bluuebunny/crossref_metadata_2025 huggingface dataset:
SOMATIC EMBRYOGENESIS AND PLANT REGENERATION IN TISSUE CULTURES OF PANICUM MAXIMUM JACQ.
Authors: Lu Chin‐Yi , Vasil Indra K.
Published: January 2018

Callus tissue cultures were initiated from immature embryos, mature embryos and young inflorescences of Guinea grass (Panicum maximum Jacq.) on Murashige and Skoog's (MS) medium supplemented with 2.5–10 mg/l 2,4‐dichlorophenoxyacetic acid (2,4‐D). Calluses were transferred onto the same nutrient medium with 0.2 mg/l 2,4‐D, or without 2,4‐D. In callus cultures derived from immature embryos and young inflorescence segments, plantlets were produced via somatic embryogenesis after 3–5 wk. Young plants were successfully transplanted to pots and grown in the greenhouse. Plant development in callus obtained from mature embryos took place through the organization of shoot meristems. Regenerated plants were shown to have the normal tetraploid chromosome number of 2n = 4x = 32.
STIPE ANATOMY, WATER POTENTIALS, AND XYLEM CONDUCTANCES IN SEVEN SPECIES OF FERNS (FILICOPSIDA)
Authors: Woodhouse Robert M. , Nobel Park S.
Published: January 2018

Anatomy and water relations were studied for the desert fern Notholaena parryi, as well as six other ferns representing three different orders which occupied xeric as well as mesic habitats. Tracheid number and diameter, and total xylem cross sectional area increased during leaf development for N. parryi; the whole plant conductance (volume flow of water through a stipe divided by the rhizome‐to‐leaf water potential drop) increased but tended to level off as the leaves matured. The reported occurrences of very steep water potential gradients (about 25 MPa m–1) in stipes of N. parryi were confirmed. The ferns with the highest whole plant conductances (Alsophila australis, Botrychium dissectum, and Adiantum capillus‐veneris) had the largest or greatest number of tracheids. Numerous tracheids in Botrychium dissectum offset a low tracheary conductivity, whereas Marsilea vestita had few tracheids resulting in a low whole plant conductance. Whole plant conductances for the ferns were 2 to 3 orders of magnitude less than those generally observed for angiosperms and 6 orders less than for gymnosperms. However, the relative conductivity (whole plant conductance times stipe xylem length divided by xylem area) was only 5‐ to 10‐fold less than for angiosperms and about the same as for the gymnosperms. Stipe water relations in these ferns are discussed in relation to the evolution of xylem anatomy.
ULTRASTRUCTURE OF THE BIFLAGELLATE MOTILE CELLS OF ULVARIA OXYSPERMA (KÜTZ.) BLIDING AND PHYLOGENETIC RELATIONSHIPS AMONG ULVAPHYCEAN ALGAE
Authors: Hoops Harold J. , Floyd Gary L. , Swanson Joel A.
Published: January 2018

The detailed fine structure of the biflagellate motile cells of Ulvaria oxysperma (Kiitz.) Bliding is described. These cells demonstrate most of the features presently used to characterize the ulvaphycean motile cell, i.e., the capping plate, terminal cap, alternating two‐ and four‐membered rootlets, rhizoplasts that extend posteriorly into the cell, the striated microtubule‐associated component (SMAC) near the two‐membered rootlets, microtubule septations in the basal bodies and flagella, and scales covering the external surface of the cell. In addition, the anterior end components have 180° rotational symmetry. The rootlets insert into the basal body complex in the anterior region just beneath the capping plate, and the rhizoplasts insert into triangularshaped proximal fibers that connect the basal bodies. The features of many other ulvaphycean algae are summarized and compared with Ulvaria oxysperma. Based on comparative ultrastructure, it is suggested that the Ulvaphyceae diverged from the Chlorophyceae after the separation of these two classes from the Charophyceae.
DNA CONTENT AND HETEROCHROMATIN VARIATIONS IN VARIOUS TISSUES OF PEANUT (ARACHIS HYPOGAEA)
Authors: Dhillon Sukhraj S. , Miksche Jerome P.
Published: January 2018

The average 2C DNA amount for the peanut (Arachis hypogaea L.) genome is 4.21 pg, and 73% of the dormant peanut cotyledon nuclei displayed 8C DNA amounts or higher, as compared to 0 to 4% in root‐shoot apices and leaf tissue. Thermal melt profiles and heterochromatin values indicated replication of the whole genome. Cotyledon nuclear DNA declined in the percent of polyploid nuclei as well as DNA amounts within ploidy classes during germination. The presence of high DNA C levels in cotyledons generated during embryogeny is interpreted to increase the protein‐synthesizing capacity and subsequently supplies a ready source of nucleosides and phosphates during early embryo growth as a result of DNA degradation. However, the later DNA decline at the onset of cotyledon senescence was age related similarly to leaf senescence. The change in proportion of heterochromatin was related to the metabolic state of the tissue and not to the DNA content, as dormant and senescing nuclei contained a higher proportion of heterochromatin as compared to nuclei from metabolically active tissue such as germinating roots. The shift in heterochromatin is interpreted to be involved in gene expression.
MITOTIC INDUCTION AND SYNCHRONIZED CELL DIVISION IN OEDOGONIUM CARDIACUM (HASS.) WITTR.
Authors: Fussell Catharine P.
Published: January 2018

