bluuebunny/crossref_metadata_2025 huggingface dataset:
ULTRASTRUCTURE OF CEPHALEUROS VIRESCENS (CHROOLEPIDACEAE; CHLOROPHYTA). IV. ABSOLUTE CONFIGURATION ANALYSIS OF THE CRUCIATE FLAGELLAR APPARATUS AND MULTILAYERED STRUCTURES IN THE PRE‐ AND POST‐RELEASE GAMETES
Authors: Chapman Russell L. , Henk Margaret C.
Published: January 2018

Transmission electron microscopy of pre‐release and post‐release biflagellate gametes ofCephaleuros virescenshas produced comparative data on these cells and on the detailed absolute arrangement of the flagellar apparatus. In all major respects including the presence of two multilayered structures (MLS's) the closely compacted, non‐motile but mature pre‐release gametes are similar to the mature, free swimming post‐release gametes. The elongated shape of the free‐swimming gametes differs from the more compact form of the pre‐release gametes, but does not reflect a major difference in the arrangement of internal components. The flagella are bilaterally keeled and each keel contains a cylindrical element. Each flagellar base is encircled by a densely staining collar of modified plasmalemma at the point of entry into the apical papilla. The equal anterior flagella enter the papilla from opposite sides; their basal bodies are parallel and overlapping. Each terminates in a densely staining terminal cap. No capping plate is present. Each basal body is associated both with a three‐layered MLS, the anterior layer of which becomes a lateral microtubular spline of 2 to 8 microtubules, and with an additional medial compound root of two layers of microtubules (2 over 4 or 5). Both the compound microtubule root and the spline may acquire additional microtubules as they extend distally in close proximity to mitochondria and the plasmalemma. No striated roots, or rhizoplasts, have been observed. Two densely staining plaques are associated with the plasma membrane at specific anterior sites and may be comparable to the presumptive mating structures seen in other green algal motile cells. The reversed bilateral symmetry of the cells produces two possible arrangements of the flagellar apparatus, namely, a 11/5 (or left‐handed) arrangement or a 1/7 (or right‐handed) arrangement. Only 11/5 cells have been found. Despite the presence of distinct multilayered structures, some aspects of the gametes ofCephaleurosquite closely resemble the cruciate motile cells of algae now regarded by some authors as typical of Ulvophyceae, sensu Stewart and Mattox.
COMPARATIVE FLOWER DEVELOPMENT IN THE CLEISTOGAMOUS SPECIES VIOLA ODORATA. II. AN ORGANOGRAPHIC STUDY
Authors: Mayers Anna M. , Lord Elizabeth M.
Published: January 2018

Comparative ontogenetic study of the shoot apices and floral primordia of Viola odorata revealed significant differences between the dimorphic flowers in this cleistogamous (CL) species. Both the shoot apices and floral primordia of plants in the chasmogamous (CH) phase are larger than those in the CL phase. Form divergence occurs at petal initiation, and by the time of meiosis in the anthers, the CH flower is considerably larger in size. Mature CL flowers exhibit morphological modifications of the anterior petal spur, repressed growth of the staminal nectaries, and a recurving of the style which remains enclosed within the cone formed by five terminal anther caps. Pollination in the CL flower occurs as a result of pollen tubes penetrating the wall of an undehisced anther sac and growing to the stigmatic cavity nearby.
TILLERING AND MORTALITY OF THE SALT MARSH CORDGRASS, SPARTINA ALTERNIFLORA
Authors: Reidenbaugh Thomas G.
Published: January 2018

Recruitment and mortality of Spartina alterniflora tillers and culms were estimated from measurements of live standing crops at Wallops Island, Virginia. Stands of tall and medium form grass produced from 452 to 1,227 tillers m−2 yr−1. Those tillered in spring lengthened into culms their first year, while those tillered in late summer and fall may have overwintered and lengthened into culms their second year. Biennial growth was most prevalent in tall form Spartina. Fifty‐six to sixty‐one percent of all tillers died before lengthening into culms. Of the remainder, 9 to 56% died as culms before the time of flowering. Sixty‐three percent of the surviving culms of tall form Spartina flowered, compared to only 14 to 23% in medium form. Mortality of tillers and culms removed 16 to 35% of the annual production of Spartina biomass from live standing crops before the time of flowering.
QUANTITATIVE STUDIES OF THE VEGETATIVE SHOOT APEX OF EQUISETUM SCIRPOIDES
Authors: Gifford Ernest M. , Kurth Eva
Published: January 2018

Equisetum scirpoides Michx., propagated from a single clone, was grown in a controlled growth chamber at 24 ± 1 C under a photoperiod of 16 hr light/8 hr darkness. The apical cell of aerial vegetative shoots gives rise to derivatives (merophytes) in a helical sequence. Each newly formed merophyte divides anticlinally to form two superposed cells that are parallel to a lateral face of the apical cell. Radial longitudinal divisions then take place in the two superposed cells. Shoot tips were fixed every 2 hr for 24 hr to determine the mitotic index of the apical cell, six subjacent cells, and the remaining cells above the level of leaf initiation. Average mitotic indices for the 24‐hr period were 3.9%, 3.9%, and 7.0%, respectively. The results indicate that the apical cell is quite active mitotically; there was no clear evidence of endopolyploidy in cells of the shoot apex, young leaves or in the developing cortex, based upon cytophotometric measurements of DNA content.
ULTRASTRUCTURE AND DEVELOPMENT OF THE INACTIVE STOMATA OF ANABASIS ARTICULATA (FORSK.) MOQ.
Authors: Gedalovich E. , Fahn A.
Published: January 2018

