present paper, morphological data on the allopolyploid plants from the 8th to the 10th generation are reported. A comparison between the characters of the allopolyploid and its parents is also presented.
Fine structure of latent infections by Rhabdocline parkeri on Douglas-fir, with observations on uninfected epidermal cells
Authors: Stone Jeffrey K.
Published: April 2011

Rhabdocline parkeri Sherwood-Pike, Stone, & Carroll, an endophyte of Douglas-fir, infects healthy foliage by direct penetration of the host epidermal cell wall. Penetration is accomplished by a very fine penetration hypha. Intracellular infections are established in a single epidermal cell and result in the death of the cell. Haustoria lacking neckbands are produced from the intracellular hyphae at the onset of needle senescence. The intracellular hyphae contain large quantities of stored lipid and numerous mitochondria and peroxisomes. Although not growing, the hyphae appear to be metabolically active. Douglas-fir epidermal cells are alive at maturity and contain rudimentary chloroplasts. Small quantities of lipids and starch are present in the healthy epidermal cells. The large central vacuole of the epidermal cells contains primarily condensed tannins and tannin precursors.
Pithomyces chartarum isolated from Poa pratensis swards
Authors: Wilkinson H. T.
Published: April 2011

Pithomyces chartarum (Berk. & Curt.) M. B. Ellis was isolated from bluegrass sod (Poa pratensis L.) in Illinois, Indiana, and Wisconsin during July and August 1986. This is the first report of Pithomyces chartarum in the north central United States and the first report of the fungus in bluegrass sod. The fungus appears to be a saprophyte on senescent bluegrass leaves; its interest as a possible mycotoxin producer is underlined.
The different influence of magnesite emissions on the surface waxes of Norway spruce and silver fir
Authors: Bermadinger E. , Grill D. , Golob P.
Published: April 2011

The difference in vigour between Picea abies (L.) Karst. and Abies alba Mill, in an area exposed to fine dust containing MgO is reflected in scanning electron microscope studies of the needle surfaces. The greater vitality of the silver fir is correlated with intact wax structures and a somewhat lower dust load. In contrast, the spruce reveals a marked effect on the epicuticular wax by a heavy fine-dust load. Possible causes and physiological consequences are discussed.
Dormancy and survival in buried seeds of proso millet (Panicum miliaceum)
Authors: Colosi Joseph C. , Cavers Paul B. , Bough Marguerite A.
Published: April 2011

Survival, dormancy, and germination of buried seeds of 30 populations of proso millet (Panicum miliaceum L.) were investigated. The effects of duration and depth of burial and type of soil were considered. The 30 populations belong to three agronomic groups: crop, croplike weed, and black-seeded weed. Black seeds exhibited much greater overwinter survival and dormancy than did seeds of the other two groups. Crop seeds had almost no survival through the winter. Only one croplike weed population exhibited appreciable (13–40%) survival after one winter in the soil. A combination of endogenous and enforced dormancy in black seeds effected an adaptive germination pattern of little (1%) germination at both the surface and 20 cm deep and much greater (40%) germination at 5 cm deep. Surviving crop and croplike weed seeds germinated irrespective of position in or on the soil. In a longer term experiment with only three populations both the croplike weed and black-seeded populations survived best in a well-drained soil. For the black-seeded population greater germination in the well-drained soil depleted that seed bank earlier than those in the medium-drained or poorly drained soils. The crop and croplike weed populations produced only transient seed banks in all three soil types, whereas some black seeds survived for 4 years.
Erratum: The role of water in the regulation of plant development
Authors: McIntyre Gordon I.
Published: April 2011

not available
Metabolism of enzymes with imbibition and germination of seeds of jack pine (Pinus banksiana)
Authors: Pitel J. A. , Cheliak W. M.
Published: April 2011

The level of soluble proteins and the total activities of 14 enzymes were determined in embryo and megagametophyte tissues of jack pine (Pinus banksiana Lamb.) seeds during imbibition and germination. For embryos, enzyme activities were low in the dry seed and during imbibition but increased rapidly upon germination following emergence of the radicle and to the end of the sampling period of 13 days. For gametophytes, enzyme activities generally increased at a slower rate than embryos, with highest activity present for seeds after 8–10 days of germination. Levels of soluble protein in the gametophytes were highest shortly after emergence of the radicle, while for the embryos levels were highest at the end of the germination period.
Soil and plant chemistry of an Atlantic white cedar wetland on the Inner Coastal Plain of Maryland
Authors: Whigham Dennis F. , Richardson Curtis J.
Published: April 2011

