bluuebunny/crossref_metadata_2025 huggingface dataset:
SEED SET AND SEED PREDATION IN PEDICULARIS FURBISHIAE, A RARE ENDEMIC OF THE ST. JOHN RIVER, MAINE
Authors: Menges Eric S. , Waller Donald M. , Gawler Susan C.
Published: January 2018

We measured seed set and losses due to mammal and insect predation during 1983 in seven northern Maine populations of Furbish's Lousewort (Pedicularis furbishiaeS. Wats.; Scrophulariaceae), a perennial herb endemic to the banks of the St. John River. Only about a quarter of initiated flowers developed a capsule with a full complement (mean = 25) of seeds. Secondary (lateral) inflorescences matured a smaller proportion of capsules than primary (terminal) inflorescences. About 58% of the initiated flower primordia were aborted or did not develop mature seeds by early September; this was probably not due to pollinator limitation.

Several agents could have reduced seed production. Although spittlebugs infested between 3 and 30% (average 20%) of developing flower scapes by population, they did not depress the number of inflorescences initiated or the number of capsules matured. In contrast, 74% of capsules containing a lepidopteran seed predator (the plume mothAmblyptilia pica[Walsingham], newly discovered as a seed predator onP. furbishiae) had no seeds (mean = 3 seeds). Seed predation affected 39% of the potentially maturable capsules. In 6–30% of all capsules preyed upon, the lepidopteran was parasitized by an ichneumonoid wasp larva; these capsules matured about 7 seeds. Herbivory by rabbits, rodents, and deer also reduced seed set, eliminating 98% of the scapes at one site, and averaging 40% for other populations. Mammals and insects together removed at least 62% of maturable seeds. Populations varied widely in predation and seed set. Predispersal seed loss inP. furbishiae,coupled with slow seedling growth and occasional catastrophic mortality from ice scour and erosion, could limit population growth in this rare endemic.
COMPARATIVE DEVELOPMENT OF SECRETORY CAVITIES IN THE TRIBES AMORPHEAE AND PSORALEEAE (LEGUMINOSAE: PAPILIONOIDEAE)
Authors: Turner Glenn W.
Published: January 2018

The tribes Amorpheae and Psoraleeae of the Leguminosae (Papilionoidae) share the characteristics of one‐seeded fruits and gland‐dotted foliage. Because of this, they traditionally have been considered closely related (either a single tribe or two closely related tribes). However, Barneby (1977) has suggested that the Amorpheae and Psoraleeae are not close but previously had been combined on the basis of a superficial resemblance. This paper describes the structure of the secretory cavities responsible for the gland dots. Approximately 50% of the species of each tribe were surveyed for cavity structure with leaflet clearings. Eight species were then chosen for developmental studies of their glands. Several distinct kinds of secretory cavities are present in these plants. Trabeculate cavities (found only in the Psoraleeae) are traversed by many elongated cells. This type of cavity and nontrabeculate cavities of the Psoraleeae initiate with localized dorsiventral elongation of protodermal cells to form a hemispherical protuberance on the leaf primordium surface. Development proceeds with separation of the cells of a protuberance along their lateral walls facing the protuberance center. As the leaf expands, the protuberance sinks until its apex is flush with the leaf surface. The result is a cavity lined by an epithelium of modified epidermal cells. Trabeculate cavities have more cells in the initial protodermal bump than nontrabeculate “epidermal” cavities, and the central cells of the protuberance are not involved in epithelium formation, but become separated from other cells on all lateral sides, transversing the cavity as trabeculae. Cavities of the Amorpheae are all nontrabeculate and subepidermal. They initiate with periclinal divisions of protodermal cells that result in two cell layers. The exterior layer differentiates into epidermis, while the interior layer divides to produce a small spherical group of cells (“epithelial initials”). Schizogeny occurs in the center of these cells to produce an epithelium‐lined cavity. Previous studies of cavity development in the Amorpheae described lysigenous and schizo‐lysigenous cavities for most species. These early reports are reviewed, and the possible role of preparation artifacts in producing images of lysigenous development in general is discussed.
POLLINATION DYNAMICS IN EPILOBIUM CANUM (ONAGRACEAE): CONSEQUENCES FOR GAMETOPHYTIC SELECTION
Authors: Snow Allison A.
Published: January 2018

Several hand‐pollination experiments have shown that pollen tube competition leads to gametophytic selection, and thus affects genotypic and phenotypic characteristics of the next generation. This study is one of the first to quantify natural levels of pollen tube competition. In a population of Epilobium canum, I measured both the amount of pollen deposited on stigmas and the timing of deposition. Approximately 20 tetrads were required for full seed set within fruits. Hummingbirds deposited >20 tetrads at 50–70% of the flowers examined, often in a single load. When pollen arrived in 2 loads, a portion of the ovules within each ovary was probably sired by competing pollen from the second load. Competition may be relatively weak unless at least 30 tetrads compete for ovules. About 20% of the flowers received >30 tetrads in the first load, and 13% acquired > 30 tetrads in 2 loads. The frequency and intensity of pollen tube competition varied among plants. In some styles, 80% of the pollen tubes were excluded from access to ovules, but in others no competition occurred. Further studies of pollination rates and progeny fitness are needed before we can assess the role of pollen tube competition in natural populations. Potential effects of gametophytic selection are discussed.
HISTOCHEMICAL STUDY OF ENZYME ACTIVITY IN THE SHOOT APICAL MERISTEM OF BRASSICA CAMPESTRIS DURING TRANSITION TO FLOWERING. IV. GLUCOSE‐6‐PHOSPHATASE
Authors: Orr Alan R. , Schoneman Teresa A.
Published: January 2018

