bluuebunny/crossref_metadata_2025 huggingface dataset:
GENETIC DIVERGENCE IN GALVEZIA (SCROPHULARIACEAE): EVOLUTIONARY AND BIOGEOGRAPHIC RELATIONSHIPS AMONG SOUTH AMERICAN AND GALÁPAGOS SPECIES
Authors: Elisens Wayne J.
Published: January 2018

Nineteen populations representing all species of Galvezia were examined for electrophoretic differentiation at 23 loci. Allozyme variation within G. leucantha is minimal, suggesting that a genetic bottleneck, possibly resulting from a single colonization event, accompanied establishment of Galvezia in the Galàpagos Islands less than 1.5 million years ago. South American species have higher levels of genetic polymorphism. Interspecific divergence patterns in Galvezia are characterized by many qualitative allelic differences, including one to six marker alleles for each species. Isozyme data support delimitation of four species. Geographic modes of speciation predominate. Allozyme data indicate that the Galàpagos endemic is not a recent derivative from a continental progenitor; rather, it is most likely the sister species to G. fruticosa or to a lineage of G. fruticosa and an undescribed species from southern Peru. It is hypothesized that the presence of six fixed, unique alleles in G. leucantha identifies a relictual genotype from an extinct South American progenitor. Biogeographic patterns and the presence of an allele shared between G. leucantha and two populations from the Sechura Desert indicate that northern Peru is the probable source region for the Galàpagos introduction. Estimates of elapsed divergence times and paleoecological data suggest that continental species diverged in the late Pliocene or during the Pleistocene as a result of geographic isolation caused by climatic and vegetational change.
SILICIFIED PINUS REMAINS FROM THE MIOCENE OF WASHINGTON
Authors: Miller Charles N.
Published: January 2018

Silicified leaves, dwarf shoots, pollen cones, and seed cones of Pinus from a Late Miocene chert bed within the Yakima Basalt Formation near Yakima, Washington are interpreted as coming from a single new species, P. foisyi. The needles and dwarf shoots are those of a three‐needle pine. The needles contain two to four medial resin canals, a biform hypodermis, and endodermal cells with uniformly thickened walls. The pollen cones are ellipsoidal and about 1 cm long, and many contain bisaccate pollen grains. The seed cones are at least 6 cm long and are slightly asymmetrical. The cone axis has a broad sclerotic outer cortex, and the seed wing extends from a thick parenchymatous base. The scale apex bears a conspicuously swollen projection. The foliage and seed cones are identifiable with the Subgenus Pinus, Section Pinus, Subsection Oocarpae independently of one another, and together indicate a fossil species related to the modem Californian closed cone pines. Pinus foisyi represents one of the earliest occurrences of cone asymmetry associated with this group. However, cone serotiny characteristic of the modem species appears to have evolved after the Late Miocene.
CYCLIC INVASION OF TAPETAL CELLS INTO LOCULI DURING MICROSPORE DEVELOPMENT IN NYMPHAEA COLORATA (NYMPHACEAE)
Authors: Rowley John R. , Gabarayeva Nina I. , Walles Björn
Published: January 2018

In work withNymphaea colorataPeter three distinct intervals were recorded during which tapetal cells (protoplasts) protruded into anther locules either as bridges and partitions or as invasive cells between or around tetrads of microspores. Before these intervals and between and after them, tapetal cells, while variable in shape, were noninvasive. Observations were based on sections of over 60 fixed and epoxy‐embedded anthers covering the relatively brief interval from the end of meiosis through the vacuolate microspore stage. The progression of development, from early microspore stages through the microspore vacuolate period, is illustrated by transmission electron micrographs showing change in proexine and exine size and complexity. Our results indicate cycles of tapetal cell differentiation and dedifferentiation in this species.
THE RELATIONSHIPS BETWEEN THE PRIMARY VASCULAR SYSTEM AND PHYLLOTACTIC PATTERNS OF ANAGALLIS ARVENSIS (PRIMULACEAE)
Authors: Kwiatkowska Dorota
Published: January 2018

The various primary vascular systems of shoots of Anagallis arvensis L. (Primulaceae) can be distinguished in relation to the number of leaves (two, three, or four) at each node. In this study, shoot segments (single intemodes and the nodes above them) were examined. The arrangement of segments within shoots was also recorded. The vasculature forms a closed system with the number of sets of bundles usually equal to twice the number of leaves. Irregularities are found in the following features of the system: the number of bundles composing leaf half‐traces; occurrence of anastomosing bundles; the number of intemodes through which bundles extend; levels of leaf attachment to the stem at the node; and distribution of parenchyma within the vascular cylinder, which determines the number of bundles in sets and the number of bundle sets. The irregularities occur with different frequencies for segments exhibiting different phyllotactic patterns. Comparison of these frequencies leads to the following conclusions: anastomosing bundles occur only in decussate or trimerous shoot segments, whereas sets of bundles united within intemodes and displaced leaves occur only in tetramerous or trimerous ones; decrease of the number of bundles per leaf and displacement of leaves at the nodal level are correlated; variation between segments exhibiting the same phyllotactic pattern is greatest for trimerous, less for tetramerous, and least for decussate segments; the vascular system of decussate shoot segments is more stable than that of the other systems; and trimerous segments seem to be intermediate between the other two segment types.
CELLULAR BASIS FOR GROWTH AND TISSUE DIFFERENTIATION PATTERNS IN LINUM USITATISSIMUM (LINACEAE) STEMS: THE STEM UNIT
Authors: Meicenheimer Roger D.
Published: January 2018

