bluuebunny/crossref_metadata_2025 huggingface dataset:
FOSSIL LATICIFERS FROM EOCENE BROWN COAL DEPOSITS OF THE GEISELTAL
Authors: Mahlberg Paul G. , Field Donald W. , Frye James S.
Published: January 2018

Thick mats of cellular remains from Eocene brown coal deposits of the Geiseltal near Halle, DDR, were determined to be fossil nonarticulated laticifers. Nuclear magnetic resonance analyses of intact strands showed they consisted of eis‐1,4‐configuration rubber representing the polymerized isoprenoid contents of individual laticifers. Only remains of laticifers are present; other cells are absent as a result of biodegradation. The long laticifers, often with a surrounding cell wall, retained a tubular shape during their preservation. The isoprenoid content, which filled the entire lumen, possessed a cribriform structural character. The interstices within the rubber represent areas of former protoplasm of the cell. Various configurations in the protoplasm molded by the rubber during the initial phase of fossilization appear as negative images of former nuclei, organelles, and possibly membrane surfaces. The laticifer axes possess branches of several configurations comparable in morphology to those in branched, nonarticulated laticifers in extant plants. Acetone extracts of the rubber contents analyzed by gas‐liquid chromatography identified the presence of several hydrocarbons which form a characteristic profile for the laticifer. It is suggested that the distinctive cellular micromorphology, rubber configuration, and hydrocarbon profile of these laticifers can be employed as markers in comparative studies with extant plants to identify the generic or species origin of these laticifers.
VASCULARIZATION OF DEVELOPING LEAVES OF GLEDITSIA TRIACANTHOS L. II. LEAFLET INITIATION AND EARLY VASCULARIZATION
Authors: Larson Philip R.
Published: January 2018

Leaflets of Gleditsia triacanthos are vascularized identically, whether they develop from the rachis of a once‐pinnate leaf or the rachilla of a bipinnate leaf. The vascularization process of a leaflet is also similar to that of a rachilla departing the rachis of a bipinnate leaf. Vascularization in all cases involves a rotation and reorientation of the participating bundles to form either a new midvein or a rachilla axis. During this process, the vasculature of the parent axis is progressively depleted. The ventral ridge bundle, however, is partially depleted when each new organ is vascularized and reconstituted after it departs. Observations suggest that the ridge bundles also contribute to formation of the ventral trichome glands that accompany the departure of each new organ. Young, expanding leaflets are vascularized by secondary veins that depart in an acropetal sequence from a consolidated midvein. Major secondary veins that progressively deplete the midvein vasculature are interspersed with minor secondary veins. The lamina expands laterally by anticlinal divisions in the plate meristem between secondary veins. Periclinal divisions that contribute to new cell layers also occur in the plate meristem in association with the secondary veins. No evidence of a recognizable marginal meristem was found. A marginal vein was always present in the leaf margin and cell divisions appeared to occur in association with this vein. Bridge bundles uniting adjacent veins were frequent in the plate meristem. Bridge bundles also occurred between the midvein and the nearest secondary vein and between the marginal veins and leaf margin.
FORAGER ATTRACTION BY SYMPATRIC IPOMOEA HEDERACEA AND I. PURPUREA (CONVOLVULACEAE) AND CORRESPONDING FORAGER BEHAVIOR AND ENERGETICS
Authors: Stucky Jon M.
Published: January 2018

Flowers of Ipomoea purpurea are larger, more colorful, more numerous per plant, and more conspicuous than those of I. hederacea. Because the nectar supply per flower is less variable i: I. purpurea and because the flowers of this species are visually more attractive, Bombus pennsylvanicus demonstrated a foraging preference and greater constancy for I. purpurea than for I. hederacea in experimental and natural sympatric populations in accordance with expectations derived from optimal foraging theory.
EFFECT OF GROWTH RATE, MORPHOGENIC ACTIVITY, AND PHYLOGENY ON SHOOT APICAL ULTRASTRUCTURE IN OPUNTIA POLYACANTHA (CACTACEAE)
Authors: Mauseth James D.
Published: January 2018

Dormant short shoot apices of Opuntia polyacantha were cultured under three conditions: cytokinin and high sucrose to stimulate the formation and rapid growth of a leafy long shoot; cytokinin and no sucrose (slow growth of a leafy long shoot); gibberellic acid and high sucrose (rapid growth of a spiny short shoot). These meristems, and also dormant (uncultured) ones, were analyzed by stereological, ultrastructural techniques. By comparing meristems growing with cytokinin but with or without sucrose, correlations between metabolic rate and apical ultrastructure were studied; comparison of leaf‐producing and spine‐producing meristems permitted examination of correlations with morphogenic role; comparison with published data for four other species permitted study of phylogenetic effects, and comparison with dormant apices revealed information about meristem activation. Ultrastructure varied according to each condition: metabolic rate, morphogenic activity and species can be distinguished by quantitative methods. Apical ultrastructure is most strongly correlated with rate of growth such that apices of differing species resemble each other if growing at similar rates, whereas apices of a single species differ markedly if growing at differing rates or if performing different morphogenic activities. Hyaloplasm is an excellent indicator of metabolic rate; mitochondria, nuclei, and vacuoles are not.
THE DEVELOPMENT AND DYNAMICS OF THE ROOT APICAL MERISTEM
Authors: Feldman Lewis J.
Published: January 2018

