bluuebunny/crossref_metadata_2025 huggingface dataset:
ANATOMY OF MACROZAMIA COMMUNIS LATERAL ROOTS AND ROOT NODULES FORMED IN VITRO STUDIED WITH LIGHT AND SCANNING ELECTRON MICROSCOPY
Authors: Webb David T. , Slone J. Henry
Published: January 2018

The anatomy of Macrozamia communis L. Johnson lateral roots and nodules was studied following axenic culture in light and darkness. Pointed lateral roots from dark cultures had an open apical organization similar to that of other cycads and gymnosperms. A distinct protoderm‐derived epidermis was not observed. At the apex, the dermis was formed by the outer root capcortical cell layer. Subapically, the outer cortex formed the dermis. No evidence of an algal zone was observed in these roots. The stele was bounded by a distinct endodermis and contained an exarch, diarch xylem. Apogeotropic nodules which developed at the root‐shoot junction in darkness, branched dichotomously and had rounded tips covered by tangentially‐enlarged root cap cells. The root cap was reduced to a few cell layers and was confined to the extreme nodule apex. The central region of the apical meristem was enlarged, and meristematic cells contained differentiated amyloplasts. A presumptive algal zone was present in some but not all nodules and divided the cortex into inner and outer regions. Stelar anatomy was similar to that observed in pointed, dark‐grown lateral roots, except that there was greater xylem differentiation. Nodules which developed in the light were similar to dark‐formed nodules, except that root cap cells were radially enlarged and extended over the flanks of the nodule forming a persistent root cap. The heteromorphic lateral roots of M. communis formed a developmental continuum not a heterorhizic root system.
ULTRASTRUCTURAL COMPARISION OF POLLEN GRAINS FROM 2n, 3n, AND 4n PLANTS OF EUPHORBIA DULCIS
Authors: Murgia M. , Wilms H. J. , Cresti and M.
Published: January 2018

Pollen development in plants with different ploidy levels of Euphorbia dulcis is similar but some ultrastructural differences do occur. In pollen of diploid plants large aggregations of rough endoplasmic reticulum [RER] are attached to the pollen wall near the young generative cell but such aggregations are not present in other karyotypes. Plastids are detected only in young generative cells of triploid plants. In diploid plants the generative cell becomes spindle‐shaped, in triploid and tetraploid plants it remains round during the movement from the pollen wall to the center of the vegetative cell. The intine surrounding the generative cell in 3n plants is thinner than that found in 2n and 4n plants. Pollen grains in tetraploid plants are twice as large as those in diploid plants. Pollen viability is 90% in 2n plants, but only 10% in 4n plants.
VARIATION IN NECTAR SUGAR COMPOSITION AT THE INTRAPLANT LEVEL IN IPOMOPSIS LONGIFLORA (POLEMONIACEAE)
Authors: Freeman C. Edward , Wilken Dieter H.
Published: January 2018

The nectar sugar composition of individual flowers from single plants in both greenhouse and field populations was determined by High‐Performance Liquid Chromatography (HPLC). Intraplant variability in nectar sugar composition of greenhouse‐grown plants was significantly greater than can be attributed to the analytical methodology. Individual greenhouse‐grown plants had significantly different sugar compositions, suggesting genetic differences. Under field conditions the situation was complex. Variation among flowers from single plants in field populations was significantly greater than that of plants under greenhouse conditions. Unprotected flowers of some field populations were more variable at the intraplant level than others. Field experiments showed that, in untreated (open‐visited) flowers, the percent sucrose relative to other sugars declined significantly and coefficients of variability increased significantly with flower age. However, nectars never exposed to the natural environment did not change significantly with flower age. Further, within single plants it was found that percent sucrose in nectars varied in a small but significant way during the growing season. The data suggest that, in this species, both intrinsic and extrinsic factors affect nectar sugar composition and it is desirable to obtain samples from numerous flowers to accurately characterize the nectar sugar composition of an individual under field conditions.
BREEDING SYSTEMS OF SELECTED GALAPAGOS ISLANDS ANGIOSPERMS
Authors: McMullen Conley K.
Published: January 2018

The breeding strategies of 52 Galápagos Islands angiosperms from 30 families were examined. Controlled pollinations were performed to determine if self‐incompatiblity was more prevalent than previously thought, thus acting as an enforcer of outcrossing, or if instead, both dioecism and self‐incompatibility are poorly represented and self‐compatibility is the rule. The plants tested were located in each of the seven major vegetation zones on the southern slope of Isla Santa Cruz. Fruit and seed yields were compared between tagged but uncovered flowers (controls) and others that were subjected to various manipulations. Of the 52 species studied, one was dioecious, 11 yielded inconclusive results, and the remaining 40 showed self‐compatibility. All but three of the latter group also demonstrated automatic self‐pollination. This study suggests that on the Galápagos Islands hermaphroditic and dioecious plants occur in relatively the same proportions as found in their mainland source areas. Of the two hermaphroditic breeding strategies considered in this study, self‐compatibility and self‐incompatibility, the former is highly represented in the Galápagos flora.
A SYSTEMATIC REVISION OF PHYLLANTHUS SUBSECTION URINARIA (EUPHORBIACEAE)
Authors: Rossignol L. , Rossignol M. , Haicour R.
Published: January 2018