Glucose‐6‐phosphatase (G6P) activity was determined in fresh‐frozen, cryostat sections in the shoot apical meristem of Brassica campestris L. Enzymatic activity was differentially distributed in a zonate pattern in the vegetative meristem, but not in the transition and floral meristem. Vegetative apices showed a heterogenous localization with the highest activity in the central zone and the pith‐rib meristem zone. At the early transition stage of development, G6P activity in the peripheral zone increased slightly. At the late transitional (prefloral) stage, G6P activity was not localized within the peripheral zone in island‐like areas of activity. This is the first demonstration of G6P in shoot apical meristem at the vegetative, transition, and floral stage. The results indicate that G6P activity 1) is an accompanying event of evocation, but 2) does not mark incipient floral primordia. G6P may play an important role in the maintenance of glucose‐6‐phosphate homeostasis in an evoked shoot apical meristem.
DIFFERENTIATION AMONG POPULATIONS OF TETRAPLOID GRINDELIA CAMPORUM
Authors: McLaughlin Steven P.
Published: January 2018

Ten populations of 4N Grindelia camporum (Asteraceae) were investigated in a common‐garden study of phenotypic and genetic variability. This species is a long‐lived perennial herb and an obligate outcrosser which would be expected to display considerable gene flow among populations based on its life‐history traits. Each of the 17 morphological, phenological, and physiological traits examined showed significant differences between populations. Average within‐population heritability was 0.39. The variation between populations averaged 3.3 times the variation within populations, indicating that the populations are well‐differentiated for each of the 17 traits. Two possible explanations for the differentiation are given: populations may have diverged from a common ancestor in very little geologic time, or the species may have a polytopic origin.
SEASONAL NUTRIENT DYNAMICS, NUTRIENT RESORPTION, AND MYCORRHIZAL INFECTION INTENSITY OF TWO PERENNIAL FOREST HERBS
Authors: Boerner Ralph E. J.
Published: January 2018

Patterns of mycorrhizal infection, seasonal foliar nutrient concentrations, nutrient allocation to shoots and rhizomes, and nutrient resorption were measured in relation to soil nutrient availability in two species of perennial forest herbs, Geranium maculatum L. and Polygonatum pubescens Pursh., in four forest stands in southern and central Ohio. The percentage of plants with V‐A mycorrhizae and the proportion of root length colonized by VAM structures increased with decreasing nutrient availability in both species. Foliar N and P concentrations in plants from lower fertility sites were as high, or higher, than those in plants from higher fertility sites; as a result, tissue nutrient enrichment ratios (foliar concentration/soil available concentration) increased with decreasing fertility. Proportional resorption of N and P generally decreased with decreasing nutrient availability, a pattern inconsistent with those exhibited by woody plants in these forest stands. We hypothesize that the inverse relationship between nutrient uptake efficiency (via mycorrhizae) and nutrient use efficiency (resorption) exhibited by these forest understory herbs, but not by trees or herbs from high‐light environments, may be related to low‐light limitation of energy reserves in the forest understory.
LATEX AND LATICIFER STARCH CONTENT OF DEVELOPING LEAVES OF EUPHORBIA PULCHERRIMA
Authors: Spilatro Steven R. , Mahlberg Paul G.
Published: January 2018

Laticifer starch accumulation was compared to laticifer growth for developing leaves of Euphorbia pulcherrima Willd. (poinsettia). Measurements of the laticifer‐specific triterpenol, cycloartenol, in latex and in whole leaf extracts were used to calculate the total latex volume in leaves of different developmental stages. Latex volume and starch concentration in the latex were used to determine total laticifer starch and to compare laticifer growth and starch synthesis. Young leaves contained the highest latex and laticifer starch contents on dry wt and leaf area bases. In older expanding leaves, laticifer growth produced an increase in total latex volume accompanied by an increase in total laticifer starch. Laticifer growth and starch accumulation stopped upon cessation of leaf expansion. Starch concentration was similar in latex from all leaves, but differed between plant organs. Thus, laticifer starch accumulation correlated with laticifer growth, but mobilization of the starch out of the laticifer was not observed in old or senescent leaves. This is evidence that laticifer starch grains function within the laticifer independently of degradation or export to other cell types.
COMPARATIVE BUNDLE SHEATH AND MESOPHYLL DIFFERENTIATION IN THE LEAVES OF THE C4GRASSES PANICUM EFFUSUM AND P. BULBOSUM
Authors: Dengler Nancy G. , Dengler Ronald E. , Hattersley Paul W.
Published: January 2018

The two C4Panicumspecies examined differ in C4acid decarboxylation type and in developmental origin of bundle sheaths in major veins of their leaf blades. InPanicum effusumR.Br. (NAD‐malic enzyme type) both mesophyll (PCA) and chlorenchymatous bundle sheath (PCR) cells are derived from ground meristem. In contrast, inPanicum bulbosumH.B.K. (NADP‐malic enzyme type), bundle sheath cells are derived from procambium, while mesophyll develops from ground meristem. To test the hypothesis that the developmental divergence of bundle sheath and mesophyll cells would occur earlier when these two tissues had different ontogenetic origins (inP. bulbosum) than when these tissues had the same origin (inP. effusum), the development of major veins in each species was investigated. We measured cell length and cross sectional area, plastid and mitochondrial number, plastid area, vacuole area fraction, wall thickness and fraction adjacent to intercellular space using direct and digitizer measurements of transmission electron micrographs of leaf cross sections of successive developmental stages. Many of the statistically significant changes in the structural parameters measured occurred late in development of both species. The magnitude of developmental change inP. effusumPCR cells was sometimes more dramatic, viz. changes in cell and PCR plastid area, and in mitochondrion number per cell. However, earlier divergence of PCR and PCA length and volume, and wall fraction adjacent to intercellular space inP. bulbosumthan inP. effusumindicates that ontogenetic origin of PCR cells from procambium could determine the timing of at least some developmental events.
BIDENS PILOSA COMPLEX (ASTERACEAE) IN NORTH AND CENTRAL AMERICA
Authors: Ballard Robert
Published: January 2018

