bluuebunny/crossref_metadata_2025 huggingface dataset:
IMPLICATIONS OF MORPHOLOGICAL AND ANATOMICAL VARIATION IN ABIES BALSAMEA AND A. LASIOCARPA (PINACEAE) FROM WESTERN CANADA
Authors: Parker William H. , Maze Jack , Bradfield Gary E.
Published: January 2018

Abies balsamea and A. lasiocarpa are closely related North American balsam firs that are generally thought to hybridize and intergrade where their ranges overlap in west‐central Alberta. To test this hypothesis, a series of collections was made from ten populations along an east‐west transect between western Saskatchewan and central British Columbia. Each tree was scored for various vegetative and cone characters. The resulting data were analyzed by Principal Components Analysis and Canonical Variates Analysis. Analyses based on vegetative data produced somewhat different results from analyses based on cone data, indicating that vegetative and sexual features of the trees respond to different selection pressures at the ecologically diverse sample sites. The combined results of analyses of vegetative and sexual data indicate that the ten populations do not represent elements of two morphologically distinct taxa. Instead, the results apparently reflect population differentation within a single, regionally variable complex in response to local selection pressures following east‐west gene flow. It is recommended that the separate species designations, A. balsamea and A. lasiocarpa, be retained since: 1) present day elements of the complex are evidently derived from separate refugia isolated by the Rocky Mountains during past glacial periods, and 2) gradual morphological differences exist between populations on each side of the Rocky Mountain crest.
AFTER‐RIPENING AS A FACTOR IN LETTUCE SEED GERMINATION RESPONSE
Authors: Suzuki Yoshihiro
Published: January 2018

The physiological state of lettuce seeds could be divided into three distinct stages. The first is the dormant stage, the second is the nondormant one and the third is the deteriorating one. The dormant and the deteriorating stages can be classified further into three phases, respectively, by the actions of germination temperature, red light, and chemical substances.

The effects of an exposure to red light and of the application of gibberellic acid A3 and thiourea on germination can be divided into two functions: 1) dormancy‐releasing effect on dormant seeds, and 2) stimulating effect on aged seeds which have reduced their germinability.
BEETLE POLLINATION OF CYCLANTHUS BIPARTITUS (CYCLANTHACEAE)
Authors: Beach James H.
Published: January 2018

The morphology, inflorescence phenology, and insect visitors of Cyclanthus were observed during two reproductive seasons at Finca La Selva in the Atlantic lowlands of Costa Rica. The inflorescence of Cyclanthus is an elongate spadix that is subtended and enclosed by four large, cymbiform bracts. Staminate and pistillate flowers are arranged in separate cycles along the length of the spadix and show marked dichogamy. Pollinators of Cyclanthus are beetles of the genus Cyclocephala (Scarabaeidae). The beetles arrive at the inflorescence while it is in the pistillate phase, during the first evening of the 2‐day flowering period. They remain in the inflorescence for 24 hrs, until the end of staminate anthesis. The bracts of the inflorescence produce specialized tissue that the beetles consume along with pollen. Chemical analysis of the food tissue indicates that it is almost 50% lipid by dry weight. The scarabs use the inflorescence as an aggregation site for mating. Experiments with bagged inflorescences showed that no seeds are produced in the absence of pollinators, which suggests that Cyclanthus is obligately allogamous.
THE BALANCE BETWEEN CHASMOGAMY AND CLEISTOGAMY IN COLLOMIA GRANDIFLORA (POLEMONIACEAE)
Authors: Wilken Dieter H.
Published: January 2018

The extent of cleistogamy (CL) and chasmogamy (CH) was investigated in natural populations of Collomia grandiflora Dougl. ex Lindl. The ubiquitous occurrence of CL flowers was documented in 18 populations from throughout the geographic range of the species. The interrelationship of environmental perturbation, vegetative weight, and the balance between CH and CL flowers was investigated by means of a factorial experiment which varied plant density, incident light and soil mix. An ANOVA revealed that total plant weight increased significantly under conditions of low density, low light and low sand content, with density accounting for most of the variance in plant weight. Interactions involving density were not significant. The number of CH and CL flowers and estimated percent outcrossing increased significantly with increased plant weight, low density, low light, and low sand content, although an analysis of covariance showed that plant weight and density accounted for most of the variance in these traits. Among large, multibranched plants, the proportion of CL flowers increased in a basipetal pattern, whereas most of the CH flowers were restricted to the terminal and upper inflorescences. The smallest plants produced only a single terminal inflorescence comprising entirely CL flowers. The proportion of reproductive effort allocated to outcrossing was dependent upon plant size as estimated from total weight, whereas the proportion allocated to ***selfing was relatively independent. Studies of outcrossed vs. inbred progenies of five populations revealed little evidence for immediate inbreeding depression with respect to plant weight and the number of CH or CL flowers, but indicated that significant quantitative genetic differences exist for these traits among populations of diverse ecological or geographical origin.
COMPETITION AS A CONTROL MECHANISM IN SUBALPINE MEADOWS
Authors: Moral Roger del
Published: January 2018

Interspecific competition in a stable subalpine meadow was investigated experimentally. Vegetation responds to gradients of moisture and disturbance which control species composition. Moisture and snow melt patterns produce a productivity gradient that affects the importance of competition in this vegetation mosaic. Reciprocal transplant and selective removal experiments demonstrated that the intensity of competition is directly related to productivity and that seedlings are more susceptible to competitive effects than are established plants. Competition may reduce diversity in stable, productive habitats, while disturbance and stress limit diversity directly. Habitats of moderate productivity and minor disturbance have maximum diversity. The experiments and observations combine to suggest that habitat heterogeneity and local disturbance interact to control biotic interference and that the relative importance of each varies with productivity.
MORPHOLOGICAL STAGING OF WHEAT CARYOPSIS DEVELOPMENT
Authors: Rogers Scott O. , Quatrano Ralph S.
Published: January 2018