The examination of several taxa from various tropical regions of the world, previously classified as Phyllanthus urinaria L., indicates that they do not belong to a single species. On the basis of morphology, cytology, genetics, and biometry, a new classification is presented in which the collective species P. urinaria, or “urinaria complex,” is elevated to the subsection level: Phyllanthus subsection Urinaria. Within the subsection, two subgroups may be recognized on the basis of seed coat ornamentation. Each of these lines is represented by two species which differ from each other in chromosome number: P. embergeri nov. spec. (2n = 100) and P. nozeranii nov. spec. (2n = 50) in the “spiraled” line, P. hookeri Muell. Arg. (2n = 100) and P. urinaria L. (2n = 50) in the “radiated” line. In the latter species, which has undergone diversification, two subspecies may be distinguished: P. urinaria urinaria and P. urinaria nudicarpus subspec. nova.
A PERMINERALIZED FLOWER FROM THE MIDDLE EOCENE OF BRITISH COLUMBIA
Authors: Stockey Ruth A.
Published: January 2018

A permineralized flower bud, two stamen clusters and one isolated stamen of similar morphology have been found in the black cherts of the Middle Eocene Allenby Formation of Princeton, British Columbia. Specimens were studied using a modified cellulose acetate peel technique and hydrofluoric acid. The single flower specimen, 4.5 mm long and 4.0 mm in diameter, represents half of a relatively mature bud of a bisexual flower with a superior ovary. The two‐loculate pistil is 2.5 mm long with a solid style and a lobed stigmatic surface. No ovules have been observed in attachment. Twenty‐two to 24 stamens are borne in three whorls or a tight helix. Pollen sacs of the anther are elongate with a thin connective while filaments are laminar. Anther walls contain rectangular cells with dark contents that also can be identified in isolated stamens or stamen clusters. Abundant stephanocolpate (pentacolpate), psilate pollen grains 20 μm in diameter have been isolated and examined using scanning and transmission electron microscopy. Grains are tectate, columellate with a broad foot layer that thins near the apertures, and an endexine of small platelets. The remains of four petals are surrounded by one large sepal, suggesting two in the whole flower. Morphological features of this flower are comparable to taxa of the Flacourtiaceae and Papaveraceae, but show closest similarities to the Eschscholziaeae of the Papaveraceae. Difficulties with reconciling the placement of this flower in the Eschscholziaeae and the known environment of deposition of the Princeton chert are discussed. The fossil material represents a new angiospermous taxon: Princetonia allenbyensis Stockey gen. et sp. nov., family Incertae sedis.
ULTRASTRUCTURE OF MAIZE ENDOSPERM SUSPENSION CULTURES
Authors: Felker Frederick C.
Published: January 2018

Suspension cultures derived from developing maize (Zea mays L.) endosperm were examined by electron microscopy, after both glutaraldehyde‐OsO4 and KMnO4 fixation, and compared with intact endosperm. Tissue clumps consisted of interconnected cell clusters without any organization of the different cell types. The cultures were comprised of cells with dense cytoplasm and small vacuoles, large vacuolate cells, and cells in which storage products (starch, protein bodies, or lipid) accumulated. The endomembrane system of cultured cells was more highly developed than that of cells of the intact endosperm. In particular, arrays of smooth endoplasmic reticulum were seen only in the cultured cells. An abundance of endoplasmic reticulum, dictyosomes, and ribosomes is consistent with the recently reported extracellular secretion of enzymes by these cultures. Cell wall ingrowths, a characteristic of basal endosperm transfer cells, were observed occasionally in cultured cells, but cells with ingrowths had no histological organization. Some of the observed features may have resulted from perturbation of normal cellular events caused by the conditions of in vitro growth. These cultures are a useful tool for studying cellular mechanisms of protein secretion and storage product accumulation in developing maize endosperm.
POSITIONAL AND SEASONAL VARIATION IN OAK (QUERCUS; FAGACEAE) LEAF MORPHOLOGY
Authors: Blue Marguerite P. , Jensen Richard J.
Published: January 2018

Within‐tree and seasonal variation in quantitative characters of oak leaves were evaluated by factorial analysis of variance. All linear and areal measurements illustrate marked within‐tree and seasonal variation. Numbers of lobes and bristle tips and primary vein angle appear relatively stable within trees and among seasons. In many instances, size‐correction reduces both within‐tree and seasonal variance to nonsignificant levels. However, all characters do not illustrate the same trends either within trees or across the seasons. The results have important implications for those attempting to evaluate among‐tree and among‐population variation.
MECHANICAL PROPERTIES WITHIN THE GROWTH ZONE OF CORN ROOTS INVESTIGATED BY BENDING EXPERIMENTS II. DISTRIBUTIONS OF MODULUS AND COMPLIANCE IN BENDING
Authors: Beusmans Jack M. H. , Silk Wendy Kuhn
Published: January 2018

A bending technique was used to infer the spatial distributions of rheological properties within the growth zone of the root of corn, Zea mays. “Bending modulus” (ratio of stress to strain, calculated from engineering theory of bending) falls from 20 MPa near the root tip (3 mm from the tip) to 6 MPa at the location 6 mm from the tip and then remains uniform through the basal region of the growth zone. Where growth stops, at 11–12 mm, there is a sharp rise in bending modulus. The profile of bending moduli is not changed by root incubation temperature during the growth period prior to bending, but it is shifted to the left in roots growing more slowly than the average at either of two temperatures (19 and 29 C). The spatial distribution of “compliance” (reciprocal of bending modulus and a measure of tissue extensibility) resembles the distribution of swelling in response to osmotic perturbation. The distribution of compliance does not parallel that of growth rate. Attempts to explain the discrepancy between compliance and growth rate lead us to examine the theoretical basis for the calculations and to suggest that the dependence of compliance on rate of stretching is physiologically important.
VINE PHOTOSYNTHESIS AND RELATIONSHIPS TO CLIMBING MECHANICS IN A FOREST UNDERSTORY
Authors: Carter Gregory A. , Teramura Alan H.
Published: January 2018