Field observations, chromosome counts, flavonoid chemistry, breeding system data, hybridization experiments, and a quantitative analysis of twelve morphological features combine to show that the North and Central American populations of B. pilosa sensu Sherff actually include three distinct species: B. odorata (n = 12), B. alba (n = 24), and B. pilosa (n = 36). All these taxa are square‐stemmed, white‐rayed or discoid annuals with linear, obcompressed‐quadrangulate achenes, but each species can be distinguished morphologically by differences in ray length and width, in outer phyllary length, width and shape and chemically by differences in the chalcones accumulated in their leaves. New combinations are proposed and two varieties, B. odorata var. oaxacensis and B. odorata var. chilpancingensis, are described as new. Descriptions, distribution maps, synonymies, and a key to all taxa are provided.
SLOUGHED PERIPHERAL ROOT CAP CELLS: YIELD FROM DIFFERENT SPECIES AND CALLUS FORMATION FROM SINGLE CELLS
Authors: Hawes Martha C. , Pueppke Steven G.
Published: January 2018

Peripheral root cap cells can be isolated by gentle agitation of the root in water for less than 60 sec. Filtration of the detached cells through a 30‐μm mesh screen results in a suspension of single cells. Yields of peripheral root cap cells from 28 species in 10 families ranged from fewer than 10 per root from tobacco to more than 5,000 per root from pine. The viability of freshly isolated cells from most species, including legumes and cereals, was 85% to 95%. Cultured cells from pea and soybean exhibited cytoplasmic streaming for more than a month. When incubated at an initial density of 105 cells per ml of liquid B5(P) medium, 6% to 8% of isolated pea root cap cells divided and grew into callus.
ORIGIN OF ADVENTITIOUS SHOOTS REGENERATED FROM CULTURED TOBACCO LEAF TISSUE
Authors: Marcotrigiano Michael
Published: January 2018

Leaf discs from Nicotiana tabacum L., N. glauca Grahm., and a series of interspecific periclinal chimeras were cultured on Murashige and Skoog (MS) medium containing either 2.5 mg/1 6‐benzylaminopurine(BA) or 3.0 mg/16‐furfurylaminopurine (kinetin). Most shoots regenerated from chimeral leaf discs were non‐chimeral but 51 of 658 shoots were chimeral. The histogenic composition of plants regenerated from leaf discs of periclinal chimeras indicated that any cell layer in a leaf can be the ultimate source of shoots, and that shoots can be multicellular in origin. Certain periclinal arrangements were recovered more frequently and their chimeral nature was more stable during subsequent shoot growth. While N. tabacum leaf discs regenerated shoots on MS medium supplemented with either BA or with kinetin, N. glauca leaf discs did not form shoots on the medium containing kinetin. However, chimeras which possessed cells of both species arose on medium containing BA or kinetin, indicating that the morphogenetically competent (i.e., able to produce shoots in culture), N. tabacum cells either interacted with N. glauca cells leading to their competence or incorporated non‐competent N. glauca cells into nascent shoot apical meristems.
INDUCTION OF SPORE GERMINATION IN SCHIZAEA PUSILLA (SCHIZAEACEAE)
Authors: Guiragossian Helen A. , Koning Ross E.
Published: January 2018

Requirements for spore germination in the rare and native New Jersey fern, Schizaea pusilla Pursh., were examined. Spores did not germinate in darkness and gibberellins (GA) did not induce germination in the dark. However, a dark pretreatment promoted germination in a subsequent light treatment and low temperatures during the dark pretreatment greatly enhanced germination in culture. Three wks of dark pretreatment were required for maximum germination. GA3 promoted germination in red light more effectively than GA4+7. Greater than ten days of continuous illumination was necessary for germination. Spores given red light reached half‐maximum germination six days earlier than spores under white light. Red light promoted germination while blue light did not. Far‐red light alone could stimulate germination and enhanced the promotive effect of red light; typical phytochrome photoreversibility was not observed. Blue light reduced the effect of red light.
VASCULARIZATION OF A MULTILACUNAR SPECIES: POLYSCIAS QUILFOYLEI (ARALIACEAE) II. THE LEAF BASE AND RACHIS
Authors: Larson Philip R.
Published: January 2018

Multiple leaf traces depart the stem vasculature at a node to form the rachis vasculature of the odd‐pinnate leaf of Polyscias quilfoylei. The median (M) trace departs the vascular cylinder directly, but the converging lateral traces follow acropetal, oblique pathways through the en‐sheathing leaf base. The leaf traces are partitioned into sub‐bundles within the leaf base, and some sub‐bundles merge with others to form composite bundles. Most mergers in the leaf base occur among sub‐bundles of adaxial and lateral traces; cross‐overs of bundles from opposite sides of the M‐trace are infrequent. The rachis vasculature distal to the leaf base is similar in structure and appearance to that of the stem. Vascularization of the leaflet pair at each rachis node involves partitioning and reaggregating of the trace sub‐bundles. However, these processes are more extreme and bundle cross‐overs are more frequent at rachis nodes than at the leaf base. At the more distal rachis nodes, lateral traces situated nearer the M‐trace contribute to leaflet vascularization. The M‐trace contributes sparingly to vascularization of lateral leaflets; it forms that part of the midvein that extends to the extreme lamina tip of the terminal leaflet.
AMPHIPLOID ORIGIN OF TWO ENDEMIC RACES OF ASTER (ASTERACEAE) IN SOUTHERN CALIFORNIA
Authors: Allen Geraldine A.
Published: January 2018