The stem unit is defined as the smallest portion of a stem that can duplicate the stem in toto through regular rotations and dilations over successive plastochrons. In stems exhibiting k(m, n) contact parastichy phyllotaxis, the stem unit is delimited vertically and tangentially by the boundaries of four successive leaf primordia along the m‐, n‐, and (m + n)‐ parastichies and radially by these boundaries extended to the centroid of the stem. With the stem unit concept, node refers only to the region of actual leaf insertion, rather than the entire transverse level of insertion. Many of the conflicting and complicating aspects of the traditional node‐intemode subdivisions of stems are demonstrated, and the utility of the stem unit in circumventing these is illustrated. The stem unit is proposed as a more useful analytic subunit of the stem with which to examine stem growth and tissue differentiation processes than the more traditional node‐intemode subdivisions of stems.
EXISTENCE OF TWO STOMATAL SHAPES IN THE GENUS DENDROBIUM (ORCHIDACEAE) AND ITS SYSTEMATIC SIGNIFICANCE
Authors: Yukawa Tomohisa , Ando Toshio , Karasawa Kohji , Hashimoto Kiyoshi
Published: January 2018

On the basis of the shape and size of the outer stomatal ledge, 153 species of the genus Dendrobium (Orchidaceae) were divided into three groups, i.e., species group I, species group II, and section Grastidium. Student's t‐test and principal components analysis using seven stomatal characters suggest that the first two groups are quite distinct from each other. The values for section Grastidium, however, are scattered and indicative of heterogeneity. Our data suggest a high probability that species groups I and II are monophyletic sister groups. However, section Grastidium, in which stomatal diversification has occurred, may be para‐ or polyphyletic relative to the genus Dendrobium.
EFFECTS OF DISPLAY SIZE, FLOWERING PHENOLOGY, AND NECTAR AVAILABILITY ON EFFECTIVE VISITATION FREQUENCY IN COMPARETTIA FALCATA (ORCHIDACEAE)
Authors: Rodríguez‐Robles Javier A. , Meléndez Elvia J. , Ackerman James D.
Published: January 2018

Comparettia falcata is an epiphytic, neotropical orchid that produces nectar as a pollinator reward. In Puerto Rico, C. falcata is allogamous and pollinated by the endemic hummingbird Chlorostilbon maugaeus. Autogamous pollinations are possible, but may result in reduced fruit set. For the 1989 and 1990 flowering seasons, the probability of pollinarium removals and natural pollinations increased with individual inflorescence display size. However, the frequency of effective pollinator visits was independent of flowering phenology in both years. A positive correlation between inflorescence size and reproductive success occurred in 1990 but not in 1989. In 1990 plants produced longer spurs, a higher standing crop of nectar, and a more concentrated nectar than in 1989. There was no relation between nectar availability (= standing crop of nectar) and sugar concentration in either year. Nectar availability and sugar concentration did not vary among the first four flowers of an inflorescence in either season. Nectar availability was not a good predictor of effective visitation. Comparettia falcata has a higher natural fruit set than tropical deceptive orchids, suggesting that pollinator visitation may be enhanced by nectar reward. The small, dilute nectar volumes secreted by C. falcata may benefit the plant by increasing interplant pollinator movement and pollen dispersal.
NUCLEAR DNA CONTENT VARIATION WITHIN THE ROSACEAE
Authors: Dickson E. E. , Arumuganathan K. , Kresovich S. , Doyle J. J.
Published: January 2018

Nuclear DNA content has been estimated using flow cytometry for 17 species and eight cultivars of Malus and for 44 species of 29 other genera within the Rosaceae. Compared to other angiosperms, diploid genome sizes vary little within the family Rosaceae and within the genus Malus. C‐values of genera within the subfamilies Spiraeoideae and Rosoideae are among the smallest of flowering plants thus far reported. In general, the Maloideae have the largest diploid genomes of the family, consistent with their higher chromosome numbers and presumed polyploid origin.
CHLOROPLAST DNA POLYMORPHISM SUGGESTS NIGERIAN CENTER OF DOMESTICATION FOR THE COWPEA, VIGNA UNGUICULATA (LEGUMINOSAE)
Authors: Vaillancourt R. E. , Weeden N. F.
Published: January 2018

Twenty‐one independent chloroplast DNA polymorphisms were identified in Vigna unguiculata defining 19 different chloroplast DNA molecules (plastome types). Two plastome types, differing by a single character, were found among 32 accessions of cultivated cowpea (Vigna unguiculata ssp. unguiculata). Eighteen different plastome types were found among 26 accessions of wild cowpea (V. unguiculata ssp. dekindtiana). The very low level of chloroplast DNA diversity found in cultivated accessions relative to wild cowpea suggests that 1) the domesticated form was derived from a narrow selection of the wild germplasm and 2) chloroplast gene flow between wild and cultivated types has been very limited. Cladistic analysis of the cpDNA data generated a robust tree completely lacking homoplasy. Three wild accessions from Nigeria possessed a plastome type indistinguishable from one present in cultivated accessions, suggesting that Nigeria represents one center of domestication of the cowpea. The other plastome type within the cultivated germplasm was not found among wild accessions.
PARTITIONING GROWTH AND PHOTOSYNTHESIS BETWEEN LEAVES AND STEMS DURING NITROGEN LIMITATION IN SPARTIUM JUNCEUM
Authors: Nilsen Erik Tallak
Published: January 2018

