bluuebunny/crossref_metadata_2025 huggingface dataset:
SOMATIC EMBRYOGENESIS AND ORGANOGENESIS FROM CALLUS CULTURES OF SOLANUM CAROLINENSE
Authors: Reynolds Thomas L.
Published: January 2018

Culture of stem segments of Solanum carolinense L. on medium supplemented with 10 mg/1 2,4‐dichlorophenoxyacetic acid and 1 mg/1 kinetin, induced callus formation. When subcultured on medium lacking 2,4‐D but containing a cytokinin, the callus regenerated. The mode of regeneration depended on the type and concentration of cytokinin employed; high concentrations of benzyladenine and all concentrations of kinetin promoted organogenesis, while low concentrations of benzyladenine induced somatic embryogenesis in addition to organogenesis. With age and continued subculture on 2,4‐D containing medium, callus progressively lost its ability to regenerate when the auxin was replaced by cytokinin. In conjunction with previous studies on regeneration from anther cultures of S. carolinense, it appears that in both cases, 2,4‐D is required for callus initiation and proliferation but must be exchanged for a cytokinin before differentiation will occur. However, since it was not possible to induce embryogenesis in pollen‐derived callus, developmental potential may be influenced by the ploidy level of responding cells in culture.
CYCLIC HETEROPHYLLY IN SYNGONIUM (ARACEAE)
Authors: Ray Thomas S.
Published: January 2018

Species in the genus Syngonium germinate on the ground and mature on the trunks of the trees. These vines consist of relatively unbranched shoots which grow through the forest for considerable distances both horizontally and vertically. In the three species of this study, the shape of the segment, measured as internode diam/length, falls into two distinct classes, leafy and elongate, and varies cyclicly along single shoots. Two cycles are recognized. One cycle occurs in small diam terrestrial shoots in which cycling seems to be controlled by endogenous factors, and occurs with a period of a few tens of segments. The other cycle occurs in shoots of larger diam which climb and descend from trees. In this cycle, alternation between the two forms is controlled by gain or loss of contact with trees, and shoots may remain within a phase of the cycle for hundreds of segments, as long as the substrate does not change.
PATTERNS OF GENOTYPIC DIVERSITY IN CLONAL PLANT SPECIES
Authors: Ellstrand Norman C. , Roose Mikeal L.
Published: January 2018

We compile and analyze data on the population genetic structure of broad‐sense clonal plant populations where sexual recruitment is rare or absent. The data from 27 studies show a common theme: multiclonal populations of intermediate diversity and evenness tend to be the rule, most clones are restricted to one or a few populations, and widespread clones are exceptional. While a few studies have demonstrated that ecological differences among sympatric clones do occur, more experimental and theoretical studies are necessary to determine the role of selection and other evolutionary forces in maintaining clonal polymorphism.
NUTRITIONAL STUDIES OF THE SUBMERGED MARINE ANGIOSPERM THALASSIA TESTUDINUM I. GROWTH RESPONSES OF AXENIC SEEDLINGS TO NITROGEN ENRICHMENT
Authors: Durako Michael J. , Moffler Mark D.
Published: January 2018

Algae‐ and bacteria‐free seedling cultures of the seagrass Thalassia testudinwn Banks ex König were utilized to evaluate effects of nutrient enrichment on growth and chemical composition. Seedlings cultured in media based on both synthetic seawater and NH‐15 medium amended with inorganic nitrogen (NH4+) and organic nitrogen (glutamine, glutamate, urea and yeast extract) exhibited no growth enhancement relative to controls in the growth parameters measured. General decreases in green leaf areas and leaf widths after one month coupled with relatively high C:N ratios after 3 months in culture suggest utilization and depletion of stored reserves with little or no assimilation of exogenous nutrients. These observations coupled with previous results in non‐axenic seedling cultures indicate microbial associations may play a critical role in the nutrient physiology of this species.
INTERPOPULATIONAL VARIATION IN FRUIT PRODUCTION: THE ROLE OF POLLINATION‐LIMITATION IN THE OLYMPIC MOUNTAINS
Authors: Campbell Diane R.
Published: January 2018

Fruit set varied from a mean of 44% to 93% among six populations of Veronica cusickii L. (Scrophulariaceae) spanning a distance of 13 km in the Olympic Mountains, WA. Hand pollinations in three populations showed that this variation resulted primarily from differences in the level of limitation by insect pollination. In every pollination, hand‐pollinated flowers averaged at least 82% fruit set. In 1981 and 1982, addition of excess pollen significantly increased mean fruit set per plant in the Blue Mountain population, but not in two other populations with higher natural fruit sets. At Blue Mountain, hand pollination more than doubled the mean seed set of V. cusickii and also significantly increased seed set in two of three other species visited primarily by flies or solitary bees. Pollination‐limitation appears to be common at this site where the weather is frequently cold and damp.
ALGAL BIOMASS AND PRIMARY PRODUCTION WITHIN A TEMPERATE ZONE SANDSTONE
Authors: Bell Robert A. , Sommerfeld Milton R.
Published: January 2018