Growth and size measurements as well as morphological characteristics of wheat (Triticum aestivum L. cv. Chinese Spring) caryopsis development are classified into five (I–V) groups, each representing a distinct developmental stage. Such staging will hopefully aid in experimental approaches and comparative studies of wheat embryo and endosperm development.
EVOLUTIONARY STUDIES OF ATRIPLEX: CHROMOSOME RACES OF A. CONFERTIFOLIA (SHADSCALE)
Authors: Stutz Howard C. , Sanderson Stewart C.
Published: January 2018

Atriplex confertifolia (Torr. and Frem.) S. Wats., a species endemic to western United States, occurs as 2n, 4n, 6n, 8n and 10n chromosome races. In the Great Basin, diploids occur altitudinally above the upper levels of Pleistocene lakes; the polyploids are in valley bottoms and sides. Diploids are larger in all respects than tetraploids, hexaploids, and octoploids. Decaploids are the most robust of all. Diploids can be distinguished in early seedling stages by having broader leaves and shorter internodes than polyploids. Polyploid plants are currently produced sporadically in natural populations and appear to be easily generated by unreduced gametes. Most polyploid populations in the Great Basin apparently arose recently and erupted into extensive stands because of the sudden availability of large, relatively uniform domains provided by the disappearance of Pleistocene lakes.
A THREE‐DIMENSIONAL RECONSTRUCTION OF THE VASCULAR SYSTEM TO THE LODICULES, ANDROECIUM, AND GYNOECIUM OF A FERTILE FLORET OF PANICUM DICHOTOMIFLORUM (GRAMINEAE)
Authors: Pizzolato Thompson Demetrio
Published: January 2018

A three‐dimensional reconstruction of a fertile floret stele of Panicum dichotomiflorum approaching anthesis was made by a new technique using superimposition of tracings of 80, 1‐μm thick serial sections, cleared tracing film, and mounting adhesive. From a collateral bundle, which also served as the median trace to the fertile lemma, most of the vascular tissue branched adaxially and horizontally to become the sole vascular supply to the two lodicules, three stamens, and pistil. The xylem branched at a low level to form a broad and long vessel plexus. The phloem branched at a higher level to overlay the vessel plexus on the right and left with an arc of horizontal sieve tubes in a phloem plexus. Those sieve tubes and vessels which rose after branching from the horizontal plexi assumed a more vertical course in the floret stele. Traces to the right and left lodicules arose from the lower abaxial portions of the flanks of the floret stele. Vessels ascended vertically from the xylem plexus and passed through the phloem plexi and joined with the sieve tubes there to exit at the same level and become the right and left lodicule traces. The vascular tissues to the three filament traces arose from different higher levels of the stele. The sieve tubes for the median filament trace arose vertically from the abaxial side between but above the lodicule traces. At higher levels the sieve tubes for the lateral filaments rose from the horizontal arcs of the flanks of the stele and departed it tangentially. The vessels destined to the filament traces arose in the center of the floret stele from adaxial portions of the horizontal plexus, ascended between the arcs of phloem, exited the stele simultaneously above the phloem of the traces, and followed the courses of their respective sieve tubes. The adaxially displaced apex of the floret stele then contained the vascular tissue related to the pistil. All the sieve tubes and vessels of the floret stele were embedded in a matrix of intermediary cells. The peripheral intermediary cells associated with the vessel plexus were xylem transfer cells with pronounced wall ingrowths. At higher levels in the floret stele, intermediary cells in scattered locations near sieve tubes or vessels had less conspicuous wall ingrowths. No preferred orientation of transfer cells with any particular trace was noted.
EFFECT OF THE NON‐MYCORRHIZAL PIONEER PLANT SALSOLA KALI L. (CHENOPODIACEAE) ON VESICULAR‐ARBUSCULAR MYCORRHIZAL (VAM) FUNGI
Authors: Schmidt Steven K. , Reeves F. Brent
Published: January 2018

The effects of Salsola kali (Russian thistle) on chlamydospore numbers and viable propagules of the vesicular‐arbuscular mycorrhizal fungus Glomus fasciculatum were monitored for 18 wk under laboratory conditions. When S. kali or Agropyron smithii (a mycorrhizal species) were grown for 6 wk, the number of chlamydospores in soil declined to the same number as in the control (non‐planted) soil; the number of chlamydospores in the S. kali and control soils continued to decline over the 18 wk period. However, using a Zea mays bioassay, the per cent colonization of corn roots obtained from soil in which S. kali grew for 6, 12, or 18 wk was significantly greater than in the control soil. These results suggest that S. kali may stabilize mycorrhizal infectivity of disturbed soils for at least short periods of time.
SEXUAL REPRODUCTION AND MEIOSIS IN PERIDINIUM INCONSPICUUM LEMMERMANN (DINOPHYCEAE)
Authors: Pfiester Lois A. , Timpano P. , Skvarla J. J. , Holt J. R.
Published: January 2018

InPeridinium inconspicuumLemmermann, sexual reproduction occurs in both nitrogen‐enriched and nitrogen‐deficient media. In this homothallic strain, protoplasmic fusion begins between two thecate gametes; but zygote formation is completed in a space outside the fusing pair. This diploid cell can form a plated theca which is shed as the cell enlarges. This spherical zygote then forms a new non‐plated theca. The process of ecdysis and the formation of a new non‐plated theca is repeated several times. During this process the zygote gradually elongates and by cytoplasmic infurrowing becomes peanut‐shaped. Eventually two cells are formed.

