bluuebunny/crossref_metadata_2025 huggingface dataset:
LEAF TURNOVER RATES OF ADENOSTOMA FASCICULATUM (ROSACEAE)
Authors: Jow William M. , Bullock Stephen H. , Kummerow Jochen
Published: January 2018

The age structure of the foliage of a 26‐yr‐old stand of Adenostoma fasciculatum H. & A. (chamise) was analyzed. The mean number of standing leaves and the yearly increase in leaf scars on the leaf‐producing short shoots allowed an estimate of annual leaf production. The average chamise leaf persists for two seasons. Short shoots produce 4–6 leaves per yr; however after 4–5 yr their productivity declines. About 72% of the standing leaves were produced during the current and 28% during the foregoing season. Nearly one‐half of all the leaves produced was found on current‐year short shoots (i.e., on long shoots that had developed during the spring of the same year). Thus, earlier estimates of leaf production in chamise based only on current‐year long shoot growth were too low.
PITTING IN PSILOPHYTON DAWSONII, AN EARLY DEVONIAN TRIMEROPHYTE
Authors: Hartman Christine M. , Banks Harlan P.
Published: January 2018

Tracheids of Psilophyton dawsonii Banks, Leclercq, and Hueber 1975 from calcareous pebbles of late Early Devonian age on the Gaspé Peninsula, eastern Canada, are shown to have scalariform bordered and circular bordered pits. Macerated tracheids embedded in Spurr epoxy resin and sectioned at 2 μm; peels, ground sections, SEM and petrographic observations all indicate that interconnections between the scalariform bars are composed of secondary wall material and that the patterns produced are not artifacts of preservation. The interconnections produce a wide range of patterns from simple vertical strands, to reticula, to more extensive interconnections that outline circular openings. The circular openings result in scalariform bordered pits that are considered to be multiaperturate. P. dawsonii is believed to illustrate the most complex pitting yet demonstrated conclusively in Early Devonian time. Among trimerophytes P. forbesii, tracheids of P. charientos, and Hostinella from Röragen, Norway lack only the circular bordered pits.
CATKIN FREEZING AND ACORN PRODUCTION IN GAMBEL OAK IN UTAH, 1978
Authors: Neilson R. P. , Wullstein L. H.
Published: January 2018

In May 1978, a general freeze of the male flowers of Gambel oak (Quercus gambelii Nutt.) was observed in northern Utah. In August, transect reconnaissance was conducted throughout Utah to assess acorn production and the incidence of freeze damage in Gambel oak. It was found that below ca. 1950 m elevation acorn production was relatively low while the incidence of freeze damage was high. Above ca. 1950 m elevation, where the oaks were still dormant at the time of the freeze, acorn production was relatively high while freeze damage was relatively low. Occasional acorn production observed at low elevations appeared to be associated with subterranean pooling of water and/or cold air drainage. Some biogeographic implications of freeze stress are discussed.
A NEW NITROGEN‐FIXING NON‐LEGUME: CHAMAEBATIA FOLIOLOSA (ROSACEAE)
Authors: Heisey Rod M. , Delwiche C. C. , Virginia Ross A. , Wrona Anne F. , Bryan Barbara A.
Published: January 2018

Specimens of Chamaebatia foliolosa Benth. with nodule structures on their roots fix atmospheric nitrogen. The nodules are similar to those of other non‐legumes in gross morphology and structure, containing hyphal strands, some with club‐shaped vesicles at their ends. A fixation rate of 130 nmoles N2 per g fresh weight per hr is reported by using 15N2 as a tracer. Equivalent rates of acetylene reduction were observed.
STRUCTURE OF FLORAL NECTARIES OF ALFALFA (MEDICAGO SATIVA L.) IN RELATION TO NECTAR PRODUCTION
Authors: Teuber L. R. , Albertsen M. C. , Barnes D. K. , Heichel G. H.
Published: January 2018

Alfalfa (Medicago sativa L.) plants differ in nectar volume production per floret. These differences are heritable, but no information is available on what type of structural variation may be responsible for these differences. One high, one intermediate, and one low nectar‐volume‐producing clone was selected from each of two alfalfa cultivars. Results from light and scanning electron microscopy indicated that alfalfa has an annular nectary located on the staminal column and primarily on the receptacle. It is composed of several cell layers subtended by vascular bundles containing both xylem and phloem. Vascular tissue does not extend into nectariferous tissue. Permanently open stomata are present in the epidermal layer and are thought to function in nectar secretion. These stomata did not respond to stimuli known to affect leaf stomata. Number of stomata per nectary among the six clones ranged from 24.7 ± 1.9 to 6.8 ± 0.5. Nectar‐reservoir diameters among clones ranged from 1.07 ± 0.09 mm to 0.70 ± 0.01 mm. Clones producing the most nectar were characterized by a large nectar reservoir and moderate to high numbers of stomata.
A FERTILE SPECIES OF TRIPHYLLOPTERIS FROM THE EARLY CARBONIFEROUS (MISSISSIPPIAN) OF SOUTHWESTERN VIRGINIA
Authors: Skog Judith E. , Gensel Patricia G.
Published: January 2018

The first occurrence of attached fertile structures to foliage assignable to the form genus Triphyllopteris Schimper is reported from the early Carboniferous Price Formation of southwestern Virginia. Sporangium‐bearing branch systems consisting of a basal undivided foliar region and a distal much‐divided fertile region are described as a new species T. uberis Skog and Gensel. Ovoid fusiform sporangia, 2.0 mm long and 0.5 mm wide and containing trilete spores, terminate ultimate divisions of the branch systems and collectively form masses up to 4 cm in all dimensions. T. uberis is compared to previously known sporangiate organs of Late Devonian and early Carboniferous age, many of which lack attached foliage. Similarities in the overall branching pattern of many of these non‐synangiate, sporangiate organs of early Carboniferous age is noted. The possible mode of dispersal and affinities of the plant bearing T. uberis fertile foliage is discussed.
RADIAL GROWTH IN THE CYCADALES
Authors: Stevenson Dennis Wm.
Published: January 2018

