bluuebunny/crossref_metadata_2025 huggingface dataset:
Perithecial distribution patterns in standard and variant strains of Neurospora crassa
Authors: Griffiths A. J. F. , Rieck A.
Published: April 2011

When crosses are made homozygous for the mutation fl, which completely eliminates conidiation, the patterns of sexual morphogenesis may be observed unobscured by effects due to conidia and conidial dispersal. In one cross, arbitrarily chosen as the standard, a striking double line of perithecia is seen, bordering a distinct clear central zone. Other crosses show a complex array of mating reactions, some involving an apparent invasion of one culture by nuclei of the opposite mating type, either through heterokaryotization or through overgrowth of one culture by the other. The width of the clear zone and the direction of invasion are variable and strain specific. The extent of heterokaryotization in the standard and variant crosses is discussed in relation to the situation found in other species. A complex genetic control of these reactions is indicated from inheritance patterns.
Variations in size, leaf morphology, and fruit characters among 25 populations of Luffa aegyptiaca
Authors: Okusanya O. T. , Ola-Adams B. A. , Bamidele J. F.
Published: April 2011

Variations in 25 populations of Luffa aegyptiaca L. in southwestern Nigeria and their possible causes were studied. The variations were most pronounced in the leaf, especially in texture, invagination, area, and dry weight. Shoot and fruit dry weights also showed considerable variation. While mean seed dry weight showed remarkable constancy in the populations studied, mean seed number per fruit varied greatly.Populations growing in acid soil with low nutrient content had deep leaf invaginations, small leaf areas per shoot, and small leaf, shoot, and fruit dry weights, while populations growing in neutral or basic soils with high nutrient content had shallow leaf invaginations, large leaf area per shoot, and large leaf, shoot, and fruit dry weights.When seeds from a population with deep leaf invagination and small leaf area were grown in soil from the site of a population with shallow leaf invagination and large leaf area, the resulting plants developed the characteristics of the second population. The reciprocal procedure gave a similar result. The variations in soil were thought to be responsible for the variation noted in leaf morphology, size, and weight and for variation in shoot and fruit dry weights. Light was partially responsible for the variations in the leaf colour and in the prominence of leaf veins.
Sexual reproduction in subalpine fir (Abies lasiocarpa)
Authors: Singh Hardev , Owens John N.
Published: April 2011

Reproductive phenology and anatomy of postdormancy phases of a population of Abies lasiocarpa (Hook.) Nutt. (subalpine fir) from a natural stand near Prince George, B.C., have been studied. The plants exhibited a 1-year type of reproductive cycle. By the end of March, the pollen cones had broken dormancy and contained pollen mother cells (PMC) in premeiotic stages. The PMCs entered meiosis in the 1st week of April and formed tetrads in the 3rd week. The tapetal cells, meanwhile, became binucleate, and then several went through endomitoses. The tapetal cell walls dissolved as the microspores separated from the tetrads. Orbicules were present around the degenerating cytoplasms of tapetal cells. Pollen grains were shed at the five-celled stage in the 3rd week of May.By the end of March, the ovulate cones had also broken dormancy and the ovules contained one to three hypodermal archesporial cells. Initiation of the integument and the formation of megaspore triads were observed in the 3rd week of April. By the 3rd week of May, at the time of pollination, the integument had developed a stigmatic micropylar funnel which received the pollen grains. During the postpollination stages the flange of the funnel became folded, and the nucellus grew up closer to the pollen grains. The nucellar cells at its tip degenerated to form a pollen chamber which contained the pollen grains. Pollen germination, pollen tube growth through the nucellus, and syngamy took only 4–6 days, and occurred at the end of June.The female gametophyte was rather long and narrow and bore two to three archegonia. The proembryo comprised four tiers of four cells each. The first set of suspensors developed from the subterminal tier of cells. The four terminal cells formed the embryonal mass but they contributed unequally. The proximal cells of the embryonal mass formed a massive secondary suspensor. Differentiation of root initials and the initiation of cotyledons in the young embryo took place in the 4th week of July, and the seeds matured in the 3rd week of August. The mature seed comprised a long and well-differentiated embryo, the female gametophyte, most of whose cells were gorged with protein bodies and lipid droplets, and a thick seed coat which was internally differentiated into three tissue layers. The outermost layer of gametophytic cells was devoid of any storage products.
Morphology of the balsam fir needle gall induced by the midge Paradiplosis tumifex (Diptera: Cecidomyiidae)
Authors: West R. J. , Shorthouse J. D.
Published: April 2011

Paradiplosis tumifex induces a simple, single-chambered, prosoplasmic gall on the adaxial surface of current-year needles of balsam fir. Proliferating and enlarged mesophyll cells surround the immature larva except for an ostiolar opening on the adaxial surface. The vascular bundle is not affected by gall formation, but the cells lining the resin ducts are altered. As the gall matures the epidermis and one or two layers of underlying mesophyll cells become lignified. Concentrations of starch granules are retained in gall cells after starch has been dissipated in tissues beyond the gall and in nongalled needles. Host damage occurs when galled needles dry and abscise prematurely.
Mycocalicium viscinicola sp. nov. (Caliciales) on mistletoe viscin in South America
Authors: Funk A. , Kuijt Job
Published: April 2011