During the past ten years our concepts of the root apex and how it functions have expanded considerably. Through the use of several unique root tissue systems investigators have characterized the populations of cells which comprise the apex and have refined our views of the ways in which these populations interact to regulate aspects of root development. The aim of this paper is to present a summary of current thoughts on root development with emphasis on the activities of the cells comprising the root apex.
A DEVELOPMENTAL STUDY OF SILICIFICATION IN THE ABAXIAL EPIDERMAL CELLS OF SUGARCANE LEAF BLADES USING SCANNING ELECTRON MICROSCOPY AND ENERGY DISPERSIVE X‐RAY ANALYSIS
Authors: Sakai William S. , Sanford W. G.
Published: January 2018

A developmental study of the accumulation of silicon and other elements in the abaxial epidermis of sugarcane (Saccharum officinarum L.) leaf blades using scanning electron microscopy and energy dispersive x‐ray analysis showed that accumulation of silicon progresses at different rates in each epidermal cell type. In basal cells of two‐celled microhairs and in prickles there is accumulation of silicon while the leaf is immature and still enclosed within the spindle cluster of leaves and not involved in transpiration. After transpiration begins, all epidermal cells rapidly accumulate silicon. However, there are differences in the rate of silicon accumulation and in the maximum amount of silicon accumulation among the various cell types. This may relate to differences in their physiology or structure.
DISTRIBUTION OF DEFENSE NECTARIES IN IPOMOEA (CONVOLVULACEAE)
Authors: Keeler Kathleen H. , Kaul Robert B.
Published: January 2018

The structure and distribution of defense nectaries in the genusIpomoea(Convolvulaceae) were investigated. These nectaries do not reward pollinators and probably contribute to antiherbivore defense. Of 22 species sectioned, 15 had defense nectaries on the sepals. Of 12 other species observed, ten had sepal nectaries and two did not. Structurally, 14 of the species sectioned had crypt sepal nectaries and one had a basin nectary. Of the 14 species with crypt nectaries, two had invaginated spaces adding greatly to the internal area of these nectaries, and forming the most complex nectaries that have been reported. We term these labyrinthine crypt nectaries. All three types of nectaries are lined with secretory trichomes along the proximal surfaces of the crypts. Species with defense nectaries on the sepals tend to have petiolar defense nectaries as well, but the two locations may have different nectary types; e.g., basins on the petiole and crypts on the sepals. Since most reports of the function of these nectaries have shown antiherbivore defense by nectar feeders, the distributions of defense nectaries with respect to region and life history of the species were sought. Plants without sepal nectaries were found to have significantly smaller seeds than plants with sepal nectaries; they were also more frequently annuals. No significant relationship was found between region or breeding system and defense nectaries.
STUDIES ON THE LEAF OF POPULUS DELTOIDES (SALICACEAE): MORPHOLOGY AND ANATOMY
Authors: Russin William A. , Evert Ray F.
Published: January 2018

Mature field‐ and growth‐chamber‐grown leaves of Populus deltoides Bartr. ex Marsh. were examined with light and scanning electron microscopes to determine their vasculature and the spatial relationships of the various orders of vascular bundles to the mesophyll. Three leaf traces, one median and two lateral, enter the petiole at the node. Progressing acropetally in the petiole these bundles are rearranged and gradually form as many as 13 tiers of vascular tissue in the petiole at the base of the lamina. (Most leaves contained seven vertically stacked tiers.) During their course through the midrib the tiers “unstack” and portions diverge outward and continue as secondary veins toward the margin on either side of the lamina. As the midvein approaches the leaf tip it is represented by a single vascular bundle which is a continuation of the original median bundle. Tertiary veins arise from the secondary veins or the midvein, and minor veins commonly arise from all orders of veins. All major veins–primaries, secondaries, intersecondaries, and tertiaries–are associated with rib tissue, while minor veins are completely surrounded by a parenchymatous bundle sheath. The bundle sheaths of tertiary, quaternary, and portions of quinternary veins are associated with bundle‐sheath extensions. Minor veins are closely associated spatially with both ad‐ and abaxial palisade parenchyma of the isolateral leaf and also with one or two layers of paraveinal mesophyll that extend horizontally between the veins. The leaves of growth‐chamber‐grown plants had thinner blades, a higher proportion of air space, and greater interveinal distances than those of field‐grown plants.
INFLUENCE OF OCTOPINE, CALCIUM AND COMPOUNDS THAT AFFECT CALCIUM TRANSPORT ON ZEATIN‐INDUCED BUD FORMATION BY PYLAISIELLA SELWYNII
Authors: Spiess Luretta D. , Lippincott Barbara B. , Lippincott James A.
Published: January 2018

Decreasing the calcium chloride content of the medium for the moss, Pylaisiella selwynii (Kindb.) Steere and Anderson, reduces the number of developed buds obtained in the presence of zeatin (1 μm), whereas similar changes in magnesium sulfate concentration have no effect. Cobalt (10 μm), lanthanum (10 μm), zinc (10 μm) and cadmium (0.01 μm) chlorides inhibit zeatin‐induced bud formation even in the presence of 680 μm calcium, the normal concentration in the medium. Chlorpromazine (0.1 μm), cyclic adenosine 3′,5′‐monophosphate (100 μm), and glutamate (100 μm) also inhibit zeatin‐induced bud initiation. Ethylene glycol‐bis(β3‐aminoethyl ether)N,N,N′,N′‐tetraacetic acid (1 μm), the antibiotic A23187 (100 μm) and octopine (100 μm) each act synergistically with zeatin in promoting bud development and are generally more effective at calcium concentrations of 6.8 μm or less. The combination of either ethylene glycol‐bis(β‐aminoethyl ether)N,N,N′,N′‐tetraacetic acid, A23817 or octopine with zeatin plus any of the inhibitory metals or compounds results in more buds than are obtained with zeatin alone and these combinations are more effective relative to zeatin response at calcium concentrations lower than 6.8 μm. Experiments with Funaria hygrometrica (L.) Sibth. indicate a similar response to calcium, octopine and glutamate. These results appear to be related through changes in calcium availability at or within moss protonemal cells.
PATTERNS OF STEM VASCULATURE IN PHILODENDRON
Authors: French J. C. , Tomlinson P. B.
Published: January 2018