The guard cells of Anabasis articulata mature and senesce a short distance from the intercalary meristem in which they form. When the guard cells reach final size, their ultrastructure is similar to that of stomata of other plants. At this stage, they contain clearly definable, numerous mitochondrial profiles, chloroplasts with starch grains and plastoglobuli, active Golgi bodies, a large nucleus that stains deeply for chromatin and large vacuoles. During later stages of development the whole protoplasmic content becomes very dense, with myelin‐like figures and crystals appearing in the vacuoles. The cell walls thicken considerably. This is especially true of the tangential walls, where the microfibrils of different lamellae vary in their orientation. It is suggested that as a result of these ultrastructural changes the guard cells lose the ability to move.
ORIGIN OF TRIPSACUM ANDERSONII (GRAMINEAE)
Authors: deWet J. M. J. , Fletcher G. B. , Hilu K. W. , Harlan J. R.
Published: January 2018

Tripsacum andersonii Gray (Gramineae) is a species with 2n = 64 chromosomes. Chromosome behaviour during meiosis of microsporogenesis suggests that the species combines three homologous haploid Tripsacum genomes of x = 18 (54 chromosomes), and an alien haploid genome of x = 10 chromosomes. Cytogenetic studies indicate that T. andersonii originated as a hybrid between a species of Tripsacum (2n = 36) and a species of Zea (2n = 20). Comparative morphology and flavonoid chemistry fail to identify the Zea species involved in this intergeneric hybrid. Chromosome morphology suggests that it was either Z. mays L. subsp. mays (domesticated maize) or subspecies mexicana (Schrad.) Iltis (annual teosinte). The Tripsacum parent probably was T. latifolium Hitchc. of Central America. It resembles T. andersonii in vegetative morphology. Tripsacum maizar Hernandez et Randolph and T. laxum Nash, which resemble T. andersonii in flavonoid chemistry, are eliminated as possible parents on the basis of growth habit and the morphology of their hybrids with maize.
LICHEN HERBIVORE PREFERENCE: A TEST OF TWO HYPOTHESES
Authors: Lawrey James D.
Published: January 2018

Field data from a saxicolous lichen community in Shenandoah National Park, Virginia, suggested that the slug Pallifera varia grazed more frequently on certain lichen species than would be expected if it fed randomly. Two hypotheses might explain this grazing pattern. The preference hypothesis, that slugs select lichens of highest quality, was tested by measuring the concentration of essential elements in lichens eliciting high and low preference by slugs. Lichens with the highest element contents were assumed to be of the highest quality to herbivores. The avoidance hypothesis, that preference by slugs actually results from the rejection of unpalatable species, was tested by offering slugs choices of baited filter‐paper disks impregnated with secondary products of the lichen species in question. Results suggested that preferred lichens had significantly lower concentrations of N, P, and Ca, and that avoided lichens produced secondary products that effectively inhibited Pallifera grazing activity. These results suggested that the avoidance hypothesis was the better explanation for nonrandom Pallifera grazing patterns. Furthermore, they suggested that lichens with the highest concentrations of essential elements are most likely to produce defense compounds, an observation that supports predictions to explain patterns of chemical defense in vascular plants.
COMPARISON OF STAGES OF VESICULAR‐ARBUSCULAR MYCORRHIZA FORMATION IN SUDANGRASS GROWN AT TWO LEVELS OF PHOSPHORUS NUTRITION
Authors: Schwab S. M. , Menge J. A. , Leonard R. T.
Published: January 2018

Several stages of the infection process by the vesicular‐arbuscular mycorrhizal fungus, Glomus fasciculatus, were compared in roots of sudangrass (Sorghum vulgare) grow in phosphorus‐deficient or phosphorus‐amended soil. Germination of fungal spores in soil and morphology of the fungus within the root were not affected by phosphorus amendment. There were no significant differences between phosphorus treatments in the percent of root infected or total length of root infected by the fungus until 25 days after inoculation. Between 25 and 35 days after inoculation, the percent of root infected increased 5‐fold, and the total length of infected root increased nearly 30‐fold in the phosphorus‐deficient plants. Neither percent nor total length of infected root increased significantly over the same time period in the phosphorus amended plants. The increase in mycorrhiza formation in the phosphorus‐deficient plants was associated with an increase in the number of penetrations into the root by the fungus, but not with an increase in the size of individual infections. Proliferation of external hyphae was greater in phosphorus‐deficient than phosphorus‐amended plants 25 days after inoculation. These data suggest that phosphorus nutrition of the host does not affect prepenetration stages of mycorrhiza formation by G. fasciculatus. However, external hyphal growth following initial penetration of the host is reduced with phosphorus amendment. The subsequent ability of the fungus to form secondary penetrations is thus decreased, ultimately resulting in the overall decrease in mycorrhiza formation commonly observed in plants receiving high levels of phosphorus.
ULTRASTRUCTURE OF OSMOPHORES IN RESTREPIA (ORCHIDACEAE)
Authors: Pridgeon Alec M. , Stern William Louis
Published: January 2018

Osmophores of the myophilous genus Restrepia (Orchidaceae) were studied developmentally at the ultrastructural level. They are located at petal apices and on the adaxial surface of the dorsal sepal apex. Up to and through anthesis a dense, osmiophilic exudate is synthesized probably in endoplasmic reticulum or in plastids of papillose epidermal cells, and then appears to be transported through the plasmalemma by granulocrine elimination. As the exudate is amassed, the cuticle ruptures to form numerous pores that extend from the cell wall. Mitochondria and amyloplasts are especially abundant at anthesis. From anthesis to post‐anthesis, lipid droplets appear in the cytoplasm and vacuoles of epidermal cells, and frequency of cell organelles drops markedly with increasing vacuolation.
SCHIZOGENY AND ULTRASTRUCTURE OF DEVELOPING LATEX DUCTS IN MAMMILLARIA GUERRERONIS (CACTACEAE)
Authors: Wittler George H. , Mauseth James D.
Published: January 2018