Atlantic white cedar (Chamaecyparis thyoides (L.) BSP.) wetlands are widely distributed along the Atlantic coast, yet there is very little information on their nutrient dynamics. In this paper we present data on the chemical composition of soils and plant tissues for one of the last remaining stands of Chamaecyparis on the Inner Coastal Plain of Maryland. Comparisons are made among the Chamaecyparis site, five similar nearby wetlands without Chamaecyparis, and other Chamaecyparis sites. The Atlantic white cedar site in Maryland had a distinct soil chemistry characterized by significantly higher Ca, Mg, and Na concentrations and high pH. There were significant differences between wetlands, within wetlands (forested versus bog habitats), and between types of plants (herbaceous versus woody) for most plant nutrients. Woody and herbaceous species at the Atlantic white cedar site almost always had higher concentrations of the 15 elements measured than they did at the other sites. However, nutrient concentrations of Chamaecyparis shoots, when compared with reported plant requirements, indicate a possible deficiency of N and P, low K, and a pronounced accumulation of Pb.
Soil–plant water relations of two subalpine herbs from Mount St. Helens
Authors: Chapin David M. , Bliss L. C.
Published: April 2011

The subalpine environment of Mount St. Helens and other southern Cascade volcanoes is characterized by porous, pyroclastic soils and summer droughts. To evaluate plant drought stress in this environment, we examined plant water relations of Eriogonum pyrolifolium, a wintergreen, shallow-rooted, rosette perennial, and Polygonum newberryi, a deciduous, deep-rooted semierect perennial (both in Polygonaceae), at a subalpine site (elevation 1575 m) on Mount St. Helens. In a very dry summer, soil moisture below 20 cm remained above −0.1 MPa, but surface tephra deposits developed soil water potentials below −4.0 MPa. Surface tephra deposits had a mulching effect on underlying pre-eruption soils. Predawn xylem pressure potentials for adults of each species were never below −0.8 MPa, but midday xylem pressure potentials were often measured near or below the estimated turgor-loss point when vapor pressure deficits were high (maximum 3.1 kPa). Compared with Polygonum, Eriogonum had lower xylem pressure potentials, a lower turgor-loss point (mean −1.00 and −1.42 MPa, respectively), and higher conductance. In both species there was no midday depression in leaf conductance and little photosynthetic response to high evaporative demand. Thus, these species are not particularly conservative in water use and appear to rely on abundant soil moisture throughout the short growing season.
Growth performance of triazine-resistant and -susceptible biotypes of Solanum nigrum over a range of temperatures
Authors: Jacobs Brian F. , Duesing John H. , Antonovics Janis , Patterson David T.
Published: April 2011

Growth of triazine-resistant and -susceptible biotypes of Solanum nigrum was studied over a range of temperatures to test whether resistant biotypes show reduced performance under high temperatures. Each biotype was represented by parental lines and reciprocal F1 crosses. Resistant biotypes were inferior in growth relative to susceptible biotypes. Temperature had no differential effect on the relative performance of resistant and susceptible biotypes. Our results with Solanum nigrum do not support the hypothesis that the infrequent occurrence of the resistant biotypes in southern regions is explained by their decreased growth at high temperatures.
A histological comparison of fungal colonization in tomato seedlings susceptible or resistant to Fusarium crown and root rot disease
Authors: Brammall R. A. , Higgins V. J.
Published: April 2011

Root colonization of tomato cultivars susceptible or resistant to Fusarium crown and root rot disease, caused by the pathogen Fusarium oxysporum f.sp. radicis-lycopersici Jarvis & Shoemaker, was studied histologically. In seedlings of susceptible cultivars ('Ohio MR13', 'Bonny Best', and 'Vendor') held at 22 °C, direct penetration of epidermal cells occurred by 24 h after inoculation and colonization of suberized hypodermal cells and adjacent intercellular spaces by 72 h. The cortex was colonized between 72 and 96 h after inoculation and the stele was commonly colonized by 120 to 144 h. Colonization of the cortex and stele was associated with the breakdown of parenchymatous cell walls and middle lamellae near fungal hyphae. In cultivars resistant by a single dominant gene ('CR6', 'Larma', and 'B82-865') colonization was similar to that in susceptible cultivars until 72 h after inoculation. By this time, papillae were abundant within hypodermal cells. Successful colonization of hypodermal sites was associated with the incorporation of phenolic or lignin-like materials and suberin within cell walls of the underlying cortex. These cortical wall modifications were paralleled by the deposition of electron-opaque material into cortical cell walls and middle lamellae and the production of finely granular bands around the peripheries of colonized intercellular spaces. Phenolic-containing structural defensive barriers (i.e., papillae and modified cortical cell walls) appear to be important in limiting fungal colonization in cultivars possessing single dominant gene resistance to this disease.
The effect of infection by Lactarius rufus or Scleroderma flavidum on the uptake of 63Ni by paper birch
Authors: Jones Melanie D. , Dainty Jack , Hutchinson Thomas C.
Published: April 2011