A new species, Mycocalicium viscinicola (Ascomycetes: Caliciales) is described from the viscin covering of the seed of the mistletoe Tristerix longibracteatus (Desr.) Barlow and Wiens in South America.
Nitrogen fixation and net primary production in a young Sitka alder stand
Authors: Binkley Dan
Published: April 2011

Biomass, net primary production and nitrogen fixation rates were measured in a 5-year-old Sitka alder (Alnus sinuata (Regel) Rydb.) stand. Acetylene reduction assays yielded a nitrogen fixation estimate of 35 kg N ha−1 year−1. The biomass of leaves, stems, roots, and nodules was 13 720 kg ha−1 and aboveground net primary production was 6000 kg ha−1 year−1.
The genus Chenopodium in Canada
Authors: Bassett I. J. , Crompton C. W.
Published: April 2011

A key, descriptions of morphological characters (especially those of the seed testa and pericarp), chromosome numbers, and the distributions of 31 species of Chenopodium occurring in Canada are presented. Many names of the native taxa are typified and several nomenclatural problems are clarified. Chenopodium album L. var. missouriense (Aellen) I. J. Bassett et C. W. Crompton comb. nov. is reported here for the first time as occurring in Canada.
Étude ultrastructurale des coiffes des racines de chêne (Quercus robur). I. Les pivots
Authors: Dexheimer Jean , Muller Jean , Riedacker Arthur
Published: April 2011

Three zones may be distinguished in rootcaps of orthogeotropic taproots of oak seedlings.(1) The meristematic zone: cells have no distinctive characteristics except that they always have small rounded vacuoles.(2) The statocytes have amyloplastids accumulating in the lower cell portion. The nucleus is near the upper end. Unlike the herbaceous species studied, these cells have large central vacuoles. This may be a characteristic of woody species. This hypothesis is discussed.After a 90 or 135° rotation in a vertical plane, amyloplastids become progressively concentrated in the new lower end of the statocyte. Orientation of the endoplasmic reticulum also changes, and the vacuolar system is reorganized. At room temperature root curvature begins to appear more than 2 h after the rotation.(3) The outside cell layers are composed of mucilage secreting cells with dictyosomes producing large vesicles containing polysaccharides. These accumulate in the periplasmic area. A strong inosine diphosphatase activity is shown in the vesicles.
Studies of phosphorus and potassium deficiencies in Trifolium subterraneum based on electrical measurements
Authors: Greenham Charles G. , Randall Peter J. , Müller Warren J.
Published: April 2011

Electrical measurements were used to indicate changes in plant tissue due to alterations in nutrient status. An experiment with Trifolium subterraneum L., grown in soil at five rates of applied P, showed that inadequate P produced high values for (1) resistance to low frequency current (RLM) and (2) radius of the impedance locus (r). With increasing P the values of these two parameters fell, reaching a minimum at the P level giving maximum growth. Increasing the P supply above the optimum had no further effect.A study of K-deficient and of P-deficient plants showed the feasibility of diagnosing either deficiency or of discriminating between the two deficiencies, from changes in certain impedance parameters of the petiole tissue following correction of the deficiencies. Changes in membrane phase angle were consistent with K deficiency delaying and P deficiency hastening aging of the plasma membrane. RLF of both petioles and leaflets was increased by P deficiency, and the value for attached but not detached petioles from P-deficient plants was reduced by treatment with phosphate. RLF values for attached P-deficient leaflets decreased in response to phosphate treatment during leaf development but no longer responded (within 6 days of treatment) after a certain stage of maturity.Changes in RLF and r resulting from the correction of P deficiency show that some factor in addition to increase in tissue K is involved, most likely the plasmodesmata. The differences between RLF changes due to correction of nutrient deficiencies and those due to injury are noted.
A comparison of the Bradford and Lowry methods for the analysis of protein in chlorophyllous tissue
Authors: Eze J. M. O. , Dumbroff E. B.
Published: April 2011

A comparison of the dye-binding method of Bradford (1976) with the Folin phenol method of Lowry et al. (1951) for the assay of protein in chlorophyllous tissue is described. Additions of chlorophyll to protein standards precluded reliable determinations with either method. Absorbance readings were increased by nearly 20% with the Bradford assay and by over 400% using the Lowry procedure. Trichloroacetic acid precipitation of the proteins effectively eliminated any significant interference by chlorophyll; however, the practice of washing the protein precipitate with 80% acetone to remove residual chlorophyll resulted in large protein losses. Eluting leaf tissue with acetone prior to extraction of protein increased protein yield significantly. Both assay procedures provide satisfactory measurement of leaf proteins once chlorophyll is removed. The dye-binding method is fast, simple, and more sensitive, but the Lowry procedure gives better linearity at high protein concentrations and better stability once color has developed.
Cleistothecia of Eupenicillium ochrosalmoneum form naturally within corn kernels
Authors: Wicklow D. T. , Horn B. W. , Cole R. J.
Published: April 2011