The schizo‐lysigenous latex ducts of Mammillaria guerreronis, sect. Subhydrochylus, were examined by optical and electron microscopy. These ducts are complex having a distinct outer epithelium without intercellular spaces and an inner epithelium in which schizogenous spaces arise. Schizogeny begins with formation of bulbous pockets and/or production of dark streaks in certain walls. Spaces formed by these processes ultimately contain a combination of electron dense materials, vesicles, and numerous thin, convoluted wall layers. Schizogeny may be responsible for initial formation of lumen and latex and may also separate some inner epithelial cells from the surrounding layers. Lysigeny of the inner epithelial cells contributes materials to the latex and allows enlargement of the duct. The inner epithelial cells contain mitochondria, dictyosomes, apparently functional nuclei, and numerous vesicles. The outer epithelium has fewer vesicles than the inner epithelium. Schizo‐lysigeny in the members of sect. Subhydrochylus is considered to be ancestral to the strict lysigeny of the members of sect. Mammillaria. The inner and outer epithelia of M. guerreronis are thought to be homologous to the lumen and epithelium respectively of M. heyderi.
ANATOMICAL AND ULTRASTRUCTURAL ASPECTS OF THE ANT‐FOOD CELL OF PIPER CENOCLADUM C.DC. (PIPERACEAE)
Authors: Rickson Fred R. , Risch Stephen J.
Published: January 2018

Piper cenocladium is a common understory species in the wet primary forested areas of Costa Rica. The plant possesses a petiole chamber which is usually occupied by the ant Pheidole bicornis. The plant/ant relationship is unique in that the ant must be present for meaningful numbers of ant‐food bodies to be differentiated. The food body is a lipid storing, single cell developed from one adaxial petiole epidermal cell. Cellular aspects of this differentiation process are described with particular reference to nucleolar ultrastructure.
AXENIC CULTURE OF THALASSIA TESTUDINUM BANKS EX KÖNIG (HYDROCHARITACEAE)
Authors: Moffler Mark D. , Durako Michael J.
Published: January 2018

Cultures ofThalassia testudinumwere established and maintained in the absence of other detectable organisms. Axenic cultures were initiated using surface sterilized seeds which were aseptically dissected from surface sterilized fruits. Seedlings were cultured in 75‐ml (25‐mm × 200‐mm) culture tubes containing 30 ml of rooting substrate and 40 ml of chemically defined seawater media. Seedlings and culture media were analyzed for microbial contamination after 42 days of culture utilizing standard marine bacterial/fungal isolating procedures and by light and scanning electron microscopy. Axenic seagrass cultures allow physiological studies such as nutrient assimilation kinetics, rhizosphere and phyllosphere microbial interactions through mono‐ and poly‐axenic seagrass‐microbial cultures.
SPECIES RESPONSES TO FIRE ON THE FLORIDA LAKE WALES RIDGE
Authors: Abrahamson Warren G.
Published: January 2018

The responses of native plant species to prescribed and lightning‐caused burns were recorded using permanent line transects and quadrats, sampled over a 5‐yr period, 1977–1982. The dominant species of more frequently burned associations (southern ridge sandhills, scrubby flatwoods, flatwoods, swales, and seasonal ponds) either recover from fire by sprouting or survive by resisting fire, rather than by seeding. The dominants of less frequently burned associations (sand pine and rosemary scrub) are killed by fire and recover by seeding. Quercus myrtifolia, Q. inopina, Q. chapmanii, Q. geminata, Serenoa repens, and Sabal etonia exhibited resiliency, rapidly returning to their preburn levels of dominance. Of the palmettos, Serenoa responded more vigorously than Sabal. Vegetation measures for Gaylussacia dumosa and Vaccinium myrsinites increased and then decreased dramatically after fire with 2‐, and 3‐ to 4‐yr cycles, respectively. Myrica cerifera var pusilla, Quercus minima, and Hypericum reductum were more gradual in their responses. A strong inverse relationship, mediated by both abiotic and biotic factors, was found between density and accumulated aboveground biomass in Hypericum edisonianum. Pinus elliottii var densa showed a high degree of resistance to fire with several abiotic and biotic variables affecting mortality. A number of species exhibited an increased incidence of flowering after fire. Late spring/summer fires stimulated a vigorous flowering response in Aristida stricta, Panicum abscissum, and Andropogon spp., whereas winter fires encouraged only a vegetative response. The ridge species do not require fire in the sense of maintaining a fire subclimax. Rather, fire revitalizes species’ populations, but does not initiate succession in the Clementsian sense.
THE ULTRASTRUCTURE OF DEVELOPING LATEX DUCTS IN MAMMILLARIA HEYDERI (CACTACEAE)
Authors: Wittler George H. , Mauseth James D.
Published: January 2018

Electron microscopy was used to investigate early development of latex ducts in Mammillaria heyderi (Cactaceae). Numerous vesicles (secondary vacuoles) form from invaginations of the plasmalemma near sites of wall thinning, from endoplasmic reticulum (ER), and from vesiculate grana of degenerate plastids. Dictyosomes, though they occur in young duct cells, do not seem to be responsible for the formation of vesicles. Cytoplasmic vesicles may contain fibrillar, globular, or crystalline materials, or may be devoid of any type of particulate matter. They may be responsible for storage of numerous laticiferous components. Lysosomal materials could be stored in some vesicles and contribute to the degradation of the protoplast. Some nuclei contain condensed chromatin and are subject to deformation and collapse. Mitochondria and lipid bodies are common in young duct cells but ER is rare. When ducts form in young tissues, plastids in the lumen do not produce starch grains or extensive membranous networks. The plastids eventually degenerate to become a part of latex. If ducts form in older, established tissues having mature plastids, the plastids undergo extreme modification.
MOTILE CELL ULTRASTRUCTURE AND THE CIRCUMSCRIPTION OF THE ORDERS ULOTRICHALES AND ULVALES (ULVOPHYCEAE, CHLOROPHYTA)
Authors: Floyd Gary L. , O'Kelly Charles J.
Published: January 2018