The development of radial growth which leads to the pachycaulous form was investigated in eight of the 10 genera of the Cycadales; i.e., Ceratozamia, Cycas, Dioon, Encephalartos, Macrozamia, Microcycas, Stangeria, and Zamia. In all taxa, development of radial growth is essentially the same: a primary thickening meristem is differentiated in the stelar region of the cotyledonary node of the seedling at germination and produces derivatives mainly centrifugally. This primary thickening meristem (PTM) then differentiates acropetally and becomes continuous with the peripheral zone of the shoot apex. At first the PTM is a vertical cylinder, but as the seedling continues to grow into an adult plant, the PTM shows a more horizontal orientation (like an open umbrella) and produces the broad cortex. Secondary growth is by a vascular cambium which produces secondary xylem to the inside and secondary phloem to the outside. The broad pith originates from derivatives of the rib meristem of the massive shoot apex. The seedling and young plant is composed of a shortened shoot (i.e., no internodes) produced by the PTM and rib meristem, and a large fleshy primary root which results from a diffuse growth pattern. Individual cells in both the pith and cortex of the root divide. Their derivatives divide at right angles to the original division plane. Thus, quartets and even octets of cells are recognizable and can be traced to individual parent cells.
MORPHOMETRY OF ORCHID SEEDS. III. NATIVE CALIFORNIA AND RELATED SPECIES OF GOODYERA, PIPERIA, PLATANTHERA AND SPIRANTHES
Authors: Healey Patrick L. , Michaud Justine D. , Arditti Joseph
Published: January 2018

Morphometric analysis of orchid seeds indicates that testa and embryo dimensions, color and morphology as well as the presence, absence or nature of reticulation on seed coat walls are of diagnostic value. These studies also point to structure and function correlations in orchid seeds.
STUDIES ON THE POLLINATION ECOLOGY OF TIPULARIA DISCOLOR (ORCHIDACEAE)
Authors: Whigham Dennis F. , McWethy Margaret
Published: January 2018

Tipularia discolor, a woodland orchid, flowers in mid‐summer when reproductive activity is minimal within the herb synusia. Tipularia is insect‐pollinated, and artificial crosses showed that seeds are produced after self‐pollination, intra‐inflorescence pollination, and outcrossing. The single nocturnal pollinator, Pseudaletia unipuncta (Noctuidae), located Tipularia populations within a day or two of anthesis. Pollinators were shown to be capable of utilizing portions of the inflorescences that contained the most nectar. After total nectar resources declined, pollinators were no longer active on the inflorescences, even though flowers and nectar were still available. The mode of pollinator activity seems to be closely related to floral morphology, although the moths are able, early in the flowering phenophase, to successfully obtain nectar without effecting any change in the reproductive status of flowers.
CHROMOSOME COUNTS OF COMPOSITAE FROM LATIN AMERICA
Authors: Jansen Robert K. , Stuessy Tod F.
Published: January 2018

Chromosome counts of Compositae are reported from Mexico, Central America, Ecuador, and Chile. First counts are reported for 20 species in Baccharis, Calea, Erigeron, Eupatorium, Heliopsis, Isocarpha, Liabum, Monactis, Pinaropappus, Senecio, Sigesbeckia, Simsia, Spilanthes, Verbesina, and Viguiera. Additional counts also are provided for 65 populations of taxa counted previously, of which 10 are new numbers. The systematic implications of certain of these counts are discussed.
EARLY OVULE DEVELOPMENT, MEGASPOROGENESIS AND MEGAGAMETOGENESIS IN SOLIDAGO GRAMINIFOLIA VAR. NUTTALLII AND SOLIDAGO CANADENSIS VAR. CANADENSIS (ASTERALES: ASTERACEAE: TUBULIFLORAE: ASTEREAE)
Authors: Smith Bruce B. , Johnson L. K.
Published: January 2018

A description of developmental sequences leading to maturity of the megagametophyte in two species of Solidago (L.) is presented to allow comparisons in: (1) dimensional relationships; (2) simultaneity of homotypic meiotic divisions of megasporogenesis; and (3) tetrad formation. A lack of consistency in the coordination of nucellar and integumental development, the occurrence of asynchrony in the mitotic divisions of megagametogenesis, polyantipodality in mature female gametophytes, and ease of tissue clearing are attributes common to both species. They are presented as additional distinguishing features to augment the characterization of the megagametophyte generation of Solidago, a highly plastic genus which is, embryologically, virtually unknown.
ULTRASTRUCTURE OF GLANDULAR OVARIAN TRICHOMES OF CYPRIPEDIUM CALCEOLUS AND C. REGINAE (ORCHIDACEAE)
Authors: Swanson Elizabeth S. , Cunningham William P. , Holman Ralph T.
Published: January 2018

Trichomes on the orchid ovary are a possible site of synthesis and secretion of the floral scent. Scanning electron microscopy of these trichomes shows a bulbous cell on a two‐celled stalk. Thin sections of the tip cell revealed the morphology of an active, secretory cell with unusual coated vesicles in the extra‐cellular deposition. Abundant smooth endoplasmic reticulum (ER) aggregated beneath the plasma membrane in the apical region of the cell and the limited dictyosomes in the cell suggest direct secretion by ER. Numerous lipid droplets are present in the apical area. Plastids, found only in the basal region of this cell, are more round in profile than typical chloroplasts and contain only a few unstacked thylakoids and a limited membranous reticulum. In addition to the normal plastid envelope, a double layer of membrane (probably ER) is tightly appressed to each dense, starch‐free plastid. Highly specialized morphology and subcellular localization of organelles suggest the secretory nature of these trichomes.
THE MARINE DIATOM THALASSIOSIRA OESTRUPII: STRUCTURE, TAXONOMY AND DISTRIBUTION
Authors: Fryxell G. A. , Hasle G. R.
Published: January 2018