A clone of Spartium junceum (Spanish broom) was used to evaluate the consequence of different soil nitrogen regimes on growth and assimilation of leaves and stems. Nitrogen limitation caused a general reduction in aboveground growth, and NO3‐ limitation resulted in a greater reduction in leaf area compared to stem area. Supplemental soil nitrogen, from NH4+, caused increased growth and a greater increase in stem area compared to leaf area. Excess NH4+ caused decreased growth of leaves and stems. Under nitrogen‐limiting conditions, a greater amount of nitrogen was in stems than in leaves, particularly on a surface area basis. Both stem and leaf assimilation were reduced under limiting nitrogen, but the net effect was an increase in the stem contribution to daily carbon gain compared to a decrease for leaves. Stem and leaf assimilation had similar linear relationships with tissue nitrogen concentration. Nitrogen use efficiency increased under nitrogen limitation. Thus, as the proportion of whole plant nitrogen in the stems increased compared to that in leaves at low nitrogen availability, the nitrogen use efficiency increased.
LOCAL POLYPLOID VARIATION IN THE NATIVE PRAIRIE GRASS ANDROPOGON GERARDII
Authors: Keeler Kathleen H.
Published: January 2018

The microscale distribution of polyploid variants of the dominant grass big bluestem (Andropogon gerardii) in virgin tallgrass prairie was mapped using flow cytometry. The correlation between DNA content and polyploidy allows the use of flow cytometry for nondestructive determination of polyploidy in intact plants. At Konza Prairie, local plots contained from 0 to 100% hexaploid cytotypes but most showed fine‐scale mixing of the polyploid variants. The relationship of cytotype frequency to moisture availability or burning history was nonsignificant.
REPRODUCTIVE ATTRITION IN THE RARE CHAPARRAL SHRUB FREMONTODENDRON DECUMBENS LLOYD (STERCULIACEAE)
Authors: Boyd Robert S. , Serafini Lisa L.
Published: January 2018

We examined reproductive attrition in Fremontodendron decumbens to characterize sexual reproduction in this rare California shrub. Reproductive individuals produced an average of 2,900 flower buds in a season, with no significant difference in bud production between two seasons. Because of intense insect predation, <;2% of initiated flower buds became mature fruits. A threefold decrease in predation of flower buds between seasons resulted in an increase in seed output the second season, indicating that seed production was partially predator‐limited. Most seeds (97.8%) were dormant due to an impermeable seed coat. Breaking of the coat, mechanically or by heat, allowed high levels of germination. Chamise charate and ash added to the potting medium resulted in the highest level of germination and emergence. Rodents were more important than birds as seed predators, destroying 90% of seeds under parent shrub canopies within 8–10 months. Seeds already integrated into the seed bank were comparatively safe from predation, relative to newly added seeds. If predation was prevented, seeds were long‐lived under field conditions (>;80% survived after 5.75 years). Most seedlings produced in unburned chaparral by planting heat‐treated seeds in openings between shrubs were destroyed by predators (rodents and insects). All seedlings that escaped predation died during the summer drought. We concluded that sexual reproduction was limited by (in order of importance): 1) lack of fire, 2) predehiscence predation by insects, and 3) postdehiscence predation by rodents. Size distributions from two populations revealed that, despite the apparent absence of sexual reproduction in unbumed chaparral, two unbumed sites contained a large proportion of individuals in small size classes. Excavation of several small individuals demonstrated they were sprouts from the roots of nearby larger shrubs. Because asexual reproduction by rootsprouting circumvents the high attrition of sexual reproductive effort on unbumed sites, rootsprouting may be a significant reproductive strategy of some ‘sprouter’ species in chaparral.
EFFECT OF REMOVAL OF CO‐OCCURRING SPECIES ON DISTRIBUTION AND ABUNDANCE OF ERYTHRONIUM AMERICANUM (LILIACEAE), A SPRING EPHEMERAL
Authors: Hughes Jeffrey W.
Published: January 2018

Growth of spring ephemerals in northern forests is limited to early spring when competition for resources from other species is at a minimum. The abundance of resources during this vernal period suggests that spring ephemerals might grow continuously over a wide range of sites, but distributions tend to be patchy. I hypothesized that co‐occurring plants that grow later in the season compete for resources to a limited extent, but that competition from these other species is sufficient to restrict the spread of spring ephemerals into unoccupied sites. Population dynamics of Erythronium americanum were compared on sites at the Hubbard Brook Experimental Forest in New Hampshire subjected to varying removals of cooccurring plants. During the 3‐year period after removal of only overstory trees the density and frequency of occurrence of Erythronium increased by 225% and 180%, respectively, and removal of all co‐occurring vegetation after 1 year's regrowth had an even more pronounced effect (400% and 195% increases, respectively). The abundance of Erythronium in the undisturbed forest did not change over the 3‐year period. Elevational distribution of Erythronium also was directly related to the extent of removal of summer plants. Recruitment was mostly vegetative, but flower production on the tree removal site increased by a factor of six, and some distant sites apparently were colonized by seedlings. For several years following large‐scale disturbances that eliminate co‐occurring vegetation, the vernal growing season is lengthened and resources are more available, and spring ephemerals such as Erythronium americanum exploit these resource‐rich opportunities to expand populations and colonize new sites. It appears that, as forest succession proceeds, the size and survival of newly established colonies are gradually constrained by competition from co‐occurring species that grow later in the season.
ZEA MAYS EMBRYO SACS IN CULTURE. I. PLANT REGENERATION FROM 1 DAY AFTER POLLINATION EMBRYOS
Authors: Campenot Mary K. , Zhang Guichang , Cutler Adrian J. , Cass David D.
Published: January 2018