Photosynthesis in a deciduous forest understory was studied for three exotic vine species (Pueraria lobata, Lonicera japonica, and Hedem helix) and five common native species (Rhus radicans, Clematis virginiana, Smilax rotundifolia, Vitis vulpina, and Parthenocissus quinquefolid) possessing a variety of climbing mechanisms. The adventitious‐root climbers (H. helix and R. radicans) had the lowest maximum photosynthetic rates of all species (5.5 and 6.4 μmol m–2 s–1, respectively). The twining vine P. lobata was the most poorly adapted to the understory with a high light‐compensation point (43 μmol m–2 s–1), low photosynthesis under low light (0.5 μmol m2 s–1 at 50 μmol m–2 s–1), and the highest light requirement for obtaining 90% of maximum photosynthesis (860 μmol m–2 s–1). Lonicera japonica, another twining vine, was better‐adapted to low light conditions, but vines with tendril climbing mechanics were physiologically the best adapted to low light. The adhesive‐tendril climber P. quinquefolia was the most highly adapted to shade, with a low light compensation point (20 μmol m–2 s–1), a high photosynthetic rate under low light (3.5 μmol m–2 s–1), and a low light saturation point (160 μmol m–2 s–1). Results suggest that physiological adaptability of vines to low‐light environments may be related to climbing mechanics.
PERISTOME DEVELOPMENT IN MOSSES IN RELATION TO SYSTEMATICS AND EVOLUTION. II. TETRAPHIS PELLUCIDA (TETRAPHIDACEAE)
Authors: Shaw Jonathan , Anderson Lewis E.
Published: January 2018

The Tetraphidae is a small subclass of mosses with a nematodontous peristome that has frequently been interpreted as primitive among the true mosses. The developmental cell sequence leading to the formation of the four peristome teeth of Tetraphis pellucida is described for the first time. Comparisons are made with sequences known for other nematodontous and arthrodontous mosses. Peristome development in T. pellucida is more like that described previously for arthrodontous peristomes than to published developmental sequences for nematodontous peristomes of species in the Polytrichaceae. On the other hand, our observations confirm a basic uniformity of the earliest developmental stages in all mosses studied thus far, regardless of their systematic position.
ADVENTIVE EMBRYOGENESIS IN CITRUS (RUTACEAE) II. POSTFERTILIZATION DEVELOPMENT
Authors: Wakana Akira , Uemoto Shunpei
Published: January 2018

Cytological and histological studies on postfertilization development of ovules were carried out in six facultatively apomictic Citrus cultivars. At the time of anthesis, adventive embryo initial cells (AEICs) were detected mainly in the cell layers of the nucellus around the chalazal half of the embryo sac. During the approximately 40 days rest period of the AEICs after fertilization, rapid cell division and enlargement in the endosperm and the chalazal half of the nucellus resulted in the split of AEICs into several separated areas forming the micropylar, lateral and chalazal islands surrounding the enlarging embryo sac. Both in diploid seeds with triploid endosperm and triploid seeds with pentaploid endosperm, the AEICs located in the micropylar half successfully developed into adventive embryos. In diploid seeds, almost all AEICs located in the chalazal half did not develop beyond the initial‐celled stage, while in the triploid seeds, those located in the chalazal half occasionally developed into cotyledonary embryos. In seeds with aborted endosperm, the AEICs located in the chalazal half often developed into cotyledonary embryos. The chalazal expiants from normal seeds produced a large number of embryos in vitro. Four results can be summarized from these studies on adventive embryogenesis as follows: 1) All AEICs are initiated prior to anthesis. 2) Whether or not the AEICs successfully developed into adventive embryos is dependent upon their position in the seed. 3) The farther the AEICs are located from the micropylar end, the more adventive embryogenesis is suppressed by endosperm. 4) The degree of adventive embryogenesis in the chalazal half is affected by time and extent of malfunction of the endosperm. Under natural conditions, these regulatory systems of adventive embryogenesis contribute to high production of zygotic seedlings in apomictic Citrus species and cultivars.
REGENERATION FROM SEED OF SINARUNDINARIA FANGIANA, A BAMBOO, IN THE WOLONG GIANT PANDA RESERVE, SICHUAN, CHINA
Authors: Taylor Alan H. , Zisheng Qin
Published: January 2018

Seed production ofSinarundinaria fangianawas low on plants that flowered in 1984, one year after clones mass‐flowered. Insects killed 41% of flower ovaries or developing seed on 1984 plants. Soil seed bank samples suggest that 34% of flowers produced seed in 1983 when the species mass‐flowered. Viability of seed produced in 1983 was 22–34%.Sinarundinaria fangianaseed germinated in both 1984 and 1985. Germination and establishment were greater in sites with a closed canopy forest than in clearcuts. Removal of the forest canopy appears to retard 5.fangianaregeneration from seed. Forestry practices should be altered from clearcutting to selective cutting in areas adjacent to panda reserves to prevent compositional change in the forest understory that may be detrimental to pandas.
PATTERNS OF VARIATION IN THE STELLARIA LONGIPES COMPLEX: EFFECTS OF POLYPLOIDY AND NATURAL SELECTION
Authors: Macdonald S. Ellen , Chinnappa C. C.
Published: January 2018