A survey of 480 collections of stem material of Philodendron has established five patterns of vascular organization. Species representing each of these patterns were analyzed by cinematographic methods to allow a three‐dimensional interpretation of the course of vascular bundles over extended distances. Pattern 1 has mainly collateral organization, but with some bipolar bundles. Pattern 2 has a majority of central bundles aggregated into compound (multipolar) bundles; Pattern 3 differs in that almost all bundles of the central cylinder are multipolar. Patterns 4 and 5 include compound vascular bundles in which the individual strands are not very discrete so that in Pattern 5, which is the most common in the genus, the bundles might be described as amphivasal. In Section Pteromischum, which has monopodial construction, the majority of species exhibit Pattern 2 which is exclusive to this group. Other correlations with subgeneric groupings are emphasized.
CELLULAR VOLUME AND TISSUE PARTITIONING IN CAPS OF PRIMARY ROOTS OF ZEA MAYS
Authors: Moore Randy
Published: January 2018

Cellular and tissue volumes were measured in caps of primary roots of Zea mays. There is an 850% increase in cellular volume as cellular function changes from that of being meristematic (i.e., calyptrogen cells) to graviperception (i.e., columella cells), and a 22% increase in cellular volume during the functional transition from graviperception to the production and secretion of mucilage. Cellular volume does not change significantly after cells cease mucilage production and are sloughed from the cap. Root caps of Z. mays allocate 7.5% of their volume for regeneration, 14.9% for graviperception, 24.3% for the transition of function from graviperception to mucilage production and secretion, and 38.7% for the production and secretion of mucilage. The remaining 14.5% of the cap volume is comprised of cells being sloughed from the cap.
THE ROLES OF PLANT HORMONES IN THE GROWTH OF THE COROLLA OF GAILLARDIA GRANDIFLORA (ASTERACEAE) RAY FLOWERS
Authors: Koning Ross E.
Published: January 2018

Corolla elongation and the roles of plant hormones in this process in Gaillardia grandiflora Van Houtte ray flowers were examined. The sterile ray flowers elongated during a 2‐day period, and corolla growth was accompanied by fresh and dry weight increases and epidermal cell elongation (greatest near the base of the corolla) but not by cell division. Corollas excised from young ray flowers were measured during treatment in vitro with solutions of plant growth regulators. They elongated in response to gibberellins and fusicoccin but did not respond to auxins, cytokinins, abscisic acid, ethylene, or inhibitors of ethylene biosynthesis. Sequential and simultaneous hormone applications indicated no additive or synergistic effects between hormones, but auxin did reduce gibberellin‐promoted growth. Analyses of endogenous auxins showed no significant variation, and ethylene production decreased prior to elongation, while a 20‐fold increase in endogenous gibberellin activity was observed just prior to rapid corolla elongation. It appears that corolla growth in Gaillardia is accomplished by an increase in gibberellin activity alone, that multiple hormone interactions are not important in the control of corolla growth, and that part of the mode of action of gibberellin is acid‐induced growth.
SHOOT APICAL MERISTEMS AND MUTATION: SELECTIVE LOSS OF DISADVANTAGEOUS CELL GENOTYPES
Authors: Klekowski Edward J. , Kazarinova‐Fukshansky Nina
Published: January 2018

The previously described mathematical model of stochastic apical meristem growth (Klekowski and K.‐Fukshansky, 1984) was used to study the fate of initials with disadvantageous genotypes. Such initials are heterozygous for somatic mutations with some dominant effects and consequently have lessened viabilities (V < 1) in contrast to initials with only wild type alleles (V = 1). Computer simulation studies show a dramatic increase in the loss of such mutations with increasing number of apical initials and/or the number of cell divisions of the initials and their daughter cells before the subsequent set of initials are chosen. Among plants with stochastic apices (most seed plants and some lower vascular plants), the major phylogenetic and ontogenetic trends are correlated with the development of apices with greater buffering against mutations. Whether these correlations reflect a causal relationship is of course unknown.
HORMONAL REGULATION OF MORPHOGENESIS IN STREPTOCARPUS AND ITS RELEVANCE TO EVOLUTIONARY HISTORY OF THE GESNERIACEAE
Authors: Rosenblum Irwin M. , Basile Dominick V.
Published: January 2018

Two morphogenetic patterns have contributed to phylogenetic diversification within the Gesneriaceae: accrescence of one of the paired cotyledons (anisocotyly), which serves to differentiate the subfamily Cyrtandroideae; sustained growth of the accrescent cotyledon accompanied by prolonged suppression and displacement of the embryonic apical meristem, which gives rise to an acaulescent, dorsiventral vegetative plant body (phyllomorph) and further serves to differentiate species of Cyrtandroideae found in two tribes and several genera including Streptocarpus. It was possible to prevent cotyledonary accrescence and induce caulescence at will, either by supplying exogenous GA3 or inhibiting auxin transport in species of Streptocarpus that normally manifest an extreme, phyllomorphic morphology. It was also possible to induce sustained, phyllomorphic development of cotyledons that are normally non‐accrescent with exogenous cytokinin. Therefore morphogenetic capacities previously thought to be “lost” or “lacking” in subgenus Streptocarpus and, with respect to isocotyly, the tribe Cyrtandroideae, are, in fact, present but suppressed. An hypothesis regarding the role of hormones with respect to morphogenesis and phylogeny of Streptocarpus is suggested.
SEEDLING GROWTH AND ROOT CONTRACTION IN THE SOAP PLANT, CHLOROGALUM POMERIDIANUM (LILIACEAE)
Authors: Jernstedt Judith A.
Published: January 2018