Nickel tolerance of birch seedlings is increased by infection with one ectomycorrhizal fungus, Scleroderma flavidum, but not by another, Lactarius rufus. The possibility that this difference is related to differences in uptake and (or) translocation of Ni was investigated using 63Ni. Mycorrhizal and nonmycorrhizal seedlings were grown either with or without Ni for 22 weeks before the presentation of 63Ni to roots. Both control and pretreated seedlings were exposed to 63Ni, in 85 μM Ni, for periods of 2 min to 48 h. After Ni uptake, the roots were desorbed with 50 mM Ca at 5 °C for 30 min. Total nonexchangeable 63Ni uptake into roots was unaffected by inoculation treatment, either in the presence or absence of dinitrophenol, a general metabolic inhibitor. However, the amount of Ca-exchangeable Ni was significantly affected by infection, and was lowest in S. flavidum infected seedlings. Additionally, infection influenced the effect of dinitrophenol on Ni uptake into shoots. Application of dinitrophenol increased Ni uptake into the shoots of L. rufus infected and uninfected plants, but this increase did not occur in S. flavidum infected plants. All shoots absorbed similar amounts of Ni in the absence of dinitrophenol. Thus, the S. flavidum birch mycorrhizae do not require metabolic energy to reduce Ni translocation from roots to shoots, while the other seedlings do. This may contribute to the increased Ni tolerance of this mycorrhizal association.
The fine structure of mitosis in Pavlova (Prymnesiophyceae)
Authors: Green J. C. , Hori T.
Published: April 2011

The ultrastructure of mitosis in the algal flagellates Pavlova lutheri and P. salina has been examined, the observations have been compared with those reported previously from other species included in the class Prymnesiophyceae, and a number of important differences have been noted. For example, mitosis is preceded by the replication of the chloroplasts and flagellar apparatus, but in contrast to other prymnesiophytes, separation of the replicated systems does not occur until a late stage in cell division. Furthermore, there is a close relationship between the spindle microtubules and the fibrous root of the longer of the two markedly unequal flagella, and instead of the usual straight prymnesiophycean spindle, the longitudinal axis of the Pavlova mitotic spindle has a marked U- or V-shape which persists throughout metaphase, anaphase, and telophase. It is concluded that such features emphasize the validity of the order Pavlovales as a natural group within the class.
Effects of ozone and acid rain on white pine (Pinus strobus) seedlings grown in five soils. II. Mycorrhizal infection
Authors: Stroo Hans F. , Reich Peter B. , Schoettle Anna W. , Amundson Robert G.
Published: April 2011

Mycorrhizal infection of white pine (Pinus strobus L.) seedlings was measured after 4 months of exposure to simulated acid rain and ozone, applied either alone or in combination. Increasing rain acidity consistently reduced the number of mycorrhizal short roots. In general, infection decreased linearly versus rain pH. Plants exposed to simulated rain at pH 3.0 had approximately 20% fewer mycorrhizal roots than plants exposed to pH 5.6 rain. The decrease in the number of mycorrhizal roots was a result of decreases both in the number of short roots available for infection and in the percentage of roots infected. Ozone had no effect on mycorrhizal infection if applied 3 alternate days/week at concentrations ranging from 0.02 to 0.14 ppm. However, there were significant changes in infection in plants exposed to ozone for 5 days/week. There was no evidence for an interaction between the two pollutants. Percent mycorrhizal infection was highly correlated with seedling nitrogen concentration across all soil types and rain treatments. These observations suggest that increases in available nitrogen may have been largely responsible for the observed effects of acid rain on mycorrhizae.
The status of Juncus oronensis (Juncaceae)
Authors: Catling P. M. , Spicer K. W.
Published: April 2011

Juncus oronensis has been treated as a species, a hybrid of uncertain parentage, or a synonym of J. tenuis. Various qualitative morphological and anatomical features and discriminant analyses using quantitative morphological characters suggest that the type material from Orono, Maine, is a hybrid of J. vaseyi and J. tenuis. The Canadian reports of J. oronensis are based on material referable to J. vaseyi and to a putative hybrid involving J. dudleyi and J. vaseyi.
The genus Antennaria (Asteraceae: Inuleae) in North America: multivariate analysis of variation patterns in Antennaria rosea sensu lato
Authors: Chmielewski J. G. , Chinnappa C. C.
Published: April 2011