We have examined the motile cell ultrastructural features of several green algal species having filamentous or foliose thallus morphology and probable affinities with the Ulvophyceae, and compared them with the structural, reproductive, and life history features known for these taxa. We separate the algae studied into the orders Ulotrichales and Ulvales on the basis of consistent variations in terminal cap and proximal sheath structure that correlate well with life history patterns and certain features of sporangial and gametangial structure and development. Body scales are present only in certain members of the Ulotrichales. Both orders encompass a variety of thallus forms, demonstrating parallel evolution of thallus morphology. Flagellar apparatus features common to all the motile cells examined include 180° rotational symmetry, counterclockwise absolute orientation, the positioning of the basal bodies in an apical papilla, and the presence of one or more sets of striated bands associated with the X rootlets. Additional features that are usually present include basal body overlap and orientation roughly perpendicular to the long axis of the cell during forward swimming, striated distal fibers, and a single, striated, microtuble‐associated component underlying each two‐membered rootlet. These similarities indicate to us that the two groups are closely related members of the Ulvophyceae. We suggest that the Ulotrichales is the most primitive ulvophyceous assemblage known, but that all groups studied have advanced features relative to those supposed to have been present in the ancestral members of the Ulvophyceae.
A STARCH‐AGAR GEL METHOD FOR THE LOCALIZATION OF STARCH HYDROLYZING ENZYMES IN THE COTYLEDONS AND HYPOCOTYLS OF BEANS
Authors: Nolan Mary C. , Davis Bill D.
Published: January 2018

A starch‐agar gel assay was developed for the localization of enzyme activity in the cotyledons and hypocotyls of beans. The four major starch hydrolyzing enzymes, α‐amylase, β‐amylase, debranching enzyme and phosphorylase, were assayed with this technique using gels containing different substrates and buffers. Hypocotyls and cotyledons were sectioned by hand and the sections were incubated on the gel for varying lengths of time. Only α‐amylase was observed to increase significantly. While virtually absent in ungerminated axes and hypocotyls from young seedlings, it increased first in the basal region and subsequently in progressively higher portions of the hypocotyl. High activities were first observed in the pith and later in the cortex. The increased activity was most obviously associated with the degradation of the pith, suggesting a regulation relative to cellular autolysis.
SOMATIC EMBRYOGENESIS IN LONG‐TERM CALLUS CULTURES OF ZEA MAYS L. (GRAMINEAE)
Authors: Vasil Vimla , Vasil Indra K. , Lu Chin‐yi
Published: January 2018

Long‐term (1 yr), soft, embryogenic callus tissue cultures were established from excised immature embryos of a commercial cultivar of hybrid maize (Zea mays L.). Plant regeneration occurred by the formation of somatic embryos, and the regenerated plants were morphologically normal with 2n = 20 chromosomes. Such cultures may be useful for the isolation of mutants and the establishment of embryogenic cell suspension cultures.
HYDRILLA INVADES WASHINGTON, D.C. AND THE POTOMAC
Authors: Steward Kerry K. , Van Thai K. , Carter Virginia , Pieterse Arnold H.
Published: January 2018

The aquatic weed hydrilla (Hydrilla verticillata Royle) was discovered growing in the Potomac River, south of Alexandria, VA, in Kenilworth Aquatic Gardens, Washington, D.C., and in the Chesapeake and Ohio (C&O) Canal near Seneca, MD. Cultures in Florida of the Kenilworth clone produced male flowers. This is the first report of the occurrence of the male in the U.S. Two distinct isoenzyme patterns have been identified for plants from various locations in the U.S., corresponding to a monoecious strain and a dioecious female. The occurrence of the wild colonies of the monoecious Hydrilla greatly increase the potential for physiological diversity through sexual reproduction, which may have serious consequences for the management of this weed.
RHIZOME AND ROOT GROWTH RATES AND CYCLES IN PROTEIN AND CARBOHYDRATE CONCENTRATIONS IN GEORGIA SPARTINA ALTERNIFLORA LOISEL. PLANTS
Authors: Gallagher John L. , Wolf Paul L. , Pfeiffer William J.
Published: January 2018

Root and rhizome growth and composition were measured in a Georgia salt marsh. Root growth was less seasonal than rhizome growth; none of the latter occurred during the first quarter of the year. The depth of underground growth shifted downward during the fall. Sugar and starch concentrations were relatively low in roots throughout the year. They remained relatively high in the rhizomes, but varied in distribution depending on the season.
ULTRASTRUCTURAL BASIS AND DEVELOPMENTAL CONTROL OF BLUE IRIDESCENCE IN SELAGINELLA LEAVES
Authors: Hébant Charles , Lee David W.
Published: January 2018

The iridescent blue color of several Selaginella species is caused by a physical effect, thin‐film interference. Predictions for a model film have been confirmed by electron microscopy of S. willdenowii and S. uncinata. For the latter species iridescence contributes to leaf absorption at wavelengths above 450 nm and develops in environments enriched with far‐red (730 nm) light. This evidence supports the involvement of phytochrome in the developmental control of iridescence.
BIRD‐DISPERSAL OF PHYTOLACCA AMERICANA L. AND THE INFLUENCE OF FRUIT REMOVAL ON SUBSEQUENT FRUIT DEVELOPMENT
Authors: McDonnell Mark J. , Stiles Edmund W. , Cheplick Gregory P. , Armesto Juan J.
Published: January 2018