The use of dimethyl sulfoxide (DMSO) to extract chlorophyll a and l4C‐labelled photosynthate from endolithic algae of sparsely vegetated, cold temperate grasslands on the Colorado Plateau in Arizona has yielded the first estimates of biomass and photosynthesis for this unusual community. These subsurface microorganisms are found widespread in exposed Coconino Sandstone, a predominant formation in this cold temperate region. The endolithic community in Coconino Sandstone, composed primarily of coccoid blue‐green and coccoid/sarcinoid green algae, yielded a biomass value (as chlorophyll a content) of 87 mg m‐2 rock surface area and a photosynthetic rate of 0.37 mg CO2 dm 2 hr‐1 or 0.48 mg CO2 mg‐1 chl a hr‐1. The endolithic algal community contributes moderate biomass (5–10%) and substantial photosynthesis (20–80%) to the sparse grassland ecosystem.
CHARACTERIZATION OF ROOT AGRAVITROPISM INDUCED BY GENETIC, CHEMICAL, AND DEVELOPMENTAL CONSTRAINTS
Authors: Moore Randy , Fondren W. Mark , Marcum Heidi
Published: January 2018

The patterns and rates of organelle redistribution in columella (i.e., putative statocyte) cells of agravitropic agt mutants of Zea mays are not significantly different from those of columella cells in graviresponsive roots. Graviresponsive roots of Z. mays are characterized by a strongly polar movement of 45Ca2+ across the root tip from the upper to the lower side. Horizontally‐oriented roots of agt mutants exhibit only a minimal polar transport of 45Ca2+. Exogenously‐induced asymmetries of Ca result in curvature of agt roots toward the Ca source. A similar curvature can be induced by a Ca asymmetry in normally nongraviresponsive (i.e., lateral) roots of Phaseolus vulgaris. Similarly, root curvature can be induced by placing the roots perpendicular to an electric field. This electrotropism increases with 1) currents between 8–35 mA, and 2) time between 1–9 hr when the current is constant. Electrotropism is reduced significantly by treating roots with triiodobenzoic acid (TIBA), an inhibitor of auxin transport. These results suggest that 1) if graviperception occurs via the sedimentation of amyloplasts in columella cells, then nongraviresponsive roots apparently sense gravity as do graviresponsive roots, 2) exogenously‐induced asymmetries of a gravitropic effector (i.e., Ca) can induce curvature of normally nongraviresponsive roots, 3) the gravity‐induced downward movement of exogenously‐applied 45Ca2+ across tips of graviresponsive roots does not occur in nongraviresponsive roots, 4) placing roots in an electrical field (i.e., one favoring the movement of ions such as Ca2+) induces root curvature, and 5) electrically‐induced curvature is apparently dependent on auxin transport. These results are discussed relative to a model to account for the lack of graviresponsiveness by these roots.
NEW DEPSIDES FROM LICHENS: MICROCHEMICAL METHODOLOGIES APPLIED TO THE STUDY OF NEW NATURAL PRODUCTS DISCOVERED IN HERBARIUM SPECIMENS
Authors: Culberson Chicita F. , Culberson William Louis , Gowan Sharon , Johnson Anita
Published: January 2018

A high‐performance liquid chromatographic method originally devised to provide a reproducible measure of retention is used to determine chemical structures of new compounds in lichens. The method relates retention to a standard homologous series so that retention indices of members of other homologous series are linear with carbon number. When two or more homologs are known, retention of new members of the same series can be accurately predicted. Combining this method with other microchemical techniques allows the determination of structures of lichen depsides in small samples of crustose species for which the total material is meager and known only from the herbarium. The conditions are sufficiently mild that chemical decompositions of labile depsides are avoided. Eight new orcinol‐type p‐depsides with seven‐ or nine‐carbon oxidized sidechains on one or both rings are reported from an endemic Japanese species, Haematomma pachycarpum. The nine‐carbon sidechain is the longest ever found in lichen depsides. These new compounds are higher homologs of the known lichen products confluentic, 2‘‐O‐methylperlatolic, 4‐O‐methylolivetoric, and 2‘‐C‐methylmicrophyllinic acids. In addition, an isocoumarin with a nine‐carbon sidechain occurs in some specimens. Haematomma pachycarpum has the most complex secondary‐product chemistry thus far reported for any lichen species. The significance of the technique used here lies in providing a way to characterize new compounds in rare or endangered species, thereby completing data sets for phylogenetic reconstructions.
SPORE WALL ULTRASTRUCTURE OF PROTOSALVINIA
Authors: Taylor Wilson A. , Taylor Thomas N.
Published: January 2018

Protosalvinia is an enigmatic fossil which has been historically assigned to several major taxonomic groups. Stratigraphically, the fossil occurs in a narrow range of Upper Devonian sediments. Tetrads of spores are associated with shallow depressions on the surface of approximately 5% of the specimens collected from the Ohio Shale in Columbus, OH. Spores are approximately 250 μm in diameter and have a spore wall which is composed of at least two distinct layers. The outer layer is coarsely laminated in regions where adjacent spores are in contact. Individual laminar units are thinnest toward the inside and gradually thicker toward the surface of the spore. In non‐contact regions, the outer layer is composed of globular units. The inner layer of the wall has little discernable structure except for the presence of a distinct suture beneath the proximal trilete mark. This firmly establishes the meiotic nature of these structures. Comparison with eggs and tetraspores of several extant phaeophycean algae shows little similarity.
USE OF REPEATED DNA SEQUENCES AS CYTOLOGICAL MARKERS
Authors: Rayburn A. Lane , Gill B. S.
Published: January 2018