Patterns of morphological variation were examined among pistillate and staminate plants of Antennaria rosea Greene s.l. and northwestern microspecies in section Dioicae which are often placed in synonomy with A. rosea. The variation observed among pistillate plants was not correlated with geography, but in certain regions such as southern Yukon, Banff and Jasper national parks, the Cypress Hills of southeastern Alberta, and in the southern range limits the likelihood of finding atypical specimens increases. The northwestern taxa A. breitungii, A. elegans, A. incarnata, A. laingii, A. leuchippi, A. oxyphylla, and atypical forms of A. subviscosa, although similar in many characteristics to A. rosea, do represent distinct morphological entities. The fact that these taxa maintain their distinctive morphologies under controlled transplant studies suggests that their species rank may be maintained. Staminate plants in the northeastern portion of their distribution were consistently larger than those found elsewhere. The importance of vegetative and vegetative–reproductive characters in the discriminant function suggests that the morphological differences are in response to environmental factors.
Embryology of Epidendrum ibaguense. I. Ovule development
Authors: Yeung Edward C. , Law Sandra K.
Published: April 2011

The orchids are unique among angiosperms in that ovule development is initiated after successful pollination. The monandrous orchid Epidendrum ibaguense has three placental ridges at anthesis. After pollination, mitotic activities result in the formation of a dichotomously branching system of outgrowths. The tip of each branch consists of five to six nucellar cells covered by the epidermis. A subterminal nucellar cell differentiates into the archesporial cell approximately 12 days after pollination. By day 18, it differentiates directly into a megasporocyte. The first meiotic cell division produces a dyad in which the micropylar cell begins prompt degeneration. The second meiotic cell division results in the formation of two megaspores of unequal size. The larger cell at the chalazal end will become the functional megaspore. Callose is present in the walls of the megasporocyte, the micropylar dyad cell, and the megaspore destined to degenerate. The development of the megagametophyte conforms to the Polygonum type. One of the chalazal nuclei delays its final mitotic division until fertilization, making it appear that only two antipodals are present. The mature ovules are bitegmic and have an anatropous orientation.
Nutrient cycling in the epilithon of running waters
Authors: Paul B. J. , Duthie H. C.
Published: April 2011

The development and physiology of microcommunities established on glass slides was investigated in the Matamek River, Quebec, during the summer of 1985. Microorganisms loosely attached to the substrate (overstory) and those strongly adhering to the substrate (understory) were considered separately. Community biomass accumulation resulted from increases in the overstory. Cell numbers remained relatively unchanged in the understory. As the community developed, the uptake of glucose, inorganic carbon, ammonia, and phosphate increased, mainly because of autotrophic organisms in the overstory. Organisms in the understory, especially bacteria, appeared to contribute significantly to the assimilation of glucose. The spiralling concept of nutrient reutilization in running waters was assessed in view of the changing physiology of the microorganisms comprising a developing biofilm. Release, downstream translocation, and subsequent biological assimilation of recently fixed bicarbonate, glucose, and orthophosphate was measured. The translocation of bicarbonate and glucose release products was similar in both poorly developed and well-developed communities, whereas orthophosphate metabolites were reassimilated more rapidly in well-developed assemblages. The apparent conservation of phosphate by the epilithic community was considered to be a physiological adaptation in response to the low nutrient concentration of the waters. Organic carbon, conversely, was probably not limiting and therefore was not rapidly reutilized. We conclude that the intensity at which compounds are reutilized is directly proportional to their degree of limitation in the epilithic community.
Light microscope observations of histological changes induced by Ophiostoma ulmi in various nonhost trees and shrubs
Authors: Rioux Danny , Ouellette G. B.
Published: April 2011

Ophiostoma ulmi (the Dutch elm disease pathogen) was inoculated into 13 nonhost tree and shrub species. Four classes were recognized based on their susceptibility to this pathogen. In Prunus pensylvanica (class I), bubbles formed in vessel members within 3 days after inoculation, and gels formed 5 days later. At day 5, the vascular cambium covering the colonized zone became altered. A barrier zone was formed in 60% of the inoculated twigs. When twigs wilted, the vessels around the twig were occluded, and barrier zone formation was partial. In Populus balsamifera (class II), tyloses formed in vessels of invaded xylem within 8 days after inoculation followed by accumulation of compounds suspected to be phenolics in parenchyma cells. Barrier zone formation occurred in 66% of the inoculated twigs. In Sorbus americana (class III), a pronounced dark discoloration developed rapidly in the invaded xylem. Sparse gels and O. ulmi cells were present in vessel members. Gel formation was limited to vessels that were adjacent to parenchyma cells. Pit membranes of bordered and half-bordered pit pairs became thicker and more darkly stained than in controls. These observations suggest that the first steps of pathogenesis are induced by the action of harmful metabolites of O. ulmi. Few noticeable changes occurred in the species of class IV.
Submersed macrophyte communities before and after an episodic ice jam in the St. Clair and Detroit rivers
Authors: Nichols S. J. , Schloesser D. W. , Hudson P. L.
Published: April 2011