Characteristics of fruits, seeds, and ripening of Phytolacca americana were studied in New Jersey, USA to assess their importance in the dispersal strategy of this species. Removal by birds was directly related to the percent of ripe fruits available on a raceme. Fruit removal from a raceme resulted in lower fruit pulp and seed weights for fruits developing on the same raceme, but these differences probably do not influence probability for dispersal by birds. We demonstrate that characteristics of the fruit pulp may decrease seed availability for the primary seed predator, Peromyscus leucopus, and increase the time fruits are available for dispersal. We speculate on the significance of the sequential fruiting in Phytolacca and the relationship to availability of dispersal agents and high‐lipid fruits. Sequential ripening and protection from predation result in seed dispersal from late August to early December.
SHOOT TIP CULTURE OF HELIANTHUS ANNUUS—FLOWERING AND DEVELOPMENT OF ADVENTITIOUS AND MULTIPLE SHOOTS
Authors: Paterson Karol E.
Published: January 2018

Shoot multiplication of Helianthus annuus was optimal from half shoot apices cultured on MS media with 0.1–1.0 mg/1 benzyl adenine or kinetin. Auxins inhibited multiplication and promoted callusing. Rooting was poor and was not promoted by auxins. Flowering of multiple shoots was observed after as little as 3 wk of culture. A number of plant growth regulators and environmental conditions had no effect on flowering which supports the determinate apex theory for sunflower (Habermann and Sekulow, 1972). Adventitious shoots were induced on leaves of the multiple shoots in some inbreds.
THE EFFECTS OF SO2 ON PHOTOSYNTHESIS AND CARBOHYDRATE TRANSFER IN THE TWO LICHENS: COLLEMA POLYCARPON AND PARMELIA CHLOROCHROA
Authors: Fields Rebecca D. , Clair Larry L. St.
Published: January 2018

Exposure of Parmelia chlorochroa and Collema polycarpon to 1 and 2 ppm gaseous SO2 (4‐, 8‐, and 12‐hr fumigations) initially stimulated photosynthesis but prolonged exposure depressed it. Carbohydrate transfer decreased in both species but increased significantly after a 12‐hr exposure in C. polycarpon. Interference with normal oxidation‐reduction and denaturation of enzymes and membrane proteins by sulfite and bisulfite ions may account for the observed results. Increased conductivity of leachates reflected SO2‐induced damage at both 1 and 2 ppm sO2.
FORMATION AND MORPHOLOGY OF AN IRON PLAQUE ON THE ROOTS OF TYPHA LATIFOLIA L. GROWN IN SOLUTION CULTURE
Authors: Taylor Gregory J. , Crowder A. A. , Rodden R.
Published: January 2018

Roots of Typha latifolia L. exposed to Fe2+ under reduced conditions in solution culture developed visible coatings (plaques) of an oxidized Fe compound that extended as much as 15‐17 μm into the rhizosphere. Iron concentrations were significantly less and discoloration was not apparent on the surface of roots exposed to Fe‐(BPDS)3, Fe3+, Fe‐EDDHA, and Fe‐EDTA. The extent of plaque formation increased with the concentration of Fe2+ in solution and with pH of the solution in the range of 3.0 to 4.6. Above pH 4.6, oxidation of Fe2+ in the culture solution may have reduced precipitation of Fe on the root surface. Plaque development was most extensive approximately 1.0 cm from the root tip, but all root surfaces showed some Fe staining. Scanning electron micrographs of plaqued roots, grown both in solution culture and in the field, provided support for a model of cast formation by oxidation and precipitation of Fe on external cell surfaces.
POLLINATION SYSTEMS OF SYMPATRIC IPOMOEA HEDERACEA AND I. PURPUREA AND THE SIGNIFICANCE OF INTERSPECIFIC POLLEN FLOW
Authors: Stucky Jon M.
Published: January 2018

Mathematical models estimated that xenogamy accounted for 7% and 35% of the stigmatic pollen loads of Ipomoea hederacea and I. purpurea, respectively, in experimental populations. The xenogamy estimate for I. hederacea agreed closely with outcrossing estimates previously reported for this species. The discrepancy between the xenogamy estimate and the previously reported outcrossing estimate for I. purpurea could be explained by differing pollinator flight patterns between experimental and natural populations and/or by selection for cross pollen in the pistil of I. purpurea. Interspecific pollen flow from I. purpurea to emasculated flowers of I. hederacea reduced seed production in the latter. The possible significance of interspecific pollen flow from I. purpurea for the evolution of autogamy in I. hederacea was discussed.
POLLINATION ECOLOGY OF VACCINIUM STAMINEUM (ERICACEAE: VACCINIOIDEAE)
Authors: Cane James H. , Eickwort George C. , Wesley F. Robert , Spielholz Joan
Published: January 2018

Successful fruit set by deerberry,Vaccinium stamineum(Ericaceae: Vaccinioideae) requires floral visitation by insects, and in particular by bees that collect its pollen by sonication of anthers (“buzz‐pollination”). A diversity of bees visit deerberry flowers, but most species are either 1) infrequent, 2) polylectic (broad host range for pollen), or 3) principally nectar‐seeking, and so are unimportant as pollen vectors. Both sexes of the solitary, oligolectic beeMelitta americana5(Melittidae) are abundant at flowering deerberry bushes in central New York State. FemaleM. americanasonicate the deerberry anthers while imbibing nectar, and carry virtually pure scopal loads of deerberry pollen, unlike the other common visitor,Xylocopa virginica(Anthophoridae). Comparative analyses of bee 1) abundances, 2) buzz‐pollination behaviors, 3) pollen fidelities, and 4) pollination efficiencies, all indicate thatMelitta americanais the primary pollinator ofVaccinium stamineum.
REPRODUCTIVE BIOLOGY OF APIACEAE. II. CRYPTIC SPECIALIZATION AND FLORAL EVOLUTION IN THASPIUM AND ZIZIA
Authors: Lindsey Anne H. , Bell C. Ritchie
Published: January 2018