The majority of DNA that is found in most of the flowering plants appears to be non‐coding DNA. Much of this excess DNA consists of nucleotide sequences which exist as multiple copies throughout the genome and are designated as repetitive sequences. Those sequences which are found in moderately high to high numbers of copies are observed to be of the greatest value as cytological markers. Moderately high copies may exist as sequences which are dispersed throughout the chromosomes of some species and not dispersed in other more distantly related species. By taking advantage of this characteristic and the technique of in situ hybridization with biotinylated probes, breakpoints of chromosomal translocations may be observed between species such as wheat and rye. Many of the high copy number repetitive sequences are organized in a tandem fashion in specific loci in the chromosome. Chromosomal identification may be accomplished by using the in situ hybridization technique. Upon in situ hybridization with a repetitive sequence isolated from Aegilops squarrosa, the patterns of the sites of hybridization allowed the D‐genome chromosomes to be identified. The sequence was also observed only on the D‐genome chromosomes of several polyploid species indicating its usefulness as a genome specific marker. Using this genome specificity, assessment of the orientation of the D‐genome chromosomal segments of hexaploid wheat carrying the sequence during interphase and prophase of mitotic root tip cells was possible. Repetitive DNA sequences, therefore, provide cytological markers necessary for studies of chromosomal identification, genome allocation, and genome orientation. The use of biotin‐labeled DNA probes allows the technique of in situ hybridization to be performed much more rapidly and with a greater degree of safety and reliability.
SURVIVORSHIP AND FECUNDITY OF THE POLYCARPIC PERENNIAL MENTZELIA NUDA (LOASACEAE) IN NEBRASKA SANDHILLS PRAIRIE
Authors: Keeler Kathleen H.
Published: January 2018

Survivorship and fecundity of the polycarpic perennial Mentzelia nuda were investigated to help understand its population dynamics. Between 1978 and 1984, all 685 individuals found in a Nebraska sandhills prairie plot were marked and their fate followed. Three plants lived seven years, but the average lifespan was less than two years. Most plants spent their first year as nonflowering rosettes: only 9% flowered the first summer after germination. Overall, first‐year survivorship ranged from 0.20 to 0.50 between 1978 and 1984. Fifty‐two percent of rosettes survived to flower. Survivorship of flowering individuals was about the same as the survivorship of rosettes, although actual survivorships varied significantly between years. Both rainfall and age affected survivorship and fecundity.
ROLE OF STEM GROWTH IN LINUM USITATISSIMUM LEAF TRACE PATTERNS
Authors: Meicenheimer Roger D.
Published: January 2018

Linum usitatissimum stem growth parameters were quantified by computer‐assisted analyses of scanning electron micrographs of shoot apical meristems throughout ontogeny. There were progressive decreases in the plastochron and relative plastochron rates of radial and vertical stem growth which resulted in the generation of progressively higher orders of contact parastichy phyllotaxis throughout ontogeny. The change in the relative spacing of primordia initiation on the stem coupled with the iterative differentiation of leaf gap and interfascicular ray parenchyma associated with each leaf primordium resulted in the delimitation of progressively higher orders of leaf trace interconnections throughout ontogeny. A set of developmental rules was generated which should permit simulation of many leaf trace patterns.
SYSTEMATIC OCCURRENCE OF A SCLEROTIC HYPODERMIS IN ROOTS OF ARACEAE
Authors: French J. C.
Published: January 2018

A survey of the systematic occurrence of a sclerotic hypodermis was made in 91 genera and over 280 species of Araceae. The sclerotic hypodermis in roots consists of a cylinder inside the exodermis, one to five or more cells wide, with thickened, lignified cell walls. The cells are elongated, pitted, and often septate. A sclerotic hypodermis occurs in roots of only eight genera of Araceae, including Culcasia, Montrichardia, Cercestis, Rhektophyllum, Furtadoa, Homalomena, Philodendron, and Anubias. In Philodendron section Philodendron a sclerotic hypodermis is present in aerial and absent from subterranean roots. These results are consistent with other anatomical studies in supporting a transfer of Culcasia from Pothoideae, and Cercestis, Rhektophyllum, and Montrichardia from Lasioideae into an expanded Philodendroideae, as recently proposed by Grayum. Further, these and other anatomical results both provide support for a closer taxonomic association of Culcasia, Cercestis, Rhektophyllum, Philodendron, Montrichardia, Homalomena, Anubias, and Furtadoa than has previously been recognized.
TAXONOMIC SIGNIFICANCE OF CHROMOSOME OBSERVATIONS IN CARIBBEAN SPECIES OF LANTANA (VERBENACEAE)
Authors: Sanders Roger W.
Published: January 2018

Chromosome numbers and, in most cases, meiotic configurations are provided for 12 taxa and 5 morphological intermediates of Lantana collected in the Bahamas, Dominican Republic, Florida, the Lesser Antilles, Puerto Rico, and Texas. Reported for the first time are Lantana bahamensis, n = 11; L. microcephala, n = 12; L. leonardiorum, n = 11; L. odorata, n = 12; L. reticulata, n = 24; L. subcordata, n = 11; L. urticifolia, n = 11, 22. Numbers differing from previous reports were obtained for L. involucrata, n = 12, 24, and L. trifolia, n = 27. Triploids indicate the natural occurrence of hybridization between diploid and tetraploid taxa. Bivalents are formed regularly, except in the triploids and in morphologically intermediate tetraploids. These reports confirm that Lantana is based on at least two numbers, x = 11 and 12, and that the genus comprises polyploid complexes in each of these basic lines. The polyploids are weedier and more widely distributed than are the diploids. Chromosome numbers and configurations aid in the delimitation of diploid foundation species and in the recognition of naturalized hybrids.
FLEXURAL RIGIDITY OF CHIVE AND ITS RESPONSE TO WATER POTENTIAL
Authors: Niklas Karl J. , O'Rourke Thomas D.
Published: January 2018