The first and second meiotic divisions are greatly separated in time. The first meiotic division occurs in the spherical non‐thecate zygote. The second meiotic division can occur in the peanut‐shaped zygote before it completes cytokinesis. This meiotic division may not be synchronous, occasionally resulting in a trinucleate stage. Eventually four flagellated, haploid products are produced.
EXPERIMENTAL STUDIES OF HAUSTORIUM INITIATION AND EARLY DEVELOPMENT IN AGALINIS PURPUREA (L.) RAF. (SCROPHULARIACEAE)
Authors: Baird Wm. Vance , Riopel James L.
Published: January 2018

In parasitic angiosperms the haustorium, an organ specialized for attachment and penetration of host tissue, functions in the transport of water and nutrients from the host to the parasite. In Agalinis purpurea (L.) Raf. (Scrophulariaceae) these organs are initiated laterally along its roots, opposite a primary xylem pole. Analyses of haustoria distribution and cellular root profiles show that the portion of the root which is most sensitive to haustorial elicitor molecules is the area distal to the zone of elongation and near the root meristem. Sectioned material supports this finding and, further, indicates that the cells which are the first to respond to haustorial elicitors are located in the inner cortex. Haustoria develop rapidly in response to a host root or to isolated chemical elicitors (xenognosins) normally contained in host root exudate. By 6 hr, vacuolation and radial cellular enlargement are observed in the cortex, and a lateral swelling along the root is visible. By 12 hr, cells of the epidermis divide anticlinally to establish a group of densely cytoplasmic cells at the apex of the haustorial swelling. Accompanying these divisions is the differentiation of specialized hair cells which elongate from epidermal cells flanking the presumptive haustorial apex. Next, the internal, radially enlarged cortical cells divide periclinally. Periclinal divisions are subsequently initiated in the pericycle as early as 18 hr post‐induction. Cellular division and enlargement continue so that by 24–36 hr a mature pre‐contact haustorium is formed. There is a reduction in root elongation concomitant with haustorial initiation. Depending upon the number of haustoria produced, elongation typically returns to the preinduction level within 2 or 3 days.
PHYTOTOXIC VOLATILES FROM TRICHOSTEMA LANCEOLATUM (LABIATAE)
Authors: Heisey Rod M. , Delwiche C. C.
Published: January 2018

Trichostema lanceolatum Benth. (vinegar weed), an annual herb of the California grassland, contains 2.9 ml of volatile essential oil per 100 g of fresh foliage. Vapors from leaves and extracted oil inhibited growth of other plants in laboratory tests. Volatiles from 0.12–0.15 g green Trichostema leaf caused a 50% reduction in radicle elongation of Bromus mollis L. and Hordeum vulgare L. seeds in petri dishes. Vapors from 1.5 and 3.2 μl essential oil in sealed and non‐sealed dishes, respectively, had a similar effect on Hordeum seeds. Exposure of dry Bromus seeds for 1 day, and dry Hordeum seeds for 3 days, to volatiles from Trichostema foliage inhibited growth when the seeds were later moistened. The toxic volatiles had a high affinity for vegetable oil and were not readily removed from seeds by rinsing with water. The major volatile inhibitor from Trichostema was terpinen‐4‐ol. This monoterpene alcohol was about 0.3 and 1.9 times as inhibitory as camphor and 1,8‐cineole, terpenes that have previously been shown to influence vegetation patterning near Salvia leucophylla Greene shrubs. These results suggest Trichostema lanceolatum may also have allelopathic potential.
IN‐OVULO EMBRYO CULTURE OF VITIS VINIFERA L. C.V. ‘THOMPSON SEEDLESS’
Authors: Emershad Richard L. , Ramming David W.
Published: January 2018

In‐ovulo embryo culture of Vitis vinifera L. c.v. 'Thompson Seedless' was investigated as a method to enable the hybridization of stenospermic seedless grapes. Fertilized ovules taken 68 days after anthesis were cultured on two basal media: 1) Cain's medium; and 2) Stewart and Hsu's (1977) medium, both tested with five separate addenda (IBA, Ergostim, tartaric acid, L‐glutamine and L‐cysteine). Addition of 10 mm L‐cysteine to C medium promoted the growth of more embryos. Three months after culture, embryos were excised and subcultured. Thirty embryos were recovered by this method but only one embryo grew into a plant.
ABSOLUTE CONFIGURATION ANALYSIS OF THE FLAGELLAR APPARATUS IN CLADOPHORA AND CHAETOMORPHA MOTILE CELLS, WITH AN ASSESSMENT OF THE PHYLOGENETIC POSITION OF THE CLADOPHORACEAE (ULVOPHYCEAE, CHLOROPHYTA)
Authors: Floyd Gary L. , O'Kelly Charles J. , Chappell Dorothy F.
Published: January 2018