Eupenicillium ochrosalmoneum Scott & Stolk formed cleistothecia in insect-damaged and fungus-infested preharvest corn from fields near Tifton, GA. When fungus-infested ears were incubated in moist chambers (21 days dark incubation; 25 °C), large numbers of immature sclerotioid cleistothecia (50–150) developed within individual kernels, often filling them. The cleistothecia were exposed by removing sections of the kernel pericarp. Isolates of E. ochrosalmoneum that were obtained from individual surface sterilized cleistothecia proved to be prolific cleistothecial producers. Cleistothecia also formed within kernels inoculated after autoclaving. Production of the teleomorphic state typical of E. ochrosalmoneum was observed when these kernels were incubated up to 10 weeks. This represents the first time that any species assigned to the Trichocomaceae has been shown to form cleistothecia within the seeds of vascular plants. Citreoviridin, a potent neurotoxin, was produced in culture media inoculated with one of the isolates (NRRL 6568).
Fine structure of the thraustochytrid Ulkenia amoeboidea. I. Vegetative thallus and formation of the amoeboid stage
Authors: Kumar S. Raghu
Published: April 2011

Development of the thraustochytrid Ulkenia amoeboidea was investigated at the ultrastructural level. The mature thallus possesses a lamellate wall, a nucleus with intranuclear vesicles and lamellae, several Golgi bodies, mitochondria, bundles of microfilaments, multivesicular bodies, dilated perinuclear continuum with filamentous material, endoplasmic reticulum, sagenogenetosomes, and two centrioles. Several unit membrane bounded, variously electron-dense inclusion bodies with electron-dense globular units are present. Wall scales are produced in Golgi cisternae which inflate to form vesicles. These vesicles deposit the wall material to the outside by exocytosis. An aggregate of unit membrane bounded electron-dense cisternae (paranuclear body) is found adpressed to the nucleus. A close association between the paranuclear body and the mitochondria, the former often producing finger-like projections in mitochondrial vicinity, is present. A protocentriole-like structure is seen near the nucleus of young thalli. At later stages, the ectoplasmic net elements disappear. Closely adpressed membrane arrays appear between the cell wall and plasmalemma. These are accumulated in bundles at various places in the cell and are later found in presumed autophagic vacuoles. Before the cell contents escape as an amoeboid mass, the cell wall becomes thinner owing to the peeling off of wall scales and the cell contents round up, with the plasmalemma becoming detached from the cell wall. Various vesicles are closely associated with the plasmalemma.
The morphology and growth cycle of Anemone patens
Authors: Wildeman Alan G. , Steeves Taylor A.
Published: April 2011

The morphology and development of Anemone patens L. has been studied. An examination of the ontogeny of buds revealed a number of interesting developmental phenomena, and brought to attention the need to study more native prairie plants in their natural habitat. Two types of buds are produced annually: one replaces the terminal bud, which is transformed to a flowering apex, and one becomes dormant. During its first season of growth the former bud produces foliage leaf primordia, which expand the following season, and several bud-scale primordia. During the second season it produces additional bud scales before itself transforming to a floral apex; the resulting flower bud remains enclosed by the bud scales until the spring of the third season. The second type of bud produced annually is generally smaller, and after producing protective bud scales enters what may be a prolonged dormancy. The initiation of these two types of bud follows a regular pattern; the bud which replaces the main apex is normally found in the axil of the uppermost bud scale enclosing the developing flower bud, while the bud which will become dormant is formed in the axil of the uppermost expanding foliage leaf. The growth pattern of A. patens appears to be well suited to the plant's habitat. The reserve of viable dormant buds is augmented annually, and enables the plant to regenerate new branches if terminal apices are damaged. The largest, most highly branched specimens are frequently found in locations that are grazed or burned, and such periodic disturbances may in fact help the plant to thrive.
Cytology of meiosis I and chromosome number of Cochliobolus heterostrophus (Ascomycetes)
Authors: Guzman Doralinda , Garber Robert C. , Yoder Olen C.
Published: April 2011

Meiosis I was examined in the ascomycete Cochliobolus heterostrophus using light microscopy, following an iron-hematoxylin procedure which stained chromosomes, nucleoli, and spindle pole bodies. The behavior of C. heterostrophus chromosomes during meiosis I is similar to that described for other ascomycetes. The haploid chromosome number for C. heterostrophus, determined at pachytene, is eight.
Glycerol and myo-inositol as carbon sources for the induction of xylogenesis in explants of Lactuca
Authors: Roberts L. W. , Baba S.
Published: April 2011

Glycerol (2% w/v) and myo-inositol (2% w/v), respectively, functioned as the principal exogenous carbon source for the induction of tracheary element differentiation in cultured expiants of lettuce pith (Lactuca sativa cv. Romána). Although tracheary elements were first observed after 3 days on a xylogenic medium supplemented with either glucose (2% w/v) or myo-inositol (2% w/v), the induction of xylogenesis in explants cultured on a similar medium containing glycerol (2% w/v) required a minimum of 6 days. Tracheary elements formed in the presence of glycerol and myo-inositol, respectively, were characterized by various patterns of scalariform-reticulate secondary wall thickenings which were indistinguishable from tracheary elements produced under similar cultural conditions in the presence of glucose as the principal carbon source. This is the first report of a major exogenous carbon source other than a carbohydrate supporting the cytodifferentiation of tracheary elements under in vitro conditions.
Association between the fungus Acremonium curvulum and Eurasian water milfoil, Myriophyllum spicatum
Authors: Andrews John H. , Hecht Elizabeth P. , Bashirian Stephanie
Published: April 2011