The classification of specialized floral syndromes has imposed a bias in the interpretation of pollination systems which may be either more generalized, or more specialized, than we have universally acknowledged. An analysis of floral biology in two umbellifer genera,ThaspiumandZizia, was undertaken in order to determine the extent to which cryptic floral or inflorescence variations determine pollination specialization despite a broad visitor spectrum and open reward system. Separate analyses were made of the primary attractants, nectar and pollen, and the secondary attractants, floral color and floral and inflorescence structure in conjunction with analyses of pollinator movements, stigmatic pollen loads and fruit set. All data support the conclusion that cryptic variation in floral and inflorescence characters enhance specialization for pollination by solitary bees or syrphid flies. In addition, evidence is presented for the importance of the oligolectic relationship between taxa ofThaspiumandZiziaand the solitary bee,Andrena ziziae.The need for more experimental work both to further define the oligolectic relationship and to understand how floral and inflorescence color and structure affect insect movements is especially revealed by this study. The degree of pollination specialization inThaspiumandZiziais not uncommon in Apiaceae and has important implications for floral evolution in this family and other plant groups with pollination systems categorized as “promiscuous.”
THE GYNOECIAL DEVELOPMENT AND SYSTEMATIC POSITION OF ALLAMANDA (APOCYNACEAE)
Authors: Fallen Mary E.
Published: January 2018

Allamanda exhibits an unusual type of gynoecial development in which the two carpels are free at initiation, but fuse completely during development, resulting in a unilocular ovary with parietal placentation at maturity. Whereas the majority of the Apocynaceae are characterized by an advanced type of gynoecium that is secondarily apocarpous, in Allamanda gynoecial evolution has proceeded one step further to secondary syncarpy. This condition is not known to occur in any other genus in the Apocynaceae and provides further evidence of the isolated position of Allamanda within the family.
SOMATIC EMBRYOGENESIS AND PLANT REGENERATION IN HYOSCYAMUS NIGER
Authors: Cheng Jinchen , Raghavan V.
Published: January 2018

Culture of segments of leaves, petioles, and stems and of germinated seeds and whole ovaries enclosing unpollinated ovules of Hyoscyamus niger in a medium containg 2, 4‐dichlorophen‐oxyacetic acid caused massive growth of calluses. In cultured germinated seeds and ovaries, calluses were formed from the hypocotyl and placenta, respectively. Leaf and stem explants generally gave rise to hard, white, and compact calluses. Upon transfer of these calluses to an auxin‐free medium they regenerated roots or buds but showed no further signs of morphogenesis. Calluses formed on petioles, germinated seeds, and ovaries were a mixture of the white, compact and brown, friable types. Subsequent morphogenesis of the friable calluses in a medium lacking auxin was characterized by the formation of somatic embryos whose pattern of development was similar to that of zygotic embryos.
ELEMENT RESPONSES OF AGAVES
Authors: Nobel Park S. , Berry Wade L.
Published: January 2018

To help identify possible element stresses, seedling responses of Agave deserti to high concentrations of various elements were examined by monitoring both 12‐day growth in hydroponic solution and 6‐month growth in sand culture. In addition, nocturnal acid accumulation by adult plants of six agave species was related to element levels in their chlorenchyma. Compared with common agronomic plants, seedlings of A. deserti were quite sensitive to salinity, with 50 mm NaCl greatly reducing root elongation in hydroponic solution and watering with 25 mm NaCl preventing growth in sand culture. The seedlings were rather insensitive to Ca concentrations from 0.2 to 5 mm and to pH from pH 5 to 8. They also tolerated high levels of B and of the heavy metals Cu and Zn. Nocturnal acid accumulation by adult plants of the six agave species was positively correlated with levels of 10 elements in the chlorenchyma, especially N (r2 = 0. 70), B (r2 = 0.51), and Ca (r2 = 0.46). In contrast, nocturnal acid accumulation was weakly and negatively correlated with chlorenchyma Na (r2 = 0.13), consistent with the deleterious effects of salinity on the growth of seedlings. Correlations between nocturnal acid accumulation and element content were consistent with previous fertilizer experiments with N, B, Ca, K, and P on A. sisalana. Element levels in the chlorenchyma of the six agave species were generally similar to those of previously studied cacti, including a low Na and high Ca level compared with agronomic plants.
OVARIAN INFLUENCE ON POLLEN TUBE GROWTH, AS INDICATED BY THE SEMIVIVO TECHNIQUE
Authors: Mulcahy Gabriella Bergamini , Mulcahy David L.
Published: January 2018

With the semivivo technique, pollen tubes grow from the bases of cut styles. The length of pollen tubes protruding from such styles, or growing through intact styles, is greatly enhanced by allowing initial pollen tube growth to occur before the ovary is removed. The presence of other floral parts has no apparent effect in this study. This improved semivivo method provides an abundant supply of pollen tubes that may show fewer artifacts than do those produced with in vitro growth. It also suggests that the ovary plays an important role in pollen‐style interactions.
IMPERMANENT INITIALS OF THE SHOOT APEX AND DIPLONTIC SELECTION IN A JUNIPER CHIMERA
Authors: Ruth Jennifer , Klekowski Edward J. , Stein Otto L.
Published: January 2018

Shoot meristems of Juniperus davurica cv. Expansa Variegata possess an apical zonation pattern similar to that found in some angiosperms. Anticlinal divisions predominate in the outer layer, the tunica. The underlying core of cells, the corpus, has cell divisions oriented in all directions. Typically, this variety exists as a periclinal chimera, the outer layer genotypically albino and the inner core composed of normal, chlorophyll‐producing cells. In this condition a shoot appears green. Occasionally a tunica cell divides periclinally and displaces an initial in the apical region of the corpus. This event subsequently is expressed during ontogeny as an albino sector on the stem and leaves.