One day after pollination, embryo sacs of Zea mays, containing zygotes and a few endosperm nuclei, were partially isolated and grown in culture. The zygotes underwent normal embryo development, and 40% germinated on a modified Murashige and Skoog medium with 0.1 mg/liter 6‐benzylaminopurine. After the appearance of a root and a shoot, individual plantlets were transferred to soil and grown to sexual maturity. The techniques for partial mechanical isolation and successful growth to maturity of such young embryos provide the tools necessary for the recovery of plants from in vitro‐fertilìzed embryo sacs.
FUNCTIONAL DIOECY IN ECHINOCEREUS COCCINEUS (CACTACEAE): BREEDING SYSTEM, SEX RATIOS, AND GEOGRAPHIC RANGE OF FLORAL DIMORPHISM
Authors: Hoffman M. Timm
Published: January 2018

The breeding system of the hedgehog cactus, Echinocereus coccineus Engelm. (Cactaceae), was studied at two sites in the northern Chihuahuan Desert, New Mexico. Two distinct flower types, restricted to separate plants, were observed. One was hermaphroditic and the other male‐sterile. Hand‐pollinations and field observations showed them to be functionally male and functionally female, respectively. There were significant quantitative intersexual differences in floral morphology. The main pollinators of the populations studied are probably two species of halictid bee. Sex ratios based on the number of plants and flowers at the two sites did not differ significantly from 1:1. Significant differences in fruit set existed between functional female plants from the two sites. The floral dimorphism described here appears confined to eastern and northwestern populations, at the periphery of the range of E. coccineus. Floral dimorphism was not observed in three closely related species.
EFFECTS OF ETHEPHON, ITS NONETHYLENE‐GENERATING ANALOG ETHYLPHOSPHONIC ACID, AND PHOSPHOROUS ACID IN ASEPTIC CULTURE OF ORCHID SEEDLINGS
Authors: Ernst Robert , Bjornsen Jacquelyn E. , Arditti Joseph
Published: January 2018

Seeds of Cattleya aurantiaca (Orchidaceae) were germinated and grown aseptically on Knudson C medium containing 2.5, 5, 10, 20, and 50 mg l‐1 of 2‐chloroethylphosphonic acid (Ethephon), ethylphosphonic acid, or the inorganic acid moiety of both, phosphosphorous (phosphonic) acid. 2‐Chloroethylphosphonic acid, an ethylene precursor, reduced leaf length at 5–50 mg l‐1 proportional to increasing concentrations. Seedlings produced fewer leaves within the range of 20–50 mg l‐1 Ethephon compared to lower concentrations (2.5–10 mg l‐1). Germination was not affected adversely. Cultures containing the homologous, but not ethylene‐generating ethylphosphonic acid in the same concentrations brought about similar but generally less severe reductions in leaf length and number. Phosphorous acid at the same concentration levels did not reduce the number and length of leaves. Our observation suggests that the intact organic phosphonates contribute to the inhibition of leaf growth caused by ethylene, which is released slowly from Ethephon in the culture medium and/or plant tissue, following uptake.
EFFECTS OF POSTDISPERSAL SEED PREDATION ON SPATIAL INEQUALITY AND SIZE VARIABILITY IN AN ANNUAL PLANT, ERODIUM CICUTARIUM (GERANIACEAE)
Authors: Harmon G. D. , Stamp N. E.
Published: January 2018

By decreasing seed density, ants introduced into flats of uniformly sown seeds of Erodium cicutarium (Geraniaceae) created differences in the neighbor‐free area available to individual plants. The changes in spatial patterns brought about by the ants were greater when a higher proportion of seeds was removed but were independent of initial seed density. These spatial changes and differences in seed density were examined for their effects on plant size and reproduction. Gini values were calculated to determine inequalities. As the inequality in space among individual plants increased, the variation in final biomass increased. The number of individuals reproducing was constant among treatments, and yet seed production per plant was significantly greater for populations in which the spatial pattern was influenced by seed predation. The decrease in density and changed spatial pattern, due to previous seed predation, resulted in a few individuals having much more space than others and consequently producing many more seeds. The increase in reproductive effort per flat was much greater than could be explained by the changing density alone. Our experiment demonstrates that spatial inequality, such as that generated by seed predators, can be more important than density in generating size inequalities in plant populations. This result can profoundly alter the competitive interactions between plants and determine which plants produce seed for the next generation.
I. LIFE HISTORY FEATURES OF THREE SEXUAL MORPHS OF ATRIPLEX CANESCENS (CHENOPODIACEAE) CLONES GROWN IN A COMMON GARDEN
Authors: Pendleton Burton K. , Freeman D. Carl , McArthur E. Durant , Pendleton Rosemary L.
Published: January 2018

Reproductive and growth parameters of Atriplex canescens were examined in a common garden study. Cloned ramets of male, female, and hermaphrodite individuals from two natural populations were planted in irrigated and nonirrigated portions of the garden. Sexual differences in growth and flowering schedules suggest tradeoffs in resource allocation between growth and reproduction. Males flowered with the greatest frequency and intensity while producing the smallest growth parameters. Females had the largest measures of vegetative growth, but flowered with the least frequency and intensity. Hermaphrodites appear to have a biology distinct from males and females, being more like females in growth and more like males in reproduction.
SECONDARY WALL INGROWTHS ON VESSEL ELEMENTS IN OMBROPHYTUM SUBTERRANEUM (BALANOPHORACEAE)
Authors: Mauseth James D. , Montenegro Gloria
Published: January 2018