Patterns of morphological variation were studied in herbarium specimens of Stellaria longipes, an herbaceous perennial and subsequently in a growth chamber experiment using three cytotypes (4x, 6x, 8x) of S. longipes and diploids of its proposed progenitor S. longifolia. Despite extensive phenotypic plasticity in many traits, patterns of variation resulting from ecotypic differentiation within S. longipes could be detected in the field. A distinct form of S. longipes, which is restricted primarily to arctic and alpine tundra locations, shows genetic differentiation for the following traits: few flowers per ramet, a low proportion of flowering ramets, and ovate leaves. The three cytotypes of S. longipes could be distinguished by their mean genotypic value for leaf length and number of flowers per ramet. The extent of phenotypic plasticity in these traits makes it unlikely that the cytotypes could be distinguished in the field. The direction and extent of morphological divergence between S. longifolia and S. longipes suggest an alloploid origin for S. longipes. Variational trends (among‐habitat types and cytotypes) in trait means are similar to those reported previously for the pattern of plasticity. This supports the argument that similar forces guide evolution of the mean and pattern of plasticity of a trait.
INTERACTIONS BETWEEN CROWN STRUCTURE AND LIGHT ENVIRONMENT IN FIVE RAIN FOREST PIPER SPECIES
Authors: Chazdon Robin L. , Williams Kimberlyn , Field Christopher B.
Published: January 2018

Measurements of light variation among leaves within crowns of fivePiperspecies were compared with estimates of spatial variation in light within understory, forest edge, and clearing habitats to estimate the extent to which crown structure contributes to variation in leaf light environment. Daily photon flux density (PFD) varied greatly within and among crowns. Coefficients of variation for daily PFD among sensors within a single crown ranged from 26 to 79%. Within a single crown located in a clearing, the range in daily PFD among leaves was nearly as great as the range over the entire sample of plants. In the understory, localized sunfleck activity contributed to a high degree of spatial variation in instantaneous and total PFD among leaves within individual crowns. Much of the microsite variation in sunfleck activity, however, reflected environmental conditions within the understory habitat. Within an array of sensors placed next toPipercrowns in the understory, correlations were poor for light sensors spaced only 0.2 m apart, and only 8% of the variance in light readings was explained by measurements made 0.5 m away. In the clearing habitats, microsite heterogeneity among leaves was more strongly influenced by leaf positions within crowns and leaf angles than by spatial heterogeneity within the habitat.
VASCULAR ARCHITECTURE IN ISOPHYLLOUS AND FACULTATIVELY ANISOPHYLLOUS SPECIES OF PENTADENIA (GESNERIACEAE)
Authors: Morgan Martin T. , Dengler Nancy G.
Published: January 2018

The organization and differentiation of primary vascular tissue in isophyllous shoots of Pentadenia crassicaulis and facultatively anisophyllous shoots of P. orientandina (Gesneriaceae) were compared using serial reconstructions and quantitative methods. Despite clear differences in shoot symmetry, both species are vascularized by four sympodia, with trilacunar, split‐lateral nodal anatomy. Leaf trace tracheary element number and diameter reflect leaf size differences in P. orientandina: these parameters are significantly greater in the large ventral leaves than in the small dorsal leaves. The median and lateral traces of ventral leaves of this species have a similar number of tracheary elements of equal diameter, while there are significantly more tracheary elements in the median than lateral traces of dorsal leaves. The pattern seen in P. crassicaulis is similar to that seen in the dorsal leaves of P. orientandina. In both species, protoxylem development anticipates differences in mature shoot vasculature. Changes in tracheary element number during ontogeny precede or are approximately coincident with changes in leaf size. These results suggest that the facultative expression of leaf size differences in P. orientandina is associated with opportunistic development and differentiation of the lateral trace.
MICRODISTRIBUTION OF THE BEACH PLANT CAKILE MARITIMA (BRASSICACEAE) AS INFLUENCED BY A RODENT HERBIVORE
Authors: Boyd Robert S.
Published: January 2018

The microdistribution of a beach plant, Cakile maritima, was examined relative to patches of an introduced beachgrass, Ammophila arenaria. Sampling was done with belt transects oriented parallel to the beachfront to minimize the influence of physical factors along the land/sea gradient. No Cakile individuals were found within Ammophila patches, and a 3–4 m wide zone of decreased abundance occurred outside of patch borders.