Thalassiosira oestrupii (Ostenfeld) Hasle was studied from the southern Indian Ocean, Wed‐dell Sea, and northern Atlantic Ocean. It has the longer extension of the strutted process inwards, with three small columnar supports. A single strutted process near the central areola is 2‐3 areolae away from the single labiate process; both are usually visible in the light microscope. Two bands are septate: the valvocopula (intercalary band next to the mantle) is ribbed with a complex pattern of pores, while the other intercalary band (copula) present has but a single ring of large pores. T. oestrupii var. venrickae is described from warmer water with similar bands but with differences in areolae array and spacing of marginal strutted processes. It was found in the Gulf of Mexico, eastern and western Atlantic Ocean, Indian Ocean, and western Indian Ocean. The two varieties appear to differ in their ecology and distribution, with T. oestrupii var. oestrupii apparently a cosmopolitan oceanic taxon and T. oestrupii var. venrickae a tropical and subtropical continental shelf taxon.
EFFECTS OF ACIDIC SOLUTIONS ON SEXUAL REPRODUCTION OF PTERIDIUM AQUILINUM
Authors: Evans Lance S. , Conway Christine A.
Published: January 2018

Experiments were performed to determine the effects of acidic solutions on spermatozoid motility and fertilization of gametophytes of Pteridium aquilinum. Buffered solutions (0.0025 m) were used to simulate exposures to acidic precipitation for up to a 3.5 hr exposure. Experimental results suggest that the spermatozoid population can be subdivided into several groups with respect to pH sensitivity; about 25% spermatozoids are immobile one min after exposure to pH 6.1 buffer while about an equal percentage remain motile after 30 min exposure to buffer of pH 5.1. Between these two response extremes are two other subpopulations. One is quite sensitive to pH but shows some recovery if pH is between 5.6 and 6.1, while the second subpopulation does not seem to exhibit any motility recovery at all but is more resistant to acidity than the first subpopulation. To complement experiments that evaluate spermatozoid responses, experiments were performed to view the process of fertilization under controlled environmental conditions as well as under the canopy of a forest. Fertilization of gametophytes in uncovered petri dishes under a forest canopy was similar to results in aseptic culture after gametophytes were exposed to various pH levels and 86.6 μM sulfate. Although there were some differences between results obtained under aseptic culture conditions and cultures maintained under a forest canopy, it is evident that a lower buffer pH decreased fertilization. Fertilization at pH 4.5 and 3.6 was about one‐half that occurring at pH 6.1. Fertilization in gametophytes exposed to pH 3.0 was about 10‐20% of that occurring at pH 6.1. Addition of 86.6 μM sulfate decreased fertilization under all culture conditions. These experimental results suggest that fertilization in P. aquilinum may be used as a bioindicator of contaminants in rainwater. The results demonstrate that spermatozoid motility (and the process of fertilization) is more acid sensitive than gametophytic and sporophytic tissues.
DEVELOPMENTAL ANATOMY OF SECRETORY CAVITIES IN THE MICROSPOROPHYLLS OF GINKGO BILOBA L.
Authors: Ameele Randall J.
Published: January 2018

Two to five secretory cavities develop in the hump region of the microsporophylls of Ginkgo biloba. A developing cavity is first recognized as a spherical pocket of large, densely cytoplasmic cells (central secretory cells) in the median portion of a microsporophyll primordium. These cells degenerate and a small cavity is formed which is filled with the contents of the degenerating cells. Flattened incurved cells (parietal secretory cells) develop around the disintegrating central secretory cells and slough off into the enlarging cavity. Thus, the cavities develop by lysigeny. A mature cavity is surrounded by senescent parietal secretory cells, scanty parenchyma, and a loosely fitting epidermis. Histochemical tests indicate the presence of lipid and pectic substances in the cavities. Previous reports on the morphological interpretation and possible function role of the cavities are discussed in the light of the present investigation.
EFFECTS OF LIGHT AND DENSITY ON RESOURCE ALLOCATION IN A FOREST HERB, ASTER ACUMINATUS (COMPOSITAE)
Authors: Pitelka Louis F. , Stanton David S. , Peckenham Mary O.
Published: January 2018

Recent studies show that forest herbs have low sexual reproductive efforts (SRE) and high vegetative reproductive efforts (VRE) and that a variety of factors may affect the levels of reproduction and the distribution patterns of forest species.Aster acuminatusis a micro‐successional forest herb common in northern New England. Resource allocation patterns were determined for seven aster patches varying in density and light level. Plant density affects neither plant size nor any aspect of resource allocation, and VRE remains constant over all density and light levels. Light level is, however, significantly correlated with patch location, average plant size and average patch SRE. Only large plants produce flowers suggesting that light affects sexual reproduction indirectly through effects on plant size. The high rhizome and low seed survivorship of this species may partly explain the constant VRE and varying SRE levels, although the resource allocation patterns observed do not correspond well with the predictions of certain theoretical models.
UPTAKE AND LOSSES OF HEAVY METALS IN SEWAGE SLUDGE BY A NEW ENGLAND SALT MARSH
Authors: Giblin Anne E. , Bourg Alain , Valiela Ivan , Teal John M.
Published: January 2018

