bluuebunny/crossref_metadata_2025 huggingface dataset:
SAFE SITES AND THE ECOLOGICAL LIFE HISTORY OF LORINSERIA AREOLATA
Authors: Cousens Michael I. , Lacey Deborah G. , Scheller John M.
Published: January 2018

The life history biology of the fern Lorinseria areolata was studied at three sites adjacent to the Escambia River, Florida, which represented part of its habitat diversity in the Gulf Coastal Plain. Site 1 was dominated by Pinus elliottii and was flooded only during hurricanes. Site 2 was dominated by Magnolia virginiana and Gordonia lasianthus and was flooded for 3–5 months of the year. Site 3 was dominated by Nyssa sylvatica var. biflora and Taxodium distichum and was flooded for 9–12 months of the year. Lorinseria areolata coverage was 92, 61, and 16% of total understory at sites 1, 2, and 3. Rhizome length varied 5‐fold between sites. Microtopography varied little at site 1. Microtopography at sites 2 and 3 consisted of distinctive hummocks and hollows. Association analysis documented that L. areolata was distributed randomly with regard to microtopography at site 1, and was strongly associated with hummocks at sites 2 and 3. Seven life history classes (LHCs) for L. areolata were discriminated based on field collections and seasonal observations over three years. Density of LHCs decreased logarithmically, with the exception of older LHCs whose age could not be determined beyond 30 months. Spore storage in dead erect sporophylls allowed the establishment of gametophytes throughout the year. Up to 25% of the gametophyte population survived the cold and relative drought of winter. More than half of field collected gametophytes were small males, and up to a third were larger bisexual gametophytes. Safe sites for completion of the life cycle were limited to decayed pine stumps and twigs at site 1, and to hummocks at sites 2 and 3. It was hypothesized that the acidifying action of Pinus elliottii litter on soil contributed to the abundance of Lorinseria areolata at site 1, and that parts of the microhabitat mosaic at sites 2 and 3 which most closely approached edaphic characteristics of site 1 provided safe sites for the fern.
POLLINATION QUALITY, SEED SET, AND FLOWER TRAITS IN POLEMONIUM VISCOSUM: COMPLEMENTARY EFFECTS OF VARIATION IN FLOWER SCENT AND SIZE
Authors: Galen Candace , Newport Mary Ellen A.
Published: January 2018

Seed set in naturally pollinated flowers of the alpine skypilot, Polemonium viscosum, is influenced by two components of pollination quality: the number of outcross pollen grains received by a flower over its lifetime and the purity, or percentage of conspecific grains in the pollen mixture. Plants of this species have flowers that are either sweet or skunky in scent. Sweet flowers are larger on average than skunky ones. In populations frequented by a fly‐dominated assemblage of pollinators, skunky‐scented flowers tended to receive more outcross pollen than sweet‐scented flowers, regardless of their size. In contrast, in predominantly bumble bee‐pollinated populations, floral scent and size were both correlated with pollination quality. These results illustrate that advantages associated with flower phenotypes are habitat dependent. With bumble bee pollination, plants having large sweet‐scented flowers received purer pollen mixtures and more outcross grains than neighboring plants with smaller skunky‐scented flowers. When variation in pollination quality with flower size was accounted for statistically, floral scent differences remained correlated with differential outcross pollination. While both flower scent and size are secondary attractants, they affect independent components of pollination quality and have complementary effects on seed set.
SECRETORY RESERVOIRS (DUCTS) OF TWO KINDS IN GIANT RAGWEED (AMBROSIA TRIFIDA; ASTERACEAE)
Authors: Lersten Nels R. , Curtis John D.
Published: January 2018