Acremonium curvulum W. Gams was isolated during three growing seasons from the stems, leaves, and roots of Eurasian water milfoil (Myriophyllum spicatum L.) that grew submerged in University Bay of Lake Mendota, Wisconsin. Despite substantial variation, an overall trend suggested more frequent incidence of this fungal-plant association as the season progressed. Surveys of eight other Wisconsin lakes located in three drainage basins showed this relationship to be of general occurrence. Acremonium curvulum occurred with seeds and, more commonly, with vegetative fragments of milfoil. Anatomical evidence from sectioned or fractured milfoil cells, scanning electron microscopy of stem and leaf surfaces, and plating of surface-disinfested tissue pieces indicated that Acremonium grew both epiphytically and endophytically. Healthy plants harbored the fungus, which was apparently eliminated by immersion of shoots in a solution of the fungicide thiabendazole. If milfoil was stressed by environmental or mechanical manipulations, proliferation of A. curvulum accompanied decline of the plant. Healthy, Acremonium-free, cultured milfoil immersed in a conidial suspension developed systemic basal necrosis that spread acropetally to involve about two-thirds of the tissue within 1 week. Dry weight and shoot elongation of inoculated, diseased milfoil were slightly less than those of control plants, although new growth was usually initiated from adventitious buds within 3–4 weeks. Recovery of infected plants was promoted somewhat by thiabendazole.
La paroi des asques chez les Pyrénomycètes : étude ultrastructurale. I. Les asques bituniqués typiques
Authors: Parguey-Leduc A. , Janex-Favre M. C.
Published: April 2011

A complex and homogeneous organization is present in the ascus wall of typical bitunicate Pyrenomycetes. First unitunicate, the wall soon becomes bitunicate. A clear space then separates both tunicae (exoascus and endoascus); it is formed by the lysis of the external part of the endoascus. In the mature ascus the exoascus is composed of two superposed layers and the endoascus of a single layer which shows remarkable accordion-like fibrillas.The essential structural feature of the bitunicate ascus wall is the presence, in the Pyrenomycetes as well as in lichenized and nonlichenized Discomycetes, of two tunicae, the inner (endoascus) presenting a wavy or folded fibrillar structure. In the Pyrenomycetes such a structure is much more distinct, however; a clear space in addition separates the exoascus and the endoascus.
Effects of shortened day length upon translocation and starch accumulation by maize, wheat, and pangola grass leaves
Authors: Sicher Richard C. , Harris William G. , Kremer Diane F. , Chatterton N. Jerry
Published: April 2011

Rates of leaf starch accumulation in maize, wheat, and pangola grass were approximately doubled when plants were shifted from long to short day lengths, 4 days prior to measurement. There were only small changes in carbon assimilation rates and specific leaf weights. After a brief exposure to 14CO2 and after a 2-h-chase period, total label was higher in leaves of long to short day length than in long day length plants. Most of the increased 14C radioactivity in leaf extracts of long to short day length plants was recovered in the starch, protein, and neutral fractions. The translocation of 14C-labeled assimilates to roots was less in long to short day length then in long day length plants. Sucrose was increased in leaves and decreased in roots following a shift from long to short day lengths. The above findings indicated that the accumulation of assimilates in leaves of long to short day length plants was due in part to a lowered rate of sucrose transport. The rate of sucrose movement was not directly proportional to its total pool size in source leaves.
Protein bodies in umbelliferous seeds. I. Structure
Authors: Spitzer Ernest , Lott John N. A.
Published: April 2011

The structure of the protein bodies from seeds of the family Umbelliferae has not been studied extensively since late in the 19th century. Using light and electron microscopy structural aspects of the protein bodies of carrot (Daucus carota L. cv. Imperator 408), wild carrot (Daucus carota L.), caraway (Carum carvi L.), anise (Pimpinella anisum L.), dill (Anethum graveolens L.), celery (Apium graveolens L. cv. Tall Utah), fennel (Foeniculum vulgare Mill), parsnip (Pastinaca sativa L. cv. Hollow Crown), parsley (Petroselinum sativum L. cv.Moss Curled), and chervil (Anthriscus cerefolium L. cv. Curled) were studied. Both endosperm and embryo protein bodies were investigated. Structurally, the protein bodies from all these genera were similar in that two types of protein bodies were found. One type consisted of a homogeneous, proteinaceous matrix and a number of variously sized, globoid crystal inclusions. The other type consisted of a homogeneous, proteinaceous matrix and either an individual or, more commonly, an aggregate of calcium-rich crystals arranged in a cluster usually termed a druse. Both types of protein bodies were never found in the same cell. Only globoid crystals were found in the embryo protein bodies. Protein bodies in the embryos were smaller, more numerous per cell, and often contained a flocculent, proteinaceous matrix.
The surface activity of the phytotoxin cerato-ulmin
Authors: Russo Paul S. , Blum Frank D. , Ipsen John D. , Abul-Hajj Yusuf J. , Miller Wilmer G.
Published: April 2011