Absolute configurational analyses of flagellar apparatus components were performed on the motile cells produced by three species of Cladophora, Cl. dalmatica Kütz., Cl. flexuosa (Dillw.) Harv., and Cl. glomerata (L.) Kütz., and by Chaetomorpha aerea (Dillw.) Kütz. There was little variation among the species. All of the flagellar apparatuses demonstrated the ulvophyceous features of 180° rotational symmetry, counterclockwise absolute orientation, and basal body overlap, as well as the alignment of the basal bodies perpendicular to the long axis of the cell. Diagnostic features included the nearly complete absence of C tubules from the basal bodies and the presence of a coarsely striated component dorsal to the two‐membered rootlets in all cells, as well as, in quadriflagellate cells, a tetralobate distal fiber, the coaxial arrangement of the lowermost pair of basal bodies, and the presence of a characteristic array of basal‐body‐associated striated bands. The distal fiber architecture, the presence of a “wing” in the X‐membered rootlets, and the “flattening” of the flagellar apparatus components suggests a close relationship of the Cladophoraceae to the Dasycladales, and indicates that these two groups may have shared a common ancestor, possibly ancient in terms of the geological time scale but relatively recent in the context of ulvophyceous evolution. A sizeable phylogenetic gap exists between the Cladophoraceae and uninucleate‐celled, presumably primitive members of the Ulvophyceae.
EVIDENCE FOR XYLEM CONSTRICTIONS IN THE PRIMARY VASCULATURE OF PSILOPHYTON DAWSONII, AN EMSIAN TRIMEROPHYTE
Authors: Niklas Karl J. , Banks Harlan P.
Published: January 2018

Serial peels through the branch junctions of Psilophyton dawsonii were examined in an attempt to determine if “hydraulic constrictions” (i.e., a localized decrease in mean diameter of xylem elements) sensu Zimmermann (1983) had occurred during bifurcation. Based on the mean diameters of primary xylem tracheids measured acropetally and basipetally to branch junctions, evidence for xylem constrictions (= localized decrease in mean tracheid diameter) was found within the basalmost portions of four out of six minor axes examined near their attachment to major axes (anisotomous junctions). Xylem constrictions were not detected in branch junctions between axes of equal girth (isotomous junctions). Xylem constrictions were detected within the base of five out of seven junctions between fertile and main axes. The mean diameters of tracheids of the branch trace near its origin are larger both basipetally and acropetally from the constriction. There is no evidence for a localized decrease in the mean diameter of the xylem strand in the region of a constriction. Therefore, xylem constrictions are not the result of epidogenesis. Based on the production of “hydraulic constrictions” in extant plants, which serve to localize the formation of embolisms in lateral branches during water stress, it is speculated that P. dawsonii could protect the vasculature of major axes by a similar anatomical feature.
SCANNING ELECTRON MICROSCOPY OF ANTHERIDIA AND ARCHEGONIA OF ANEMIA MEXICANA KLOTZSCH
Authors: Nester Joan E.
Published: January 2018

Antheridia and archegonia of the fern Anemia mexicana were viewed with scanning electron microscopy (SEM). The mature antheridium is composed of a cap, ring, and basal cell with spermatozoids inside. The archegonium neck is composed of a neck canal cell surrounded by four rows of neck cells. The ventral canal cell and egg were not observed. The neck bends toward the notched meristem. The neck cells usually are uniform in shape and arrangement, but in some archegonia, shape and arrangement of neck cells was irregular. The apex of these archegonia often appeared swollen because of the random cell arrangement. In the presence of water, the antheridium cap is partially detached and the spermatozoids emerge. At this time, the neck cells open at the end of the archegonium in preparation for fertilization. The basic morphology of the antheridia and archegonia is similar to previous reports, although SEM provides more structural detail and a better three‐dimensional visualization of these reproductive structures.
ARCHITECTURE IN NEOTROPICAL PSYCHOTRIA L. (RUBIACEAE): DYNAMICS OF BRANCHING AND ITS TAXONOMIC SIGNIFICANCE
Authors: Hamilton Clement W.
Published: January 2018

Architecture of 19 species of Psychotria L. (Rubiaceae) was studied in Panama, principally on Barro Colorado Island. Three sets of data were gathered: 1) dynamics of normal branching events, by monitoring tagged plants; 2) dynamics of injury response, by monitoring experimental injuries; and 3) architecture of additional individuals and species, by static evaluation. Essentially three branching‐event types were found, herein called Types 1, 2, and 3, each of which defines a Hallé‐Oldeman (1970) whole‐plant model: Chamberlain, Leeuwenberg, and Koriba, respectively. All species were found perfectly consistent with respect to architecture. Architecture appears also to be a potentially important taxonomic character at the subgeneric and species‐group levels. Finally, nearly half the species examined do not fit a Hallé‐Oldeman whole‐plant model, often being characterized instead by a combination of branching types; three species, for instance, show Type 3 branching along the main trunk and Type 2 branching in the lateral branch complexes.
AN INTERGENERIC HYBRID IN THE SAXIFRAGACEAE: EVIDENCE FROM RIBOSOMAL RNA GENES
Authors: Doyle Jeff J. , Soltis Douglas E. , Soltis Pamela S.
Published: January 2018

The tandemly repeated multigene families encoding the 5S and 18S‐25S ribosomal RNAs were studied at the restriction enzyme level in Tolmiea menziesii, Tellima grandiflora, and in a putative intergeneric hybrid. Using restriction endonucleases that cut once per repeat, the repeat lengths of the 5S and 18S‐25S ribosomal genes were estimated. The 5S ribosomal gene repeat length is approximately 480 and 450 base pairs, respectively, in Tolmiea and Tellima. The repeat length of the 18S‐25S ribosomal genes varied from 11–13 kb in Tolmiea, and was only about 9 kb in Tellima. The putative hybrid combined the repeat lengths of both Tolmiea and Tellima for both the 5S and the 18S‐25S ribosomal genes. These data substantiate the occurrence of natural hybridization between Tolmiea and Tellima. For both the 5S and 18S‐25S gene experiments, the hybrid appears to contain fewer repeats corresponding to Tolmiea than to Tellima.
FLORAL DEVELOPMENT OF HYDROCHARIS MORSUS‐RANAE (HYDROCHARITACEAE)
Authors: Scribailo Robin W. , Posluszny Usher
Published: January 2018