All vessel elements in the parasitic dicot Ombrophytum subterraneum (Balanophoraceae) have irregular, knobby ingrowths on their secondary walls. The ingrowths have a mean spacing of about 4 μm and can be longer than 6.4 μm, thus causing considerable occlusion of all but the widest vessel elements. The adaptive value is unknown.
ENDOPHYTE‐HOST ASSOCIATIONS IN GRASSES. XVI. PATTERNS OF ENDOPHYTE DISTRIBUTION IN SPECIES OF THE TRIBE AGROSTIDEAE
Authors: White James F. , Halisky Philip M. , Sun Suichang , Morgan‐Jones Gareth , Funk C. Reed
Published: January 2018

Distribution of Acremonium endophytes in several species of Agrostideae is determined through surveys conducted in the field and in grass herbaria. Widespread geographic distribution of Acremonium in a particular grass species may indicate early colonization of the grass as a host, while a narrow pattern of geographic distribution suggests more recent colonization of the grass. Two grasses that appear to show a narrow endophyte distribution include Agrostis alba and Ammophila breviligulata. Cultural features of endophytes from several grasses are compared. A new variety of Acremonium typhinum is proposed to accommodate the endophyte from A. breviligulata. An endophyte in Agrostis alba is identified as Acremonium starrii. It is also suggested that Acremonium endophytes are spreading in grasses and may be progressively colonizing new hosts.
SOMATIC EMBRYOGENESIS AND PLANT REGENERATION FROM IMMATURE ZYGOTIC EMBRYOS OF MUSCADINE GRAPE (VITIS ROTUNDIFOLIA) CULTIVARS
Authors: Gray D. J.
Published: January 2018

Embryogenic cell lines of Vitis rotundifolia were produced from immature zygotic embryo explants obtained by culturing ovules, harvested at 20 d postanthesis, for 8 wk and then dissecting embryos from them. Ovules cultured on Nitsch and Nitsch medium with naphthoxyacetic acid and benzyladenine (BA) produced a brown exudate, necessitating three transfers to fresh medium at 2‐wk intervals during the 8‐wk culture cycle. Zygotic embryos that were subsequently isolated from cultured ovules and placed on the same medium produced a heterogenous callus from which eventually emerged embryogenic cell lines. A higher percentage of ovules from cultivars ‘Dixie’, ‘Fry’, ‘Nesbitt’, and ‘Welder’ produced zygotic embryos (31%–39%) than did those from ‘Carlos’ (3%). A higher percentage of ‘Fry’ ovules produced embryogenic lines from cultured zygotic embryos (6.3%) than did those of the other four cultivars (1%–1.6%). Embryogenic cell lines were white and composed of variably sized cell clusters, somatic embryos, and embryonic tissue embedded in a watery matrix. These lines were maintained for over 1 yr on modified Murashige and Skoog (MS) medium lacking growth regulators by transfer of selected cell clusters every 6 wk. White, opaque somatic embryos grew directly from cell clusters and passed through recognizable developmental stages. Germination was induced by transfer of somatic embryos to MS medium with BA. Although 80%–100% of embryos germinated, plant recovery was low due to poor shoot development.
COMPARATIVE ULTRASTRUCTURE OF ZOOSPORES WITH PARALLEL BASAL BODIES FROM THE GREEN ALGAE DICTYOCHLORIS FRAGRANS AND BRACTEACOCCUS SP.
Authors: Watanabe Shin , Floyd Gary L.
Published: January 2018

The chlorococcalean algae Dictyochloris fragrans and Bracteacoccus sp. produce naked zoospores with two unequal flagella and parallel basal bodies. Ultrastructural features of the flagellar apparatus of these zoospores are basically identical and include a banded distal fiber, two proximal fibers, and four cruciately arranged microtubular rootlets with only one microtubule in each dexter rootlet. In D. fragrans, each proximal fiber is composed of two subfibers, one striated and one nonstriated, and each sinister rootlet is composed of five microtubules (4/1), decreasing to four away from the basal bodies. In Bracteacoccus sp., each proximal fiber is a single unit, the sinister rootlets are four (3/1) or rarely five (4/1) microtubules, and each basal body is associated with an unusual curved structure. The basic features of the flagellar apparatus of the zoospores of these two algae resemble those of Heterochlamydomonas rather than most other chlorococcalean algae that have equal length flagella, basal bodies in the V‐shape arrangement, and clockwise absolute orientation. It is proposed that these algae with unequal flagella and parallel basal bodies have a shared common ancestry within the green algae.
POLYPLOIDY, DYSPLOIDY, AND CHROMOSOME PAIRING IN ECHEVERIA (CRASSULACEAE) AND ITS HYBRIDS
Authors: Uhl Charles H.
Published: January 2018

The 140+ species of Echeveria have more than 50 gametic chromosome numbers, including every number from 12 through 34 and polyploids to n = ca. 260. With related genera, they comprise an immense comparium of 200+ species that have been interconnected in cultivation by hybrids. Some species with as many as 34 gametic chromosomes include none that can pair with each other, indicating that they are effectively diploid, but other species with fewer chromosomes test as tetraploids. Most diploid hybrids form multivalents, indicating that many translocations have rearranged segments of the chromosomes. Small, nonessential chromosomal remnants can be lost, lowering the number and suggesting that higher diploid numbers (n = 30–34) in the long dysploid series are older. These same numbers are basic to most other genera in the comparium (Pachyphytum, Graptopetalum, Sedum section Pachysedum), and many diploid intergeneric hybrids show very substantial chromosome pairing. Most polyploid hybrids here are fertile, even where the parents belong to different genera and have very different chromosome numbers. This seems possible only if corresponding chromosomes from a polyploid parent pair with each other preferentially, strong evidence for autopolyploidy. High diploid numbers here may represent old polyploids that have become diploidized by loss, mutation, or suppression of duplicate genes, but other evidence for this is lacking. Most species occur as small populations in unstable habitats in an area with a history of many rapid climatic and geological changes, presenting a model for rapid evolution.
IN VITRO REJUVENATION OF BETULA (BETULACEAE): MORPHOLOGICAL EVALUATION
Authors: Brand Mark H. , Lineberger R. Daniel
Published: January 2018