As part of an investigation on the potential of salt marshes to act as natural waste treatment systems, we are studying the cycling of heavy metals in Great Sippewissett Marsh, Massachusetts. For the last 7 yr, varying doses of fertilizer containing sewage sludge have been added to experimental plots. Changes in metal levels in the sediment, grasses, and animals have been monitored. Marsh sediments retained 20‐35% Cd, 20‐50% Cr, 60‐100% Cu, 55‐100% Pb, 80‐100% Fe, 55‐60% Mn and 20‐45% of the Zn added in the fertilizer. When compared with low marsh, high marsh areas retained a significantly greater fraction of all the added metals except Mn.
CYCLING OF Mn, Fe, Cu AND Zn BY EELGRASS, ZOSTERA MARINA L
Authors: Drifmeyer J. E. , Thayer G. W. , Cross F. A. , Zieman J. C.
Published: January 2018

Significant (P < 0.005) differences in Mn, Fe, Cu and Zn concentrations were found in different parts of eelgrass plants; i.e., roots and rhizomes, live blades, attached dead blades, and detritus. Imported vs. exported suspended particles of eelgrass blades did not differ in Mn, Fe, Cu or Zn content. Significant location effects, which varied with the type of plant tissue, were noted for Mn, Fe, Cu and Zn for three grass beds in the vicinity of Beaufort, NC. In simplified Mn, Fe, Cu and Zn budgets, eelgrass biomass is the largest biological reservoir, while eelgrass growth, senescence, and decomposition constitute the largest biological flux of these elements in this ecosystem.
TRACE METALS IN GIANT KELP, MACROCYSTIS
Authors: North Wheeler J.
Published: January 2018

Concentrations of 38 elements present in Macrocystis tissues are listed. Mean concentrations of Cu, Zn, Fe, and Mn were similar for samples of juvenile and adult sporophytes from field sites. Cu in Macrocystis tissues rose above background levels when concentrations of 0.05 to 0.1 μm were added to the culturing medium. Above‐normal accumulation for Zn occurred at 0.1 μm and for Fe at 10 μm. Tissue Mn appeared independent of the ambient Mn concentration over the ranges studied. Computations indicated that upwelling is important for N and P renewal to Macrocystis beds but may be less significant for import of trace metals.
ULTRASTRUCTURE OF THE METABASIDIUM OF AURICULARIA FUSCOSUCCINEA
Authors: McLaughlin David J.
Published: January 2018

Maturation of the metabasidium of Auricularia fuscosuccinea was followed with light microscopy and transmission electron microscopy. The basidium was divided into four compartments by septa which developed centripetally as in hyphae. Each septum formed a septal pore apparatus with imperforate pore caps. A band of electron‐dense material was situated in the middle of the septal pore. There was a large increase in the volume of cytoplasm, excluding vacuoles, in each compartment during sterigmal outgrowth. Compartments were evacuated in basipetal sequence and vacuole enlargement began at the base of a compartment only when sterigmal formation was well advanced. The septal pore apparatus was intact until late in maturation of a compartment when septal swellings occluded the pore. The metabasidial wall was differentiated from those of other hymenial and subhymenial cells. The pattern of basidial maturation is compared with that in other phragmobasidiate and holobasidiate fungi. Use of the septal pore apparatus for phylogenetic and taxonomic purposes is discussed, as is the concept of primary and adventitious septa.
THE ULTRASTRUCTURAL CYTOLOGY OF THE DIFFERENTIATING GUARD CELLS OF VIGNA SINENSIS
Authors: Galatis B. , Mitrakos K.
Published: January 2018

Structural differentiation of the guard cells of Vigna sinensis results from the integration of the following interrelated processes: a) intense activity of ribosomes, dictyosomes, endoplasmic reticulum (ER) membranes and mitochondria and patterned organization of microtubules; b) unequal thickening and ordered micellation of their walls and opening of the stomatal pore; and c) the divergent differentiation of the plastids. In differentiating guard cells, microtubules appear anticlinally oriented and more or less evenly distributed along the unthickened part of the dorsal wall and in the middle part of the ventral wall where thickening of the future pore occurs. In periclinal walls, microtubules fan away from the margins of the increasing thickening of the ventral wall and, later, from the rims of the stomatal pore towards the dorsal walls, parallel to the depositing radial microfibrils. Microtubules may be the cytoplasmic elements underlying guard‐cell morphogenesis. Although cell‐plate organization in guard‐cell mother cells does not seem to differ from that of other protodermal cells, the middle lamella of the ventral wall becomes electron‐translucent. The stomatal pore develops schizogenously from the internal and/or external ends of the ventral wall and proceeds inwards, remaining incomplete in most of the stomata of plants grown for 30 days in darkness and in some malformed ones which were developed after a prolonged action of colchicine. The guard cell, when approaching maturity, loses its organelle complexity and plasmodesmata, but it keeps a significant portion of its cytoplasm and organelles. Perigenous stomata generally exceed the size of mesoperigenous and mesogenous ones, develop large vacuoles and appear able to induce oriented divisions in their vicinity.
THE CONTROL OF THE ORIENTATION OF CELL DIVISIONS IN FERN GAMETOPHYTES
Authors: Cooke T. J. , Paolillo D. J.
Published: January 2018