We conducted surveys in 1983 and 1984 of submersed macrophyte communities off six islands in the St. Clair and Detroit rivers using low altitude aerial photography and ground-truth collections. Sample collections in 1984 followed one of the coldest winters on record, during which ice up to 4 m thick developed in areas that were normally ice-free. Growth of many of the 20 taxa collected was delayed in the spring of 1984, as compared with the spring of 1983. By September 1984, however, total abundance of all taxa was equal to or greater than that in 1983. The location, size, and shape of plant beds in September 1984 were similar to those in 1983. We concluded that the unusual ice jam in early spring of 1984 had little, if any, permanent effect on submersed macrophytes in the St. Clair and Detroit rivers.
Helicoidal microfibril deposition in a tip-growing cell and microtubule alignment during tip morphogenesis: a dry-cleaving and freeze-substitution study
Authors: Emons Anne Mie C.
Published: April 2011

Cell wall microfibril alignment in the tubular portion of Equisetum hyemale root hairs is helicoidal. Lamellae of helicoidal texture are deposited from tip to base; thus, different microfibril orientations are aligned with the plasma membrane successively. Zones with constant mean microfibril orientation are about 300 μm long. In any such zone of dry-cleaned, shadowed preparations, the frequency of microfibrils at the proximal end is 5 to 7 microfibrils per micrometre, which decreases to 0 at the distal end. The orientation of microfibrils of the underlying lamella, the microfibril frequency of which is 5 to 7/μm throughout, is the same as the microfibril orientation of the neighbouring distal lamella. Microfibrils of the cell wall are randomly oriented in the hair dome. Microtubule alignment in these root hairs was examined by means of freeze substitution. In the extreme tip of the root hair, microtubules run parallel to the plasma membrane and transverse to the long axis of the hair; the hemisphere of the hair contains randomly oriented microtubules. From extreme tip to base of the hair dome, microtubules become more and more axially aligned, and remain axially oriented in the hair tube. Further down the hair, where microfibril alignment is transverse and microfibrils are actively being deposited, microtubules still run in the axial direction. The observations emphasize the involvement of microtubles in root hair tip morphogenesis, but not in determining the alignment of the microfibrils in the hair tube.
Effet des souches arctiques de Rhizobium sur la structure des nodules du sainfoin (Onobrychis viciifolia) et de légumineuses arctiques (Astragalus et Oxytropis spp.)
Authors: Prévost Danielle , Bordeleau L. M. , Antoun H.
Published: April 2011

Rhizobium strain N31, isolated from the arctic legume Astragalus alpinus, nodulates sainfoin (Onobrychis viciifolia) as efficiently as strain SM-2, isolated from sainfoin. Nodule shape and tissue arrangement of 70-day-old plants infected by these two strains were examined. Sainfoin nodules formed by either strain N31 or SM-2 were cylindrical, with indeterminate growth, and similar to those found on arctic legumes. However, in the active symbiotic zone of sainfoin nodules, bacteroids of strain N31 were pleiomorphic or spherical and found individually or in groups of three, surrounded by the membrane envelope, whereas the bacteroids of strain SM-2 were elongated and enclosed in clusters of 3 to 12 by each membrane envelope. Thus, arctic strain N31 affects the internal structure of sainfoin nodules. Nodules of arctic legumes A. alpinus, Oxytropis maydelliana, and Oxytropis arctobia, infected with either strain N31 or SM-2, contained lipid droplets, while sainfoin nodules did not show such characteristics. This phenomenon seems specific to arctic legumes and it is not influenced by the origin of the nodulating strain.
Genera coelomycetum. XXVI. Amarenographium, Callistospora, Hyalothyridium, Orphanocoela anam.-gen.nov., Scolecosporiella, and Urohendersoniella
Authors: Raj T. R. Nag
Published: April 2011