In both male and female flowers of H. morsus‐ranae the primordia of the floral appendages appear in an acropetal succession consisting of alternating trimerous whorls. In the male flower a whorl of sepals is followed by a whorl of petals, three whorls of stamens, and a whorl of filamentous staminodes. The mature androecial arrangement therefore consists of two antisepalous stamen whorls, an antipetalous whorl of stamens, and antipetalous staminodes. Shortly before anthesis, basal meristematic upgrowth between filaments of adjacent whorls produces paired stamens, joining Whorls 1 and 3, and Whorl 2 with the staminodial whorl. A central domelike structure develops between the closely appressed filaments of the inner stamen and staminodial whorl, giving the structure a lobed appearance. After petal inception in the female flower a whorl of antisepalous staminodes develop, each of which may bifurcate to form a pair of staminodes. During staminode development a girdling primordium arises by upgrowth at the periphery of the floral apex. The girdling primordium rapidly forms six gynoecial primordia, which then go on to produce six free styles with bifid stigmas. Intercalary meristem activity, below the point of floral appendage attachment, leads to the production of a syncarpous inferior ovary with six parietal placentae. The styles and carpels remain open along their ventral sutures. During the final stages of female floral development, several hundred ovules develop along the carpel walls, and three nectaries develop dorsally and basally on the three antipetalous styles.
GYNOECIUM AND DEVELOPMENT OF EMBRYO SAC, ENDOSPERM, AND SEED IN PHOLISTOMA (HYDROPHYLLACEAE) RELATIVE TO TAXONOMY
Authors: Berg Rolf Y.
Published: January 2018

The objective of this research was to provide data for a taxonomic evaluation of Pholistoma and for a later survey of evolutionary morphology within the tribe Hydrophylleae. The unilocular ovary bears specialized unicellular prickles. Ovary and capsule wall consist of five or seven cell layers, of which three develop thickened walls for protection and dehiscence. Two parietal placentae enlarge to fill the entire locule. The four to eight ovules per ovary, some of which degenerate, are irregularly ventral and half‐epitropous to half‐hypotropous. Each ovule is tenuinucellate, unitegmic, and anatropous with a feeble vascular strand. A large amount of ovular parenchyma is produced from two meristems, one of which is the integumentary tapetum. Cells of the ovular epidermis grow into giant cells, each with a tubular portion penetrating deep into the seed interior, thereby producing a most unusual seed coat. The embryo sac is of the Polygonum type, the embryo of the Onagrad type. The endosperm is cellular with a micropylar and a chalazal endosperm haustorium. Both haustoria produce lateral branches. The mature endosperm is porously pitted, due to the giant cells of the testa. Great similarity between the three Pholistoma species, and in particular the presence in all species of two lateral haustorium branches, of gigantic, funnel‐shaped epidermal cells, and of a porously pitted endosperm, strongly supports the notion that these three species constitute a natural entity.
THE GENUS THALASSIOSIRA (BACILLARIOPHYCEAE): MORPHOLOGY OF HETEROVALVATE RESTING SPORES OF T. SCOTIA
Authors: Johansen Jeffrey R. , Doucette Gregory J. , Fryxell Greta A.
Published: January 2018

Resting spores of Thalassiosira scotia Fryx. et Hoban were abundant in phytoplankton net hauls collected from the Scotia Sea south of South Georgia in December 1981. Primary valves are distinguished from secondary valves by the presence of marginal striae with rounded, shoelike protrusions, villi surrounding marginal areolae and marginal striae, greater numbers of central strutted processes, and differences in structure of occluded processes. Densities of marginal strutted processes also tend to differ, though ranges overlap. Thalassiosira scotia is most closely related to T. antarctica, differing from that taxon by having coarser areolation, heavier silicification, and more prominent occluded processes. Rudimentary valves of T. scotia differ from those of T. antarctica.
VARIATION IN THE BIG BLUESTEM (ANDROPOGON GERARDII)‐SAND BLUESTEM (ANDROPOGON HALLII) COMPLEX ALONG A LOCAL DUNE/MEADOW GRADIENT IN THE NEBRASKA SANDHILLS
Authors: Barnes Paul W.
Published: January 2018

Twenty four quantitative characteristics of 95 specimens of the big bluestem (Andropogon gerardii Vitman)—sand bluestem (Andropogon hallii Hack.) complex collected from six topographic positions along a local dune to meadow topographic gradient in the eastern Nebraska Sandhills were examined to determine the relationship between morphological variation and habitat variation in adjacent bluestem populations. All morphological characters showed intergradation between big bluestem and sand bluestem but based on awn length, ligule length, cilia length on pedicels and rachises, rhizome length, and hybrid indexes, as well as comparisons with isolated bluestem populations, dune and meadow bluestems were found to be morphologically distinct. Sand bluestem types occupied dry, upland sand dunes, big bluestem types were restricted to adjacent, subirrigated meadows and plants intermediate in morphology were found only in narrow dune/meadow transition zones. For all bluestems, four characters (awn, ligule, cilia and rhizome) were significantly correlated with each other but correlations were most non‐significant when only intermediates were considered; pollen stainability, however, was highly variable and was not related to morphology. Variation in leaf thickness, adaxial stomatal frequency and leaf absorptance to photosynthetically active radiation was found to exist in bluestems, which previously has not been quantitatively described in this complex. Habitat assortment in bluestem types along this dune to meadow topographic gradient was closely related to soil moisture levels which, in these sandy soils, were controlled primarily by the depth of the underlying water table.
MERISTEMATIC PRECURSORS OF VASCULAR PARENCHYMA DIFFERENTIATE FROM G2 PHASE AFTER REPLICATING DNA DISCONTINUOUSLY
Authors: Hof Jack Van't , Bjerknes Clara A. , Lamm Susan S.
Published: January 2018