Two cytological races of Aster which morphologically resemble A. ascendens but differ from it in chromosome number are found in the Transverse and Peninsular ranges of southern California. One of these races is relatively common, can usually be separated morphologically from A. ascendens, and has a somatic chromosome number of 36; it corresponds to the endemic species A. bernardinus. The other race is rare and localized, is morphologically almost indistinguishable from A. ascendens, and has a somatic chromosome number of 42. The chromosome numbers and karyotypes of the two races suggest that they originated through backcrosses of A. ascendens (x = 13) to its respective parent taxa, A. falcatus (x = 5) and A. occidentalis (x = 8).
CRASSULACEAN ACID METABOLISM IN THE GESNERIACEAE
Authors: Guralnick Lonie J. , Ting Irwin P. , Lord Elizabeth M.
Published: January 2018

The occurrence of the Crassulacean acid metabolism (CAM) was studied in four epiphytic species of the Gesneriaceae: two neotropical species, Codonanthe crassifolia and Columnea linearis, and two paleotropical species, Aeschynanthus pulcher and Saintpaulia ionantha. Gas exchange parameters, enzymology, and leaf anatomy, including mesophyll succulence and relative percent of the mesophyll volume occupied by airspace, were studied for each species. Codonanthe crassifolia was the only species to show nocturnal CO2 uptake and a diurnal organic acid fluctuation. According to these results, Codonanthe crassifolia shows CAM‐cycling under well‐watered conditions and when subjected to drought, it switches to CAM‐idling. Other characteristics, such as leaf anatomy, mesophyll succulence, and PEP carboxylase and NADP malic enzyme activity, indicate attributes of the CAM pathway. All other species tested showed C3 photosynthesis. The most C3‐like species is Columnea linearis, according to the criteria tested in this investigation. The other two species show mesophyll succulence and relative percent of the leaf volume occupied by airspace within the CAM range, but no other characters of the CAM pathway. The leaf structure of certain genera of the Gesneriaceae and of the genus Peperomia in the Piperaceae are similar, both having an upper succulent, multiple epidermis, a medium palisade of one or a few cell layers, and a lower, succulent spongy parenchyma not too unlike CAM photosynthetic tissue. We report ecophysiological similarities between these two distantly related families. Thus, the occurrence of CAM‐cycling may be more common among epiphytic species than is currently known.
MORPHOLOGY AND DISPERSAL POTENTIAL OF WIND‐DISPERSED DIASPORES OF NEOTROPICAL TREES
Authors: Augspurger Carol K.
Published: January 2018

Morphological and aerodynamic traits affecting mean potential dispersal distance are quantified for wind‐dispersed diaspores of tree species on Barro Colorado Island, Panama. The sample includes 34 species in 16 families and represents six aerodynamic groups. Mass and area (maximum cross section) each vary over six orders of magnitude among the species. In contrast, wing‐loading, defined as weight divided by area, varies over only one order of magnitude, as does the rate of descent. While the regression of rate of descent on the square root of wing‐loading is significant overall, the slopes vary significantly among five aerodynamic groups. At comparable wing‐loading values, diaspores of fluffy kapok fall faster than four other aerodynamic groups and rolling autogyros fall faster than non‐rolling autogyros. Assuming the diaspores are released from their typical tree height and experience a mean windspeed of 1.75 m sec−‐1, the expected mean dispersal distance varies among the 34 species from 22 to 194 m. Rate of descent is weakly correlated with shade tolerance of seedlings for a subset of 18 species; rate of descent is more strongly correlated with the log of dry mass of seed for all 34 species. Given these wide differences in dispersal potential, any generalizations about tropical trees that use wind dispersal are of dubious value.
WATER RELATIONS AND GROWTH CHARACTERISTICS OF PROSOPIS GLANDULOSA VAR. TORREYANA IN A SIMULATED PHREATOPHYTIC ENVIRONMENT
Authors: Nilsen Erik T. , Virginia R. A. , Jarrell W. M.
Published: January 2018

Recent studies of Prosopis glandulosa have demonstrated a unique system of a deeply rooted species with significant water stress tolerance. Several growth and developmental characteristics have been correlated with water stress and nitrogen availability during field studies. Here we present a lab experiment in which a phreatophytic regime is simulated and the availability of nitrogen and water are varied. Increased ground water salinity caused lower plant water potentials and greater osmotic adjustment without significant increases in leaf Na+ concentrations. Leaf conductance was higher in the higher salinity treatments. Low water potential was also associated with reduced leaf size, reduced leaf area per plant and increased root to shoot ratio. Specific leaf weight and the transpiration ratio were unaffected by the low water potentials induced by increased salinity. Increasing nitrogen availability caused increased growth rates but did not influence water use efficiency. Net assimilation rates increased with increasing nitrogen availability but relative growth rates were more dependent on overall plant size than treatment conditions. The responses of P. glandulosa to the simulated phreatophytic environment were similar to those predicted by field measurements.
FECUNDITY AND SIZE RELATIONSHIPS IN JACK‐IN‐THE‐PULPIT, ARISAEMA TRIPHYLLUM (ARACEAE)
Authors: Doust Lesley Lovett , Doust Jon Lovett , Turi Karen
Published: January 2018