The biomechanical relationship between the ability of a plant organ to resist bending and the extent to which tissues are hydrated is illustrated for the cylindrical leaves of chive (Allium schoenoprasnum var. schoenoprasnum L.). The flexural rigidity (EI), which measures the ability to resist bending, is maximum when leaves are fully turgid and decreases monotonically as a function of water potential (r2 = 0.99). Dehydration results in a reduction in the elastic modulus (E) of leaves. Reductions in E are correlated with geometric distortion in the transverse geometry of leaves which influences their second moment of inertia (I). The traditional theory of elastic stability (developed on the basis of the mechanical behavior of nonbiological systems) is shown to be inadequate to distinguish the behavior of E as plant organs geometrically distort during dehydration. This inadequacy results from the violation of a principal assumption made by the theory (= uniform cross‐sectional geometry). A derivation is presented that accommodates the localized geometric distortions in cylindrical plant organs and permits a valid estimate of reductions in E as tissues dehydrate. Based on this derivation, the Young's modulus of chive leaves just before mechanical failure due to buckling is shown to be less than 50% of that calculated for fully turgid leaves.
UNDERGROUND SYSTEMS OF GAMBEL OAK (QUERCUS GAMBELII) IN CENTRAL UTAH
Authors: Tiedemann A. R. , Clary W. P. , Barbour R. J.
Published: January 2018

Excavation to a depth of 1 m of a 3 × 4 m portion of a clone ofQuercos gambeliirevealed the presence of a massive underground system of lignotubers, interconnecting rhizomes and roots. Lignotubers comprised the greatest proportion (72%) of the total below ground biomass (81 t/ha). Lignotubers are distinctive in appearance: they are an enlarged stemlike structure with numerous clusters of adventitious buds on the surface. Anatomically, they are comparable to the above ground stems with growth rings. Lignotubers are lobed and distorted, giving the appearance of a burl. Rhizomes are round to I‐beam in shape with a star‐shaped pith, distinct annual rings, bud traces, and branch gaps. There were also clusters of adventitious buds on rhizomes, although not as dense as those on the lignotubers. Roots are oval in cross section with discernible growth rings, no pith, and no bud traces.
NUTRITIVE ROLE OF SEEDCOATS IN DEVELOPING LEGUME SEEDS
Authors: Murray David R.
Published: January 2018

The seedcoats of legume seeds comprise a multifunctional organ with responsibilities for protection, attraction (some times), and provision of nutrients to the embryo during its development. The transmission of solutes from phloem through seedcoats, and the processing of imported metabolites by seed coat cells prior to secretion are two important aspects of the seedcoats' nutritive function considered in this review. Some of the many important questions that remain unanswered have been posed, and scope for further research indicated.
MATING SYSTEM OF A TROPICAL RAIN FOREST TREE SPECIES
Authors: O'Malley David M. , Bawa K. S.
Published: January 2018

Canopy tree species are the dominant elements of the species‐rich, fragile and endangered tropical rain forest ecosystems, yet little is known about the genetics of these species. We provide an estimate of the outcrossing rate in a population of Pithecellobium pedicellare, a large canopy tree in the tropical rain forests of Costa Rica. The outcrossing rate was high (t = 951 ± 0.021) and the pollen pool contributing to the progeny arrays used to measure outcrossing rate showed departure from homogeneity. The high outcrossing rate indicates that individuals scattered over a large area in this low density population could be bound with each other via outcrossing. However, despite a high outcrossing rate, the potential for inbreeding in this population is not negligible. We found a relatively large number of albino and chlorotic seedlings among the progeny arrays of several seed parents. Heterogeneity of pollen pool further indicates that the population, though widely outcrossed, may be structured. A more detailed study of mating systems in tropical rain forest trees may provide additional insights into the mating patterns of these trees. Such studies will be useful not only in understanding the dynamics of micro‐evolutionary processes, but also in the conservation and management of tropical forest trees.
RELATIONSHIP BETWEEN SYNAPTOSPERMY AND DIOECY IN THE LIFE HISTORY STRATEGIES OF BUCHLOE DACTYLOIDES (GRAMINEAE)
Authors: Quinn James A.
Published: January 2018

Buchloe dactyloides (Nutt.) Engelm. is a perennial dioecious grass, exhibiting synaptospermy in that the 1–5 seeds in the dispersal unit (bur) are not released prior to germination. A major positive effect is that at least 50% of the burs contain both a male and female, making sexual reproduction possible and reducing founder effects upon colonization by one or a few burs. The objectives of this research were to examine the relationships between synaptospermy and dioecy in the life history strategies of Buchloe dactyloides, and to investigate whether the potential costs of synaptospermy would exceed its benefits if the species were not dioecious. An experiment that tested the effects of tightly clumping three seedlings vs. a uniform spacing of single seedlings at two densities and two moisture levels indicated only slightly negative effects of this aspect of synaptospermy. Although number of tillers and shoot biomass per plant were lower for clumped seedlings at all density and moisture combinations, only 50% of the possible uniform vs. clumped comparisons were significantly different. In addition, these effects, even at low moisture and/or high density, were not great enough to affect survivorship during the 16‐week growth period. Experiments under both optimal and low moisture conditions showed that seeds within burs germinated at a significantly higher percentage than isolated or “hulled” seeds; in contrast to the differential timing of germination from burs, almost all of the seedlings from hulled seeds were produced during the first of three germination periods. Although survivorship for these seedlings was quite high under optimal conditions, it was greatly reduced under low moisture, being only one‐fourth of that for seedlings arising from burs. The possible reduction in the wind dispersal of propagules due to their teeth and to their greater weight and size appears offset by more effective ungulate and water dispersal. Considering the evidence that the bur anchors the seedling in the soil, protects the seeds from fire, reduces precocious germination by requiring considerable moisture for saturation, and enhances seed longevity, the benefits of synaptospermy appear to outweigh the costs, even if those benefits related to dioecy are not considered.
PERSISTENCE OF AMBROSIA TRIFIDA POPULATIONS IN OLD FIELDS AND RESPONSES TO SUCCESSIONAL CHANGES
Authors: Hartnett David C. , Hartnett Barbara B. , Bazzaz Fakhri A.
Published: January 2018