A small population of cells representing 1% or less of those in the root‐tip meristem was identified as the precursor of vascular parenchyma and certain root‐cap cells in carbohydrate starved cultured pea roots. Autoradiography and cytophotometric measurements of nuclei labeled with [3H]‐thymidine showed that in the absence of carbohydrate the precursor cells replicate their DNA discontinuously accumulating temporarily in late S phase prior to differentiating from the G2 phase. Besides discontinuity of DNA synthesis, the nuclei of precursor cells undergo a change in morphology. The nuclei are shaped round when replicating DNA but later on, while differentiating, they become oblong. This transformation occurs within 72 hr after the starved roots are fed sucrose. Autoradiograms of serial cross‐sections of pulse‐labeled roots indicate that the cells in late S phase differentiate forming a ring around the stelar cylinder and a ring around the periphery of the root. These observations suggest that during the last half of the final S phase the precursor cells modify their chromosomal DNA and that this modification is associated with the initial steps of differentiation.
ANTHECIAL AND FOLIAR MICROMORPHOLOGY AND FOLIAR ANATOMY OF BRACHIARIA (POACEAE: PANICEAE)
Authors: Thompson Rahmona A. , Estes James R.
Published: January 2018

In an examination of the generic boundaries of Brachiaria, ten anthecial patterns are recognized for the genus, eight for the first time. A smooth surface is proposed as the basic pattern from which the ornate patterns are produced. The laminar abaxial epidermis displays panicoid microcharacters. Foliar anatomy is the type associated with the C4, PEP‐carboxykinase photosynthetic pathway. However, no species groups are discernable and the variation within Brachiaria appears to be continuous.
IDENTIFICATION OF LATICIFERS IN EMBRYOIDS DERIVED FROM CALLUS AND SUSPENSION CULTURES OF ASCLEPIAS SPECIES (ASCLEPIADACEAE)
Authors: Dunbar Kerry B. , Wilson Kathryn J. , Petersen Bruce H. , Biesboer David D.
Published: January 2018

Laticifers were identified in frozen sections of embryoids from callus and suspension cultures of Asclepias syriaca (common milkweed) by an indirect fluorescent antibody technique. Sections were treated with the IgG fraction of rabbit anti‐latex antiserum, produced with field‐collected A. syriaca latex as a source of antigens, and with fluorescein‐conjugated IgG fraction goat anti‐rabbit IgG. Laticifers were identified by their fluorescence in embryoids dissected from 3–4‐month‐old callus cultures and in embryoids from 2‐month‐old suspension cultures. Laticifers are not present in early globular embryoids of A. syriaca but embryoids similar in shape to late globular stage zygotic embryos possess branching laticifers typical of zygotic material. Sections on control slides, treated with whole serum or IgG fraction from whole serum, both from an uninjected rabbit, contained no fluorescent cells. No laticifers were detected with the fluorescent antibody assay in A. tuberosa embryoids.
EFFECT OF AGING ON GROWTH AND FLOWERING OF THE TERMINAL BUD OF PHARBITIS NIL
Authors: Owens Vivian , Paolillo Dominick J.
Published: January 2018

The tendency of the terminal bud of Pharbitis nil to flower after one long night was studied in the context of growth changes occurring with aging. Seedlings were grown under constant light and temperature, selected for uniformity and subjected to a 16‐hr dark period at ages ranging from 3 to 14 days. A decline in percent terminals flowering was observed after day 6, to zero at day 10. Flowering of the terminal was obtained in some plants, thereafter. Floral index of development scored lower for terminals flowering on days 7–9 and 11–14 than on days 3–6. Loss of the tendency to flower was associated with a decline in rate of leaf production in the terminal bud and a change in rate of elongation of the epicotyl axis. The data lend support to a nutrient‐diversion hypothesis in the control of flowering in Pharbitis.
BEETLE POLLINATION OF DIEFFENBACHIA LONGISPATHA (ARACEAE)
Authors: Young Helen J.
Published: January 2018

Dieffenbachiais an monoecious understory herb of tropical rain forests that exhibits a complex and specialized relationship with its beetle pollinators. The erect protogynous inflorescence has the spadix divided, with the female flowers in the basal half and male flowers in the upper half.Dieffenbachia longispathaEngler & Krause is pollinated by scarab beetles in the generaCyclocephalaandErioscelis.The enveloping spathe of the inflorescence opens in the evening, but no flowers are sexually functional until the stigmas become receptive about 24 hr later. Beetles fly to the inflorescence in darkness, suggesting that floral odors play a role as an attractant. Beetles remain in the inflorescence for 24 hr, eating protein‐rich staminodia that surround the stigmas. On the evening of the third day the anthers dehisce and beetles become covered with pollen as they crawl up the spadix in the process of leaving. Beetles fly an average of 80 m between inflorescences, usually to the nearest female inflorescence, although distances of 400–1,000 m have been observed. Minimal estimate of genetic neighborhood sizes are large forD. longispatha(750 to 8,900 plants) and neighborhood areas encompass 41,000 to 67,000 m2. Experiments demonstrate that the species is self‐compatible and that fruit production is pollinator limited.
MICROSPOROGENESIS IN MALE‐STERILE AND HERMAPHRODITIC PLANTS OF NINE GYNODIOECIOUS TAXA OF HAWAIIAN BIDENS (ASTERACEAE)
Authors: Sun M. , Ganders Fred R.
Published: January 2018