The extent of rejuvenation that occurs during in vitro culture and propagation of Betula was determined. Comparisons were made between half‐sib seedlings and micropropagated, grafted, and cutting‐propagated mature‐phase birch plants grown under similar conditions. To measure relative levels of juvenility, three clones were examined at 1, 4, and 8 mo postpropagation, for differences in stem and leaf morphology and the presence or absence of reproductive structures. Numerous morphological indicators of phase change in Betula were identified. Micropropagated plants are not initially morphologically identical to conventionally propagated mature plants and display many features characteristic of seedlings. Micropropagated plants that exhibited juvenile morphology developed mature morphology more rapidly than did plants grown from seed. However, some mature‐phase morphological characteristics did not return to micropropagated plants during the time frame of the study. Rejuvenation of Betula appears to occur during in vitro micropropagation, but the level of juvenility that is regained may not be equivalent to that of a seedling. Not all morphological indicators of phase change are affected equally by in vitro rejuvenation.
IN VITRO REJUVENATION OF BETULA (BETULACEAE): BIOCHEMICAL EVALUATION
Authors: Brand Mark H. , Lineberger R. Daniel
Published: January 2018

The pattern of protein production during rejuvenation of in vitro cultured Betula was determined. Comparisons were made between half‐sib seedlings and micropropagated, grafted, and cutting‐propagated mature‐phase birch grown under similar conditions. Three clones were examined at 1, 4, and 8 mo postpropagation, for differences in total denatured protein and peroxidase and esterase isozymes. Polyacrylamide gel electrophoresis was employed to produce protein banding patterns representative of each type of plant at each time postpropagation. Evaluation of total denatured protein banding patterns indicated that micropropagated plants are initially more like seedlings than mature plants. Peroxidase and esterase isozyme analyses detected differences in isozyme activity and composition between the variously propagated plants and supported evidence provided from the denatured protein patterns. The type of plant part that is evaluated is critical in determining if isozyme banding patterns can be seen. Specific proteins or enzymes that mediate phase change in birch could not be detected consistently between clones or tissue types.
MATERNAL INHERITANCE OF THE CHLOROPLAST AND MITOCHONDRIAL GENOMES IN CHEILANTHOID FERNS
Authors: Gastony Gerald J. , Yatskievych George
Published: January 2018

Molecular data from the chloroplast genome are being used to reconstruct the phylogeny and revise the problematic taxonomy of the xerically adapted cheilanthoid ferns. Chloroplast DNA based phylogenies trace maternal, paternal, or biparental lineages, depending on the mode of inheritance of the chloroplast genome, and instances of all three modes of inheritance are known in the seed plants. Evidence for biparental and uniparental inheritance in ferns has been presented, but the distinction between maternal and paternal uniparental inheritance has not been rigorously made, and the mode of inheritance in cheilanthoid ferns is completely unknown. Based on a natural hybrid population in the cheilanthoid genus Pellaea in which the maternal and paternal derivations of the hybrid are unambiguously known, restriction fragment length polymorphisms of chloroplast DNA demonstrated simple maternal inheritance of the chloroplast genome. This hybrid complex was also examined for restriction fragment length polymorphisms of its mitochondrial DNA, providing the first direct evidence that the mitochondrial genome in ferns is maternally inherited.
VASCULAR SYSTEM OF THE FERTILE FLORET OF PANICUM (GRAMINEAE: PANICOIDEAE: PANICEAE)
Authors: Pizzolato Thompson Demetrio
Published: January 2018

Serial transections of the rachilla of Panicum were used to reconstruct the vascular system of its fertile floret at anthesis. A developmental bias to the description of the floret vascular system furnishes new aspects of comparison within the subfamily Panicoideae and, outside of it, with the floret vascular systems of other subfamilies. The two collateral bundles descending the styles merge below the locule of the ovary of P. dichotomiflorum. The merging stylar bundles are joined by the descending placental bundle. The three blend into an amphivasal bundle that continues descending the rachilla as the pistil prong. It descends in the posterior of the rachilla until the level of entry and merger of the three stamen traces at the anterior of the rachilla. Horizontal unions of sieve and tracheary elements connect these erstwhile independent components. Intermediary cells specialized as transfer cells are abundant in the rachilla at this level. In the lower regions of this major interconnection, a minor trace from each of the two lodicules joins the entering lateral stamen traces. The anterior stamen trace is the major component that continues descending the anterior of the rachilla beyond the horizontal connection of stamen traces and pistil prong. In the rachilla at the lowest levels of the fertile floret, the median trace of the lemma joins, as a minor vein, the descending anterior stamen trace.
PHYLOGENY OF NORTH AMERICAN ORYZOID GRASSES AS CONSTRUED FROM MAPS OF PLASTID DNA RESTRICTION SITES
Authors: Duvall Melvin R. , Peterson Paul M. , Terrell Edward E. , Christensen Alan H.
Published: January 2018