Arisaema triphyllum is a gender‐labile woodland herb in which sex expression is correlated with the abundance of stored resources. Larger plants are female or monoecious, smaller ones are male. Among females larger plants produce more flowers, fruits and seeds, and the rate of successful fruit and seed formation is greater for plants of greater ht and corm diam. Average seed wt is greater in larger plants. Seed number per fruit and average seed wt per fruit taper towards the top of the infructescence. Pollinator limitation and resource supply may both contribute to the regulation of yield; their effects can be interpreted sequentially.
EFFECTS OF ARTIFICIAL ACID MIST ON GROWTH AND REPRODUCTION OF TWO ALPINE PLANT SPECIES IN THE FIELD
Authors: Funk Dale W. , Bonde Erik K.
Published: January 2018

Plants of Acomastylis rossii and Bistorta vivipara were treated in the field with artificial acid mists prepared with sulfuric acid, nitric acid, or mixtures of equal parts of these at pH 2.5, 3.5, or 4.5. Highly significant reductions in flower production in A. rossii were noted with sulfuric acid treatments at pH 2.5 and in bulblet production in B. vivipara with nitric acid at pH 2.5 and 3.5, with sulfuric acid at pH 3.5, and with nitric‐sulfuric acid mixtures at all pH's. These results apparently relate to the growth forms of the plants, which cause pooling of the acid solutions at their bases. Significant increases in flowering and in leaf number were noted for B. vivipara treated with sulfuric acid, possibly as a promotive effect of sulfate. No effects on vegetative growth were noted in A. rossii. The germinability of seeds (A. rossii) and bulblets (B. vivipara) also was not affected. Differential sensitivity of plant species to artificial acid mist implies that acid precipitation could cause a change in species composition of Colorado alpine plant communities.
HOW ROOTS PERCEIVE AND RESPOND TO GRAVITY
Authors: Moore Randy , Evans Michael L.
Published: January 2018

Graviperception by plant roots is believed to occur via the sedimentation of amyloplasts in columella cells of the root cap. This physical stimulus results in an accumulation of calcium on the lower side of the cap, which in turn induces gravicurvature. In this paper we present a model for root gravitropism integrating gravity‐induced changes in electrical potential, cyto‐chemical localization of calcium in cells of gravistimulated roots, and the interdependence of calcium and auxin movement. Key features of the model are that 1) gravity‐induced redistribution of calcium is an early event in the transduction mechanism, and 2) apoplastic movement of calcium through the root‐cap mucilage may be an important component of the pathway for calcium movement.
ELECTROPHORETIC EVIDENCE FOR INBREEDING IN THE FERN BOTRYCHIUM VIRGINIANUM (OPHIOGLOSSACEAE)
Authors: Soltis Douglas E. , Soltis Pamela S.
Published: January 2018

An electrophoretic investigation of Botrychium virginianum was conducted to determine the levels and distribution of genetic variation within and among populations of this species. A total of 18 loci representing seven enzymes was examined. For the four polymorphic loci, observed heterozygosity was substantially lower than expected heterozygosity. Values of F were extremely high, indicating a significant deviation from random mating, probably due to inbreeding. We suggest that the high inbreeding coefficients obtained result from a life cycle involving subterranean gametophytes which restrict sperm movement. The study also demonstrates the value of using F‐statistics and gene diversity statistics to analyze genetic subdivision in a fern species. Despite the high chromosome number reported for B. virginianum (n = 90), there is no genetic evidence to support the contention that this species is highly polyploid.
CLUSTER ANALYSIS OF ANTHER‐DERIVED PLANTS OF SOLANUM PHUREJA (SOLANACEAE) BASED ON MORPHOLOGICAL CHARACTERISTICS
Authors: Pehu Eija , Veilleux Richard E. , Hilu Khidir W.
Published: January 2018

The feasibility of grouping anther‐derived plants of Solarium phureja according to ploidy based on their morphological characteristics was studied. Canonical discriminant analysis identified four characteristics (anther length, number of chloroplasts per pair of guard cells, leaf width, corolla width at widest diam) of nine measured as the most effective combination for diagnosing ploidy. Data for these characteristics from two sets of plants were subjected to two clustering techniques, one using the average linkage clustering (UPGMA of the NT‐SYS programs) and the other using centroid sorting (SAS‐Fastclus). Screening of anther‐derived plants by cluster analysis proved to be an efficient means of separating monoploids from the other ploidy levels.
LEAF FOLDING IN MIMOSA PUDICA (FABACEAE): A NUTRIENT CONSERVATION MECHANISM?
Authors: Wallace L. L. , Timpano P. , Durgin P.
Published: January 2018

Ten plants of Mimosa pudica L. were exposed to artificial rain following anesthesia of the leaves of half of the plants. Anesthetized plants, which no longer displayed the seismonastic response of this species, were hypothesized to show greater rates of foliar leaching of nutrients than their unanesthetized counterparts. Leachate was collected and analyzed for levels of K, Na and Ca. Levels were corrected for the amount of leaf area exposed to rainfall. No differences were noted between treatments for rainfall durations of either 6 or 20 min. Leaf surface morphology was examined and lattice‐like extrusions of epicuticular wax were found. We feel that the leaf surface structure may act to keep raindrops from coming in contact with the surface of the leaf thereby minimizing foliar leaching. It appears that the seismonastic response of the leaves plays only a minor role in nutrient conservation.
STEREOLOGICAL STUDY OF ULTRASTRUCTURAL CHANGES IN THE SHOOT APICAL MERISTEM OF NICOTIANA TABACUM DURING FLORAL INDUCTION
Authors: Kanchanapoom Malee L. , Thomas Judith F.
Published: January 2018