Microsporogenesis was investigated in hermaphroditic and male‐sterile plants in nine gynodioecious taxa of Hawaiian Bidens. Normal microsporogenesis in hermaphrodites and the onset of abortion in male steriles were similar in all taxa and in a hybrid between two gynodioecious species. The early abnormal vacuolation of tapetal cells is the first visible evidence leading to premeiotic abortion of microsporogenesis in male steriles. The sporogenous cells disintegrate rapidly after the vacuolation of the tapetum, resulting in a shrunken, indehiscent anther which is composed of only the epidermal layer with some remnant cells of the endothecium and the connective at anthesis. In hermaphrodites, the tapetal cells remain dense and undergo karyokinesis to become binucleate during meiosis I. The tapetum becomes plasmodial after microspores are released from tetrads and gradually disappears during pollen formation. The genetic factor(s) which cause the abortion act with remarkable precision and consistency in all taxa investigated. This suggests that gynodioecy in all Hawaiian Bidens is homologous and the establishment of male sterility in Hawaiian Bidens occurred only once. The spread of the genetic male‐sterile factor(s) may be the result of adaptive radiation of the original gynodioecious species or natural interspecific hybridization.
COMPLEX PALEOZOIC FILICALES IN THE EVOLUTIONARY RADIATION OF FERNS
Authors: Rothwell Gar W.
Published: January 2018

Filicalean frond segments bearing indusiate sori with gradate development have been discovered in Pennsylvanian deposits of eastern North America. The specimens combine characters of Schizaeaceae, Gleicheniaceae, Cyatheaceae and Hymenophyllaceae, and together with data from other sources, indicate that the Filicales were in the midst of an evolutionary radiation during the late Paleozoic. Evidence from fossil and extant species prompts the hypothesis that filicalean ferns originated near the base of the Carboniferous, and have undergone three major evolutionary radiations.
CHARACTERIZATION OF VEGETATIVE GROWTH OF DWARF SOYBEAN GENOTYPES INCLUDING A GIBBERELLIN‐INSENSITIVE GENOTYPE WITH IMPAIRED CELL DIVISION
Authors: Birnberg Paul R. , Cordero Robert E. , Brenner Mark L.
Published: January 2018

The response of normal soybean (Glycine max [L.] Merrill) cultivars to gibberellins (GAs) and to an inhibitor of GA biosynthesis indicated that, as in other species, endogenous GAs are involved in controlling internode length. The responses to GA of several pairs of isogenic dwarf and normal genotypes (isolines) were compared. Dwarf genotypes T209, T244, T256, and M64–503‐Duddy apparently are not dwarfed by lesions in the biosynthetic pathway similar to the well‐studied mutations in pea and corn. Although these genotypes responded to GA3, their growth as a percentage of initial shoot length was less than that of the normal isolines following GA3 treatment. Dwarf genotype T210 responded to GA3 treatment with a much smaller increase in stature than the other dwarf genotypes. Roots of T210 seedlings were of normal size, which indicated that the mutation in T210 primarily affects shoot growth. Transport and metabolism of GA3 were equivalent in T210 and its non‐dwarf isoline, Lincoln. The slight response in shoot length of T210 to GA3 was accounted for by cell elongation, which GA3 promoted to at least the same extent as in Lincoln. Gibberellin A3 had no effect on cell number in T210, although GA3 increased cell number in Lincoln by 53%. Thus, T210 is dwarfed by an inability to carry out GA‐promoted cell division.
TROPICAL AMERICAN TERTIARY FLORAS AND PALEOENVIRONMENTS: MEXICO, COSTA RICA, AND PANAMA
Authors: Graham Alan
Published: January 2018

Three Tertiary microfossil floras from northern Latin America are considered with reference to paleoenvironments and paleoenvironmental trends, especially paleotemperatures: Gatuncillo (middle (?) to late Eocene, Panama), Uscari (early Miocene, Costa Rica), and Paraje Solo (late Miocene, Veracruz, Mexico). The composition of the floras reflect lower temperatures in the late Miocene for terrestrial environments at ca. 18°N latitude, and temperatures comparable to the present for the middle (?) to late Eocene and early Miocene at ca. 9°N latitude. These values are consistent with Tertiary paleotemperature curves derived from 18O and 13C isotope studies of marine invertebrates, and show that the global drop in temperature at the end of the Miocene affected terrestrial biotas at least as far south as 18°N latitude. Comparison of the paleobotanical data with paleotemperature curves further reveals that the late Miocene was not only a likely time for the introduction of northern temperate elements into the Latin American biota (viz., establishment of the floristic and faunal relationship between eastern United States and eastern Mexico), but that earlier times were progressively less favorable because of generally rising temperatures and more tropical conditions. Information on the Tertiary history of vegetation in the Gulf/Caribbean region is also being monitored with reference to the effect of global sea level changes, although the specific influence of these fluctuations cannot as yet be detected.
CHLOROPHYLL‐DEFICIENT CELL LINES WHICH ARE GENETICALLY UNCHARACTERIZED CAN BE INAPPROPRIATE FOR USE AS PHENOTYPIC MARKERS IN DEVELOPMENTAL STUDIES
Authors: Marcotrigiano Michael , Morgan Pamela A.
Published: January 2018