Restriction sites for six enzymes were mapped for the plastid DNAs of eight species of oryzoid grasses from temperate North America together with Olyra latifolia using biotin‐labeled probes from Oryza sativa. Cladistic analysis of the data indicated the existence of one, most‐parsimonious cladogram of 56 steps. Two species of Leersia differed by only one restriction site mutation, and two species of Zizania differed by only two mutations, whereas Luziola fluitans and L. bahiensis differed by 15 mutations. The restriction sites data strongly support two monophyletic clades corresponding to Oryzinae and Zizaniinae, but only weakly support the traditionally hypothesized alliance of Zizaniinae with other monoecious oryzoid grasses.
COMPARATIVE MEASURES OF DESICCATION‐TOLERANCE IN THE TORTULA RURALIS COMPLEX. I. VARIATION IN DAMAGE CONTROL AND REPAIR
Authors: Oliver Melvin J. , Mishler Brent D. , Quisenberry Jerry E.
Published: January 2018

A mechanism for desiccation‐tolerance in bryophytes based on carbon balance, damage limitation, and cellular repair is proposed. These criteria are incorporated into an experimental framework to measure desiccation‐tolerance comparatively. In this report we utilize measures of damage control and damage repair to determine relative differences in tolerance between populations of three tolerant moss species: Tortula caninervis, T. ruralis, and T. norvegica. The measurement of damage control by electrolyte leakage alone was demonstrated not to be useful in determining levels of tolerance by traditional criteria in these closely related and highly tolerant species. Measurement of protein synthetic differences between hydrated and desiccated‐rehydrated treatments was used to distinguish between the capabilities of the three moss species to repair cellular damage and to formulate a measure of tolerance. The overall ranking of the three species in descending order of tolerance is calculated to be: Tortula caninervis, T. ruralis, and T. norvegica. However, individual populations of each of these species exhibit variation in tolerance levels that span this broader classification. These rankings correlate well with the perceived ranking of water stress in the species' natural habitat.
MOLECULAR PHYLOGENETICS OF CALYCADENIA (COMPOSITAE) BASED ON ITS SEQUENCES OF NUCLEAR RIBOSOMAL DNA: CHROMOSOMAL AND MORPHOLOGICAL EVOLUTION REEXAMINED
Authors: Baldwin Bruce G.
Published: January 2018

Phylogenetic patterns within Calycadenia were estimated from 18–26S nuclear ribosomal DNA sequences of the internal transcribed spacer (ITS) region in 19 representatives of all species in Calycadenia, including Osmadenia (C.) tenella, and in two outgroup species. In pairwise comparisons among the Calycadenia and Osmadenia sequences, divergence ranged from 0 to 11.2% of nucleotides in ITS 1 and from 0 to 8.6% in ITS 2. Of 62 nucleotide sites with potential phylogenetic information, 51.6% were in ITS 1, 46.8% were in ITS 2, and 1.6% were in the 5.8S subunit. A highly resolved, strict consensus tree from Wagner parsimony analysis of these data agrees well with morphological and cytological evidence. This tree suggests that: 1) the monotypic Osmadenia tenella is the sister‐group to Calycadenia; 2) the base chromosome number in Calycadenia is n = 7, from which other numbers were derived; 3) species with multiple T‐glands on cylindrical bracts and chromosome numbers of n = 5 or 6 (or 7 in C. oppositifolia) form a monophyletic group derived from an n = 7 species similar or identical in genomic structure to C. hooveri or C. villosa; 4) C. spicata (n = 4) is the product of an independent dysploid reduction from n = 7; 5) C. multiglandulosa and C. pauciflora, sensu Keck, are not monophyletic taxa; and 6) loss of chromosomal homology between Calycadenia species, as reflected by meiotic chromosomal association in hybrids, is positively correlated with time since evolutionary divergence. These results offer little evidence of homoplasy in chromosomal and phenotypic characters in Calycadenia and provide further support for the phylogenetic utility of plant ITS sequences.
MICROPYLAR EXUDATE IN GASTERIA (ALOACEAE) AND ITS POSSIBLE FUNCTION IN POLLEN TUBE GROWTH
Authors: Franssen‐Verheuen Martinie A. W. , Willemse Michiel T. M.
Published: January 2018

The micropylar exudate of Gasteria verrucosa (Mill.) H. Duval was studied using light and electron microscopic techniques. Ovules may contain micropylar exudate before stigma receptivity. During successive phases of stigma receptivity, the number of ovules with micropylar exudate and the amount of micropylar exudate per ovule increases. At the late phase of stigma receptivity, large amounts of micropylar exudate with a smooth to cauliflowerlike appearance were observed. Micropylar exudate is viscous and contains, among other components, proteins and carbohydrates. At all stages of the stigma investigated, ovules situated at the base of the ovary contain a larger quantity of micropylar exudate than those at the top. The appearance of micropylar exudate is related to the degree of development of the embryo sac and it originates primarily from the filiform apparatus. It is assumed that an uptake of water by the ovule initiates the outflow of micropylar exudate from the filiform apparatus into the micropyle. Both ovular pollen tube ingrowth and seed set mark the optimum pollination stage of the stigma, which for both events lies around the onset of stigma receptivity. When pollen tubes have reached the ovary, young micropylar exudate stimulates their growth rate. The presence of micropylar exudate seems to be a requirement for pollen tube penetration, and an interaction between the pollen tube and the micropylar exudate has been proposed. Possibly, the micropylar exudate serves as a nutritional source and, in an optimum condition, as an attractant for approaching pollen tubes.
POROSIMETRIC STUDY OF THE LICHEN FAMILY UMBILICARIACEAE: ANATOMICAL INTERPRETATION AND IMPLICATIONS FOR WATER STORAGE CAPACITY OF THE THALLUS
Authors: Valladares F. , Wierzchos J. , Ascaso C.
Published: January 2018