Shoot apices of a short‐day sensitive line of Nicotiana tabacum L. cv. NCTG‐22 have been examined by electron microscopy for ultrastructural changes which occurred in the central zone over a 17‐day period during the transition from vegetative to reproductive growth. Plants were grown in controlled‐environment chambers of the NCSU Phytotron and exposed to an inductive photoperiod after a 6‐wk juvenile phase. Ultrastructural changes were investigated from photomicrographs using a semi‐automatic stereological procedure and a microcomputer. After exposure to only one inductive cycle cell and nuclear cross sectional areas in short‐day plants were significantly larger than in long‐day controls. Subsequently, under short days cross sectional areas of cells, nuclei, vacuoles and proplastids decreased, while mitochondrial cross sectional area and relative volume increased during the course of the induction period. In induced apices as cross sectional areas and relative volumes of vacuoles and proplastids decreased, their profile numbers increased. The reduction in cross sectional areas of cells and most organelles was associated with an increase in rate of leaf initiation and size of the apical dome. The demand for sufficient energy input to maintain the surge in growth and activity preceding floral initiation was reflected by the significant increases in cross sectional area, profile numbers and density of the mitochondria population. Even though the transition period is quite long for Nicotiana, cells and organelles in the central zone were observed to progress through similar changes in morphology that are known to occur in Sinapis and Xanthium which exhibit a more rapid and absolute response to photo‐induction.
REPRODUCTIVE BIOLOGY OF PETAL COLOR VARIANTS IN WILD POPULATIONS OF RAPHANUS SATIVUS: I. POLLINATOR RESPONSE TO COLOR MORPHS
Authors: Stanton Maureen L.
Published: January 2018

Pollinator response to petal color polymorphism in wild radish (Raphanus sativus) was investigated. Behavior of insect visitors was observed within experimental flower arrays, each containing two of the petal color forms seen intermixed in California populations: white, yellow, pink, and bronze. Honeybees, which accounted for almost 90% of all visits, typically preferred yellow or white flowers and discriminated against bronze. Their preference for white increased significantly as the Raphanus flowering season progressed. Syrphid flies were also frequent visitors and increased in abundance near the end of the season. Syrphids typically preferred pink to other colors. Individual honeybees tended to specialize on either yellow or pink flowers on a short‐term basis. This foraging pattern provides the potential for positive assortative mating among plants with yellow or pink flowers. Intraspecific pollinator discrimination may influence genotypic frequencies as well as the relative maternal and paternal reproductive success of color morphs.
VARIATION AND LOCALIZATION OF FLAVONOID AGLYCONES IN HELIANTHUS ANNUUS (COMPOSITAE)
Authors: Rleseberg Loren H. , Soltis Douglas E. , Arnold Doug
Published: January 2018

Flavonoid aglycone variation within Helianthus annuus, a species widely distributed throughout North America, was analyzed. Flavonoid aglycones of H. annuus consist of two types, flavones and chalcones. The flavone aglycones are sequestered in glandular trichomes that occur on both leaf surfaces, whereas the chalcone aglycones appear to be incorporated in the waxy leaf cuticle. Considerable variation in flavonoid profile was observed with some plants exhibiting as few as one, and others as many as seven of the eight aglycones detected. No definable phytogeographic patterns were observed for this flavonoid variation. Flavonoid aglycone variation also did not differentiate the infraspecific taxa within H. annuus.
ELECTROPHORETIC ENZYME ANALYSIS OF NORTH AMERICAN AND EASTERN ASIAN POPULATIONS OF AGASTACHE SECT. AGASTACHE (LABIATAE)
Authors: Vogelmann James E. , Gastony Gerald J.
Published: January 2018

Agastache sect. Agastache consists of seven species in North America and one disjunct in eastern Asia. Starch‐gel electrophoresis of enzymatic proteins was employed to assess genetic relationships among these species and to estimate the amount of genetic divergence between the North American and Asian populations. Species of the western United States appear to be better adapted for outcrossing than are the others and are much more genetically variable, with higher levels of heterozygosity per individual, more alleles per species, and higher percentages of polymorphic loci per population. Nonmetric multidimensional scaling of Nei's genetic distances among 32 populations partitioned the section into four discrete groups: 1) A. nepetoides (eastern North America), 2) A. scrophulariifolia and A. foeniculum (eastern and central North America), 3) the four species of the western United States (A. urticifolia, A. occidentalis, A. parvifolia and A. cusickii) and 4) A. rugosa (eastern Asia). Asian Agastache, separated from its American congeners for over twelve million years, differed from American populations at two of fifteen loci surveyed. Nei's genetic distances between Asian and North American populations ranged from 0.2877 to 0.6734.
INTRACELLULAR RNA DURING MEIOSIS IN MICROSPORANGIA OF TAXUS BACCATA
Authors: Pennell R. I. , Bell P. R.
Published: January 2018