Waves of mitosis are induced in Oedogonium cardiacum grown under a 15 hr light/9 hr dark cycle. Mitosis starts 4 to 5 hr after the start of the dark period. Each mitotic stage has a high initial rate which plateaus at a lower rate for several additional hours. Partial synchronization of mitotic stages results from this induction of cell division. Mitotic divisions last 9 to 10 hr after induction. During the remainder of the 24‐hr light/dark cycle, cells are in interphase. Along a filament, several dividing cells tend to be adjacent, with the most advanced stage in the cap cell. Progressively earlier mitotic stages are basal to the dividing cap cell. This pattern of mitotic division differs from the state in nature where only the cap cell usually divides. Chromosomes probably maintain a telophase arrangement during interphase. The suitability and advantages of Oedogonium, a haploid alga with sexual reproduction, as an experimental plant for cytological, developmental, biochemical, and genetic studies is pointed out.
DIFFERENTIAL PRESERVATION OF PROTOPLASM IN FOSSIL ANGIOSPERM LEAF TISSUES
Authors: Niklas Karl J.
Published: January 2018

Examination of Miocene angiosperm leaf compressions from the Clarkia and Succor Creek localities of Idaho and Oregon reveals a characteristic and predictable pattern of protoplasmic deterioration. Remnants of chloroplasts are preserved in 63.9% of the 8,800 randomly selected cells, while mitochondria (18.6%) and nuclei (11.3%) are less commonly preserved. This pattern appears to be independent of the presumed environment of deposition associated with fossilization. Leaf tissues from sediments thought to be derived from shallow and deeper waters of the Miocene Clarkia lake (Chloro = 34.6%, Mito < 3%, Nuc < 1% and Chloro = 90.1%, Mito = 26%, Nuc = 4.3%, respectively) show similar patterns of ultrastructural preservation to leaves preserved in volcanic ash‐fall deposits (Chloro = 80%, Mito = 45.4%, Nuc = 39.5%). Analyses of the data for the relative abundance of various organelles per cell (e.g., in living plants Chloro/Nuc = 250) in fossil tissues and referable modern taxa indicate that the chances of the observed preferential degradation of nuclei being the results of chance is <0.001.

The data are interpreted to be evidence for the preferential preservation of chloroplasts and degeneration of nuclei. The pattern of protoplasmic degeneration, reconstructed from the frequencies of organelle preservation, is in contrast to that of the pattern observed in modern plant cell necrosis or senescence where nuclei are the most stable organelle and persist until the death of the cell. Preliminary data indicate that regimes of dehydration and compression may duplicate the pattern of protoplasmic degeneration observed in fossil plant cells.
SCLEREID DEVELOPMENT IN CAMELLIA PETIOLES
Authors: Boyd Dennis W. , Harris William M. , Murry Lynn E.
Published: January 2018

Sclereid initials are distinguishable from neighboring cells by their large centralized nuclei. During the younger stages of development, they are densely cytoplasmic and have an abundance of cellular organelles—mitochondria, endoplasmic reticulum, Golgi bodies, and ribosomes. In maturing sclereids, plastids occur infrequently and have few inner membranes, and the nuclei display unique undulations. Secondary wall synthesis occurs during maturation or with the cessation of apical intrusive growth of branches. The secondary wall differs from the primary wall by its hyaline region, homogeneous and electron‐translucent appearance and presence of numerous pit canals.
THE OCCURRENCE, EVOLUTION, AND PHYLOGENETIC SIGNIFICANCE OF PARENCHYMA IN COLEOCHAETE BRÉB. (CHLOROPHYTA)
Authors: Graham Linda Edwards
Published: January 2018

Thalli of four species of the charophycean green algaColeochaeteBréb.;C. irregularis, C. soluta, C. orbicularis, andC. scutata, were examined using light and electron microscopy. The parenchymatous nature of the plant bodies ofC. orbicularisandC. scutatabecame apparent when the degree of cellular association in these species was compared with that of parenchymatous land plant tissues, the pseudoparenchymatous thalli ofC. soluta, and the branched filaments ofC. irregularis. Coleochaete solutawas shown to be morphologically and phylogenetically transitional between the more primitive branched filamentous species (C. irregularis) and the more advanced discoid species (C. orbicularisandC. scutata). The branching patterns observed inC. solutasuggested a possible pathway for the evolutionary development of land plant parenchyma from branched, filamentous charophycean green algae.
DEVELOPMENTAL POTENTIAL OF AXILLARY BUDS OF WATER HYACINTH, EICHHORNIA CRASSIPES SOLMS. (PONTEDERIACEAE)
Authors: Richards Jennifer H.
Published: January 2018

Buds axillary to foliage leaves of water hyacinth can elongate either as vegetative stolons or as renewal shoots produced in association with the terminal inflorescence. Stolons differ from renewal shoots in position within the shoot system, morphology, and function. Renewal shoot buds always expand, whereas stolon buds may or may not. A stolon bud develops in conjunction with the subtending leaf; as that leaf matures, the stolon bud reaches a critical period in development. At this point, the bud either continues to expand, producing a stolon, or it stops growth and matures. Maturation is not irreversible, but the probability of a bud expanding decreases as bud age increases. In the field, buds on plants at the water hyacinth mat edge frequently produce stolons, whereas buds on plants inside the mat rarely do so. Leaf morphology also varies between plants in these two regions of the mat. The particular association of leaf and branch type found in the field, however, can be reversed experimentally, indicating that although leaf and bud development are coordinated, the particular course of each is independent.
THE INFLUENCE OF WATER STRESS AND TEMPERATURE ON LEAF PUBESCENCE DEVELOPMENT IN ENCELIA FARINOSA
Authors: Ehleringer James
Published: January 2018