Time‐lapse observations of filamentous fern gametophytes were used to evaluate whether the plane of cell division is referable to the plane of minimal surface area before and during the transition to two‐dimensional growth. Cell dimensions of the apical cell were related to the length/width ratios associated with minimal area in the transverse plane vs. longitudinal plane, by modeling the apical cell as a hemisphere subtended by a cylinder. Our working hypothesis predicts that filamentous growth is perpetuated by an apical cell geometry that makes the transverse division plane the orientation of minimal surface area, whereas the transition to two‐dimensional growth (longitudinal division of the apical cell) occurs once the longitudinal plane becomes the position of minimal surface area. The predictions of this hypothesis are fulfilled regardless of variations in light intensity and light quality, the presence of regulators of metabolism, or whether the experimental perturbation causes a corresponding selective inhibition of the transition to two‐dimensional growth. Thus, the control of the plane of cell division in this system seems to depend on thermodynamic considerations of surface area. Furthermore, we favor the conclusion that the role of the genome in the transition to two‐dimensional growth involves its influence on apical cell dimensions rather than the induction of specific genes for specific morphogenetic mRNAs.
A QUANTITATIVE STUDY OF VARIATION IN THE CHENOPODIUM ATROVIRENS‐DESICCATUM‐PRATERICOLA COMPLEX
Authors: Reynolds James F. , Crawford Daniel J.
Published: January 2018

Multivariate analyses were applied to 96 populations (OTUs) of plants, traditionally referred to Chenopodium atrovirens, C. desiccatum, and C. pratericola, in an attempt to evaluate the numerous and often contradictory taxonomic treatments of plants in this complex. The study consisted of two major parts. The first involved the use of cluster and principal components analyses using 14 morphological characters on the entire set of 96 OTUs to search for phenetically distinct groupings; these analyses were conducted without knowledge of traditional taxonomic designations of individual OTUs. Three reasonably well‐defined groups emerged from these preliminary analyses. When traditional taxonomic designations were applied to member OTUs of each group, one group was composed primarily of C. atrovirens, another of C. pratericola and the third of C. desiccatum. The second part of the study utilized canonical analysis to: 1) confirm the integrity of the phenetic groups, 2) to classify OTUs difficult to identify to species using traditional methods, and 3) to provide an evaluation of characters important in the separation of these groups. This analysis confirmed the integrity of the groups and provided a classification to species of nearly all of the otherwise difficult OTUs. In addition, canonical analysis demonstrated that a combination of characters was important in the separation of the phenetic groups.
TRICHOMES AND CANNABINOID CONTENT OF DEVELOPING LEAVES AND BRACTS OF CANNABIS SATIVA L. (CANNABACEAE)
Authors: Turner Jocelyn C. , Hemphill John K. , Mahlberg Paul G.
Published: January 2018

Trichome density and type and cannabinoid content of leaves and bracts were quantitated during organ ontogeny for three clones of Cannabis sativa L. Trichome initiation and development were found to occur throughout leaf and bract ontogeny. On leaves, bulbous glands were more abundant than capitate‐sessile glands for all clones, although differences in density for each gland type were evident between clones. On pistillate bracts, capitate‐sessile glands were more abundant than the bulbous form on all clones, and both types decreased in relative density during bract ontogeny for each clone. The capitate‐stalked gland, present on bracts but absent from vegetative leaves, increased in density during bract ontogeny. The capitate‐stalked gland appeared to be initiated later than bulbous or capitate‐sessile glands during bract development and on one clone it was first found midway in bract ontogeny. Nonglandular trichomes decreased in density during organ ontogeny, but the densities differed between leaves and bracts and also between clones. Specific regulatory mechanisms appear to exist to control the development of each trichome type independently. In addition, control of trichome density seems to be related to the plant organ and clone on which the gland type is located. Cannabinoid synthesis occurs throughout organ development and is selectively regulated in each organ. Typically, cannabinoid synthesis occurred at an increasing rate during bract development, whereas in developing leaves synthesis occurred at a decreasing rate. Cannabinoid content on a dry weight basis was generally greater for bracts than leaves. Analyses of leaves indicate that other tissues in addition to glands may contain cannabinoids, while for bracts the gland population can accommodate the cannabinoid content for this organ. The functional significance of trichomes and cannabinoids in relation to evolution is discussed.
ALLELOPATHIC MECHANISMS OF VELVETLEAF (ABUTILON THEOPHRASTI MEDIC., MALVACEAE) ON SOYBEAN
Authors: Colton Craig E. , Einhellig Frank A.
Published: January 2018

Sampling in a soybean field established that presence of velvetleaf (A. theophrasti) weeds interfered with soybean production. Number of soybean pods and number of pods/stem were significantly lower in transect segments adjacent to velvetleaf plants. In bioassays for phytotoxicity of velvetleaf, several dilutions of aqueous extracts from fresh field‐collected leaves depressed germination of radish seeds and inhibited growth of soybean seedlings. Seed germination bioassays from eluates of chromatograms developed in one dimension showed that two of three bands containing phenolic compounds were inhibitory to radish seed germination. Soybeans inhibited by aqueous velvetleaf extracts had increased diffusive resistance, suggesting partial stomatal closure. Inhibited plants also gave evidence of water stress, with leaf water potentials often as low as –20 bars and reduced water content, when compared with controls. Quantification of chlorophyll on a leaf area basis showed that chlorophyll of inhibited plants was below controls. These data demonstrate the allelopathic potential of velvetleaf and suggest that interference with water balance and chlorophyll content may be two mechanisms of inhibitory action of toxins present in the leaves of velvetleaf.
AN ANATOMICAL BASIS FOR THE DIVERGENT FLORAL FORMS IN THE CLEISTOGAMOUS SPECIES, LAMIUM AMPLEXICAULE L. (LABIATAE)
Authors: Lord Elizabeth M.
Published: January 2018