A population of Ambrosia trifida L. (Asteraceae) in an annually ploughed field and an adjacent 15‐year old population in an old field were compared to determine how plant responses, genotypic composition, and genetic variability change in populations over successional time. The two populations were originally part of a large contiguous population in an annually ploughed field. When individuals from the two populations were grown from seed in a common garden, they showed several significant differences in characteristics indicating different genotypic compositions in the two populations. Individuals from the old field population showed earlier emergence, lower leaf mortality, and greater numbers of leaves, biomass, seed production, and reproductive allocation relative to plants from the annually ploughed field. When sown in the field in a reciprocal transplant experiment, individuals from the two populations also differed in patterns of emergence, survivorship, yield, and fecundity. When grown together in a pairwise competition experiment, individuals from the old field population showed competitive superiority with respect to growth and seed production. This genetic differentiation between populations of different successional ages may be explained by natural selection imposed by the changing environment over successional time. However, the history and characteristics of these populations are such that founder effects may also be important in explaining the differences between them. A comparison of levels of variability in 14 different characters of individuals of the two populations showed no evidence that genetic variability in A. trifida populations declined over successional time.
REGENERATION OF LIRIODENDRON TULIPIFERA (FAMILY MAGNOLIACEAE) FROM PROTOPLAST CULTURE
Authors: Merkle S. A. , Sommer H. E.
Published: January 2018

Protoplasts were isolated enzymatically from suspension cultures of two embryogenic lines of yellow‐poplar (Liriodendron tulipifera L.) and cultured in droplets of a regeneration medium supplemented with 1 mg/1 2,4‐D and 0.25 mg/1 6BA and solidified with agarose. Suspension cultures grown in the light yielded substantial numbers of protoplasts, while insignificant numbers were isolated from cultures grown in the dark. The protoplasts reformed cell walls within three days, and 75 percent of them divided at least once within one week in culture. Embryogenic suspension or callus cultures were regenerated by placing agarose droplets containing protoplast‐derived microcalli directly into liquid conditioning medium or onto plates of conditioning medium solidified with agar. Embryogenesis was obtained by transferring the callus to a hormone‐free induction medium.
DEVELOPMENT OF WHEAT (TRITICUM AESTIVUM) POLLEN. II. HISTOCHEMICAL DIFFERENTIATION OF WALL AND UBISCH BODIES DURING DEVELOPMENT
Authors: El‐Ghazaly Gamal , Jensen William A.
Published: January 2018

The histochemistry of different developmental stages of the pollen wall, aperture, and Ubisch bodies of Triticum aestivum is examined with light and transmission electron microscopy. Various parts of the callosic envelope of the tetrad spores stain differentially. At the late tetrad stage, the probacules and the coat of pro‐Ubisch bodies are densely stained for acidic polysaccharides, protein, and neutral polysaccharides. The protectum and the core of pro‐Ubisch bodies are moderately stained. Upon release of microspores from the callosic cell envelope, the stainability for acidic polysaccharides increases in the exine and in the wall of Ubisch bodies, becoming very intense in the wall of mature pollen grains and Ubisch bodies. The stainability for neutral polysaccharides is decreased in the mature pollen wall and in the Ubisch bodies, while the stainability for protein increases. The results also indicate the probability of the presence of unsaturated lipids and the absence of free aldehydes in the pollen wall and Ubisch bodies.
GENETIC DIVERGENCE AND ISOZYME NUMBER VARIATION AMONG FOUR VARIETIES OF ALLIUM DOUGLASII (ALLIACEAE)
Authors: Rieseberg Loren H. , Peterson Paul M. , Soltis Douglas E. , Annable Carol R.
Published: January 2018

Allium douglasii comprises four, allopatric varieties confined to the northwestern United States: var. columbianum, var. constrictum, var. douglasii, and var. nevii. Although no apparent karyotypic differences distinguish the four taxa, evidence from starch gel electrophoresis indicates that they are very distinct at genes coding for enzymes. The mean genetic identity for pairwise comparisons of populations of all four varieties is 0.84. This value is lower than identity values generally observed for subspecific taxa, and may be indicative of a long period of geographic separation and subsequent lack of gene flow among the varieties. However, a higher genetic identity of 0.93 was observed between var. constrictum and var. columbianum relative to other varietal comparisons. In addition, var. constrictum exhibited two biochemical autapomorphies: 1) loss of expression for the gene coding for Tpi‐3, and 2) duplication or reactivation of an ADH gene. These data indicate that var. constrictum may be a recent derivative of var. columbianum. The distribution of genetic variation within and among populations of the putative progenitor/derivative pair also supports this hypothesis.
A FOSSIL LITHOSPERMUM (BORAGINACEAE) FROM THE TERTIARY OF SOUTH DAKOTA
Authors: Gabel Mark L.
Published: January 2018