The degree of leaf pubescence development in the arid land shrub Encelia farinosa Gray is affected by air temperature, leaf water potential, and previous history of the apical meristem during the current growing season. Changes in leaf pubescence levels change leaf spectral characteristics and affect both leaf temperature and photosynthesis. Decreasing leaf water potentials and increasing air temperatures both independently increase pubescence development as measured by decreased leaf absorptances. During any one growing season leaf absorptance may change reversibly coincident with air temperature changes, but with respect to water stress leaf absorptance only decreases as the season progresses. The ecological significance of regulation of the leaf spectral characteristics is discussed.
PLASTICITY OF TREE ARCHITECTURE: SPECIFIC AND ECOLOGICAL VARIATIONS FOUND IN AUBREVILLE'S MODEL
Authors: Fisher Jack B. , Hibbs David E.
Published: January 2018

The crown form and branching pattern of sapling and adult trees of Terminalia catappa, T. latifolia, and an unidentified species of Manilkara are described. Leaf distribution (leaf positions within the crown) and leaf area index are given for the three species. Although they all exhibit the same architectural model, the two species of Terminalia maintain a tiered canopy in both sapling and large adult trees, while Manilkara has a sapling with poorly defined tiers and an adult with a hollow, hemispherical crown. Thus, the same architectural model (Aubréville's) can give rise to different crown shapes due to quantitative differences in branch geometry, degree of reiteration, and longevity of leaf‐bearing branch units. Conversely, similar crown shapes can be produced by trees with different models. Manilkara conforms to the monolayer model of leaf arrangement at maturity, but Terminalia cannot easily be described as a monolayer or a multilayer. Adaptive geometry of a tree and its architectural model are not equivalent nor necessarily comparable.
MUTATION IN FERNS GROWING IN AN ENVIRONMENT CONTAMINATED WITH POLYCHLORINATED BIPHENYLS
Authors: Klekowski Edward J. , Klekowski Elizabeth
Published: January 2018

Polychlorinated biphenyls (PCBs) are ubiquitous and persistent environmental contaminants. The Housatonic River in Massachusetts is heavily contaminated with PCBs in the vicinity of the city of Pittsfield. The ostrich fern, Matteuccia struthiopteris, forms extensive populations in the flood plain of this river. The frequency of somatic mutations was determined in these fern populations as well as control populations growing in uncontaminated environments in the Connecticut River and its tributaries. The frequency of somatic mutations in the Housatonic River populations was 5.26–6.14 times the controls. Whether similar genetic damage has occurred to other inhabitants of the Housatonic environment is unknown.
THE PRESENCE OF PROTEASE‐DIGESTIBLE MATERIAL IN GOLGI VESICLES DURING ENDOSPERM DEVELOPMENT OF SELECTED CEREALS
Authors: Bechtel Donald B. , Gaines Ronald L.
Published: January 2018

The presence of dictyosomes secreting densely stained vesicles throughout endosperm protein body formation was confirmed for four cereals (rice, Oryza sativa L.; hard red winter wheat, Triticum aestivum L.; winter feed barley and spring malting barley, Hordeum vulgare L.; oats, Avena sativa L.). The contents of the Golgi vesicles and protein bodies were digested with proteases for all cereals except rice. It was found in the case of rice that OsO4 altered the proteins in the Golgi apparatus and protein bodies making them resistant to protease digestion. These results imply that the Golgi apparatus plays an important role in the concentration and transport of storage proteins into vacuoles.
SPECIAL PAPER: MERISTEMS AND EVOLUTION: DEVELOPMENTAL CORRESPONDENCE AMONG THE RHIZOMORPHS OF THE LYCOPSIDS
Authors: Paolillo Dominick J.
Published: January 2018

This paper deals with a comparison of the rooted axes (rhizomorphs) of Isoetes with those of Stigmaria, Pleuromeia and other fossil lycopsids from the standpoint of developmental correspondence. The objective is to present a mechanistic approach to the problem of evaluating possible interrelationships among the genera. The results complement those from other comtemporary approaches to the same problem. These main points are advocated: 1) The rhizomorphs of Isoetes and Stylites correspond. Because neither of these contains an apical meristem, neither corresponds to Stigmaria with respect to organization of the axis or root production. 2) Rooted portions of Isoetes and Pleuromeia correspond, although external lobing in Pleuromeia parallels lobing of the stele, whereas in Isoetes external lobing occurs between the lobes of the stele. In both cases, lobing of the stele is associated with root production. 3) Paurodendron rhizomorphs appear to correspond to Stigmaria developmentally with regard to the presence of an apical meristem and the arrangement of roots, but Paurodendron rhizomorphs are shorter. If several lines of root production were added to the vascular cambium of the kind of rhizomorph seen in Paurodendron, a plant part like the rooted portion of Pleuromeia could result. Further extrapolations of the Paurodendron form of growth are explored for their bearing on comparison of rhizomorphs among the lycopsids.
SYSTEMATICS OF THE TRIBE ORCUTTIEAE (GRAMINEAE) AND THE DESCRIPTION OF A NEW SEGREGATE GENUS, TUCTORIA
Authors: Reeder John R.
Published: January 2018

The two genera Neostapfia and Orcuttia, recognized as being closely allied and sharing unusual features, are treated as the sole members of the tribe Orcuttieae. Neostapfia is monotypic; Orcuttia comprises eight taxa, six of which are universally treated as species, and two as varieties. Studies reported here are based on field work throughout the ranges of these two genera and examination of 550 herbarium specimens. Chromosome counts and seed protein analyses for all taxa are presented. These data indicate that each taxon is worthy of specific status and that Orcuttia, as traditionally treated, consists of discordant elements. It is concluded that a more satisfactory taxonomy results when this group is split into two genera. A new genus, Tuctoria, is described, and the combinations T. fragilis (Swallen) J. Reeder, T. greenei (Vasey) J. Reeder, and T. mucronata (Crampton) J. Reeder are proposed.
CHEMICAL AND PHYSICAL CHARACTERISTICS OF SHALLOW GROUND WATERS IN NORTHERN MICHIGAN BOGS, SWAMPS, AND FENS
Authors: Schwintzer Christa R. , Tomberlin Thomas J.
Published: January 2018