Periclinal chloroplast chimeras are genetic mosaics which possess shoot apices composed of one or more chlorophyll‐deficient histogens and can exist as a series of arrangements of normal and mutant layers (A‐B‐B, A‐B‐A, etc.). Three periclinal chimeral cultivars of Sansevieria trifasciata L., each of which possesses normal green cell layer(s) but a genetically different chlorophyll‐deficient cell layer(s), were utilized to study the effect of genotype on the ability of the cell layers of leaf cuttings and of cultured leaf tissue to regenerate shoots. The epidermis and LI derivatives were apparently incapable of shoot regeneration via leaf cutting, yet in two cultivars produced some shoots in vitro. In two of the cultivars, the chlorophyll‐deficient cells never produced shoots. In the third, the capability of chlorophyll‐deficient cell layers to produce shoots was less in vitro than in vivo, indicating that when determining morphogenic potential, direct comparisons between in vitro and in vivo systems may not be valid. Results also demonstrate that because genetically different albino cell layers can differ in their morphogenic response, utilizing a series of periclinal chimeras is useful only if the series is composed of the same two genotypes.
MEGAGAMETOPHYTE AND NUCELLUS IN RESTIONACEAE AND FLAGELLARIACEAE
Authors: Rudall P. J. , Linder H. P.
Published: January 2018

Restionaceae are characterized by Polygonum‐type development, a well‐developed hypostase, the presence of starch grains in the mature female gametophyte, and a thick nucellus that is uniseriate at the micropylar end. Flagellaria indica differs in these characters. In general, proliferation of antipodals occurs in South African taxa of Restionaceae but not in Australasian taxa. The presence of multiplied antipodals is the usual condition in the allied family Poaceae, but the sporadic occurrence of this character in Restionaceae cannot be used to support the view that the two families are sister groups.
POLLEN MORPHOLOGY OF THE TRIBE SWARTZIEAE (SUBFAMILY PAPILIONOIDEAE: LEGUMINOSAE). 1. INTRODUCTION AND ALL GENERA EXCLUDING ALDINA AND SWARTZIA
Authors: Ferguson I. K. , Skvarla J. J.
Published: January 2018

The pollen morphology of 9 of the 11 genera of the tribe Swartzieae is described together with that of Holocalyx and Cyathostegia, two genera recently removed from the tribe based on macromorphology. The pollen is small, spheroidal to subprolate, primarily tricolporate with a perforate tectum and generally typical of the Leguminosae. Nonetheless, many of the genera have distinctive pollen morphology. Baphiopsis is 6‐colporate. The genera Harleyodendron, Lecointea and one species of Exostyles have supratectal spinules. Bocoa viridiflora has striate/rugulate ornamentation very distinct from the other species of the genus Bocoa. The exine stratification is varied but Candolleodendron has a very thick endexine and narrow foot layer. The pollen of African taxa does not differ significantly from that of South American taxa. Pollen morphology does not clarify the taxonomic relationships of the tribe and provides little evidence to assist in positioning Holocalyx and Cyathostegia.
ISOLATION OF EXINES FROM GYMNOSPERM POLLEN
Authors: Southworth Darlene
Published: January 2018

Exines of certain Gymnosperms spontaneously separate from the intine during the process of hydration preceding pollen germination. Exines of pollen of Calocedrus decurrens, Chamaecyparis lawsoniana, Juniperus occidentalis, Sequoia sempervirens, and Pseudotsuga menziesii were isolated from hydrated, autoclaved pollen. Free exines were purified by centrifugation on a discontinuous sucrose gradient of densities 1.14 to 1.27 g/ml. The outer intine dissolved on autoclaving. This method may be applicable to a wide range of genera. Purified exines are of potential use in chemical analyses of sporopollenin and in production of antibodies to exine.
ENDOTHECIAL THICKENINGS IN ANTHERS OF PORATE MONOCOTYLEDONS
Authors: Gerenday A. , French J. C.
Published: January 2018

A survey of the presence of endothecial thickenings in 20 genera from 11 families of porate monocotyledons tested the long‐standing hypothesis that porate anther dehiscence is correlated with the absence of thickenings. Although this hypothesis is widely repeated in texts, it has been supported by a limited, biased data base from studies of Ericaceae and Melastomataceae, two large families of dicotyledons. The results of our broad study of monocotyledons show that endothecial thickenings are present in most porate monocotyledons. Thickenings are absent in only two of the 11 porate families surveyed, Mayacaceae and Commelinaceae, both in the Commelinales. Thickenings are also absent in Xyris (Xyridaceae), a nonporate genus. These findings indicate that in monocotyledons porate anther dehiscence and the absence of thickenings are not as closely related as previously supposed.
EFFECTS OF ULTRAVIOLET‐B IRRADIATION ON SEEDLING GROWTH IN THE PINACEAE
Authors: Sullivan Joe H. , Teramura Alan H.
Published: January 2018

Ten conifer species were grown in an unshaded greenhouse at the University of Maryland under 3 levels of biologically effective ultraviolet‐B radiation. Ultraviolet‐B radiation was supplied by Westinghouse FS‐40 sunlamps and effective daily doses were 0, 12.4, and 19.1 kJ m–2. During the irradiation period, seedling growth and the development of stress symptoms were monitored. After 22 weeks of irradiation, seedlings were harvested and morphological characteristics analyzed. Visual symptoms included needle discoloration and stunting in three of the ten species tested. Seedling height was significantly reduced by supplemental UV‐B in Pinus contorta (lodgepole pine), Pinus resinosa (red pine), and Pinus taeda (loblolly pine). Biomass increased in Picea engelmannii (Engelmann spruce). Abies fraseri (Fraser fir), Pinus edulus (pinyon pine), and Pinus nigra (black pine) were unaffected by UV‐B while biomass reductions exceeding 5% were observed in all other species tested. These deleterious effects occurred despite the presence of morphological characteristics which would tend to reduce UV‐B effectiveness. Generally, the effects of supplemental UV‐B dose were less for those species native to higher elevations, implying the presence of natural adaptations to UV‐B.