Using microfluorimetry the variations in the level of insoluble RNA in the nucleolus, nucleus and cytoplasm, have been followed during meiosis I in the microspore mother cells of Taxus baccata, in which meiosis extends over approximately six weeks. The concentration of RNA in nucleus and cytoplasm showed ordered changes during prophase, there being indications of a fall in the value in the nucleus at the beginning of prophase followed by a rise to a maximum at diakinesis. When the relative volumes of the cytoplasm were taken into account, and confidence limits applied, it became clear that there was no evidence of any significant loss of RNA from the cell during prophase. The amount in fact increased between zygotene and pachytene, and then showed little change until metaphase. With regard to movements between the compartments of the cell, the confidence limits do not allow firm conclusions, but the consistency of the data is in conformity with a slight movement from cytoplasm to nucleus at the time of formation of the synaptonemal complexes, followed by a fall in nuclear RNA and a rise in that of the cytoplasm. The data do not support the concept of a massive loss of RNA from the cytoplasm during prophase. The universality of this phenomenon is questioned, and the significance of the results is sought in the duration of meiosis I.
GENETIC VARIATION IN THE EPIPHYTES TILLANDSIA IONANTHA AND T. RECURVATA (BROMELIACEAE)
Authors: Soltis Douglas E. , Gilmartin Amy Jean , Rieseberg Loren , Gardner Sue
Published: January 2018

The genetic structure of two epiphytic species, Tillandsia ionantha and T. recurvata, was investigated using enzyme electrophoresis. Electrophoretic data suggest that T. ionantha and T. recurvata differ in breeding system, in agreement with predictions based on their strikingly different floral morphologies. Electrophoretic data suggest extremely high levels of inbreeding for T. recurvata, whereas Tillandsia ionantha exhibits characteristics of an outcrossing species. Values of P, H, and mean number of alleles per locus are much higher in T. ionantha than in T. recurvata. The mean value of FIS for T. ionantha is low (0.056), closely approaching expectations at Hardy‐Weinberg equilibrium. In contrast, the mean value of FIS in T. recurvata (1.000) indicates a complete absence of heterozygotes. The two species also differ in genetic structure. Low FST values for T. ionantha indicate little variation in allele frequencies among populations. In contrast, FST values are high for T. recurvata, suggesting substantial genetic heterogeneity among populations. In addition, the mean value of I is higher in T. ionantha (0.995) than in T. recurvata (0.931). Population genetic data are in agreement with the suggestion of Benzing (1978), who proposed that extreme epiphytes such as T. recurvata, would be characterized by increased autogamy ensuring high seed set. Due to high chromosome numbers in Bromeliaceae (most taxa have x = 25), the family has been considered polyploid. However, with the exception of an additional isozyme for PGM in T. recurvata, the two species are isozymically diploid.
THE EFFECT OF MODERATE SALT STRESS ON LEAF ANATOMY IN HIBISCUS CANNABINUS (KENAF) AND ITS RELATION TO LEAF AREA
Authors: Curtis Peter S. , Läuchli André
Published: January 2018

Kenaf responded to salt stress in a manner that was typical of moderately salt tolerant non‐halophytes. Increase in leaf area was more sensitive to salinity than either leaf emergence rate or dry matter accumulation. Dry weight was reduced only above a threshold of approximately 37 mM NaCl while leaf area was already significantly reduced at this salt concentration. Measurement of epidermal cell cross sectional area and epidermal cell numbers showed that the salt induced reduction in leaf area was due primarily to smaller epidermal cell size. Epidermal cell numbers were also significantly reduced by salinity. Stomatal density increased with increasing salt stress and there was no effect on leaf thickness.
EVOLUTION OF HEAVY METAL TOLERANCE IN BRYOPHYTES II. AN ECOLOGICAL AND EXPERIMENTAL INVESTIGATION OF THE “COPPER MOSS,” SCOPELOPHILA CATARACTAE (POTTIACEAE)
Authors: Shaw Jonathan
Published: January 2018

About six bryophyte species (including both mosses and liverworts) are generally thought to be restricted to copper‐enriched substrates and are consequently known as “copper mosses.” One of these, Scopelophila cataractae (Pottiaceae), is known from several sites in southern Arizona and occurs at six localities in the eastern United States. Chemical analyses of substrates from the eastern U.S. localities showed that all but one population grew on copper‐enriched soil. The one substrate sample low in copper was very high in iron. Plants from five of the six eastern U.S. localities for S. cataractae were grown experimentally on four soil types ranging from highly to not contaminated, and all grew best on the soil contaminated with copper, lead, and zinc. There was no significant variation in growth between populations on the four soil treatments. This lack of population differentiation is in contrast to flowering plants and may be related to the absence of sexual reproduction in S. cataractae in North America.
IN VITRO CULTURE OF EAR SHOOTS OF ZEA MAYS AND THE EFFECT OF KINETIN ON SEX EXPRESSION
Authors: Bommineni V. R. , Greyson R. I.
Published: January 2018

Immature ear primordia of maize when cultured on a defined liquid medium grew and differentiated in response to two variables: 1) size of initial explants and 2) concentration of kinetin in the medium. Overall growth of primordia, less than 15 mm at explanting, reached an optimum fresh weight and ear length when kinetin was 10–6m. Ears less than 10 mm, in the presence of kinetin, produced many male spikelets with well‐developed stamens in both upper and lower flowers. Ears greater than 15 mm, at explanting, produced only female flowers regardless of the kinetin concentration. Different proportions of male and female and bisexual flowers were produced depending upon the initial size of inflorescences and the concentration of kinetin.
COMPARATIVE CACTUS ARCHITECTURE AND PAR INTERCEPTION
Authors: Geller Gary N. , Nobel Park S.
Published: January 2018