Fifteen chemical and physical characteristics were examined in samples of shallow ground water taken in midsummer at 15‐30 cm below the surface in six bogs, 15 swamps, and six fens. The wetland types were identified on the basis of their vegetation. Three groups of covarying water characteristics were identified by factor analysis. Factor I included Ca, Mg, Si, pH, alkalinity, conductivity and to a much lesser extent Na, and reflects the degree of telluric water influence in the wetland. Factor 2 included reactive‐P, total‐P, NH3‐N, and to a lesser extent K, and consists of elements that primarily enter interstitial water via organic matter decomposition. Factor 3 included Na, Cl, and to a much lesser extent K.

The wetlands formed two distinct groups with respect to water chemistry: weakly minerotrophic (pH 3.8‐4.3) including all bogs and moderately to strongly minerotrophic (pH 5.5‐7.4) including all swamps and fens. The bogs had very low values for Factor 1 characteristics and moderate values for the remaining characteristics. The swamps and fens had moderate to high values for Factor 1 characteristics and showed considerable overlap in this respect. The fens had consistently low values for Factor 2 characteristics but overlapped with some swamps which also had low Factor 2 scores. Failure to completely separate the vegetationally very distinct swamps and fens from each other on the basis of their physical and chemical water characteristics indicates that another factor, probably water level regime, is of major importance in determining their vegetation type.
COMPARATIVE ANATOMY OF THE PETIOLE AND INFRAGENERIC RELATIONSHIPS IN JATROPHA (EUPHORBIACEAE)
Authors: Dehgan Bijan
Published: January 2018

Anatomical features of the petiole in several species of Jatropha L. (Euphorbiaceae) are presented as evidence in support of infrageneric relationships. A trilacunar 3‐trace nodal pattern is typical for the genus. The vascular supply to the stipules is derived from the branching of the two peripheral leaf traces. The number of vascular bundles range from 11 through 9, 7, 5 and 3, and occur in a ring, as free traces, a medullated cylinder, or as U‐shaped free traces. The reduction from nine to three bundles is correlated with the gross morphological features while 11, which occurs only in the section Peltatae (Pax) Dehgan & Webster, presents an increase. Reduction in the number of petiolar traces follows the evolutionary advancement of various taxa. This reduction in traces corresponds with south‐north distribution of the species and consequential adaptation to colder and more arid climates in Central America and Africa. Smaller leaves, fewer primary veins and fewer vascular traces have resulted as a response to reduced need for water. Presence of dorsal (super‐numerary) bundles which supply the petiolar glands in subgenus Jatropha (= Adenoropium Pax) is considered significant, since African taxa of the section (subsection Pubescentes Pax) have retained these bundles despite the loss of petiolar glands. The latter glands are prominent in the South American and Indian species. Sectional lines in the genus can, therefore, be drawn generally on the basis of numerical constancy and relative uniformity in the arrangement of petiolar traces. The continuity of vascular bundles from the stem into the petiole and variations of bundle arrangements are depicted in three‐dimensional drawings.
BIOCHEMICAL DETERMINATION OF Mg2+, K+‐DEPENDENT, DIETHYLSTILBESTROL‐INHIBITED PHOSPHATASE ACTIVITY IN THE OVULES OF SAINTPAULIA IONANTHA BEFORE FERTILIZATION
Authors: Mogensen H. Lloyd , Rossiter Peggy P.
Published: January 2018

The occurrence of phosphatase activity that was dependent on Mg2+ and K+ and inhibited by diethylstilbestrol has been detected in unfertilized African violet ovules with the use of biochemical techniques. Since cation‐dependent phosphatase activity is believed to be involved in ion transport across cell membranes, these results are interpreted as lending indirect support to cytochemical evidence that suggests the innermost integumentary cells of African violet ovules are involved in active transport of solutes to the embryo sac.
CHARACTERIZATION OF AN EMBRYOGENIC CELL SUSPENSION CULTURE DERIVED FROM CULTURED INFLORESCENCES OF PENNISETUM AMERICANUM (PEARL MILLET, GRAMINEAE)
Authors: Vasil Vimla , Vasil Indra K.
Published: January 2018

An embryogenic suspension culture was established from cultured inflorescence segments of Pennisetum americanum in Murashige and Skoog's medium supplemented with 2.5 mg/1 2,4‐dichlorophenoxyacetic acid (2,4‐D) and 5% coconut milk. The suspension was composed of two major cell types: 1) small, richly cytoplasmic and starch‐containing cells, generally found in small, compact clumps, here termed embryogenic cells; and 2) elongated, thick‐walled cells with large vacuoles. By manipulating the duration of culture and dilution ratios (cell suspension: fresh medium) at the time of subculture, suspensions consisting predominantly of embryogenic cells were obtained. Suspensions grown for 2‐3 wks were transferred to agar media with reduced amounts of 2,4‐D. This resulted in the production of hundreds of globular and early cotyledonary embryoids. Further development of the embryoids was promoted by their transfer to a medium containing abscisic acid. Many of the embryoids germinated and produced normal green plants. Atypical embryoids, some containing many shoot meristems and a leafy scutellum, were also observed. The relevance of such atypical embryoids in the interpretation of organogenesis and embryogenesis reported in tissue cultures of cereal species is discussed. It is also suggested that somatic embryogenesis occurs in tissue cultures of most, if not all, species of cereals and grasses.
POLYPLOIDY AND DIPLOIDY: NEW PERSPECTIVES ON CHROMOSOME PAIRING AND ITS EVOLUTIONARY IMPLICATIONS
Authors: Jackson R. C.
Published: January 2018