I hypothesized that this microdistribution was due to foraging behavior of deer mice, Peromyscus maniculatus, which nest in Ammophila patches and forage outward from them. Manipulative experiments using fruits and seedlings of Cakile confirmed that herbivory was higher inside patches and in border areas. Seedlings protected from herbivory by wire cages survived and grew equally well both inside and outside of Ammophila patches, demonstrating that differences in other habitat factors were not of major importance in determining Cakile microdistribution. Herbivory by mice was concluded to be of primary importance in determining the microdistribution of Cakile relative to Ammophila. Rodent herbivory may influence microdistributions of beach plants along the land/sea gradient, and may also be partly responsible for decreased plant species richness often observed in Ammophila‐dominated areas on the West Coast.
QUANTITATIVE STUDIES OF PINNULE DEVELOPMENT IN THE FERNS ADIANTUM RADDIANUM AND CHEILANTHES VIRIDIS
Authors: Zurakowski Kathi A. , Gifford Ernest M.
Published: January 2018

Pinnule development was investigated in two fern species, Adiantum raddianum Presl cv. Decorum and Cheilanthes viridis (Forsk.) Swartz, by using clearings to facilitate the recording of mitotic divisions. Both species were found to possess a marginal meristem. This meristem consists of both a marginal row of large initials and a submarginal meristematic zone. The marginal meristem in these ferns is responsible for establishing the layers of the lamina, providing new cells which by enlargement will expand the pinnule, establishing general pinnule form, initiating the procambial stands, and forming the false indusia. The cells of the submarginal meristem were found to divide parallel to the pinnule margin more frequently if they were to become ground tissue, while dividing perpendicular to the margin more frequently if they were to become procambial. Details of vein dichotomies were also studied. Perimeter expansion was found to be associated with dichotomy of the veins, and venation pattern was found to be correlated with leaf form. The marginal meristem is active from the time of pinnule initiation until the pinnule reaches about 50% of its final length or width. Leaf development in leptosporangiate ferns resembles the traditional concept of development in angiosperms somewhat more than it does the more recent concepts. It is clear, though, that there is not a high degree of convergence in the marginal growth of fern and angiosperm leaves.
RECOLONIZATION OF SMALL DISTURBANCE PATCHES IN A NEW ENGLAND SALT MARSH
Authors: Hartman Jean Marie
Published: January 2018

Availability of colonizers and edaphic conditions were tested in relation to rates of recolonization of open patches in salt marsh vegetation. The density of buried viable seeds was estimated by counting seedlings in undisturbed vegetation and germinating seeds in the laboratory. A low density of viable seeds (<50 per m2) found in these salt marsh soils indicated the absence of an important viable seed bank in this system. Rates of recolonization in natural open patches were monitored for three years. Vegetative expansion of Spartina alterniflora, at approximately 12 cm per year, accounted for most of the recolonization of open patches, although some colonization of annual Salicornia spp. occurred from seeds. Salinity and sulfide and ammonium concentrations were measured in pore water samples from depths of 2–7 cm and 10–15 cm of soil. Comparison of the concentrations from disturbed and undisturbed plots in the marsh did not show significant differences, indicating that none of the edaphic conditions measured would be more inhibitory to plant growth in the disturbed than the undisturbed plots. Therefore, the rate at which small open patches become recolonized is primarily controlled by proximity of Spartina alterniflora and its capacity for vegetative expansion.
EFFECT OF OVULE POSITION IN THE POD ON PATTERNS OF SEED FORMATION IN TWO SPECIES OF LATHYRUS (LEGUMINOSAE: PAPILIONOIDEAE)
Authors: Hossaert Martine , Valéro Myriam
Published: January 2018

Using a combination of observations of fate of ovules in matured fruits and of fluorescence techniques to study pollen tube growth and fertilization of ovules, we examined patterns of seed formation within pods in natural populations of two species of Lathyrus, L. sylvestris and L. latifolius. We also examined variation in these patterns within and among populations and between two consecutive years. In both species, only a portion of the ovules were fertilized. Fertilization occurs over a period of several days and ovules at the stigmatic end of the fruit are the first to be fertilized. Fertilized ovules farthest from the stigma are closest to the maternal nutrition. The pattern of embryo abortion is interpreted as a balance between the early start and genetic quality of embryos near the stigma, on the one hand, and the nutritional advantage of proximity to maternal nutrients, on the other. Differences between the two species in patterns of seed maturation are postulated to be related to differences in breeding system. In L. sylvestris, a higher frequency of selling leads to less genetic diversity of pollen deposited on the stigma, lower competition among potential sires, and a more nearly random pattern of ovule fertilization and maturation within the pod.
MICROTUBULES ASSOCIATED WITH SIMULTANEOUS CYTOKINESIS OF COENOCYTIC MICROSPOROCYTES
Authors: Brown Roy C. , Lemmon Betty E.
Published: January 2018

Microtubule arrays associated with simultaneous cytokinesis in the coenocytic microsporocytes of Lonicera japonica and Impatiens sultani were studied by indirect immunofluorescence. The future division planes are not predicted prior to meiosis by either a preprophase band of microtubules or cytoplasmic lobing. Cleavage planes appear to be determined by position of the four haploid nuclei and the development of postmeiotic microtubule systems. Perpendicular second division spindles in Lonicera result in tetrahedrally arranged tetrads while parallel spindles in Impatiens result in tetragonal arrangement. Immediately following meiosis bands of microtubules, the secondary spindles, develop between both sister and nonsister nuclei. These arrays give way to systems of microtubules that radiate equally from each of the four nuclei in the coenocytic sporocyte. Simultaneous cytokinesis is initiated by centripetal wall deposition at the periphery of the sporocyte and proceeds along planes marked by interaction of the opposing arrays of nuclear‐based microtubules.
SURVEY OF SHOOT ORGANIZATION IN THE ARACEAE
Authors: Ray Thomas S.
Published: January 2018