The glycoprotein cerato-ulmin, which shows surface activity at concentrations as low as 30 ng/mL, has been found to stabilize air bubbles, both spheroidal and of unusual morphology, in aqueous and aqueous ethanol solutions. In response to stress on a cerato-ulmin thin film, perhaps a monolayer, at an air–water interface, cylindrical and fibrilliform air bubbles are generated. They may be manipulated by application of tension, pressure, or temperature. The relationship of these observations to elm trees infected with the cerato-ulmin producing fungus Ceratocystis ulmi suggests a mechanism whereby exceedingly low concentrations of cerato-ulmin may be concentrated and delivered to intercellular openings, thereby blocking the vascular system of elm trees. The correctness of this mechanism as a major factor in any tree wilt disease remains to be tested.
Flavonoid studies in four species of the Oxytropis campestris complex (Fabaceae–Galegeae)
Authors: Elisens W. J. , Denford K. E.
Published: April 2011

Thirteen flavone and eight flavonol glycosides from four taxa of Oxytropis campestris (L.)DC. s. lat. have been isolated and identified. The compounds are based on five aglycone moieties and have several characteristic glycosidic patterns. Unlike some previously examined polyploid complexes, the component taxa have markedly divergent flavonoid profiles. It appears that considerable phytochemical differentiation has accompanied morphological and cytological diversification within the complex. These data support taxonomic recognition of the component taxa at the specific level.
The free sterol, steryl ester, and steryl glycoside content of tomato cultivars resistant and susceptible to Phytophthora infestans
Authors: Bradford B. , Moore L. D. , Orcutt D. M.
Published: April 2011

Leaf sterols were extracted from three late blight resistant ('Nova,' 'New Yorker,' and 'West Virginia 63') and three late blight susceptible ('Beefsteak,' 'Jubilee,' and 'San Marzano') cultivars of tomato (Lycopersicon esculentum Mill.). There were no significant differences (P < 0.05), either quantitatively or qualitatively, between the sterol contents of the resistant and the susceptible cultivars. Of the six cultivars only the steryl glycoside class of 'San Marzano' was significantly higher than that of the other cultivars. The total sterol content was 2.95–3.84 mg/g dry weight and was composed of 23–32% free sterol, 4–6% steryl ester, and 63–71% steryl glycoside. The relative susceptibility of tomato to late blight is not related to the free sterol or conjugated forms of sterols in the plant.
Conidium production from leaves and needles in four streams
Authors: Bärlocher Felix
Published: April 2011

Oak leaves and larch and spruce needles in fine-mesh (0.3 mm) and coarse-mesh (3 mm) bags were exposed in two hard-water streams in the Swiss Jura and two soft-water streams in the Black Forest. Periodically, conidium production in samples was determined under defined conditions. Generally, conidium production per unit weight was highest in oak, followed by larch and spruce. In oak and larch, an early peak was followed by a gradual decline; in spruce, conidium production reached an early plateau in the Jura streams but increased throughout the experimental period in the Black Forest streams. Percentage similarity between substrate spora and stream spora was highest for oak, followed by larch and spruce in three of the streams with deciduous riparian vegetation. The reverse sequence occurred in the remaining stream of a coniferous forest. On oak and larch, more fungal species were recovered in fine-mesh than in coarse-mesh bags; however, these additional species were numerically unimportant. Heliscus lugdunensis was the dominant species in early stages of spruce decay. It was replaced at later stages by Alatospora acuminata in the Jura streams and by two other species in the Black Forest streams. On oak and larch, the four or five most common species remained dominant throughout the experimental period.
Measurements of the volumetric and transverse elastic extensibilities of Chara corallina internodes by combining the external force and pressure probe techniques
Authors: Steudle E. , Ferrier J. M. , Dainty J.
Published: April 2011

The transverse and volumetric elastic extensibilities of Chara corallina internodal cell wall tubes were studied by simultaneous application of the external force and pressure probe measuring techniques. It was found that there is a deformation of the cell wall resulting from the concentrated force exerted by the external force, which dominates the transverse extensibility at low turgor pressures, and which can be important at high turgor pressure. The implications of the effect for the use of the external force technique on higher plant tissue are discussed.
Vascularisation de la fleur de Symplocarpus foetidus (Araceae)
Authors: Barabé Denis
Published: April 2011

The flower of Symplocarpus foetidus is characterized by an inferior unilocular ovary containing a suborthotropous ovule in apical position. Several authors consider the gynoecium of Symplocarpus to be pseudomonomerous. Our study of the organization of the vascular bundles does not confirm this hypothesis. Furthermore, pseudomonomery has yet to be demonstrated for any of the members of the Calloideae. The flower of Symplocarpus shows many similarities with that of Gymnostachys (Pothoideae) and of Aglaonema (Philodendroideae). In Symplocarpus, we also observe four vascular bundles in the style but they are not homologous to those of Aglaonema and cannot be interpreted as belonging to two different carpels.
Accumulation and release of plant nutrients in decomposing Scots pine needle litter. Long-term decomposition in a Scots pine forest II
Authors: Staaf Håkan , Berg Björn
Published: April 2011