The last widely accepted classification of polyploidy recognized three major categories: autoploidy, segmental alloploidy, and true alloploidy. Criteria for recognizing these types were based largely on chromosome pairing in F1 hybrids, but until very recently there were no quantitative criteria to distinguish autoploids from segmental alloploids. This is theoretically possible, and Jackson and Casey (1982) and Jackson and Hauber (1982) have presented models and methods to quantitatively predict the frequencies of the different meiotic configurations in autotriploids through autooctoploids. The expected numbers of configurations then can be statistically tested for goodness of fit with observed data. Synthetic and natural autotetraploids have been shown to fit the models well. However, the exceptions that do not fit are of particular interest because they indicate the presence of Ph‐like (Pairing homoeologous) genes that cause fewer multivalents and more bivalents than expected in the autoploid models. The effect of Ph‐like genes at the nuclear level apparently involves placement of chromosome attachment sites on the nuclear membrane such that different genomes occupy slightly different sites. This would be far enough apart in true alloploids so that no pairing occurred in the original F1 hybrid. In true autoploids and normal diploids, homologues are equally close so that pairing obeys probability laws that make it possible to describe expected pairing events with appropriate models and equations. From the foregoing statements, one can deduce that the terms autoploid, segmental alloploid, and true alloploid need not and indeed should not be equated with results of crosses between any taxonomic levels. Rather, they represent conditions that can be attained by one or very few genes acting on nuclear membrane attachment sites. It is possible to deduce from hybrids at the diploid level the type of polyploid that can be obtained, and such data can have great agronomic value. A generally held dogma is that the inability of chromosomes to pair in F1 hybrids is due to considerable genetic divergence and perhaps numerous structural changes at the light microscope and/or ultrastructural level. Data from various sources show that this need not be true, and there is no reason to believe this is a factor in what has been called genome divergence in the classical sense. Genome divergence in terms of pairing ability can occur at the population level due to one or a few genes.
A MORPHOMETRIC STUDY OF THE ULTRASTRUCTURE OF ECHINOCEREUS ENGELMANNII (CACTACEAE). VI. THE INDIVIDUALIZED ULTRASTRUCTURES OF DIVERSE TYPES OF MERISTEMS
Authors: Mauseth James D.
Published: January 2018

The structures of spine basal meristem cells were examined by stereological morphometric techniques and found to be different not only from shoot apical meristem cells but also from spine primordium cells in the relative volumes occupied by cellular organelles. Nineteen types of meristematic cells have been studied in E. engelmannii, and all are distinct ultrastructurally. This suggests that whereas they all appear to be primarily involved in mitosis and cytokinesis, there must be other important aspects to their physiology; possibly these cells have already begun differentiation toward their mature states even while they are parts of active meristems.
STABILITY AND COLCHICINE EFFECT OF WALL MICROFIBRILLAR ALIGNMENT IN THE NITELLA RHIZOID
Authors: Chen James C. W.
Published: January 2018

The cell wall of the Nitella rhizoid was stripped to make wedges of various thicknesses. Polarizing and interference microscopes were used to examine the post‐deposition orientation of wall microfibrils. The fibrils appeared to maintain alignment after they were deposited. Since during growth the rhizoid wall elements are static in the cylindrical part or extend isotropically in the dome (Chen, 1973), these observations provide indirect evidence that the fibrillar reorientation observed in the Nitella internode is due to a passive reorientation during the predominant longitudinal cell elongation (Gertel and Green, 1977). The static microfibrils of the secondary wall of rhizoid, however, reoriented under the influence of colchicine, the alignment becoming almost random after 48 hrs. The disturbance of alignment started in the region adjacent to the plasma membrane, increasing in thickness with prolonged treatment.
EARLY GAMETOPHYTE ONTOGENY OF GLEICHENIA BIFIDA (WILLD.) SPRENG.: PHYLOGENETIC AND ECOLOGICAL IMPLICATIONS
Authors: Haufler Christopher H. , III William W. Adams
Published: January 2018

Past investigation of gametophyte ontogeny in Gleichenia bifida indicated that there was considerable plasticity in early developmental stages (spore germination to initiation of two‐dimensional growth). Recent examination has shown that this early ontogeny is not so plastic and can be defined by a characteristic series of developmental stages. Cell divisions following germination result in a three‐dimensional mass of cells which secondarily initiates the two‐dimensional thallus. Early development as a three‐dimensional mass correlates with other gametophyte and sporophyte features which indicate Gleichenia to be phylogenetically primitive. This pattern of early ontogeny may also be of adaptive significance in enabling the gametophytes to survive the environmental fluctuations of the exposed, bare‐soil habitats which they colonize.
SPECIALIZATION OF MESOPHYLL MORPHOLOGY IN RELATION TO C4 PHOTOSYNTHESIS IN THE POACEAE
Authors: Kemp Paul R. , Cunningham Gary L. , Adams Henry P.
Published: January 2018