Radicles and adventitious roots of the soap plant are contractile and through their activity, mature bulbs of this species are buried to depths of 20–30 cm. Experiments were performed to determine rates of contraction and displacement of the shoot apex resulting from activity of the contractile radicle and the first several adventitious roots. The average displacement was 23.2 mm over a 10‐wk period and 63.8 mm over 29 weeks. Small glass beads and abortive seeds served as controls and showed no displacement through the soil column. Measurements from longitudinal and transverse sections of contracted and uncontracted portions of radicles revealed average increases of 26–64% in radial dimensions and 40–56% decreases in longitudinal dimensions of inner and middle cortical cells (excluding the endodermis) following contraction. Cells of the outermost cortex (excluding the exodermis) decreased in average longitudinal dimensions by 18–26% before becoming distorted and collapsed as contraction was completed. Average volumes of innermost cortical cells decreased by 15–54%, while two or three cell layers of the middle cortex, adjacent to collapsed outer cortical cells, increased in volume up to 75%. These middle cortical cells are identified as the “active” cells which, by their growth, are responsible for the shortening of the root. Throughout the process of contraction, the stele remains straight and undistorted, although the closer spacing of tracheary element secondary wall thickenings following contraction suggests longitudinal compression of the stele. The average number of cortical cells per transverse section does not differ in contracted and uncontracted roots and no evidence is found to support the “interdigitation” hypothesis of root contraction. However, reorientation of middle cortical cell expansion may be the mechanism of root contraction in Chlorogalum pomeridianum.
ANATOMY OF NODES VS. INTERNODES IN COLEUS: THE NODAL CAMBIUM
Authors: Bruck David K. , Paolillo Dominick J.
Published: January 2018

Secondary growth begins in the nodal regions before the internodal regions in Coleus, so that longitudinally discontinuous vascular cambia are formed in the 6th through the 9th or 10th nodes, where the internodal cambium becomes continuous between nodal cambia. The nodal cambia are identifiable by radial seriation in interfascicular regions, typical cytology of fusiform initials, and the presence of a ray system. Anatomical features distinct from the primary plant body are shared by the nodal and internodal cambia. Branching of primary vascular strands, restricted to procambium and phloem, is virtually confined to nodal regions. In secondary growth, vascular branching of xylem and phloem occurs in both nodes and internodes. Xylem strand branches are formed only from derivatives of vascular cambia. It is proposed that the cambium provides the secondary plant body an efficient channel for lateral auxin transport, by which branching across interfascicular regions is facilitated.
EMBRYOGENESIS AND SEEDLING DEVELOPMENT IN CASSIPOUREA ELLIPTICA (SW.) POIR. (RHIZOPHORACEAE)
Authors: Juncosa Adrian M.
Published: January 2018

Embryogenesis in Cassipourea elliptica (Sw.) Poir, begins with a first division of the zygote which may be oriented transversely, obliquely, or rarely longitudinally. The orientation of the second division is also variable. Though the differentiation of suspensor and embryo proper occurs early, some derivatives of the terminal cell sometimes contribute to the suspensor. Provascular tissue “differentiates” after the initiation of the cotyledons. The radicle apical meristem originates subterminally, 5–10 cell layers from the juncture of the embryo proper and the suspensor. After germination, during early seedling establishment, radicle apical organization is of an unspecialized, columellate type. Vascular differentiation occurs before germination, and there are two loci of initial xylem differentiation: one in the hypocotyl and another in the median trace of the cotyledons. After germination, additional xylem differentiates de novo (without lateral or longitudinal continuity with already‐mature vessels) inside the arcs of phloem in the hypocotyl, a pattern reported in few angiosperms. The cotyledonary node is one‐trace, unilacunar.
FLOWERING PHENOLOGY AT BIG RUN BOG, WEST VIRGINIA
Authors: Wieder R. Kelman , Bennett Charlene A. , Lang Gerald E.
Published: January 2018

In each of four major plant communities at Big Run Bog, a 15‐haSphagnum‐dominatedwetland in the Appalachian Mountains of West Virginia, the flowering phenology of 21 species was measured by counting the number of flowering stems at frequent intervals throughout the growing season. The four plant communities exhibited no consistent differences with regard to the patterns of flowering phenology. Mean flowering duration was 30 days for all species, and was 32 and 31 days for wind‐ and insect‐pollinated species, respectively. Peak flowering times for the 21 species were randomly distributed throughout the growing season. Results from Big Run Bog are not markedly different from those reported for other bogs in North America.
SEXUAL AND APOMICTIC REPRODUCTION IN CALAMAGROSTIS (GRAMINEAE) FROM EASTERN NORTH AMERICA
Authors: Greene Craig W.
Published: January 2018