Plant nutrient dynamics in decomposing needle litter were measured during a 5-year period in a Scots pine forest in central Sweden. As seen over the whole 5-year period, the nutrients were retained (to a litter weight loss of about 75%) in the order Mn < Ca < K < Mg < S < N < P. During the first 1.5 years there was a net increase of N and P whereafter a net release took place. A similar but less pronounced development could be seen for S, whereas Ca, K, Mn, and Mg were released from the start of the incubation. It is suggested that P was the most limiting element for microbial activity during this first phase. There appeared to be only little initial leaching from the litter and the different behaviours of the elements could largely be explained by their concentration in litter in relation to the needs of microorganisms and to their solubility. K and Mg were the elements that were released at rates most similar to organic matter weight loss.
Phytomass: Structural relationships for woody plant species in the understory of an Appalachian oak forest
Authors: Martin Wayne L. , Sharik Terry L. , Oderwald Richard G. , Smith David Wm.
Published: April 2011

Equations were developed for estimating total aboveground phytomass from structural dimensions of individual stems involving 17 tree and shrub species in the understory of second-growth Appalachian oak forest stands in southwest Virginia. All possible combinations of three functional forms of the equation (linear, allometric, and exponential) and three independent variables (basal area, stem height, and crown area), singly and in combination, were tested. The linear model, with stem basal area as the independent variable, provided the best fit to the data for 15 of the 17 species. The exceptions were the blueberries (Vaccinium stamineum and V. vacillans) where crown area performed better than basal area as the independent variable. With respect to Vaccinium vacillans, in particular, only 35% of the variation in aboveground phytomass could be accounted for using all three independent (structural) variables, which suggests a pattern of growth substantially different from the other species studied. Stratified sampling of stems involving broad height classes appeared to favor the application of linear models over nonlinear models.
Sexual reproduction of Pinus contorta. II. Postdormancy ovule, embryo, and seed development
Authors: Owens John N. , Simpson Sheila J. , Molder Marje
Published: April 2011

Postdormancy development of the ovule, fertilization, and embryo and seed development of Pinus contorta (Dougl.) are described. Reproductive development in lodgepole pine (P. contorta var. latifolia) growing within and outside its natural range is described in detail and compared with the phenology of shore pine (P. contorta var. contorta) growing within its natural range. The female gametophyte of lodgepole pine overwinters at the free nuclear stage, resumes development in early April, and is mature by mid-June. Fertilization occurs in mid-June and the embryo and seed are mature by early August. Seed cones of lodgepole and shore pines growing in the coastal region resume development in late March, develop more slowly at first, then complete each subsequent stage of development about 1 month earlier than lodgepole pine grown in the interior of British Columbia. Stages of the reproductive cycle as they affect potential seed production are discussed.
Studies of acid-soluble phosphorus compounds in genetically pure lines of Avena fatua with different dormancy characteristics
Authors: Jain J. C. , Quick W. A. , Hsiao A. I.
Published: April 2011

Seven genetically pure lines of wild oat selections of known dormancy characteristics were grown under uniform field conditions. Acid-soluble phosphorus components were determined in the dry seeds, in the imbibed seeds, and in imbibed seeds with dormancy-breaking treatments. No significant correlation between dormancy level and acid-soluble phosphorus composition was established for any component other than inorganic phosphorus (Pi). In dry caryopses Pi varied from 5 to 10% of the acid-soluble fraction. A highly significant inverse correlation was found between levels of Pi in the dry caryopsis and the relative depth of dormancy of the wild oat selection considered. The effect of imbibition on Pi level varied with depth of dormancy. Intact seeds of nondormant lines imbibed for 52 h showed a significant decline in Pi prior to coleorhiza protrusion from the dehulled caryopsis. More deeply dormant lines of Avena fatua (pure lines Anderson 51, Anderson 474, or Crop Science 40) required up to 10 days of incubation for significant drops in Pi to appear, while the most dormant lines (pure line Montana 73 and Idaho) did not evidence significant decline in Pi even after 10 days of incubation. The increase in Pi level associated with coleorhiza protrusion could be produced in the imbibed dormant lines by piercing them with a fine needle, by treating with gibberellic acid (GA3), or by a combination of the two treatments. The combination of piercing and GA3 treatment was much more effective than either treatment alone.
The origin and development of root buds in Asclepias syriaca
Authors: Polowick Patricia L. , Raju M. V. S.
Published: April 2011

The persistence of Asclepias syriaca L. as a weed is related to its ability to propagate vegetatively by the development of adventitious buds on roots. These root buds arise on the main root and upper lateral roots within 25 days of the establishment of seedlings and are generally associated with the bases of lateral roots. A study of root anatomy shows that the origin of these buds is endogenous, in the pericycle and (or) its derivatives. No root buds are initiated until after lateral roots have developed and some cambial activity has begun. Vascular connections from the bud to the stele of the parent root, or an associated lateral root, are made at an early stage of bud development.
Floral development in Caulophyllum thalictroides (Berberidaceae)
Authors: Brett J. F. , Posluszny U.
Published: April 2011