Our current understanding of the photosynthetic process in species utilizing the C4 photosynthetic pathway suggests that photosynthetic efficiency should be enhanced by: 1) maximizing the conductance of the gas phase transport pathway from the leaf exterior to the mesophyll cell surfaces; 2) maximizing cytoplasmic connections and metabolite transport between bundle sheath and mesophyll parenchyma cells; and 3) minimizing the conductance of the gas phase transport pathway from the bundle sheath cells to the leaf exterior. In this study we have examined several species in the Poaceae with C4 photosynthesis to determine if there is any evidence for anatomical specialization which would lead to enhanced photosynthetic efficiency by these processes. Observations with light and scanning electron microscopes revealed specializations in mesophyll cell morphology and arrangement which include branched cells forming intercellular channels. These specializations are hypothesized to contribute to photosynthetic efficiency through its influence on the above transport processes.
CHROMOSOME NUMBERS FROM THE FLORA OF THE JUAN FERNANDEZ ISLANDS
Authors: Sanders Roger W. , Stuessy Tod F. , Rodriguez Roberto
Published: January 2018

Forty‐one chromosome counts are reported for 29 species of the flora of the Juan Fernandez Islands, Chile. Counts are provided for the first time for Azara (Flacourtiaceae), Cuminia (Lamiaceae), Dysopsis (Euphorbiaceae), Raphithamnus (Verbenaceae), Robinsonia (Asteraceae) and Ugni (Myrtaceae). New species counts are in Dendroseris and Erigeron (Asteraceae), Eryngium (Apiaceae), Escallonia (Saxifragaceae), Haloragis (Haloragaceae), Libertia (Iridaceae), Myrceugenia (Myrtaceae), Pernettya (Ericaceae), Peperomia (Piperaceae), Spergularia (Caryophyllaceae), and Wahlenbergia (Campanulaceae). The level of recent polyploidy and aneuploidy in the chromosomally known flora is each estimated conservatively at 6%. Almost all of the endemic lineages appear to have evolved at the same ploidy level from their polyploid mainland relatives. Furthermore, there is no evidence for chromosomal evolution by euploidy or aneuploidy within endemic genera. The level of ancient polyploidy in the endemic Juan Fernandez flora is estimated to be 66%. This high level correlates with the idea that many of the woody endemics (comprising nearly one‐half of the woody species in our chromosomal sample) have been derived paedomorphically from herbaceous perennial mainland ancestors in temperate, orogenetically active, Andean regions, in which high levels of polyploidy would be expected.
PHYTOCHROME CONTROL OF ROOT GROWTH RATE IN LEMNA SPECIES
Authors: Chamuris George P. , Nielsen Peter T.
Published: January 2018

Root growth rate was studied in Lemna gibba L. (strains Gl and G3) and L. minor L. in relation to low energy red and far‐red light treatments. Far‐red treatments inhibited growth rate; inhibition was abolished upon subsequent treatment with red light. These effects can be observed after an 18‐hr growth period. This red/far‐red photoreversible response suggests that root growth in L. gibba L. and L. minor L. is under phytochrome control.
EFFECTS OF POLLINATION TIMING ON FRUITING IN ASCLEPIAS SPECIOSA TORR. (ASCLEPIADACEAE)
Authors: Bookman Susan S.
Published: January 2018

A series of hand‐pollination experiments was performed to test the hypothesis that pollination timing determines which flowers produce pods in Asclepias speciosa, a species with few ovaries maturing into fruit. A comparison of fruiting of different aged ovaries showed that throughout anthesis, pistils are equally receptive to pollen tube penetration and growth. Pollen declines in vigor as flowers age as indicated by comparisons of different aged pollen both in vitro and in vivo. However, the overall effect of this decline on fruiting in the field is lessened by a simultaneous decline during anthesis in the rate of pollinium removal by insect pollinators. Within an umbel, earlier pollinated flowers are more likely to form mature pods than flowers pollinated 2 days later, apparently as a result of within umbel competition between developing pods for limited resources. The longer the delay between pollinations within umbels, the more mature pods form, probably as a result of a decline in intensity of competition between pods. Pollinations during the afternoon result in fewer mature pods and seeds than morning and evening pollinations, although fruiting is not dependent on humidity or temperature at the time of pollination. Differences in mature pod production between treatments were not significant for any experiment indicating that ecological or evolutionary factors other than pollination timing have the greatest effect on fruiting.
ONTOGENY OF THE STEM‐NODE‐LEAF VASCULAR CONTINUUM OF AUSTROBAILEYA
Authors: Dickison William C. , Endress Peter K.
Published: January 2018

Developmental study of the stem‐node‐leaf vascular continuum of Austrobaileya scandens White reveals that the vasculature within each leaf originates from a single procambial strand, that becomes separated into two strands only at the junction of leaf and stem. At lower levels in the stem the two strands become incorporated into independent portions of the stele. At later stages of development the solitary vascular bundle within the young leaf undergoes considerable lateral growth, resulting in an essentially continuous arc of vascular tissue. Ontogenetic evidence indicates that the vascular bundle in the midrib of the lamina should be regarded as a fundamentally single bundle and not interpreted as two bundles that have undergone various degrees of secondary fusion. A condition of two totally separate bundles extending the entire length of the leaf was not encountered. Our observations confirm the characterization of Austrobaileya as an example of “second rank” level of leaf vasculature. Nodal anatomy emphasizes the extremely isolated taxonomic position of Austrobaileya within the primitive dicotyledons.
A PHYTOCHEMICAL APPROACH TO THE GLEICHENIACEAE
Authors: Wallace James W. , Pozner Robert S. , Gomez Luis D.
Published: January 2018

The Gleicheniaceae, containing approximately 120 species, is a family of primitive ferns distributed throughout most of the tropics and subtropics. Historically the family was considered to be monogeneric; however, most recent authors using morphological, anatomical and cytological information have subdivided the group into 5 or 6 distinct genera. Some authors have even elevated certain species to family or ordinal levels (e.g., Platyzoma and Stromatopteris). The distribution of flavonol‐3‐0‐glycosides supports the segregation of the Gleicheniaceae, sensu lato, into at least three groupings. Flavonoids similar to those identified within the Psilotaceae (flavones, biflavones, and C‐glycosylflavones) were not detected during this study.
SEASONAL AND LIFETIME ALLOCATION PATTERNS OF THE WOODY GOLDENROD, SOLIDAGO PAUCIFLOSCULOSA MICHAUX. (COMPOSITAE)
Authors: Pritts Marvin P. , Hancock James F.
Published: January 2018