Type studies have demonstrated that despite some recent assertions in the literature, certain anamorph-genera are in need of further reassessment. Hyalothyridium viburnicola Tassi, typifying the anamorph genus Hyalothyridium Tassi, is treated as a nomen dubium. As a result of reassessment of Scolecosporiella typhae, Urohendersoniella, recently considered a synonym of Scolecosporiella, is reinstated. A new anamorph-genus, Orphanocoela, is proposed to accommodate three species, two of them transfers from Hyalothrydium and one from Scolecosporiella. Amarenographium and Callistospora are redescribed and compared with Urohendersoniella. Conidia of members of the the last three genera have mucoid appendages that originate in a unique manner.
Structure and development of terminal bud scales in green ash
Authors: Merrill E. K.
Published: April 2011

Structure and development of terminal bud scales of green ash (Fraxinus pennsylvanica var. subintegerrima) were studied to provide a basis for comparison with foliage leaves of the same species. To identify early developmental stages of bud scales, structure and phenology of terminal buds were investigated first. Overwintering terminal buds have typically three or four pairs of bud scales and three to six pairs of foliage leaf primordia. Bud scales have a flattened base topped by rudimentary leaflets. After bud break, the first leaf primordia that are initiated develop and mature into terminal bud scales by early summer. Although morphology and anatomy of mature foliage leaves and bud scales are very different, primordia of leaf forms are similar until they reach a length of 500 μm. At that length both leaf forms have a base and apical leaflets. Bud scale bases widen and elongate without much thickening, while growth in the apical region is restricted. Marginal growth of the bud scale base is different from that described for most leaf blades. Terminal bud scales could be interpreted as being ontogenetically derived from foliage leaf primordia.
Two-dimensional analysis of spatial pattern in vegetation for site comparison
Authors: Dale M. R. T.
Published: April 2011

A new method for the analysis of spatial pattern in two dimensions is described. The technique uses data collected in square or rectangular grids of quadrats to examine the scale of pattern in vegetation, no matter how the grids are oriented with respect to the pattern. Its usefulness is demonstrated by application to artificial data. The method is also applied to vegetation classification data derived from LANDSAT TM satellite imagery of a valley in the Yukon, Canada, in which the effects of experimental manipulations on boreal communities are being studied. A set of 2 × 2 km squares of the valley were selected for analysis in which the vegetation composition squares varies considerably. The analysis shows that most of the squares had one and only one scale of two dimensional pattern, consistently in the range of 360–780 m.
Influence of gibberellin A3 and ancymidol on sunflower leaf anatomy
Authors: Starman T. W. , Kelly J. W. , Pemberton H. B.
Published: April 2011

The plant growth retardant ancymidol (α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol), when sprayed at 132 mg/L of active ingredient, increased leaf thickness, palisade cell length, and number of cells per unit length, and decreased intercellular space percentage in developing Helianthus annuus L. (sunflower) cv. Mammoth Russian leaves when plants were grown under 400 or 1500 μmol∙s−1∙m−2 photosynthetic photon flux density. Foliar sprays of gibberellic acid at 10–40 mg/L reversed the effects of ancymidol on leaf anatomy. Stomatal density and total stomata per adaxial leaf surface area were increased by ancymidol sprays.
Gradient analysis of forests of the Sangre de Cristo Range, Colorado
Authors: Allen Robert B. , Peet Robert K.
Published: April 2011

Interrelationships between dominant compositional and environmental gradients were studied using 186 forest stands sampled on the east slope of the Sangre de Cristo Range, Colorado. Detrended correspondence analysis and detrended canonical correspondence analysis were used to analyze indirect and direct gradients, respectively. The dominant compositional gradient was strongly correlated with elevation. Increasing elevation was associated with decreasing soil pH and percent base saturation, and increasing total soil N. Ordination of stands stratified by elevation showed the major compositional gradient within each elevation class was strongly correlated with a topographic moisture index. Most soil variables correlated with this gradient in low and high elevation classes. In mid-elevation forests, a third compositional gradient correlated with soil pH, percent base saturation, and potential solar radiation. In these forests, Pinus contorta and Pseudotsuga menziesii were associated with acidic soils on north-facing slopes, whereas Populus tremuloides and Abies concolor were associated with base-rich soils on south-facing slopes. Ordination axes accounted for least variation in comparatively young mid-elevation forests. A plausible explanation is that the mid-elevation forests represent an unpredictable stage in forest development where competition has not yet had sufficient time to sort species along environmental gradients.
Phylogenetic considerations below the sectional level in Carex
Authors: Crins William J.
Published: April 2011