The pore system within the thalli of 13 lichen taxa belonging to the family Umbilicariaceae has been studied by means of mercury intrusion porosimetry. A characteristic bimodal pore size distribution with a central depression around 0.05 μm of equivalent pore radius was obtained in all lichen samples. However, clear differences were found among the pore size distributions of each lichen taxa. The total thallus porosity was undoubtedly related to the anatomy of the medulla. In general, a radial plectenchymatic medulla conferred larger porosity to the thallus than an arachnoidal one. Maximum thallus water content closely depended on the total thallus porosity in the five lichens possessing rhizinomorphs. The species with a similar type of medulla could be grouped together in a multivariate analysis that considered three porosimetric parameters and the maximum thallus water content. Umbilicaria cinereorufescens was the most distinct species, with the lowest values of total porosity and water storage capacity and the largest value of thallus density, apparently due to its scleroplectenchymatic medulla. The pore size distribution existing inside the thallus of the species studied is discussed in relation to the often opposing problems of CO2 exchange and optimal water relations. Some results pointed to a large influence of the micropores (<0.05 μm) on the water storage capacity of the thallus, while the macropores would have a more important role in gas exchange.
TEMPERATURE EFFECTS ON SEED GERMINATION OF EAST ASIAN AND TERTIARY RELICT SPECIES OF DIOSCOREA (DIOSCOREACEAE)
Authors: Terui Keisuke , Okagami Nobuo
Published: January 2018

To obtain information relevant to the evolution of dormancy, germination responses to temperature of intact seeds and naked zygotic embryos were compared among taxonomically closely related species of Dioscorea in the section Stenophora. We examined five species from the northern half of the East Asian distribution area and four species considered to be Tertiary relict species from the Appalachians, the Caucasus, and the Balkans. Although features of germination of the intact seeds differed from species to species, the naked embryos of all species germinated over a similar wide range of temperatures without any marked differences among species. This unitary physiological feature of the embryos suggests the possibility that the temperature responses of the embryos have not changed since the Tertiary period. In the East Asian species, as the distribution area shifts to the north the seeds gradually lose their dormant features, and consequently the germination behavior of the seeds gradually changes to resemble that of their embryos. The seed of the northernmost species has no dormant features at all, and temperature responses of the seed are the same as those of the embryo. Full germination of the intact seeds of East Asian and Tertiary relict species required prior chilling treatment. Unlike the East Asian species, however, the relict species germinated to some extent at higher temperatures over a narrow range without prior chilling. However, the resultant germlings died or elongated poorly. Thus, the germination process of relict species may have become less sensitive to high‐temperature inhibition after their isolation from Asian species.
FRUITS AND SEEDS OF THE TERTIARY BRANDON LIGNITE. VII. SARGENTODOXA (SARGENTODOXACEAE)
Authors: Tiffney Bruce H.
Published: January 2018

Seeds of Sargentodoxa (Sargentodoxaceae), a deciduous vine presently restricted to southeastern Asia, are described from the Oligocene Brandon Lignite of Vermont. This is the first report of fossil Sargentodoxaceae. The Sargentodoxaceae are segregated from the Lardizabalaceae, a small family with an unusual modem distribution (six genera in East Asia, two genera in Chile). Given the close relationship of the two families, the discovery of Sargentodoxa in North America, along with one and possibly two other occurrences of Lardizabalaceae in the Northern Hemisphere, raises the possibility that the Lardizabalaceae achieved their present distribution by 1) spreading around the Northern Hemisphere in the early Tertiary as part of the “Boreotropical Flora,” followed by 2) long‐distance dispersal from north to south in the New World. Other factors argue against this interpretation.
PHOTOSYNTHETIC PATHWAYS OF HESPERALOE FUNIFERA AND H. NOCTURNA (AGAYACEAE): NOVEL SOURCES OF SPECIALTY FIBERS
Authors: Ravetta Damian A. , McLaughlin Steven P.
Published: January 2018

Hesperaloe funifera and H. nocturna are currently being studied as potential new sources of fibers for specialty papers. This study investigated canopy architecture and light interception in H. funifera, and gas exchange in both species. H. funifera is an acaulescent rosette species with stiff, upright leaves. Mean leaf angle for 3‐year‐old plants was 70° from horizontal, and more than 90% of the leaf surface was at angles greater than 50°. Vertical orientation of leaves reduced seasonal variation in light interception and midday light interception during summer months. High leaf angles are interpreted as an adaptation to arid habitats that could reduce this species' suitability for cultivation in more humid areas. Both H. funifera and H. nocturna had leaf‐tissue water contents and mesophyll‐succulence values intermediate between previously investigated Agavaceae known to be either C3 or Crassulacean acid metabolism (CAM) plants. Both species proved to have CAM, however. Gas exchange characteristics varied with leaf age, with older leaves having higher assimilation rates, greater water‐use efficiency, and a higher proportion of nighttime CO2 uptake. Interestingly, these older leaves had mesophyll succulence values closer to those of typical C3 species. These Hesperaloe species can thus be characterized as nonsucculent CAM plants. Both species showed CO2 uptake rates of 5–8 μmol m‐2 sec‐1 expressed on a total‐surface‐area basis and 10–18 μmol m‐2 sec‐1 expressed on a projected‐leaf‐area basis. Expanded cultivation of species possessing CAM in marginal areas has been recommended recently; the physiological studies reported here along with previous studies of their economic botany identify these Hesperaloe species as good crop candidates for dry regions.