Shoot organization is examined in 87 species from 29 genera representing all six subfamilies of the Araceae and of Acorus, which has been placed in a separate family. Within each taxonomic group examined, the details of shoot organization are presented, including the types of segments and articles which make up the shoot, the degree of expansion of leaf blades, and the placement of buds along the shoots. Literature on shoot organization of the 29 genera is reviewed. The degree of correlation between shoot organization characteristics and systematic groupings is examined, and the utility of these characteristics for systematics is evaluated. It is found that within the taxa observed, the pattern of shoot organization provides a distinctive “fingerprint” at the generic or sectional level, sufficient for determination of the group. Some patterns which appear are pointed out: taxa with bisexual flowers usually produce a single inflorescence at the terminus of a vegetative article. A few taxa with bisexual flowers produce pairs of inflorescences at the ends of articles. Multiple inflorescences (more than two) at an article terminus occur only among taxa with unisexual flowers. Multiple inflorescences are associated with anisophyllous or homeophyllous sympodial growth, while single or paired inflorescences are associated with homeophyllous or intermittent homeophyllous sympodial growth. These patterns might be understood as the result of selection for flexibility of reproductive effort and of seasonal reproduction.
QUANTITATIVE VARIATION OF LIFE HISTORY TRAITS IN AMPHICARPIC PEANUTGRASS (AMPHICARPUM PURSHII) AND ITS EVOLUTIONARY SIGNIFICANCE
Authors: Cheplick Gregory P. , Quinn James A.
Published: January 2018

Peanutgrass, Amphicarpum purshii, is a predominantly selling annual that exhibits an amphicarpic reproductive strategy, producing spikelets (and seeds) both above and below the soil surface. Both aerial and subterranean spikelets are self‐fertile, but only the aerial spikelets are chasmogamous and capable of cross‐pollination. This species mostly grows in disturbed areas of the New Jersey Pine Barrens. To examine life history variation, 60 quantitative characters were measured on twelve families raised from seeds collected from the aerial panicles of twelve parents grown in the greenhouse. Only 19 (= 31.7%) of the traits showed significant between‐family phenotypic variation, and the mean percentage of the total variation due to family was 14.9 (N = 60 characters). Percentage biomass allocation and vegetative characters showed the highest narrow‐sense heritabilities. Traits directly relevant to fitness such as subterranean seed set and seed weight of both seed types showed the least genetic variation. This low variation could reflect genetic fixation and/or developmental canalization of those fitness components important to survival in disturbed, early‐successional habitats.
PHENOTYPIC PLASTICITY IN PHLOX. I. WILD AND CULTIVATED POPULATIONS OF P. DRUMMONDII
Authors: Schlichting Carl D. , Levin Donald A.
Published: January 2018

We investigated the changes in amounts and patterns of phenotypic plasticity which have arisen in the Texas annual Phlox drummondii during domestication. Character means and plasticities were compared for five populations: a wild population, three cultivated varieties (a Tall cultivar and two Dwarf cultivars), and a population of an escaped Tall cultivar naturalized in Texas. To measure plasticity, we scored the responses of 10 characters to six treatments and analyzed both the amount and direction of plastic response. Wild plants are phenotypically distinct from the Tall and Escaped cultivar and from the two Dwarf cultivars. Despite its substantial phenotypic divergence from the Wild population, the Tall cultivar's plasticity has changed little during domestication. Traits most strongly correlated with fitness show the least change in their plasticities. The two Dwarf varieties have very similar plasticities, despite strong phenotypic divergence from the Tall population and despite the fact that they were derived from different Tall lines. This suggests that indirect selection on phenotypic plasticity related to selection for the Dwarf habit has resulted in the characteristic plasticity of the Dwarf lines. The Escaped cultivar has substantially different plastic responses from those of the Wild or cultivated populations.
FACILITATION OF SUCCESSION BY THE NONMYCOTROPHIC COLONIZER SALSOLA KALI (CHENOPODIACEAE) ON A HARSH SITE: EFFECTS OF MYCORRHIZAL FUNGI
Authors: Allen Edith B. , Allen Michael F.
Published: January 2018

The effects of inoculation with vesicular‐arbuscular mycorrhizal fungi on nonmycotrophic (plants which do not form a mycorrhizal association) colonizing annuals and on mycotrophic perennials were investigated in southwestern Wyoming. A subsoil containing no initial mycorrhizal inoculum was used, and seeds of the later successional perennials were planted. The annuals were removed from one‐half of the sampling quadrats to test for the interaction of competition and mycorrhizae on the perennials. During the third and fourth years of succession, the density and percent cover of Salsola kali, the most abundant nonmycotrophic annual, decreased by one‐half to one‐third with inoculation. Mycorrhizal hyphae and spores were found in the rhizosphere of S. kali, with only occasional (1–2% of the root length) penetration of hyphae into the cortex. There were no differences in tissue phosphorus and nitrogen concentrations or water relations of inoculated vs. uninoculated S. kali.