Reproductive mode and chromosome numbers were determined for populations of several species of Calamagrostis from eastern North America. Calamagrostis pickeringii (2n = 28), C. perplexa (2n = 70), C. porteri subsp. porteri (2n = ca. 88–100) and C. porteri subsp. insperata (2n = 56) all have a sexual pattern of megagametophyte formation; the basal megaspore of a tetrad develops into a Polygonum‐type embryo sac with proliferating antipodal cells characteristic of the Gramineae. In these four taxa self‐incompatability, population structure and infrequent flowering limit seed production; they persist primarily by rhizomes and occupy relatively stable, late‐successional habitats. Calamagrostis stricta subsp. inexpansa includes apomictic variants (2n = ca. 104–123)that produce megagametophytes by diplospory; the single archesporial cell divides mitotically to produce an embryo sac appearing identical to those formed by sexual species. The embryo and endosperm develop autonomously from egg cell and polar nuclei, respectively. Some apomictic individuals occasionally produce some pollen and may have the potential for reproducing sexually. Their seed set insured by apomixis, variants of subsp. inexpansa colonize disturbed, open habitats and have achieved wide distributions in glaciated regions of North America. Reinterpretation of relationships among taxa I examined necessitates the following new nomenclatural combinations; C. porteri subsp. insperata (Swallen) comb. nov. is based on C. insperata Swallen; C. stricta subsp. inexpansa (A. Gray) comb. nov. is based on C. inexpansa A. Gray and includes C. lacustris (Kearney) Nash and C. fernaldii Louis‐Marie.
THE MOTION OF WINDBORNE POLLEN GRAINS AROUND CONIFER OVULATE CONES: IMPLICATIONS ON WIND POLLINATION
Authors: Niklas Karl J.
Published: January 2018

Comparisons are presented between the three‐dimensional airflow patterns created around and by a scale model of a conifer ovulate cone and the trajectories of windborne pollen grains around Picea, Larix, and Pinus ovulate cones. Three general components of the airflow pattern around an ovulate cone model are 1) doldrum‐like eddies, rotating over the adaxial surfaces of cone scales and directed toward attached ovules, 2) airflow spiralling around the cone axis along cone scale orthostichies and parastichies, and 3) a complex pattern of vortices (“umbilicus”) directed toward the leeward surface of the ovulate cone. The observed trajectories of pollen grains around cones of Picea, Larix, and Pinus conform to two of these three airflow components: 1) pollen grains are seen to roll along cone scales toward the distal scale margin and to become reentrained in airflow directed backward toward attached ovules, and 2) pollen grains passing around the cone are deflected into the “umbilicus” airflow pattern, where they either settle on or impact with cone scales (approach trajectories), or where they approach the leeward cone surface but are deflected away by airflow passing under the cone (Z‐shaped trajectories). Vectoral analyses of pollen grain motion reveal a complex pattern of trajectories influenced by boundary layer conditions defined by ovulate cone geometry and ambient airflow speed. Wind tunnel studies of ovulate cones subtended by leaves and stem indicate that leaves circumscribing the cone act as a snowfence, deflecting windborne pollen toward the cone.

Vectoral analyses of airflow patterns and pollen grain trajectories close to ovulate cones indicate that wind pollination in conifers is a non‐stochastic aerodynamic process influenced by cone‐leaf morphology and the behavior of pollen grains as windborne particles.
SECONDARY‐FRUIT ONTOGENY IN NAVEL ORANGE
Authors: Lima Jose Eduardo O. , Davies Frederick S.
Published: January 2018

Ontogeny of the secondary fruit of navel orange (Citrus sinensis [L.] Osbeck) was studied using flower buds and fruit from groves in north central Florida. The secondary fruit, or navel, develops as a whorl of secondary‐carpel primordia within the primary‐carpel whorl when the flower bud is 1.5 to 2.0 mm in length. A complete secondary gynoecium with fused ovary but separate styles and stigmas develops within the primary gynoecium before anthesis. The stigma and style of secondary carpels are not as distinct as those of primary carpels. Three types of tissue protrusions from the secondary fruit into primary‐fruit locules were abnormal placentae, free secondary carpels, and secondary‐carpel outgrowths, the last being the most common. An abscission layer is present in the central axis of the primary fruit near the base of the secondary ovary. This layer is indistinguishable from adjacent tissues prior to commencement of secondary fruit abscission. Parenchyma cells in the abscission layer, however, contain large numbers of starch grains during abscission. Secondary and primary fruit have similar sigmoid growth patterns; however, onset of the cell‐enlargement stage is approximately 2 wk later in secondary fruit.
THE EFFECT OF SEED DIMORPHISM ON THE GERMINATION AND SURVIVAL OF SALICORNIA EUROPAEA L. POPULATIONS
Authors: Philipupillai Jeyarany , Ungar Irwin A.
Published: January 2018

Seed dimorphism influenced the germination behavior of Salicornia europaea L., with small seeds being more dormant and less salt tolerant than large seeds. All of the large less dormant seeds of S. europaea germinated prior to May, and all seedlings produced after this time were from small seeds. A persistent seed bank was maintained by the small dormant seeds. Survivorship was relatively constant during the normal germination season, but increasing salinity stress at any time during the spring reduces the chance of seedling survival. Little germination occurred from July through September because of the high surface soil salinities during this period.
SYSTEMATICS AND EVOLUTION OF ELEUSINE CORACANA (GRAMINEAE)
Authors: de Wet J. M. J. , Rao K. E. Prasada , Brink D. E. , Mengesha M. H.
Published: January 2018