Silicified nutlets of a Lithospermum from the Late Miocene Ash Hollow Formation of Bennett County, South Dakota, are described. Lithospermum dakotense sp. nov. shows similarities in size, shape, attachment, and epidermal cell patterns to extant Lithospermum species. Fossil nutlets were preserved in various stages of maturity. This is the first description of definite Lithospermum nutlets from Tertiary strata of North America.
SECRETIONS FROM THE PISTIL OF LILIUM LONGIFLORUM
Authors: Miki‐Hirosige H. , Hoek I. H. S. , Nakamura S.
Published: January 2018

The pistil of Lilium longiflorum secretes two forms of exudate, one from the stigma surface and the other from the canal cavity. Electrophoretic studies of these exudates have revealed quantitative and qualitative differences in protein profiles. The exudatic components which are transferred to the cell wall by endoplasmic reticulum and Golgi vesicles, are stored within the cell wall of the secretive tissues and secreted from the cell walls directly. The cell wall structure of these secretive tissues differs. The canal cell wall has thick characteristic ingrowths that are supplied mainly from Golgi vesicles, while the papilla cell wall of the stigma is thinner, lacks ingrowths, and is supplied from ER vesicles.
GENETIC AND ENVIRONMENTAL DETERMINATION OF LEAF EPIDERMAL ANATOMY IN PUCCINELLIA (POACEAE)
Authors: Davis Jerrold I.
Published: January 2018

Phenotypic plasticity of anatomical leaf epidermal characters was assessed in the halophytic grass genus Puccinellia, to identify those of potential taxonomic utility. Characters with the greatest taxonomic potential are those that exhibit genetic variation and low plasticity. For the analysis, field‐collected clones were divided and grown under a series of moisture and salinity regimes. Genetic variation and plasticity in response to environmental variation were assessed for 39 anatomical characters by analysis of among‐clone and among‐treatment variation, respectively. Both genetic variation and plasticity are widespread among the characters, and both are detected in greater frequency among continuously variable characters than among discretestate characters. Among continuously variable traits, average cell dimensions exhibit more plasticity than do maximum cell dimensions or ratios that reflect shapes and relative sizes. Among discrete‐state characters, plasticity in the occurrence of papillae is found in nonstomatal intercostal cellular ranks, but not in costal or stomatal intercostal ranks. In Puccinellia, anatomical characters are, in general, neither more nor less plastic than those of macromorphology.
STAMINATE BLOOM DATE AND TEMPERATURE RESPONSES OF POLLEN GERMINATION AND TUBE GROWTH IN TWO WALNUT (JUGLANS) SPECIES
Authors: Luza Juvenal G. , Polito Vito S. , Weinbaum Steven A.
Published: January 2018

Pollen was collected from ten cultivars of Juglans regia and three cultivars of the later‐blooming species, J. nigra. Extensive phenological data were available for these cultivars. Cultivars were chosen on the basis of staminate bloom date to include the earliest and latest blooming individuals available and a representative range throughout the bloom season. Mean staminate bloom dates for the cultivars examined covered a period of 46 days over which time mean daily temperatures rose 6 C. In order to determine if adaptations to temperature were expressed by the gametophyte generation, pollen was subjected to controlled temperatures from 5 to 40 C in 2 to 4 C increments and analyzed for germination percentages and pollen tube elongation. A positive relationship was found for pollen germination percentage and mean staminate bloom date such that earlier blooming individuals showed lower minimum temperature thresholds for germination, and optimum temperature for pollen germination was positively correlated with mean staminate bloom date. Differences in pollen tube growth, determined separately from hydration and germination responses, were less clear. Most J. regia clones had lower minium temperature thresholds for growth than the J. nigra clones, but there was no clear relationship to earliness of bloom within the species. No differences were discerned in optimum temperatures for pollen tube growth either between the two species or within species.
VESICULAR‐ARBUSCULAR MYCORRHIZAE FROM THE TRIASSIC OF ANTARCTICA
Authors: Stubblefield Sara P. , Taylor Thomas N. , Trappe James M.
Published: January 2018

Silicified roots from the Triassic of Antarctica show features of extant vesicular‐arbuscular mycorrhizae (VAM). Nonseptate fungal hyphae occur within and between well‐preserved parenchymatous cells of the central cortex. Terminal and intercalary swellings comparable to chlamydospores and vesicles are also present within the roots. In addition, three‐dimensionally branched structures nearly fill the host cell and resemble modern day arbuscles. Although possible mycorrhizae have been reported as early as the Devonian, and are widely accepted, fossil arbuscles, the most definitive feature of VAM, have not been previously described. The fungi associated with the Antarctic roots provide the most complete and convincing evidence for pre‐Pleistocene VA mycorrhizae in the fossil record.
COMPUTER PROGRAM FOR THREE‐DIMENSIONAL RECONSTRUCTIONS AND NUMERICAL ANALYSES OF PLANT ORGANS FROM SERIAL SECTIONS
Authors: Niklas Karl J. , Boyd Steven P.
Published: January 2018

A computer program (SECTION) is presented which allows for the three‐dimensional reconstruction of serial cross sections through biological materials. The program provides a numerical analysis of perimeter length and transverse area of each anatomical feature designated in a cross section, as well as surface area and volume computations for features that pass from one section to another. In addition to rotating and tilting the 3‐D reconstruction in any desired orientation, the program has editing capabilities which allow different combinations of anatomical features to be shown in neutral gray outline or interconnected by colored lines.
FLORAL NECTAR SUGAR COMPOSITION AND POLLINATOR TYPE AMONG NEW WORLD GENERA IN TRIBE ANTIRRHINEAE (SCROPHULARIACEAE)
Authors: Elisens Wayne J. , Freeman C. Edward
Published: January 2018