Few estimates of phylogenetic relationship below the sectional level have been proposed within the genus Carex (Cyperaceae). The reasons for this include (1) poorly circumscribed sections (paraphyletic and polyphyletic), (2) uncertain relationships among sections, and (3) difficulty in objectively assessing character state polarities. The operational difficulties posed by points 2 and 3 can be overcome through the use of character compatibility analysis, if it can be demonstrated that the section under study is monophyletic (point 1). This technique enables the investigator to generate hypotheses of relationship while minimizing the number of prior assumptions. Hypotheses of phylogenetic relationship are presented for the taxa within Carex sections Phyllostachyae, Limosae, and Ceratocystis. The topologies of these unrooted networks are assessed using external data sets (chromosome numbers, etc.) that serve as tests of the hypotheses, and may allow for a posteriori determination of character state polarities. In sections Ceratocystis and Limosae, these analyses provide strong support for the notion that chromosome evolution in Carex proceeds in a linear stepwise fashion. The results for section Phyllostachyae contradict this notion. Synthesis of all available data, coupled with phylogenetic reconstruction, will enable caricologists to provide more convincing arguments about the nature, direction, and factors influencing character state change.
Chemotaxonomy of the genus Carex (Cyperaceae)
Authors: Manhart James R.
Published: April 2011

The major categories of chemosystematic comparisons that were used successfully or are of potential use in Carex include flavonoid analysis, enzyme electrophoresis, and chloroplast DNA mapping and sequencing. The flavonoid work consists mostly of broad scale comparisons of aglycone distributions in a number of sedge genera to include some members of Carex. These comparisons proved to be of limited use in understanding phylogenetic relationships within the genus Carex. However, detailed flavonoid analyses of sections Laxiflorae and Acrocystis demonstrated the utility of flavonoid surveys in Carex at infrasectional levels and possibly at intersectional levels. Enzyme electrophoretic data were used to determine whether the morphological variability present in a species complex is the result of hybridization, phenotypic plasticity, or recent divergence. The C. crinita complex is an example in which intermediate forms are probably not the result of hybridization. Conversely, allozyme data for section Sylvaticae indicate that some of the taxa in this section are of hybrid origin. One of the most promising developments in systematic studies was the use of chloroplast DNA analysis. It was demonstrated in a number of plant groups that restriction endonuclease and sequence comparisons of chloroplast DNAs can be used to construct phylogenetic trees that have homoplasy levels much lower than those constructed from phenotypic characters.
Assessment of natural interspecific hybridization of blue and Engelmann spruce in southwestern Colorado
Authors: Ernst S. G. , Hanover J. W. , Keathley D. E.
Published: April 2011

In a partial diallel mating design among 20 blue and 20 Engelmann spruce parents, the interspecific crosses were successful only with Engelmann spruce as the female parent. No viable seed were obtained from the reciprocal cross among the 60 full-sib families attempted. Under the conditions of artificial pollination and a controlled germination environment, an average of 0.3% of the seed germinated on a total seed basis across all 20 Engelmann spruce females. Many abnormalities were observed among the germinating hybrid seed, suggesting hybrid inviability also contributes to the low crossability between these two species. Isozyme analysis was used to confirm the interspecific hybrids between blue and Engelmann spruce based on the unique genotypic compositions of the hybrids relative to the two species. No natural F1 hybrids between blue and Engelmann spruce were observed in this study based on isozyme analysis of mature individuals or their seedling progeny. Analyses included samples of open-pollinated seed from blue and Engelmann spruce females located in an area where both species are present in close proximity, often side-by-side, and where pollen shed and female strobilus receptivity in the two species are coincident. In addition, there was evidence of possible gametic selection or hybrid inviability among the full-sib progeny based on deviations of observed from expected segregation ratios for progeny isozyme genotypes. Deviations tended to favor the allele more common to both species rather than the allele unique or more common to only one species. Also, the elevationally allopatric blue and Engelmann spruce subpopulations were less divergent genetically than the sympatric subpopulations.
A crown barrier related to Cephalosporium stripe resistance in wheat relatives
Authors: Mathre D. E. , Johnston R. H.
Published: April 2011

Wheat (Triticum aestivum) and wheat relatives were tested to determine whether susceptibility to Cephalosporium gramineum was associated with fungal invasion of root or crown tissue. Tolerant lines of T. aestivum and an Agrotriticum needed more infection sites to develop the same disease incidence and severity than did a susceptible line. While differences in root tensile strength and root elasticity in field-grown plants could be detected in some years among lines, there was no correlation between disease reaction and these parameters. Speed of pathogen movement through roots and crown tissue was similar for all cultivars of T. aestivum tested and the Agrotriticum. Movement was slower in roots of Thinopyron intermedium and Elytrigia elongata, and much slower through crown tissues, than in T. aestivum lines. Thus, it appears that these wheat relatives are highly resistant to C. gramineum due to restriction of movement of the pathogen through the roots, and particularly through crown tissues. Dye translocation studies confirmed that crown tissues of these wheat relatives also restrict water movement, thus suggesting that they are more complex structurally than is the crown tissue of T. aestivum and the Agrotriticum. Key words: Triticum, Cephalosporium, wheat, disease resistance.
Harmful soil organisms in coastal foredunes involved in degeneration of Ammophila arenaria and Calammophila baltica
Authors: Putten W. H. Van der , Troelstra S. R.
Published: April 2011