Finger millet (Eleusine coracana (L.) Gaertn. subsp. coracana) is cultivated in eastern and southern Africa and in southern Asia. The closest wild relative of finger millet is E. coracana subsp. africana (Kennedy‐O'Byrne) Hilu & de Wet. Wild finger millet (subsp. africana) is native to Africa but was introduced as a weed to the warmer parts of Asia and America. Derivatives of hybrids between subsp. coracana and subsp. africana are companion weeds of the crop in Africa. Cultivated finger millets are divided into five races on the basis of inflorescence morphology. Race coracana is widely distributed across the range of finger millet cultivation. It is present in the archaeological record of early African agriculture that may date back 5,000 years. Racial evolution took place in Africa. Races vulgaris, elongata, plana, and compacta evolved from race coracana, and were introduced into India some 3,000 years ago. Little independent racial evolution took place in India.
ULTRASTRUCTURE AND DEVELOPMENT OF MESOZOIC POLLEN: CLASSOPOLLIS
Authors: Taylor Thomas N. , Alvin Kenneth L.
Published: January 2018

Because of its complexity one of the most unusual fossil pollen types is the genus Classopollis. Grains of this broadly defined Mesozoic taxon range from the late Triassic into the Cretaceous (Turonian), and include forms that are spherical with a subequatorial rimula. On the proximal pole is a trilete mark, and on the distal surface a thin area in the sporoderm termed the cryptopore. Ultrastructural studies of Classopollis have been completed on grains extracted from the pollen cone Classostrobus comptonensis collected from the Lower Cretaceous Wealden beds on the Isle of Wight, England. The sporoderm consists of clearly defined nexine and sexine components, with the mature nexine composed of approximately 20 electron dense lamellae, each about 10 nm thick. The sexine consists of four (S1–4) easily recognizable layers, with the most prominent zone formed of coarse, inwardly‐tapering elements. The S2 layer is uniformly thickened, except in specialized areas (e.g., trilete, rimula, cryptopore) where it becomes thin. The remaining wall layers include spinules that ornament the surface and a uniform series of small lacunae associated with the spinule bases. The presence of orbicules and a complex system of membranes associated with the grains extracted from less mature cones provides an opportunity to trace some developmental stages in Classopollis sporoderm ontogeny, and to compare these stages with those of selected extant pollen types. The functional significance of the infrastructure in Classopollis pollen is discussed.
AN ECOLOGICAL GENETIC STUDY OF GYNODIOECY IN LIMNANTHES DOUGLASII (LIMNANTHACEAE)
Authors: Kesseli R. , Jain S. K.
Published: January 2018

Gynodioecy in two populations of Limnanthes douglasii var. rosea was studied for its maintenance requirements, role in population structure and its influence on the levels of outbreeding. The mode of inheritance of male sterility appeared to be nucleo‐cytoplasmic, although the precise number of nuclear genes and dominance relationships could not be ascertained. Measurements on the plants sampled from natural stands and controlled experiments showed that male‐steriles and their progeny had greater biomass and more flowers per plant than hermaphrodites, though these results varied with the environmental conditions. The hermaphrodites of gynodioecious populations had higher rates of selfing than the hermaphrodite individuals in populations lacking male sterility. Estimates of the inbreeding depression and homozygosity levels were also higher in gynodioecious populations. Variation in these parameters of breeding system and relative heterozygosis among populations may explain why male sterility has a restricted distribution, as theoretical models also predict rather specific conditions for this stable polymorphism. These data suggest that the advantage of male sterility is associated with lowered inbreeding depression. However, the potential ecological resource reallocation to the female function needs to be investigated. The fitness differences observed in this study between male‐steriles and hermaphrodites appear inadequate to maintain the nucleo‐cytoplasmic male sterility but could account for the observed frequencies (10–20%) of male‐steriles in nature if the genetic system has evolved from a cytoplasmic system.
THE MYCORRHIZAE OF PIONEER SPECIES IN DISTURBED ECOSYSTEMS IN WESTERN PENNSYLVANIA
Authors: Medve Richard J.
Published: January 2018

Study plots with ten types of disturbances were established in a Solidago‐Aster community in western Pennsylvania. One year after disturbance, 93% of all species had vesicular‐arbuscular mycorrhizae (VAM) and accounted for 92% of all plant cover. After 3 yr, 96% of the species had VAM and 96% canopy coverage. An adjacent 10‐yr Solidago‐Aster community had 100% VAM species. The VAM annuals, Ambrosia artemisiifolia and Setaria glauca, were major first year dominants while VAM perennials, Agropyron repens, Solidago canadensis, and Aster ericoides, dominated at 3 yr. The mean percent mycorrhizae of all dominants at 1 yr was 39% and 34% at 3 yr. Four disturbed sites had 100% VAM colonization after 1 yr and six sites after 3 yr. Severe physical disturbances (topsoil removed and topsoil‐subsoil removed) resulted in complete colonization by VAM species and mean mycorrhizal infections of more than 75%. The plowed‐disked‐prometone and plowed‐disked‐vapam disturbances resulted in low levels of mycorrhizae after 3 yr. The plowed‐disked‐atrazine plot showed an initial severe decrease in percentage of mycorrhizae, but doubled its infection rate by 3 yr. Three non‐mycorrhizal species (Chenopodium album, Rumex acetosella, and Polygonuspersicaria) were observed during the 3‐yr period. C. album was the major dominant after 1 yr in the plowed‐disked‐fertilized site and R. acetosella a dominant in the plowed‐disked‐prometone plot.
VARIATION IN SEED WEIGHT AND ITS EFFECTS ON GERMINATION IN PASTINACA SATIVA L. (UMBELLIFERAE)
Authors: Hendrix Stephen D.
Published: January 2018