Frequent variation in the width of an albino sector throughout ontogeny suggests a temporary nature of cells in the position of apical initials. A correlation was documented between the position of axillary bud release and a subsequent increase or decrease in the width of an albino sector. A model based upon stochastic processes and diplontic selection is proposed to account for the dynamic nature of chimeric patterns observed in this plant.
EXTRAFLORAL NECTARIES AS ADAPTATIONS FOR BIRD POLLINATION IN ACACIA TERMINALIS
Authors: Knox R. B. , Kenrick J. , Bernhardt P. , Marginson R. , Beresford G. , Baker I. , Baker H. G.
Published: January 2018

Characteristics of the flowering trees ofAcacia terminalismay be interpreted as adaptations for bird pollination. Each leaf bears a single red nectary up to 12 mm long on its petiole. Nectaries show greatest secretory activity at flowering (max. 15μl/nectary/day), and nectar was found only in the early morning. The nectar contains a mean of 16% sugars (max. >50%) and is hexose rich with 18 amino acids, especially glutamine and phenylalanine. Analyses of foraging dynamics and pollen loads from feathers of passerine birds further support this interpretation.
SIEVE ELEMENTS IN THE MORPHOLOGICALLY REDUCED MISTLETOE, VISCUM MINIMUM HARVEY (VISCACEAE)
Authors: Olson A. Randall , Kuijt Job
Published: January 2018

The absence of phloem in some Viscaceae may be a direct result of morphological reduction. Viscum minimum is a highly reduced, South African mistletoe that parasitizes Euphorbia. The aerial portions of this species are 2–3 mm long and consist of only 1–2 intemodes with a terminal triad of flowers. The collateral vascular bundles are composed of tracheary elements, parenchyma, and sieve tubes with associated companion cells. The sieve‐tube members are similar to those described from other angiosperms, exhibiting simple sieve plates, P‐protein, stacks of ER, plastids, and mitochondria. The morphological reduction of V. minimum thus is not associated with a loss of phloic elements in contrast to other reduced viscaceous mistletoes.
POLLEN MORPHOLOGY IN THE GENERA MONTTEA AND MELOSPERMA (SCROPHULARIACEAE)
Authors: Argue Charles L.
Published: January 2018

Pollen of the scrophulariaceous genera Melosperma and Monttea was studied with light and scanning electron microscopy. Both have single, radiosymmetric, isopolar, trizoniaperturate pollen grains with usually ruptured colpus membranes, tectate‐perforate to semitectate exines with a columellate interstitium and pitted or perforate nexines. Intergeneric differences in pollen morphology are established based on the differential correlation of sculpturing characters. Comparisons of the pollen of Melosperma and Monttea with that of the tribe Minuleae sensu stricto reveals no difference in the case of Melosperma and the existence of intermediate morphologies and “reticulate” similarities in the case of Monttea; the taxonomic significance of this morphological intergradation is considered. The transfer of Oxycladus aphyllus to Monttea is consistent with the pollen evidence, but proposed affinities between Monttea and tribe Antonieae of the Loganiaceae are not supported.
MORPHOMETRIC VARIATIONS OF FIVE TIDAL MARSH HALOPHYTES ALONG ENVIRONMENTAL GRADIENTS
Authors: Seliskar Denise M.
Published: January 2018

Morphological characteristics of Deschampsia cespitosa, Grindelia integrifolia, Distichlis spicata, Jaumea carnosa, and Salicornia virginica varied significantly along transects between the upper and lower portions of an Oregon salt marsh. Plant height, height of the flowering shoot, leaf number and width, internode length, branching, and stem diameter varied with position in the marsh. Anatomical differences in stem structure were also obvious. Lignification of vascular bundles of D. spicata, the amount of secondary xylem in G. integrifolia, and vascular bundle size in J. carnosa were greatest in the upper marsh zone. The quantity of aerenchymatous tissue in S. virginica was greatest at the lower, wetter end of the transect. Reproductive effort was greatest at the upper distributional limit of G. integrifolia and D. spicata while greatest in J. carnosa at its lower limit. Soil moisture and soil chemical data were collected to relate morphometric variation to environmental parameters. Differences in plant structure may have application as an aid in determining wetland boundaries.
FLORAL DEVELOPMENT IN CAESALPINIA (LEGUMINOSAE)
Authors: Tucker Shirley C. , Stein Otto L. , Derstine Kittie S.
Published: January 2018

Utilizing scanning electron microscopy, we studied the early floral ontogeny of three species of Caesalpinia (Leguminosae: Caesalpinioideae): C. cassioides, C. pulcherrima, and C. vesicaria. Interspecific differences among the three are minor at early and middle stages of floral development. Members of the calyx, corolla, first stamen whorl, and second stamen whorl appear in acropetal order, except that the carpel is present before appearance of the last three inner stamens. Sepals are formed in generally unidirectional succession, beginning with one on the abaxial side next to the subtending bracts, followed by the two lateral sepals and adaxial sepal, then lastly the other adaxial sepal. In one flower of C. vesicaria, sepals were helically initiated. In the calyx, the first‐initiated sepal maintains a size advantage over the other four sepals and eventually becomes cucullate, enveloping the remaining parts of the flower. The cucullate abaxial sepal is found in the majority of species of the genus Caesalpinia. Petals, outer stamens, and inner stamens are formed unidirectionally in each whorl from the abaxial to the adaxial sides of the flower. Abaxial stamens are present before the last petals are visible as mounds on the adaxial side, so that the floral apex is engaged in initiation of different categories of floral organs at the same time.
STRUCTURE AND DEVELOPMENT OF HYPHAL SEPTA IN ALLOMYCES
Authors: Meyer Robert J. , Fuller Melvin S.
Published: January 2018