The planted grasses, all Agropyron species, had no significant increase in density or percent cover with inoculation. The percent root infection of A. smithii was 5–30%. Grass density and percent cover was greatest where S. kali was present, suggesting facilitation of grass establishment by annuals on this harsh, windy site. However, grass density was lower where 5. kali density was lower following inoculation. Mycorrhizal fungi were hypothesized to hasten the rate of succession on other sites. On this site where facilitation is an important process, inoculation of early seral plants and their subsequent decline may slow primary succession in the early years.
EMBRYO STRUCTURE AND STORAGE RESERVE HISTOCHEMISTRY IN THE PALM WASHINGTONIA FILIFERA
Authors: DeMason Darleen A.
Published: January 2018

The seed of Washingtonia filifera (Lindl.) Wendl. is hemispherical and has a smooth testa. The embryo is located on the rounded side of the seed near the raphe. The embryo consists of a prominent single cotyledon, an epicotyl, and a small root apex. The shoot apex is oriented at a right angle to the long axis of the embryo and possesses 2 to 3 leaf primordia. The cotyledon functions as a storage organ and is composed of three cell types with similar ultrastructure. These three types—the parenchyma, protoderm, and procambium—can be distinguished on the basis of position, size, and shape. The procambial strands in the cotyledon consist of a ring of bundles grouped into two distinct sympodia and extend from beneath the shoot apical meristem to the tip of the cotyledon where they are situated very close to the surface. The most prominent organelles within all cell types are protein bodies, lipid bodies, and crystalline protein fibers. The protein bodies contain small crystalline inclusions which are presumed to be phytin. Protein bodies in the protoderm were smaller, denser‐staining, and contained fewer crystalline inclusions than those in the parenchyma or procambium. On a volume basis, the parenchyma was shown to be 43% protein bodies, 25% lipid bodies, 15% cytoplasm, 7% cell wall, 4% intercellular space, 2% nuclei, and 4% other organelles (mitochondria and plastids).
A QUANTITATIVE ANALYSIS OF FEMALE GAMETOPHYTE DEVELOPMENT IN FIELD‐ AND GREENHOUSE‐GROWN PLANTS OF GLYCINE MAX AND PHASEOLUS AUREUS (PAPILIONACEAE)
Authors: George Ralph A. , George Glenda P. , Herr J. M.
Published: January 2018

A statistical analysis of size for the megasporocyte, functional megaspore, and 2‐, 4‐, 8‐nucleate, and mature female gametophytes for Glycine max and Phaseolus aureus grown in the field and greenhouse was accomplished from measurements of the length, width, and length and width intercepts for each stage. The greatest increase in mean length for Phaseolus in the greenhouse and Glycine in the field takes place between the 2‐ and 4‐nucleate stages. In alternate environments, the two genera show the greatest increase between the functional megaspore and 2‐nucleate stage. Greater similarity between the genera than shown by each genus in the two environments was also found for other features, viz., the largest mean length and width attained by each stage, the least increase in mean length and width and the overlap in confidence intervals for length and length intercepts between successive stages, and changes in the width intercept as a percent of total width as the ovule becomes campylotropous. T tests at the 0.05 level reveal significant differences between greenhouse and field plants in Phaseolus for length of the megasporocyte and 8‐nucleate stage and length and length intercept of the 2‐ and 4‐nucleate stages. In Glycine, differences appear for the length and both intercepts of the megasporocyte and the length intercepts of the mature stage. The similarity of Glycine in one environment to Phaseolus in the other coupled with the differences of statistical significance for each genus in the two conditions suggest that environment does have a pronounced effect on female gametophyte development. Statements to the contrary in previous reports to include one on these genera are correct for the qualitative aspects of development investigated, but they cannot be extended in all respects to the quantitative analysis of growth reported here. The differences recorded suggest caution in the choice of material for comparative studies. For embryological data, especially those of a quantitative nature, to be fully useful in taxonomic assessments, material for all taxa should be collected from natural habitats.
ON THE CORRELATION OF PRIMARY ROOT LENGTH, MERISTEM SIZE AND PROTOXYLEM TRACHEARY ELEMENT POSITION IN PEA SEEDLINGS
Authors: Rost Thomas L. , Baum Stuart
Published: January 2018

Pea seedlings (Pisum sativum L. cv. Alaska) were darkgrown in vermiculite. Roots of various lengths were cleared, stained and measured to determine the relative meristem height (MH), width and volume and the distance to the most proximal protoxylem tracheary element (PTE). A correlation was found between root length, MH and PTE position as follows: in roots from 4–40 mm as the root elongated the MH lengthened and PTE position increased its distance from the body/cap juncture; in roots 40–80 mm MH and PTE position remained approximately constant; in longer roots (80–120 mm) MH became shorter, and PTE position closer to the tip as the root elongated. The relationship, using our measurement procedure was that for every 0.19 mm change in MH, the PTE position changed by 1 mm. This response was partially growth rate dependent since short roots (4–80 mm) grew at a constant rate and longer roots (80–140 mm) grew slower. Root manipulations and trifluralin treatment, to inhibit cell division, caused tip swelling and modulated the position of the PTE toward the root tip. The control of the spatial relationship between meristem size and maturation position is discussed.
SHOOT STRUCTURAL EFFECTS ON NEEDLE TEMPERATURES AND PHOTOSYNTHESIS IN CONIFERS
Authors: Smith William K. , Carter Gregory A.
Published: January 2018