Pastinaca sativa (wild parsnip) produces seeds on the primary, secondary, and tertiary umbels of the flowering stalk. Within plants, variation in seed weight is about twofold. Secondary and tertiary seed weight is 73% and 50% of primary seed weight, respectively. Maximum variation in seed weight between plants is sixfold when tertiary seeds from a small plant are compared to primary seeds from a large plant. Within an umbel order, variation in seed weight between plants is correlated with plant size. Under autumn germinating conditions in the laboratory, final germination of seeds from different umbel orders does not differ but smaller seeds germinate more rapidly than larger seeds. Under spring germination conditions in the laboratory, significantly more primary and secondary seeds germinate than tertiary seeds and the rate of germination is independent of seed weight. Field germination of seeds from different umbel orders produces similar results except that in the spring both secondary and tertiary seed germination is lower than that of primary seeds. These results suggest that with respect to seed germination characteristics small seeds may have a competitive advantage over large seeds in the autumn because they germinate more quickly, but in the spring small seeds are at a disadvantage because they have lower overall germination. Because most germination in the field occurs in the spring, population recruitment from small seeds is likely to be substanially less than that from large seeds.
VARIATION OF PLASTID AND MITOCHONDRIAL DNAS IN THE GENUS DAUCUS
Authors: DeBonte Lorin R. , Matthews Benjamin F. , Wilson Kenneth G.
Published: January 2018

Plastid and mitochondrial DNAs from suspension cultures of Daucus carota subsp. sativus cv. Danvers, D. carota subsp. gummifer, D. capillifolius, and D. pusillus were compared by restriction endonuclease fragment analysis. Organelles isolated from protoplasts of suspension cultures were purified using a one‐step sucrose gradient. Plastid DNA fragment patterns for subsp. sativus, subsp. gummifer, and capillifolius were indistinguishable in Pstl, SalI and XhoI enzyme digests. No variation was detected in BamHI or HindIII digests between subsp. sativus and capillifolius. Pusillus plastid DNA varied significantly when compared to the other Daucus cultures. The size of the plastid genome of each species as determined by fragment addition, was estimated at 155 kb. Restriction digests of the mitochondrial DNAs generated a large number of fragments which when totaled established a size of 386–468 kb for the genomes. Densitometer scans of the fragment patterns indicate the bands were present in variable stoichiometry. Up to 26% of the fragments generated by PstI, SalI and HindIII digests were homologous in size among the four mitochondrial genomes. A further comparison of mitochondrial fragments indicated a closer homology of subsp. sativus to capillifolius than to subsp. gummifer or pusillus as was also found with the plastid genomes.
BREEDING SYSTEM, POLLINATION, AND POLLINATOR LIMITATION IN A PERENNIAL HERB, AMIANTHIUM MUSCAETOXICUM (LILIACEAE)
Authors: Travis Joseph
Published: January 2018

Observations of insects on Amianthium muscaetoxicum suggested that at least 16 species can serve as pollinators, although the chief pollinators appear to be beetles. Five species from three coleopteran families appear to be the most important pollinators. Experimental manipulations suggest that Amianthium is nearly self‐incompatible and that fecundity and fruit set levels are at least partly pollinator limited. Outcrossed plants have higher fruit set and fertility levels than unmanipulated plants, and unmanipulated plants display higher levels than self‐pollinated plants. Self‐pollinated plants produce a few very small seeds, of which only a small percentage are viable. Fruit set levels in unmanipulated plants in one population were consistent over a 2‐yr period.
EFFECTS OF O2 ON AMMONIUM UPTAKE AND ROOT RESPIRATION BY SPARTINA ALTERNIFLORA
Authors: Morris James T. , Dacey John W. H.
Published: January 2018

Previously the growth of Spartina alterniflora has been found to be limited by nitrogen and correlated with sediment redox potential. In this study we have investigated a possible connection between these two factors. We have found that internal O2 transport is insufficient to saturate NH4+ uptake in short S. alterniflora in hydroponic culture. Rates of NH4+ uptake and root respiration were very sensitive to O2 concentration in the rhizosphere, saturating at about 5% O2. Ammonium uptake continued at a reduced rate for at least 4 hr under anaerobic conditions. Plant to plant variations in anaerobic rates of NH4+ uptake and root respiration were significantly correlated to the diffusion rate of CH4 tracer gas from the leaves to the roots of individual plants.
LEYMUS HOCHST. (GRAMINEAE: TRITICEAE) IN NORTH AMERICA: TAXONOMY AND DISTRIBUTION
Authors: Barkworth Mary E. , Atkins Riley J.
Published: January 2018

Leymus Hochst., a segregate genus of Triticeae, can be recognized morphologically and genomically. Its members exhibit all or all but one of the following morphological characterstics: rhizomatous habit; unawned, short, often stiffly subulate, glumes that tend to lie opposite the sides rather than the midveins of the lemmas; unawned, or only shortly awned, lemmas; and long anthers. They are all polyploids based on the same pair of genomes, one from Psathyrostachys and the other from Thinopyrum. Fourteen species occur in North America, including two interspecific hybrids. One new subspecies is described, L. salinus subsp. mojavensis. A key, descriptions, and distribution maps are given. In addition, one new hybrid genus, × Leytesion, and several new combinations are published to accommodate the naturally occurring intergeneric hybrids involving Leymus.
POLYPHENOLICS OF THE MARSILEACEAE AND THEIR POSSIBLE PHYLOGENETIC UTILITY
Authors: Wallace James W. , Chapman Mary , Sullivan Joe E. , Bhardwaja Triloki N.
Published: January 2018