The presence of harmful soil organisms in the root zone of Ammophila arenaria (marram grass) was examined by biotesting. For this investigation three locations along the sandy shoreline of The Netherlands were chosen: Voorne, Texel, and Schouwen. At all three locations harmful organisms were detected in sand from stable dunes, as well as in sand from mobile dunes (degenerated and vigorous A. arenaria, respectively). In beach sand, however, no harmful organisms occurred. Since A. arenaria shows vigorous growth only when it is buried regularly by windblown sand from the beach, it is concluded that this sand deposition enables the plants to escape from harmful soil organisms. Ammophila arenaria and Calammophila baltica (purple or hybrid marram grass) from the Voorne location were grown outdoors in containers filled with sand from the beach, the mobile dunes, and the stable dunes, and sterilized sand from the stable dunes. Biomass production of both species was highest in sterilized sand from the stable dune, followed by (in descending order) beach sand, sand from the mobile dune, and unsterilized sand from the stable dune. As compared with A. arenaria, however, growth of C. baltica was reduced less and without mortality of cuttings. Degree of growth reduction by harmful soil organisms could not be related to numbers of plant parasitic nematodes. Key words: Ammophila arenaria, Calammophila baltica, coastal sand dunes, succession, harmful soil organisms.
Morphogenetic determination of the axial cells of Antithamnion plumula (Ceramiaceae, Rhodophyta): early identification of the nature of the whorls
Authors: Lambert Cécile , Buis Roger , L'Hardy-Halos Marie-Thérèse
Published: April 2011

Antithamnion plumula axial cells are either "cladomophoric" (bearing a lateral cladom) or "pleuridiophoric" (with pleuridia only). The time required for their formation (generation time) and their length were the two variables used for their early characterization. The data presented show that (i) the generation time (approximately 10 h) of the pleuridiophoric axial cell, which immediately succeeds a cladomophoric axial cell, is significantly longer than that observed for all the other axial cells (6–7 h); (ii) the initial cell length (approximately 9 μm) of the cladomophoric axial cells is significantly greater than that of the pleuridiophoric axial cells (approximately 6 μm); and (iii) during the first stages of cell elongation (when the distance to the apex does not exceed 12 cells), the difference in size between the axial cells remains significant; the lateral budding of the cladomophoric cell occurs earlier than that of the pleuridiophoric cell. Thus, the cladomophoric axial cells can be distinguished from the pleuridiophoric axial cells very early. Their state seems to be determined by that of the apical initial cell that generates them. The transition between two successive tagmas is always characterized by a significantly longer generation time. Key words: plant morphogenesis, Rhodophyta, Antithamnion plumula, ramification, apical growth, generation time.
Comparative growth response in Carduus nutans, C. acanthoides, and their F1 hybrids
Authors: Warwick S. I. , Thompson B. K. , Black L. D.
Published: April 2011

The growth response of F1 hybrids relative to parental genotypes was compared in a natural hybridization system involving the diploid species Carduus acanthoides L. (2n = 22) and C. nutans L. (2n = 16). The data were used to test models of hybrid intermediacy, superiority, or greater similarity to a single parent in response to variable soil conditions and intra- and inter-genotypic competition. Progeny from paired reciprocal crosses between the two species were used in the experiments. In each of the half-sib families produced, the rapid and early identification of F1 hybrid genotypes and parental genotypes (resulting from selfing) was confirmed using allozyme markers (Pgi-2, Tpi-1, and Tpi-2). Growth of the F1 hybrids was better than C. nutans in poor soil, and both F1 hybrid and C. nutans genotypes produced significantly more dry weight than C. acanthoides in all soil treatments. F1 hybrids grew at least as well as the maternal parental species C. nutans and significantly better than C. acanthoides in the presence of intra- and inter-genotypic competitors. The F1 hybrid genotypes formed a more aggressive competitive environment than C. nutans, as evidenced by the growth of all three genotypes. These data primarily supported the model of greater hybrid similarity to one parental species rather than hybrid intermediacy, with evidence of hybrid superiority under certain extreme conditions.