Greater needle packing (number of needles per unit stem length) among shoots of Picea engelmannii (Parry ex. Engelm.), Abies lasiocarpa ([Hook] Nutt.), and Pinus contorta (Engelm.) collected at sun‐exposed locations resulted in leaf temperatures (T1) that were well above air temperature (Ta) and which were closer to optimum for maximum photosynthesis under field conditions. Maximum photosynthesis in these species occurred at leaf temperatures well above mean maximum Ta during most of the summer growth period. An approximate doubling in needle packing on sun shoots of these species, however, led to an estimated temperature enhancement of daily photosynthetic carbon gain of 21 to 36% compared to estimations assuming T1 = Ta for the entire day. Elevated T1 due to needle packing may lead to substantial increases in summer carbon gain for conifers experiencing cold‐limited, short growth seasons.
INTERSPECIFIC GENE FLOW IN CUCURBITA: C. TEXANA VS. C. PEPO
Authors: Kirkpatrick Kurt J. , Wilson Hugh D.
Published: January 2018

The potential for interspecific genetic exchange was examined by monitoring flowering patterns, pollinator movement, and gene flow among experimental populations of the Texas gourd (Cucurbita texana) and cultivars of Cucurbita pepo. While flowering patterns and pollinator movement tended to maximize self‐pollination and local gene exchange, movement of effective pollen exceeded 1,300 m. This movement, mediated by the solitary bee Xenoglossa strenua and monitored by tracking allozyme variants, produced interspecific hybrids in 5% of the progeny from experimental plants. Interspecific gene exchange occurred in either direction with either species serving as staminate or pistillate parent. No obvious constraints to gene flow among plants representing C. texana and distinctive cultivars (vars. ovifera, medullosa, melopepo) of C. pepo were detected. Genetic exchange among different species and cultivars is enhanced by the foraging behavior of Xenoglossa. Multiple visits to either staminate (pollen carryover) or pistillate (multiple pollinations) flowers often result in the deposition of mixed pollen on receptive stigmas. The wild type (C. texana) can donate and receive effective pollen when growing under both weedy and natural conditions. The observed lack of interspecific reproductive isolation supports treatment of cultivars and wild types as a single species and, in conjunction with available data concerning temporal/geographical relationships among bees, squash, gourds, and humans in eastern North America, suggests the possibility of long‐term genetic interaction between wild types and domesticates.
PHYLOGENETIC IMPLICATIONS OF CHLOROPLAST DNA RESTRICTION SITE VARIATION IN THE MUTISIEAE (ASTERACEAE)
Authors: Jansen Robert K. , Palmer Jeffrey D.
Published: January 2018

Phylogenetic relationships among 13 species in the tribe Mutisieae and a single species from each of three other tribes in the Asteraceae were assessed by chloroplast DNA restriction site mapping. Initially, 211 restriction site mutations were detected among 16 species using 10 restriction enzymes. Examination of 12 of these species using nine more enzymes revealed 179 additional restriction site mutations. Phylogenetic analyses of restriction site mutations were performed using both Dolio and Wagner parsimony, and the resulting monophyletic groups were statistically tested by the bootstrap method. The phylogenetic trees confirm an ancient evolutionary split in the Asteraceae that was previously suggested by the distribution of a chloroplast DNA inversion. The subtribe Barnadesiinae of the tribe Mutisieae is shown to be the ancestral group within the Asteraceae. The molecular phylogenies also confirm the paraphyly of the Mutisieae and provide statistical support for the monophyly of three of its four currently recognized subtribes (Barnadesiinae, Mutisiinae, and Nassauviinae). The fourth subtribe, Gochnatiinae, is shown to be paraphyletic. Within the subtribes, several closely related generic pairs are identified. Chloroplast DNA sequence divergence among genera of the Asteraceae ranges between 0.7 and 5.4%, which is relatively low in comparison to other angiosperm groups. This suggests that the Asteraceae is either a relatively young family or that its chloroplast DNA has evolved at a slower rate than in other families.
SUSTAINED CAULOGENESIS IN CALLUS CULTURES OF LARIX × EUROLEPIS INITIATED FROM SHORT SHOOT BUDS OF A 12‐YEAR‐OLD TREE
Authors: Laliberté S. , Lalonde M.
Published: January 2018

Caulogenic callus cultures were established from vegetative short shoot buds collected from cuttings from a ca. 12‐year‐old tree of Larix × eurolepis. Schenk and Hildebrandt basal medium supplemented with various concentrations of 6‐benzylaminopurine (BAP, 2.5 × 10–7 to 1.0 × 10–5 M) or BAP (5.0 × 10–6 M) + indolebutyric acid (IBA, 1.0 × 10–6 M) was used. Subcultures were carried out on the same medium as used for initiation. Shoot formation resulted mostly from adventitious organogenesis on callus tissue, but adventitious organogenesis and axillary shoot development were occasionally observed on neoformed shoots. Series initiated in December 1984, June 1985, and August 1985 were still very productive after 32, 26, and 24 months respectively in culture. Sampling date of the primary explants had a pronounced effect on i) initial survival rate, ii) number of subcultures before establishment of continuous, vigorous cultures, and iii) number of subcultures before attaining a high percentage of caulogenic calli and good productivity. Browning of callus tissue with time during each subculture was concomitant with an increase in shoot productivity. Most neoformed shoots did not show pronounced elongation of the stem in vitro. Some shoots entered dormancy, and either stayed dormant upon subculture or resumed growth. Depending on the concentration of growth regulators used during callus culture, between 4 and 22% of excised shoots rooted when transferred first on DCR medium without growth regulator (Gupta and Durzan, 1985) and then twice on DCR‐1 medium (Gupta and Durzan, 1985). Rooted shoots elongated after a few weeks in greenhouse conditions.