Species of the Marsileaceae represent a unique group of pteridophytes of uncertain origin. The polyphenolic profiles of representative species, which include flavonol‐3‐O‐mono‐ and diglycosides, C‐glycosylflavones and C‐glycosylxanthones, have chemical features in common with the primitive leptosporangiate ferns, especially the Hymenophyllaceae. Intergeneric relationships in the family based on morphology, cytology, fossil evidence and polyphenolic profiles are discussed.
EFFECTS OF SOIL WATERLOGGING ON THE ENERGY STATUS AND DISTRIBUTION OF SALIX NIGRA AND S. EXIGUA (SALICACEAE) IN THE ATCHAFALAYA RIVER BASIN OF LOUISIANA
Authors: Dionigi Christopher P. , Mendelssohn Irving A. , Sullivan Victoria I.
Published: January 2018

The influence of soil waterlogging on the distribution and energy status of Salix nigra and S. exigua were studied in the field and laboratory. Differential flooding in natural stands of Salix spp. and under controlled conditions in the greenhouse demonstrated that S. nigra was more tolerant of waterlogged soil conditions than was S. exigua. Salix nigra exhibited a significantly higher leaf energy status and greater ability to oxidize waterlogged soil when flooded than did S. exigua. However, S. exigua appeared to be more tolerant of moisture stress than S. nigra as indicated by the significantly higher leaf resistances to water vapor exchange and higher leaf water potentials of S. exigua. These data support the theory that the reason S. nigra inhabits lower elevation sites than S. exigua in the Atchafalaya River Basin may be the differential tolerance of these two species to soil waterlogging on one extreme and moisture deficiencies on the other.
SPATIAL DISTRIBUTION OF GENETIC INDIVIDUALS IN THICKETS OF ALNUS INCANA SSP. RUGOSA, A CLONAL SHRUB
Authors: Huenneke Laura Foster
Published: January 2018

Thickets of speckled alder (Alnus incana ssp. rugosa (Du Roi) Clausen) consist of numerous discrete clumps of stems. Presumably all stems in a single clump are part of a single genetic individual, but a genet could comprise more than one clump. Starch‐gel electrophoresis was used to identify genetic individuals in four alder populations in central New York. A single genetic marker, a tetramer with three alleles, could discriminate five genotypes. Nearest neighbor analysis revealed that genotypes were distributed randomly. That is, the pattern of genotypes was statistically indistinguishable from a model where each clump is considered a unique individual and where clump genotypes are randomly distributed. Calculation of Morisita's index of dispersion confirmed that clumps of a single genotype were not aggregated. Although alder is capable of forming root suckers and offsets, lateral expansion of genets is apparently ineffective. Apparently, spatial distribution of genetic individuals within alder thickets is not influenced by clonal growth or by other factors acting to cause patterns in the genetic structure of plant populations.
PHENOLOGY, SEED DISPERSAL, AND COLONIZATION IN MUNTINGIA CALABURA, A NEOTROPICAL PIONEER TREE
Authors: Fleming Theodore H. , Williams Charles F. , Bonaccorso Frank J. , Herbst Larry H.
Published: January 2018

In this paper we describe the phenology, fruiting ecology, and colonization ability of a widespread neotropical pioneer tree, Muntingia calabura (Eleocarpaceae), in Costa Rican dry tropical forest. Individuals of M. calabura grow rapidly, flower at <2 yr age, and produce juicy red fruits containing thousands of tiny seeds that are eaten by a variety of frugivorous birds, bats, and monkeys. Although most individuals produce some flowers and fruit year‐round, peak flowering occurs in the late dry season (April–May), and peak fruit availability occurs early in the wet season (May–June). Bats and parakeets are the major seed dispersers of M. calabura at our study site, and they concentrate their attention on this species at its fruit peak when few alternate fruits are available. Germinable M. calabura seeds accumulate in the forest soil in relatively high density in areas of high frugivore activity. M. calabura can quickly invade large disturbed areas with a high density of seedlings. Adult densities decline from thousands of individuals/ha to a few individuals/ha in a relatively few years. Clumps of M. calabura trees are replaced by later successional species in < 30 yr.
FLORAL MORPHOLOGY AND CROSS‐POLLINATION IN ERYTHRONIUM GRANDIFLORUM (LILIACEAE)
Authors: Thomson James D. , Stratton Donald A.
Published: January 2018

In bumblebee visits to flowers of Erythronium grandiflorum (Liliaceae), the ratio of self‐ to nonself‐ (“outcross”) pollen grains deposited on the stigma is positively correlated with the degree of stylar exsertion beyond the anthers. Natural populations show substantial, continuous variation in stylar exsertion.
LIFETIME BIOMASS PARTITIONING AND YIELD COMPONENT RELATIONSHIPS IN THE HIGHBUSH BLUEBERRY, VACCINIUM CORYMBOSUM L. (ERICACEAE)
Authors: Pritts Marvin P. , Hancock James F.
Published: January 2018

The proportion of annual biomass production allocated to various vegetative and reproductive tissues was measured in differently aged individuals of Vaccinium corymbosum from native populations in southern Michigan. The relationship between age and allocation was determined and a lifetime pattern of biomass partitioning was developed. The proportion of biomass allocated to reproduction was higher than many have predicted for woody species, and the relationship between age and reproductive effort did not conform to optimality models. In addition, reproductive performance was not affected by previous growth or reproduction. The basis of this complex reproductive behavior was examined by quantifying the relationships among components of reproduction. In general, yield components behaved independently within a season. A high potential reproductive effort coupled with yield component independence may be an adaptation to fluctuating environments.