A study of floral development in Caulophyllum thalictroides led to a reevaluation of the structure of the flower. After the production of sepal primordia, common stamen–nectary primordia arise. Nectary primordia are produced abaxially as a result of bifurcations of the common stamen–nectary primordia. The nectaries therefore cannot be considered reduced petals as traditionally interpreted and are perhaps better regarded as staminal derivatives. Three whorls of sepals develop; the lowermost often being dimerous, while the upper two whorls are more typically trimerous. The interpretation of the lowermost whorl of sepals as bracts was questioned. The terminology with regards to the inflorescence was considered, and after examination of material from this taxon it was felt that the inflorescence is best described as a cymosely branched panicle.
A comparison of disease progress equations for cereal rust
Authors: Fleming R. A. , Holling C. S.
Published: April 2011

A continuous mathematical model of the progress of cereal rust disease was developed by including many of the natural processes underlying each recurrent infection cycle. This model is subsequently reduced to a single equation and compared with four other models prevalent in the literature: the logistic, Kiyosawa's modified logistic, Waggoner's modified logistic, and the Gompertz. The equation developed here provides a basis for exploring causal linkages between these four models and illuminating some of their implicit assumptions. It is argued that single first-order equation models must contain one or more parameters which group a number of effects to be fitted to disease progress data. This precludes unique biologically meaningful definitions for parameters of such single-parameter models as the logistic with respect to the processes underlying disease progress (e.g., infection, sporulation). The differential equation dx/dt = ax(1−x)/(1 + alx), where a is a rate parameter, l is the length of the latent period, t is time, and x is disease severity, is offered as a potentially useful alternative to previous models of disease progress. Recommendations for further research are provided.
Translocation in Saccorhiza dermatodea (Laminariales, Phaeophyceae): anatomy and physiology
Authors: Emerson C. J. , Buggeln R. G. , Bal A. K.
Published: April 2011

An anatomical, ultrastructural, histoautoradiographic, and physiological study was made of the kelp Saccorhiza dermatodea, which possesses an anatomy "atypical" of Laminariales. A freeze-substitution – histoautoradiographic procedure localized 14C-labelled organic matter in highly elongated cells (solenocysts) in the medulla of Saccorhiza. These cells are the major long-distance, symplastic translocation pathway in this alga. Solenocysts are joined to each other via numerous lateral connections involving small intermediary cells called allelocysts. Sieve plates (pore diam: ca. 0.05 μm; pore density: ca. 100 μm−2), pierced by plasmodesmata in which an occasional tubule may be seen, are present at all allelocyst–solenocyst junctions as well as at intercellular connections in the cortex and meristodermal layers. Solenocyst ultrastructure closely resembles that of typical sieve cells of Laminariales. Secondary wall deposition occurs between June and October constricting the numerous lateral sieve plates and nearly occluding the cell lumen; however, no callose plugging was observed in any of the medullary cells. In vivo14C-photoassimilate transport was monitored in S. dermatodea blades using a Geiger–Müller probe. The translocation velocity was estimated at 60–100 mm∙h−1 with a greater translocation rate during the day than at night. Amino acid analyses of the S. dermatodea exudate showed a high alanine and glycine content with maximum concentrations 300 mm above the blade base. Nearly 90% of the 14C activity in both source and sink portions of the blade was in alcohol-soluble matter at the end of 72-h experiments. The unique anatomy of the Saccorhiza blade lends it to experimental exploration of the translocation process in kelp.
Factors affecting the division frequency of pea mesophyll protoplasts
Authors: Jia Shi-rong
Published: April 2011

Mesophyll protoplasts were isolated from five pea (Pisum sativum) varieties and cultured in medium 8p, modified to test the effects of varieties, leaf ages, protoplast population densities, pH, and plant hormones on relative division frequency. Protoplasts isolated from the variety Rondo had a much greater capacity for division than those from Century, Laxton's Progress, Trapper, or Afghanistan 72-HI-2. The highest division frequency occurred in protoplasts isolated from the top expanded leaf of seedlings at the three-, four-, or five-leaf stage. The maximum frequency of division was obtained using a protoplast density of 5 × 104to 1 × 105 per millilitre and the 8p medium at pH 5.6 with 850 mg/L of CaCl2∙2H2O, 0.25–1.00 mg/L of 2, 4-D, and 2 mg/L of zeatin riboside. Gradually reducing the osmolality from 510 mosmol to 420 mosmol was essential to achieve a high frequency of cell division.
Fertilization in Plumbago zeylanica: entry and discharge of the pollen tube in the embryo sac
Authors: Russell Scott D.
Published: April 2011