The pattern of variation in mature corolla form has been documented throughout the main shoot inflorescence of the cleistogamous species Lamium amplexicaule L. A heteroblastic development occurs within the cymose inflorescence at a single node as well as between different nodes. Variation involves an increase in cell number and expansion in the upper corolla and also an increase in cell number in the anther sacs, expressed as pollen count increases, in progressively produced flowers in the inflorescence. The corolla base region in all flowers shows an increased cell expansion from the first produced cleistogamous (CL) flowers to the later produced chasmogamous (CH) flowers which expand at anthesis. Cell numbers are equivalent in the corolla base region of all flowers. It appears that in successively produced flowers in the inflorescence, prolonged cell division and expansion occurs in both the upper corolla region and the anthers until a threshold is reached, at which point flowers may undergo anthesis and become CH. The CL corolla form in Lamium amplexicaule is not caused by a lack of cell expansion alone; rather, both cell division and expansion are arrested in the upper corolla region.
A SUMMARY OF THE TAXA IN THE VASCULAR FLORA OF THE UNITED STATES, CANADA AND GREENLAND
Authors: Kartesz John T. , Bell C. Ritchie
Published: January 2018

A tabular summary, by family, of the 56,431 computerized names of those native and naturalized plant taxa included in the “Synonymized checklist of the vascular flora of the United States, Canada and Greenland” (including Alaska, Hawaii, Puerto Rico and the U.S. Virgin Islands) indicates a flora of 21,588 species in 2,921 genera in 254 families. There are also 740 named hybrids and, under current concepts, 2,491 subspecies and 8,008 varieties in our flora. There are 20,429 pertinent or “manual level” synonyms, with the number of synonyms exceeding the number of accepted names in many families (especially those families of high agricultural, horticultural or other economic importance).
INFLUENCE OF SEED SOURCE UPON PHENOLOGY OF FLOWERING OF SPARTINA ALTERNIFLORA LOISEL. AND THE LIKELIHOOD OF CROSS POLLINATION
Authors: Somers G. Fred , Grant Donna
Published: January 2018

Seedlings of Spartina alterniflora Loisel., from seed harvested from nine marshes ranging from Maine to Virginia, were grown for three seasons in plots established on two different soils in Delaware and were flooded regularly with water from two estuarine sources. Substantial differences in the time of flowering were observed. Each year plants from Maine seed flowered first and were followed by those from Connecticut and New York. Last to flower were plants from Virginia seed. The latter initiated flowering after flowering of the Maine source had been completed. These two would not cross‐pollinate under this circumstance. The phenology of anthesis and number of seeds set on inflorescences enclosed in bags indicate that this species is largely open pollinated.
OCCURRENCE OF LOW MOLECULAR WEIGHT AND HIGH CYSTEINE CONTAINING ALBUMIN STORAGE PROTEINS IN OILSEEDS OF DIVERSE SPECIES
Authors: Youle Richard J. , Huang Anthony H. C.
Published: January 2018

The proteins in the oilseeds of species from 11 families, including sunflower, mustard, linseed, almond, lupin, peanut, cucumber, Brazil nut, hazelnut, yucca, castor bean, and cottonseed were studied. Sucrose gradient centrifugation showed that a substantial proportion of the total seed protein from each species migrated with a 2S sedimentation coefficient. The 2S proteins, being water‐soluble and thus termed albumins, comprised 20–60% of the total seed proteins, while faster migrating globulins comprised the rest. The amino acid compositions of the 2S proteins were characterisitic of storage proteins by having a high amide content. However, the 2S proteins are different from the classical globulin storage proteins in having a high content of cysteine. It is proposed that 2S albumins are seed storage proteins with a wide distribution and with chemical properties distinct from those of the globulin storage proteins. They play an additional and unique role of providing sulfur reserve for germination.
STRUCTURAL CHANGES IN POPULUS DELTOIDES TERMINAL BUDS AND IN THE VASCULAR TRANSITION ZONE OF THE STEMS DURING DORMANCY INDUCTION
Authors: Goffinet Martin C. , Larson Philip R.
Published: January 2018

Morphological and anatomical changes in shoots of vigorously growing cottonwood plants (Populus deltoides Bartr.) were studied during dormancy induction in 8‐hr short days (SD) and in control plants grown in 18‐hr long days (LD). Pronounced structural changes occurred in terminal buds after 4 wk and full dormancy was achieved in 7 wk of SD. Leaf expansion ceased after 5 wk of SD as foliage leaves matured to the terminal bud base at leaf plastochron index 0 (LPI 0). Within the bud, total leaf length (lamina + petiole) decreased and stipule length increased progressively each week; thus, the ratio total leaf length/stipule length decreased rapidly, especially at the position of incipient bud‐scale leaves LPI ‐ 1 and LPI ‐ 2. These bud‐scale leaves were fully developed by wk 6 and were derived from enlarged stipules and aborted laminae. The full complement of primordia within the bud at the start of SD eventually matured as foliage leaves and the first bud‐scale leaf (LPI ‐ 1) was initiated immediately following transfer to SD. Acropetal advance of the primary‐secondary vascular transition zone (TZ) was associated with leaf maturation. However, it did not advance throughout the entire vascular cylinder as in LD, but only in those leaf traces serving mature leaves beneath the terminal bud. In both LD and SD treatments the same linear relationship was maintained between LPI of the TZ and LPI of the most recently matured leaf; both parameters simultaneously increased in LD and decreased in SD. Thus, the relationship between leaf maturation and advance of the TZ was maintained irrespective of environment.
THE TIMING OF AND EFFECT OF TEMPERATURE ON AUXIN‐INDUCED HYPONASTIC CURVATURE OF THE BEAN PRIMARY LEAF BLADE
Authors: Hayes Alice B. , Lippincott James A.
Published: January 2018