The floral nectar sugar compositions of 20 New World species from 10 genera and of five interspecific hybrids in tribe Antirrhineae have been analyzed using high‐performance liquid chromatography. Species are pollinated by short‐tongued bees, long‐tongued bees, and hummingbirds. Ornithophily represents the derived condition in the tribe and has arisen independently in subtribes Maurandyinae and Gambeliinae. All nectars analyzed are sucrose‐dominant or ‐rich, except for the hexose‐rich nectar of Mohavea breviflora. Despite the predominance of sucrose, floral nectar sugars from species pollinated by different pollen vectors have characteristic constituents. Nectar sugars from flowers visited by hummingbirds average 76.2% sucrose and have compositions remarkably similar to hummingbird nectars analyzed in previous studies of unrelated species. Long‐tongued bee nectars average 87% sucrose and differ from shorttongued bee nectars which have the lowest mean sucrose percentage (40.2%). The association of sugar constituent types and principal pollinators is concordant with previous data and supports hypotheses concerning pollinator preferences and the adaptive significance of certain nectar sugar compositions. Within this adaptive framework, phylogenetic constraint is also operative and may explain the predominance of sucrose in nectar sugars, similarities in sugar composition among hummingbird nectars in subtribes Maurandyinae and Gambeliinae, and the similarity of nectar from Galvezia leucantha (long‐tongued bee‐pollinated) to hummingbird‐pollinated species also in subtribe Gambeliinae.
SEED ABORTION AND SEED SIZE VARIATION WITHIN FRUITS OF PHASEOLUS VULGARIS: POLLEN DONOR AND RESOURCE LIMITATION EFFECTS
Authors: Nakamura Robert R.
Published: January 2018

A new plant cohort starts with the formation of zygotes at ovule fertilization. This paper presents an ecological study of the effects of resource limitation and pollen donor on the survivorship and size of plant embryos in maturing fruits of the common bean, Phaseolus vulgaris L. For naturally selfed flowers of domesticated and wild beans, embryos in basal ovular positions were more likely to abort or, if they survived, become lighter seeds than stylar embryos. Embryo survivorship was higher for the cultivar when maternal plants grew in larger pots. Early seed abortion in the cultivar was random with respect to ovular position. In late abortion basal embryos had a higher mortality than stylar ones. The basal embryos lacked gross genetic defects since they developed adult organs in embryo culture. In more outbred crosses with the cultivar the position effect in embryo survivorship and size disappeared. This difference among paternal parents implicates a genetic component to the observed position effects. The variation in mature seed size may affect adult characteristics since large seeds produced larger juvenile plants than small seeds.
DYSPLOIDY IN HYMENOXYS TEXANA (COMPOSITAE)
Authors: Strother John L. , Brown Larry E.
Published: January 2018

The two chromosome numbers recorded for Hymenoxys texana, 2n = 16 and 2n = 6, appear to represent dysploid reductions from the base number, x = 15, for the genus.
BOUGAINVILLEA INFLORESCENCE MERISTEM DEVELOPMENT: COMPARATIVE ACTION OF GA3 IN VIVO AND IN VITRO
Authors: Steffen Jody D. , Sachs Roy M. , Hackett Wesley P.
Published: January 2018

Although gibberellic acid (GA3) promotes stem elongation and inhibits flowering in Bougainvillea, no inhibition of floret initiation was observed when excised meristems were cultured in vitro in media containing GA. These results are predicted by a nutrient diversion hypothesis in which GA‐induced inhibition of flower initiation in intact plants is considered an indirect result of growth promotion of competing vegetative sinks with consequent diversion of nutrients away from the inflorescence meristem. The failure to observe GA‐induced inhibition of floret initiation in vitro was probably the result of an excess of metabolites for growth and differentiation of the excised meristems in the media.
LEAF DEVELOPMENT IN ISOPHYLLOUS AND FACULTATIVELY ANISOPHYLLOUS SPECIES OF PENTADENIA (GESNERIACEAE)
Authors: Sánchez‐Burgos Arturo A. , Dengler Nancy G.
Published: January 2018

Shoots of Pentadenia orientandina exhibit varying degrees of anisophylly, ranging from pairs of equal‐sized leaves to pairs of large ventral and small dorsal leaves. In this study we compare phyllotaxis, leaf expansion, and accompanying histological changes in extremely anisophyllous shoots of this species and in isophyllous shoots of the related species, P. crassicaulis. In P. orientandina, decussate phyllotaxis is modified at leaf initiation, and angles of leaf insertion appear to be further changed during leaf expansion. In both species, leaf primordia of a pair are not distinguishable at inception, suggesting an equivalent developmental potential. In P. orientandina, size differences between ventral and dorsal leaves become significant at the P2 or P3 stage, coincident with lamina initiation. Minute dorsal leaves are arrested in their development at the P3 stage and mature without differentiation of multiple epidermis, stomata, mesophyll and most vascular tissue. Variation in dorsal leaf structure in P. orientandina emphasizes the plasticity of leaf development in this facultatively anisophyllous species.
FLEXURAL STIFFNESS AND MODULUS OF ELASTICITY OF FLOWER STALKS FROM ALLIUM SATIVUM AS MEASURED BY MULTIPLE RESONANCE FREQUENCY SPECTRA
Authors: Niklas Karl J. , Moon Francis C.
Published: January 2018