The ultrastructural organization of the megagametophyte of Plumbago zeylanica, which lacks synergids, was examined in chemically and physically fixed ovules after entry of the pollen tube. Similar to angiosperms with conventionally organized megagametophytes, the pollen tube enters the ovule through a micropyle, formed by the inner integument, and approaches the female gametophyte by growing between nucellar cells. Unlike other described female gametophytes, however, continued pollen tube growth results in direct penetration of the base of the egg through cell wall projections forming a filiform apparatus and is completed between the egg and central cell without disrupting either of these cells' plasma membranes. A terminal pollen tube aperture forms when the pollen tube reaches an area of strong curvature near the summit of the egg; this results in the release of two sperm cells, the vegetative nucleus, and a limited amount of pollen cytoplasm. The formerly continuous chalazal egg cell wall is locally disrupted near the tip of the pollen tube and apparently is thus modified for reception of male gametes. Discharged pollen cytoplasm rapidly degenerates between the egg and central cell, but unlike pollen tube discharge in conventionally organized megagametophytes, it is unassociated with the degeneraton of any receptor cell within the female gametophyte. Sperm nuclei are transmitted, one to the egg and the other to the central cell, to effect double fertilization by nuclear fusion with their respective female reproductive nuclei. The vegetative nucleus and discharged pollen cytoplasm degenerate between the developing embryo and endosperm during early embryogenesis. The emerging concept that the egg of Plumbago possesses combined egg and synergid functions is supported by the present study and suggests that the megagametophyte of this plant displays a highly specialized egg apparatus composed exclusively of a single, modified egg cell.
Recent seedling establishment at timberline in Jasper National Park, Alta.
Authors: Kearney Michael S.
Published: April 2011

Dendrochronological investigations of the age structure of timberline seedlings at three sites in Jasper National Park suggest that the timberline in these areas experienced two major periods of seedling establishment during the past 40 years: an early episode dating from the middle 1940's to the early 1950's and a later episode dating from the late 1960's to the early 1970's. Analysis of possible factors responsible for triggering these seedling invasions indicates a strong association with higher-than-average mean minimum summer temperatures and little association with mean summer precipitation.
An ultrastructural analysis of the development of mycorrhizas in Rhododendron ponticum
Authors: Duddridge J. , Read D. J.
Published: April 2011

The sequence of events involved in the initiation, establishment, and degeneration of the ericoid mycorrhizas of Rhododendron ponticum was followed at the ultrastructural level. Seedlings were planted in inoculated sterile soil or natural soil and harvested sequentially over a period of weeks. Their roots were fixed and examined by scanning and transmission electron microscopy. Field-collected roots were also examined for comparative purposes. In inoculated soil, surface colonisation of root epidermal cells occurs within 4 weeks of inoculation, and penetration follows immediately. The functional life of the infected epidermal cell is short, evidence of degeneration of host cytoplasm being visible within 7 weeks. Host breakdown precedes fungal degeneration, which suggests that nutrient transfer between partners must occur in the short period when both have full structural integrity. Endophyte hyphae degenerate after collapse of host cytoplasm, first becoming vacuolate and then devoid of contents. The result of this pattern of infection is that most cells of the root epidermis are dead and devoid of contents. The pattern is the same in natural soil, though each stage is delayed by 2–3 weeks. The possible relationship between the structural and functional characteristics of ericoid roots is discussed and comparisons are made with other types of endomycorrhizas.
Calathea burle-marxii and Ctenanthe burle-marxii (Marantaceae): two new cultivated species from Brazil
Authors: Kennedy Helen
Published: April 2011

Two species and one variety of Brazilian Marantaceae are described as new: Calathea burle-marxii from Bahia and Ctenanthe burle-marxii and C. burle-marxii var. obscura from Espirito Santo. All three taxa are currently in the horticultural trade.
Dry weight and resource allocation patterns among individuals in populations of Plantago major and P. rugelii
Authors: Hawthorn W. R. , Cavers P. B.
Published: April 2011

The frequency distributions of log plant weight in 1st-year plants of Plantago major L. and P. rugelii Decne. were studied in greenhouse experiments, including an investigation of associated differences in allocation patterns to plant parts between individuals in various weight classes. The frequency distributions of log plant weight of both plantains were strongly negatively skewed (many large plants and few small ones) at the lowest sowing density, where little or no mortality occurred during the course of the study. At two higher sowing densities significant mortality was noted and the frequency distributions tended to "log normality" or to a significant platykurtosis. The presence of bromegrass (Bromus inermis Leyss.) reduced the weight of individual plantains and resulted in frequency distributions that were essentially "log normal." Growing the two plantains together did not alter the shapes of the frequency distributions achieved in monocultures with and without grass. A possible pattern of changes in the frequency distribution of log plant weight with the passage of time is briefly discussed. Significant differences were observed in the allocation patterns of individuals of P. major within a population to roots, caudices, leaves, supporting reproductive structures, and seeds. The allocation patterns were not normally distributed according to plant weight; thus the use of average values of allocation pattern for the population as a whole should be viewed with caution. The proportional allocation to seeds (reproductive effort) by individuals of P. major from increasingly larger weight classes generally increased at an exponential rate, and more rapidly than simultaneous decreases in root and caudex allocation. The greatest reproductive effort and the greatest number of seeds per plant of P. major were associated with the strongest negative skewness of frequency distribution of log plant weight. First-year plants of P. rugelii exhibited a different response. Very few flowered during the study. However, in a variety of treatments the allocation to root and caudex by individuals which differed in biomass by as much as two orders of magnitude was remarkably constant at about 23%. In contrast, the allocation to belowground structures was much more variable among individuals of P. major, ranging from 50% or more by the smallest individuals to less than 5% by the largest plants. This life-history trait could partly account for the greater survival over winter and longevity observed in natural populations of P. rugelii compared with those of P. major.