Detailed examination of the hyponastic curvature of the primary bean leaf blade in response to indoleacetic acid (IAA) shows that curvature begins within 15 min after application and increases to a maximal rate at 20 to 30 min. A second application of IAA results in a second curvature maximum when applied 1.5 hr or more after the first. Washing experiments indicate IAA uptake is largely complete by about 20 min after application, suggesting the return to planar form is accompanied by the uptake and passage of a wave of IAA through the responding cells. The rate of curvature decreases as the temperature is lowered, particularly below 14 C; at low concentrations (10–4 m) the rate of response to 2,4‐dichlorophenoxyacetic acid and 2,4,5‐trichlorophenoxypropionic acid is slower than that for IAA and naphthaleneacetic acid. These differences are proposed to reflect the involvement of the polar auxin transport system in the response. The leaves of bean seedlings exposed to 4 C develop hyponastic curvatures when returned to normal growth temperature; 5 min treatment is sufficient to induce this response, and with longer treatments, greater curvatures are obtained. This curvature is inhibited by application of 2,3,5‐triiodobenzoic acid (TIBA) to the undersurface of the leaf at the beginning of the cold treatment. The results are consistent with a model of planar plageotropic growth regulation in the leaf blade in which auxin produced by cells in the upper portion of the blade is transported by the polar transport system through cells in the lower portion that are growth limited by auxin supply. The hyponastic and epinastic effects caused by exogenous application of auxin or TIBA and of cold treatments are considered to result from changes in this auxin supply.
THE VEGETATIVE ANATOMY OF JAUMEA CARNOSA (LESS.) GRAY (ASTERACEAE), A SALT MARSH SPECIES
Authors: Omer Lucy St. , Moseley Maynard F.
Published: January 2018

Certain anatomical characters of Jaumea carnosa, a salt marsh plant, which are diagnostic, adaptive, or otherwise important for an ecological anatomy study are described. The characters which follow are noteworthy. The plant has a sympodial construction forming an extensively branched rhizome system, and erect lateral shoots which eventually become prostrate. The leaves have very few, and only moderately developed succulent characters, such as: poorly defined palisade tissue, central mesophyll cells which are slightly enlarged anticlinally, and a complete lack of sclerification in the mesophyll. A continuous schizogenous canal system lined with epithelial cells lies in the ground tissues of all stem forms and leaves. The phellem is composed of thin‐walled, only lightly suberized cells. Very broad parenchymatous areas develop in the secondary tissues of the rhizome, associated with a slowing of vascular cambial activity which creates depressions in the axis. Adventitious roots arise from ground tissues close to the primary xylem and from interfasicular regions close to the primary phloem in the rhizomes.
SYNGAMY AND RESTING BODY DEVELOPMENT IN CHYTRIOMYCES HYALINUS (CHYTRIDIALES)
Authors: Miller Charles E. , Dylewski Daniel P.
Published: January 2018

Somatogamy by rhizoidal anastomosis initiates sexual reproduction and resting body formation in Chytriomyces hyalinus Karling. At least two external factors influence somatogamy: the level of nutrients available and the chance association of rhizoids of young thalli (germlings). Syngamy and resting body development occurs in axenic culture when germlings are developing on a nutrient‐depleted substrate and when the rhizoids of two germlings (contributing thalli) anastomose. After anastomosis, the contents of the two contributing thalli flow into a swelling (incipient fusion body) which develops near the point of anastomosis. Nuclear fusion occurs in the fusion body (incipient resting body). After nuclear fusion, the resting body continues to enlarge, its wall thickens, and lipoid inclusions coalesce to form a large refractile globule. This sexual process is better referred to as somatogamy rather than Siphonaria‐type sexual reproduction.
FLORAL STRUCTURE AND MECHANISM IN LOASACEAE
Authors: Brown Dennis K. , Kaul Robert B.
Published: January 2018

Aspects of floral morphology and vascular anatomy, pollination, and seed dispersal are presented for 14 species of seven genera of Loasaceae, sensu lato: (Blumenbachia, Caiophora, Cevallia, Eucnide, Loasa, Mentzelia, Petalonyx). Floral specializations such as elaborate staminodia and centrifugal androecial development parallel specializations in pollination. The affinities of the subfamilies Mentzelioideae, Loasoideae, and Gronovioideae are supported by comparative vascular anatomical evidence, and differences in direction of androecial initiation are interpreted as alternative expressions of a common pattern.
DENSITY‐MEDIATED SEED AND STOLON PRODUCTION IN VIOLA (VIOLACEAE)
Authors: Thompson D. A. , Beattie A. J.
Published: January 2018

Seed and stolon production and spatial distribution were studied in two populations of Viola blanda and two populations of Viola rostrata in West Virginia. Mean individual plant biomass and the proportion of the population producing seeds and/or stolons both decreased with density. Both species possessed a characteristic “threshold” weight required before the onset of seed production; a similar minimum threshold weight was also reached before stolons were produced. It is suggested that competition at higher densities results in fewer individuals reaching the threshold weight for seed or stolon production. Thus, the density response appears as a reduction in the proportion of plants producing seeds or stolons.
POLLINATION SYSTEMS IN PASPALUM DILATATUM POIR. (POACEAE): AN EXAMPLE OF INSECT POLLINATION IN A TEMPERATE GRASS
Authors: Adams Dwight E. , Perkins W. Ethen , Estes James R.
Published: January 2018