Multiple resonance frequency spectra (MRFS) provide a rapid and repeatable method for determining the flexural stiffness and modulus of elasticity, E, of segments of plant stems and leaves. Each resonance frequency in a spectrum can be used to compute E, and removal of the distal portion of an organ produces characteristic shifts in spectra dependent upon the geometry of an organ. Hence, MRFS can be used to quantitatively determine the extent to which a particular leaf or stem morphology can be modelled according to beam theory. MRFS of flower stalks of Allium sativum L. are presented to illustrate the technique. The fundamental, f1, and higher resonance frequencies, f2 … fn, of stems and the ratios of f2/f1 f3/f1, and f3/f2 increase as stalk length is reduced by clipping. The magnitudes of these shifts conform to those predicted from the MRFS of a linearly tapered beam. Morphometric data confirm this geometry in 21 flower stalks. Based on this model, the average modulus equals 3.71 × 108 ± 0.32 × 108 N/m2, which compares favorably with values of E determined by static loading (3.55 × 108 ± 0.22 × 108 N/m2) and is in general agreement with ultrasonic measurements (3.8 × 108 to 4.4 × 108 N/m2). Data indicate that determinations of E from a single resonance frequency are suspect, since each resonance frequency yields slightly different values for E. Statistical evaluations from all the frequencies within a MRFS are more reliable for determining E and testing the appropriateness of beam theory to evaluate the biomechanical properties of plants.
COMPARATIVE STUDY ON EARLY ONTOGENY OF COMPOUND LEAVES IN LARDIZABALACEAE
Authors: Sugiyama Mitsuko , Hara Noboru
Published: January 2018

The early ontogeny of the pinnately, palmately, and ternately compound leaves in the Lardizabalaceae was studied by SEM. The leaf primordium of each of the three leaf types emerges as an identical short protrusion on the shoot apex; the leaf primordium produces the first leaflet initials laterally on its margin. Successive acropetal growth of the leaf axis and the following inception of the leaflet primordia are responsible for the pinnately compound leaf, whereas short basipetal growth accompanied with initiation of two or more pairs of leaflet initials results in a palmately compound leaf. If no elongation of the leaf axis nor additional inception of leaflet primordia occur during early ontogeny, a ternate leaf ensues.
SEED GERMINATION OF AMERICAN POKEWEED (PHYTOLACCA AMERICANA). I. LABORATORY TECHNIQUES AND AUTOTOXICITY
Authors: Edwards Maurice E. , Harris Elizabeth M. , Wagner Frederic H. , Cross M. Catherine , Miller Gregory S.
Published: January 2018

Seeds of pokeweed (Phytolacca americana L.), an underinvestigated species, were studied to determine optimal conditions for laboratory germination. Soaking seeds in acid solutions prior to sowing increased rates of germination. Concentrated (conc) H2SO4 was more effective than conc NO3 or conc HCl acids. Physiological evidence from seed germination studies suggests that autotoxicity, or intraspecific inhibition, exists in pokeweed, a species known to possess several biologically active compounds. Seed germination was investigated in the laboratory with aqueous extracts of vegetative and reproductive structures of the plant. The presence of extracts from most plant parts correlated with reduced or no germination by seeds of its own species, whereas the presence of distilled water correlated with high percentages of germination by control seeds. Whether diluted with water by 5‐fold (20% v/v) or undiluted, juice of pokeweed fruits completely inhibited the laboratory germination of pokeweed seeds. Also, extracts of freshly harvested mature leaves, stems, and immature fruits inhibited seed germination. However, results with root extracts, obtained from a single individual, depended more on concentration, since the highest concentration (50% v/v) inhibited germination, and lower concentrations (10 and 20% v/v) increased germination percentages over control samples. Results with extracts of juvenile leaves correlated with neither inhibition nor promotion of germination. Thus, except for juvenile leaves and the root, most extracts of the pokeweed plant inhibited seed germination with more mature structures exerting more inhibition and less mature structures exerting less or no inhibition. The ecological implication of autotoxicity is that seeds are more dispersed through time and space. In regard to seed germination by other species, especially those taxa known to possess biologically active compounds, these and other results suggest that the phenomenon of autotoxicity might be more widespread than previously suspected.
EFFECT OF DEFOLIATION ON GENDER EXPRESSION AND FRUIT SET IN PASSIFLORA INCARNATA
Authors: Spears E. Eugene , May Peter G.
Published: January 2018

We examined the effect of defoliation on gender expression and fruit set in a north‐central Florida population of the andromonoecious vine, Passiflora incarnata, during the 1984 flowering season. At three times during the flowering season (May, June, July), the leaves adjacent to flowers at four stages of development were removed, and subsequent sex and fate of each flower were determined. Defoliation affected gender of the flower by significantly decreasing the probability that the styles of the flower would deflex and the flower would thus function only as a pollen donor. Flowers were sensitive to defoliation at any stage before anthesis, though the sensitivity appeared to decrease in the most mature category of flower buds. Fruit set of hermaphroditic flowers remained unaffected by defoliation, but the probability of fruit set and gender expression were significantly influenced by the time of the flowering season. We conclude that the local photosynthate environment determines flower gender in Passiflora, but branch or entire plant photosynthate resources can compensate for local resource fluctuations and play an important role in fruit set and flower bud abortion. The sexual lability of Passiflora incarnata appears to be an adaptation to uncertain resource levels at a fine scale, caused by nearby developing fruits and the possibility of herbivore defoliation.