Because CO2 uptake by cacti can be limited by low levels of photosynthetically active radiation (PAR) and because plant form affects PAR interception, various cactus forms were studied using a computer model, field measurements, and laboratory phototropic studies. Model predictions indicated that CO2 uptake by individual stems at an equinox was greatest when the stems were vertical, but at the summer and the winter solstice CO2 uptake was greatest for stems tilted 30° away from the equator. Stem tilting depended on form and taxonomic group; four barrel cacti in Ferocactus and in Copiapoa and four cylindropuntias in Opuntia tilted toward a horizontal light beam by an average of 18°, 48°, and 52°, respectively, after growth periods of 1 to 4 yr. In contrast, three columnar species showed no significant phototropic response, perhaps because structural stability requires their massive stems to be erect. Field plants of the dense, multiple‐stemmed shrub Opuntia echinocarpa had stems which tended to radiate outward from the plant base, and, although this would not influence the total PAR intercepted, it would result in a more uniform PAR distribution and hence higher CO2 uptake. For O. echinocarpa and the even denser, mound‐forming Echinocereus engelmannii, PAR and chlorophyll decreased approximately exponentially with depth into the canopy. The canopies of O. echinocarpa and other cylindropuntias did not extend to the ground; in certain species, such truncation apparently resulted from a combination of very low PAR levels just below the lower canopy edge and the light‐dependent growth responses of individual stems. In addition, although the canopy surfaces of O. echinocarpa and O. acanthocarpa tilted toward the equator by about 30°, the canopies of other cylindropuntias tilted less or not at all; the computer model predicted that a 30° tilt would decrease interstem shading, increase daily PAR, and increase nocturnal CO2 uptake by as much as 54, 26, and 24%, respectively. Not only can the shape of cacti be affected by PAR, but also shape influences PAR interception and hence CO2 uptake.
ULTRASTRUCTURAL LOCALIZATION OF CELL SURFACE IMMUNOSPECIFICITY IN ANABAENA AZOLLAE USING INDIRECT FLUORESCENT ANTIBODY STAINING
Authors: Rosen Barry H. , Johnson Robert C. , Fisher Robert W. , Gates James E.
Published: January 2018

Antisera prepared against whole cells were used to differentiate between freshly isolated and cultured cyanobacteria from the nitrogen‐fixing fern Azolla filiculoides using both light and transmission electron microscopy (TEM). TEM suggested that the differentiating antigens are evenly distributed on the cell wall outer membrane of the cyanobacteria. The fluorescein isothiocyanate (FITC)‐conjugated secondary antibody accumulation was sufficiently electron‐dense to be detected without the need for either gold or ferritin labelling. Relative amounts of fluorescence which occurred on specimens viewed with fluorescent light microscopy were comparable to the thickness of electron dense material on the surfaces of these cells. Thus, it is possible to use the same immunological procedure to prepare cells for both light and TEM study.
GIEMSA C‐BANDED KARYOTYPES OF SEVEN NORTH AMERICAN SPECIES OF ALLIUM
Authors: Cai Q. , Chinnappa C. C.
Published: January 2018

The karyotypes of seven North American Allium species were studied by Giemsa C‐banding technique. Two species (A. shoenoprasum and A. tricoccum) were diploids with 2n = 16 chromosomes. Three species (A. cernuum, A. douglasii and A. geyeri) were also diploids but with 2n = 14 chromsomes. Diploid and tetraploid populations of A. textile (2n = 14, 28) were studied. The population of A. canadense studied here was a tetraploid (2n = 28). All these North American species, except A. geyeri, possessed centromeric bands in all their chromosomes and nucleolar constriction bands in their satellited chromosomes. Allium shoenoprasum contained telomeric bands in most of its chromosomes but the other species had them only in a small number of chromsomes. Only three species (A. shoenoprasum, A. textile and A. tricoccum) were found to have intercalary bands in some chromosomes. The heterochromatin distribution in B chromosomes of three species was also observed. In A. cernuum, the heterochromatin occupied most of the length of all its Bs, but in A. shoenoprasum, heterochromatin was concentrated in the centromeric region. One population of A. textile (CC1179) was found to have a B chromosome in which very little heterochromatin existed.
SEED PRODUCTION AND GERMINATION RESPONSE OF FOUR LOUISIANA POPULATIONS OF UNIOLA PANICULATA (GRAMINEAE)
Authors: Hester Mark W. , Mendelssohn Irving A.
Published: January 2018

Sea oats, Uniola paniculata, is a characteristic and often dominant perennial dune grass of the southeastern Atlantic and Gulf coasts of the United States. However, U. paniculata loses its dominance and becomes almost nonexistent along a relatively narrow portion of its range, from west of the Mississippi River delta, Louisiana, through northeastern Texas. In Louisiana, U. paniculata is abundant on the Chandeleur Islands east of the delta, but along the barrier island chain west of the delta only three sizable populations have been identified, all on the Caminada‐Moreau coast. We measured seed production and germination response to various moisture and temperature combinations in these populations. Seed production was found to range from one to three orders of magnitude less than what has been reported in areas where U. paniculata is dominant. Rates ranged from 0.091 seeds/spikelet on the Chandeleur Islands to only 0.002 seeds/spikelet on the Caminada‐Moreau coast; one population failed to produce any seeds at all. Seed germination in an 18.3–35.0 C alternating thermoperiod was high (65–88%) after exposure of the seeds to a variety of pregermination moisture and temperature conditions. Exposure to 4.4 C during imbibition did not increase percentage germination, but did significantly increase the rate of germination over the pregermination treatments that did not include moisture. The very low seed production rates of these populations could explain the limited distribution of this species along the Louisiana coast, where overwash events are frequent, and rates of coastline retreat often exceed the highest measured rates of vegetative lateral spread.