The pollination of Paspalum dilatatum was studied in south‐central Oklahoma during the summer of 1979. Pollen was liberated between 0700–0900 hr except on humid mornings (RH ≤ 80%), when there was a delay of 2–3 hr and a reduction in the total air‐borne pollen concentration. A rapid decrease in air‐borne pollen concentration with distance from the source results from: 1) individual pollen grains larger (50–70 μ in diam) than typical wind‐pollinated plants, and 2) some pollen dispersed as clusters of grains. Several floral characters of P. dilatatum led to a hypothesis that this perennial grass may be entomophilous as well as anemophilous. Not only were the pollen grains larger than most other wind‐pollinated taxa but the species produced fewer than 2,500 pollen grains per ovule. Three additional observations corroborate this view: 1) solitary bees (Halictidae) actively collect pollen during the morning, 2) the number of pollen grains per stigma was significantly (P < 0.001) greater on racemes exposed to both wind and bees than on racemes exposed only to wind, and 3) the combination of bees and wind as pollinators significantly (P < 0.001) increased seed set compared to wind alone.
SCANNING ELECTRON MICROSCOPY OF RHIZOSHEATHS OF ORYZOPSIS HYMENOIDES
Authors: Wullstein L. H. , Pratt S. A.
Published: January 2018

Structural features and microorganisms associated with rhizosheaths (sand grain root sheaths) of Oryzopsis hymenoides were examined by scanning electron microscopy. Rhizosheath structure appears to depend primarily on the extent of root hair growth and the bonding between root hairs and sand grains. Several sources of bonding agents are suggested, but plant products may be the most important. Microorganisms, usually rod forms, were frequently observed in association with coatings, resembling mucilage, on root surfaces and root hairs. The fungus Olpidium and unusual bacterial forms resembling Ancalomicrobium and Hyphomicrobium were observed on or near root surfaces. Mycorrhizae were not observed nor could the presence of actinomycetes be attested to.
EXPERIMENTAL ECOLOGICAL GENETICS IN PLANTAGO IV. EFFECTS OF TEMPERATURE ON GROWTH RATES AND REPRODUCTION IN THREE POPULATIONS OF PLANTAGO LANCEOLATA L. (PLANTAGINACEAE)
Authors: Teramura Alan H. , Antonovics Janis , Strain Boyd R.
Published: January 2018

The effects of temperature on growth rates and flowering responses of Plantago lanceolata L. populations sampled from open, shaded, and sunflecked habitats were studied in controlled environments. A large number of characteristics were phenotypically plastic in response to a broad range of temperatures. Low night temperatures substantially reduced reproductive effort, whereas high temperatures produced a reduction in total biomass. Temperature had little effect on leaf or inflorescence production rates, other than at very low temperatures. The phenotypic plasticity observed in the growth chamber correlated well with the observed seasonal phenology. Genetic differences were found in inflorescence height and total plant productivity. The rapid growth rate, the high reproductive effort, and generally broad temperature optimum to moderate temperatures are consistent with the occurrence of P. lanceolata in a wide variety of disturbed habitats in temperate latitudes.
ULTRASTRUCTURAL INVESTIGATIONS ON THE TWO‐NUCLEATE POLLEN GRAIN OF TILLANDSIA CAPUT‐MEDUSAE MORR. (BROMELIACEAE)
Authors: Brighigna Luigi , Fiordi Ambretta Cecchi , Palandri Maria R.
Published: January 2018

The fine structure of the pollen grain of Tillandsia caput‐medusae Morr. (Bromeliaceae) prior to germination has been studied. The development, after the first mitosis, is here schematized in three stages which are in accordance with the main steps described in angiosperms. The ultrastructural modifications occurring in the generative and vegetative cells are discussed in view of their different destiny. The results obtained are compared with the data known about tropical orchids and epiphyteic plants like Tillandsia. The following differences have been observed: a large vacuole in the vegetative cell; rapid thinning of the wall between the generative and vegetative cells; great quantity of ribosomes and rough endoplasmic reticulum surrounding the vacuoles in the generative cell. The above‐listed ultrastructural features may have a meaning, considering the peculiar environmental conditions in which the epiphytism of Tillandsia is achieved.
THE ONTOGENY OF THE PRIMARY THICKENING MERISTEM OF ATRIPLEX HORTENSIS L. (CHENOPODIACEAE)
Authors: Yarrow Gary L. , Popham R. A.
Published: January 2018

Seedlings of Atriplex hortensis were studied to ascertain; 1) in which organ the primary thickening meristem (PTM) first differentiates; 2) the direction of differentiation of the PTM, and 3) the pattern of differentiation of conjunctive tissue. The PTM initially differentiates in pericycle of the primary root base 11 days after emergence of the primary root. It then differentiates in the transition region of the hypocotyl, mostly in cells of pericycle between pairs of vascular bundles. In the upper hypocotyl, PTM differentiates by day 20 in the inner layer of cortical parenchyma. In the epicotyl, PTM apparently differentiates in the inner layer of cortex, by day 24. Desmogic xylem differentiates from radial files of internal conjunctive tissue cells and desmogic phloem differentiates opposite desmogic xylem strands from newly formed cells of external conjunctive tissue. No interfascicular cambium differentiates in the root, hypocotyl, or epicotyl.
ULTRASTRUCTURE AND DEVELOPMENT OF THE NEXINE AND INTINE IN THE POLLEN WALL OF SILENE ALBA (CARYOPHYLLACEAE)
Authors: Shoup Jane R. , Overton Jane , Ruddat Manfred
Published: January 2018

Nexine and intine development in Silene alba (Caryophyllaceae) was investigated by electron microscopy and enzyme cytochemistry. Nexine‐2 forms by deposition of sporopollenin along unit membrane lamellae closely associated with the microspore plasma membrane in the late tetrad stage. After the callose wall dissolves, electron density increases along the tangentially oriented fibers of the proximal primexine, forming nexine‐1. When the exine is essentially complete, the intine begins to develop. In the nearly mature microspore, acid phosphatase activity appears in the peripheral cytoplasm just prior to its extrusion into the intine of the mature pollen grain.