Development of hyphal septa (pseudosepta) in Allomyces macrogynus begins with the formation of five or more discontinuous pieces of wall material that project inward from the hyphal wall. Lateral fusion of these projections leaves a central pore in the septum that is later filled in by centripetal deposition of wall material. However, lateral fusion of the projections is not complete; peripheral pores remain in the rim of the mature septum. The position of cytoplasmic microtubules corresponds to the position of actively moving cellular particles and organelles. Allomyces reticulatus and A. arbuscula have similar septa.
GENOMIC RELATIONSHIP OF GUAYULE WITH PARTHENIUM SCHOTTII
Authors: Estilai Ali , Hashemi Ahmad , Youngner Victor B.
Published: January 2018

F1 hybrids obtained from crosses between the rubber‐bearing species, Parthenium argentatum Gray (commonly known as guayule), and P. schottii Greenman ex Millspaugh and Chase, a nonrubber‐producing species from southern Mexico, were morphologically variable. They were generally intermediate between the two species with respect to leaf size, head size, number of disk florets per head, and the length of the peduncles. Like the parental species, the hybrids had 2n = 36 chromosomes. They averaged 14.56 bivalents, 3.92 univalents, 0.56 trivalents, and 0.32 quadrivalents, indicating a high degree of homeology between the genomes of the two species. The observation of one quadrivalent at diakinesis in 32% of the PMCs and the frequent occurrence of a bridge accompanied by a fragment at late anaphase I of the F, hybrids suggested that the two species differ in a reciprocal translocation and a paracentric inversion. The ease of hybridization, the partial fertility of the hybrids, and their high degree of chromosome pairing indicate that P. schottii and P. argentatum are closely related in spite of their distinct morphological features and geographical distributions. This close relationship provides an opportunity to transfer genes from P. schottii to guayule for desirable characteristics, such as high biomass production and resistance to Verticillium dahliae Kleb, by means of interspecific hybridization.
ULTRASTRUCTURE OF THE SHOOT APEX OF TOMATO (LYCOPERSICON ESCULENTUM)
Authors: Sekhar K. N. Chandra , Sawhney V. K.
Published: January 2018

The vegetative shoot apical meristem of tomato (Lycopersicon esculentum Mill.) was examined at the ultrastructural level. The meristem consisted of a surface layer that was different from the rest of the meristem and was unique among the dicotyledonous species. The cells of the surface layer contained large distal vacuoles with relatively large electron‐dense inclusions, proplastids with membrane‐bound inclusions (MB), and differentiating chloroplasts. In addition, periclinal and oblique divisions were observed in the surface layer cells along with anticlinal divisions. The cells of the subsurface layers contained small vacuoles with fewer inclusions as well as proplastids of various shapes but without MB. Differentiating chloroplasts were not observed in these cells, but autophagic vacuoles at various stages of development were present. The normal complement of cell inclusions, e.g., the mitochondria, golgi bodies, endoplasmic reticulum (ER), ribosomes, and microtubules were observed in subsurface layers, and in many cells the ER was observed to be continuous with the outer membrane of the nuclear envelope and with the plasmalemma. Further below in the meristem, cells contained both the proplastids and differentiating chloroplasts with MB. In the latter, the outer membrane of the MB was found to be continuous with the developing lamellae, suggesting that MB probably serve as the storage centers for lamellae membranes. Near the base of the meristem, in the pith‐rib meristem, enlarged cells containing large vacuoles and differentiated chloroplasts were present.
INTRASEASONAL VARIATION IN SEED PRODUCTION AMONG FLOWERS AND PLANTS OF THALICTRUM THALICTROIDES (RANUNCULACEAE)
Authors: Lubbers Anne E. , Christensen Norman L.
Published: January 2018

Intraseasonal variation in ovule and seed production per flower and per plant of the perennial herbThalictrum thalictroides(L.) Eames and Boivin was documented at three sites during three spring flowering seasons. Shading and pollen‐addition experiments were used to assess the impact of variation in pollination and light availability on seed production. Mean seed number and percent seed set were lower in flowers open late in the season than in those open earlier. The lower percent seed set occurs primarily in flowers that are positioned laterally on the inflorescence and which open later than center flowers. Plants flowering early in the season produce more flowers, ovules and seeds than those flowering later. Mean percent seed set per plant did not change, however, indicating that temporal differences in total seed output can be traced largely to variation in total ovule number. Seed production may be limited by lack of pollination during periods of inclement weather. At least late in the season, seed output may also be resource‐limited: the decline in percent seed set among flowers coincided with the decline in light availability, and hand‐pollination of late‐opening flowers did not increase percent seed set to earlier levels. Artificial shading led to a significant reduction in percent seed set of lateral flowers, and decreased the probability of flowering again the following year. Thus, the relative selective roles of resource and pollination limitations may vary during the flowering season.
ESTABLISHMENT OF LONG‐TERM CALLUS CULTURES FROM MATURE WHITE PINE (PINUS STROBUS, PINACEAE)
Authors: Kaul Karan
Published: January 2018

Callus cultures were established from young vegetative shoots of 15 to 18‐year‐old white pine trees. The callus has been repeatedly subcultured for 15 months on a modified Murashige and Skoog's medium supplemented with 2 mg/L 6‐Benzyladenine and 0.2 mg/L α‐Naphthaleneacetic acid. Best callus proliferation occurred when 2 to 4‐week‐old shoots were used as expiants. Older shoots were heavily contaminated with microorganisms and could be only partially disinfected by heat or chemical treatments.