Both seasonal and lifetime allocation patterns were determined for S. pauciflosculosa, a woody composite, by monitoring biomass loss and gain of each age class in a population for one year. Seasonal allocation patterns were typical of woody plants in stressed environments and did not differ significantly among different aged plants of the same reproductive status. The standing biomass of a mature individual was partitioned as follows: roots 15%, stems 55%, leaves 19%, and reproductive tissues 11%. Lifetime allocation to these particular tissues were 5%, 15%, 50%, and 30% respectively. Lifetime allocation to reproduction was similar to values for related annuals. The implications of these findings for energy allocation theory are discussed.
MORPHOLOGICAL AND GENETIC VARIATION IN ECOLOGICALLY CENTRAL AND MARGINAL POPULATIONS OF RUMEX ACETOSELLA L. (POLYGONACEAE)
Authors: Farris Michael A. , Schaal Barbara A.
Published: January 2018

Six ecologically central (old field) and marginal (strip mine) populations of the hexaploid Rumex acetosella were collected, grown under uniform conditions, and examined for genetic and morphological variation. Extensive electrophoretic variation was found in alcohol dehydrogenase and phosphoglucose isomerase, while other enzymes surveyed showed little or no variation. Hedrick's genotypic measure of identity revealed mean values of 0.506 for central populations, 0.836 for marginal populations, and 0.633 for comparisons of central with marginal populations. Alcohol dehydrogenase phenotypes had significantly fewer electromorphs per individual in marginal populations. Clones of individuals from both environments were subjected to different watering regimes. No significant differences in root/shoot ratio, leaf number, total leaf area, or relative growth rate were found between strip mine and old‐field individuals within each watering treatment, although significant differences were found between watering treatments. There are small, but significant amounts of isozyme differentiation between central and marginal populations, while there was no such differentation for morphological characters.
SOME PIECES OF THE AFRICAN GENOME PUZZLE IN HIBISCUS SECT. FURCARIA (MALVACEAE)
Authors: Menzel M. Y. , Goetz S. G. , Adamson W. C.
Published: January 2018

New chromosome counts are reported for four African diploid species of Hibiscus L. sect. Furcaria DC: H. greenwayi Bak. f., H. hiernianus Exell et Mendonça, and H. mechowii Garcke, n = 18; and H. berberidifolius A. Rich., 2n = 36. Chromosome behavior is described in seven new hybrid combinations. Hibiscus greenwayi is shown to carry an A genome. Hibiscus hiernianus and H. mastersianus have similar genomes which are not homologous with that of H. mechowii. New and earlier data are integrated to elucidate genome relationships among 13 taxa–each of the four tetraploid species has a different formula encompassing 2 of 6 mutually nonhomologous genomes, A, B, G, H, X and Y (H. acetosella Welw. ex Hiern = AABB; H. meeusei Exell = AAXX; H. sabdariffa L. = AAYY; H. rostellatus Guill. et Perr. = GGHH). Diploid donors of A, B, G, X and Y are proposed on the basis of plant, flower and pollen morphology. Diploid carriers of A (H. asper Hook. f., H. cannabinus L., H. greenwayi), B (H. surattensis L.) and G (H. sudanensis Hochr.) have been verified cytologically. Cytological confirmation of X (H. hiernianus, H. mastersianus Hiern) and Y (H. mechowii) carriers is incomplete. No putative diploid carrier of H is at hand. Genome affinities of H. berberidifolius are unknown.
APICAL FOLIAR NECTARY OF POMEGRANATE (PUNICA GRANATUM: PUNICACEAE)
Authors: Turner Glenn W. , Lersten Nels R.
Published: January 2018

This is the first report of an extrafloral nectary in the Punicaceae. Each leaf of pomegranate bears a single apical nectary that consists of a closely packed spherical mass of densely staining cells, and of a surrounding layer of cells that are larger and more vacuolate, though still densely staining. The epidermis at the apex of the nectary (which is also comprised of small, densely staining cells) bulges to form a bump over a small chamber. The leaf apex lacks stomata or other specialized pores for nectar to escape. However, separation of epidermal cells and conspicuous ruptures sometimes occur. The midvein and 2–4 lateral bundles converge on the nectary. The xylem stops before reaching the nectary, but the phloem continues, curving about halfway around the nectariferous tissue. Chromatographic analysis of nectar droplets showed roughly equal amounts of fructose, glucose, and sucrose. This nectary resembles leaf apical glands of Lafoensia in the closely related family Lythraceae.
POLLEN MORPHOLOGY AND PLANT TAXONOMY OF RED OAKS IN EASTERN NORTH AMERICA
Authors: Solomon Allen M.
Published: January 2018

Identification of Quercus (oak) pollen taxa could enhance Quaternary palynological interpretations from eastern North America. A first step is to determine a morphological and taxonomic basis for such identifications. Scanning electron microscopy was utilized to examine exine‐surface features of 266 specimens representing 21 red oak (subgen. Erythrobalanus) species from eastern North America, and two intermediate oak (subgen. Protobalanus) species from the desert southwest. Twenty pollen morphological characteristics defined previously were tabulated for each of 324 pollen grains. The data were subjected to cluster analyses. Cluster diagrams were compared with traditional oak systematics. Pollen morphology and plant taxonomy compared poorly with respect to series and species relationships among the red oaks, apparently due as much to high intraspecific and low interspecific variability in pollen‐morphological characters as to the uncertain taxonomy of red oaks. Pollen morphology, however, does support the hypothesis of subgeneric oak evolution from intermediate oaks to the series Virentes of white oaks, and from more advanced white oaks to the red oak species.
PHYLETIC TRENDS IN SECTIONS EUBLEPHARIS AND CALLIOPSIS OF THE GENUS COREOPSIS (COMPOSITAE)
Authors: Smith Edwin B.
Published: January 2018

Artificial hybridization, fertility of interspecific and intersectional hybrids, chromosome numbers, and trends in habit and morphology in taxa of sections Eublepharis and Calliopsis of the genus Coreopsis are used to consider the sectional relationships and to derive a presumed phylogeny for the two sections. The two sections are closely related and show a low level of interfertility, but this level is as high as in some interspecific crosses within sections. The sections differ in base chromosome number and achene winging. The problematic C. rosea evidently should remain in section Eublepharis. Both sections probably arose from x = 13 stock resembling C. integrifolia or C. pubescens. Descending aneuploidy was involved in the derivation of section Calliopsis, while chromosome evolution in section Eublepharis has involved polyploidy.
CONIFER OVULATE CONE MORPHOLOGY: IMPLICATIONS ON POLLEN IMPACTION PATTERNS
Authors: Niklas Karl J. , U Kyaw Tha Paw
Published: January 2018

Empirically determined patterns of pollen impaction on the surfaces of pine ovulate cones are correlated with regions of nonlaminar flow created by the spatial arrangement and morphology (aspect ratios) of scale‐bract complexes. Results from the serial discharge of pollen, upwind of ovulate cones, indicate that ovules on ovulate cones are preferentially impacted by pollen from their own species. Analyses indicate that while aerodynamic factors dominate the entrapment of pollen by ovulate cones, other factors such as pollen impaction‐rebound and rebound‐reentrainment are significant. Surface characteristics in addition to the settling velocities of pollen may play important roles in determining pollination efficiency. Wind tunnel analyses of the aerodynamic effects of scale‐bract arrangement and aspect ratios indicate that each complex behaves as an aerofoil, deflecting air eddies toward the micropylar ends of ovules. The ovulate cone geometry, as a whole, deflects unidirectional wind into cyclonic vortices around the cone axis, each scale‐bract deflecting nonimpacted pollen along orthostichies and parastichies. The morphology of the typical conifer ovulate cone is interpreted as a structure that optimizes anemophilous reproduction.
STRUCTURE AND AFFINITIES OF PROTOSTIGMARIA EGGERTIANA
Authors: Jennings James R. , Karrfalt Eric E. , Rothwell Gar W.
Published: January 2018

Investigation of new, more or less complete specimens of Protostigmaria eggertiana reveals that it is a large, multilobed rooting structure produced at the base of a small arborescent lycopod. The trunk bears scars marking the point of attachment of leaves, and can be compared to the stem of Lepidodendropsis. In the largest specimens the root‐bearing base is divided into about 13 lobes. In smaller, presumably younger specimens, fewer lobes are present. The roots are arranged on the lobes in series and orthostichies comparable to those of Isoetes. New observations on five‐ and six‐lobed Isoetes plants reveal a closer correspondence between Protostigmaria and Isoetes than previously recognized; and support suspected homologies among many fossil and extant lycopsid rooting structures.
PROTEIN‐CONTAINING CELLS IN THE NECTARY PHLOEM OF PASSIFLORA WARMINGII
Authors: Durkee Lenore T.
Published: January 2018

Passiflora warmingii petiolar nectaries are characterized by the presence of large protein‐containing phloem parenchyma cells which occupy the bulk of the nectary. Immature, mature, and senescent nectaries, as well as stem tips and petioles from unexpanded and mature leaves, were studied to learn the origin and fate of the protein and to determine if similar protein‐containing cells occur in main‐path phloem. The protein is present as membrane‐limited fibrils in the phloem parenchyma of immature nectaries and in young main‐path phloem. In the nectary, it persists until leaf senescence but becomes highly dispersed and barely detectable in mature main‐path phloem parenchyma. Although superficially resembling P‐protein it is always surrounded by a membrane, has smaller dimensions than is reported for P‐protein, appears to be derived from RER, and is found in association with typical P‐protein in the same cell. Possible functions for this material are suggested.
ACCUMULATION OF NICKEL AND ZINC BY WESTERN NORTH AMERICAN GENERA CONTAINING SERPENTINE‐TOLERANT SPECIES
Authors: Reeves Roger D. , Macfarlane Roger M. , Brooks Robert R.
Published: January 2018

Nickel and zinc were determined in 57 taxa of western North American genera containing serpentine‐tolerant species. The studies resulted in the identification of three varieties of Thlaspi montanum (var. montanum, var. siskiyouense, and var. californicum) which are hyperaccumulators (> 1,000 μg/g dry mass) of nickel. These three taxa together with the previously reported Streptanthus polygaloides are the only hyperaccumulators of nickel so far reported for continental America. Significantly higher than normal nickel values (up to 664 μg/g) were recorded for the serpentinophyte Viola cuneata. Elevated zinc levels (> 1,000 μg/g dry mass) were also recorded in four of the Thlaspi taxa and confirm the tendency of many species of this genus to accumulate zinc. It is suggested that hyperaccumulation of nickel by the three varieties of T. montanum is a neo‐endemic rather than palaeo‐endemic process and that the precursor of these varieties is T. montanum var. montanum from non‐mineralized soils.