Two types of tubular secretory reservoirs occur in Ambrosia trifida, the first such example known in plants. Paraffin and resin sections, and clearings showed that, although each type consists of many separate unbranched tubes, they differ in anatomy, secretory contents, distribution, and length. Reservoirs (PAR) containing a red substance (presumably a polyacetylene) and lined with a biseriate epithelium parallel the largest leaf and stem vascular bundles. One PAR arises near the base of each leaf lobe midrib and extends through the petiole to the node or continues in the stem cortex to the node below. Other PARs start at the cotyledonary node or in cotyledons and extend down into the primary root, where they have only a single layer of unspecialized epithelium. PARs realign themselves, and more form de novo, until the primary root has two to four separate arrays of PARs abutting the endodermis, each with three to six parallel PARs. Branch roots have similar PAR arrays but unconnected to PARs of the parent root. Inflorescence PARs occur only in bracts, and in petals of male flowers. The second type of reservoir (OR) has a uniseriate epithelium and contains an unidentified oil. ORs occur in phloem, and in pith next to xylem, of stem and large leaf bundles. They dwindle in successively smaller veins until the two smallest orders lack them. ORs occur only in phloem in the hypocotyl; none occur in cotyledons, roots, or floral parts.
RECIPROCAL DIFFERENCES IN INTRASPECIFIC CROSSES OF TOBACCO RESULT FROM EMBRYO DEATH
Authors: Contolini Carol S. , Hughes Karen Woodbury
Published: January 2018

Tetraploid tobacco plants (Nicotiana tabacum) derived from cultured cell lines (TC) are partially cross‐incompatible with their diploid progenitors (C). C × TC crosses (TC‐derived tetraploids as the pollen parent) yield only 2% viable seed. The remaining seeds are normal size but lack an embryo (apoembryonic seeds). Apoembryonic seeds do not occur in the reciprocal TC × C crosses. Sections of ovules from C × TC crosses revealed that an embryo formed but that embryo growth slowed at 5 days postpollination and that by the 12th day following pollination, the embryo had disappeared although the ovule continued to develop. Endosperm degeneration occurred concurrently with embryo death. Culturing ovules from C × TC crosses has increased the yield of F1 plants from 2% to as much as 25% indicating that embryo rescue is possible. Surviving F1 plants from TC × C crosses have close to triploid chromosome numbers and are fertile.
BIOCHEMICAL BASIS OF FLORAL COLOR POLYMORPHISM IN A HETEROCYANIC POPULATION OF TRILLIUM SESSILE (LILIACEAE)
Authors: Les Donald H. , Whitkus R. , Bryan F. A. , Tyrell L. E.
Published: January 2018

A study of flavonoids occurring within a heterocyanic population of Trillium sessile was made to determine the chemical basis of a common floral color polymorphism in this species. In the study population, three floral color phenotypes (red, pink, yellow) are determined primarily by the presence or absence of anthocyanin compounds in the petal tissue, and secondarily by quantitative differences in the concentration of several flavonol glycosides. Petals of red phenotypes contain both cyanidin 3‐arabinoside and 3‐diarabinoside, petals of pink phenotypes contain only cyanidin 3‐arabinoside, and petals of yellow phenotypes lack cyanidin entirely. Quercetin 3‐0‐glucoside, quercetin 3‐0‐arabinoglucoside, quercetin 3–0‐arabinogalactoside, and quercetin 3‐0‐arabinogalactosyl, 7‐0‐glucoside occur in petals of all three phenotypes but differ in relative amounts. Petals of the red phenotype have mostly 3‐0‐biosides, but lesser amounts of both quercetin 3‐0‐glucoside and the 3,7‐0‐triglycoside. Petals of the pink phenotype contain relatively equal amounts of quercetin mono‐, di‐, and triglycosides. Petals of the yellow phenotypes contain mostly quercetin 3,7‐0‐triglycosides, and less mono‐ and di‐glycosides. Small amounts of a quercetin tetraglycoside were detected in petals of both yellow and pink phenotypes, but not in red phenotypes. The enhancement of quercetin polyglycoside biosynthesis in yellow petal phenotypes is attributed to the shunting of dihydroflavonol precursors to synthesis of quercetin compounds when their conversion to anthocyanins is blocked genetically.
POLLINATION IN LUPINUS NANUS SUBSP. LATIFOLIUS (LEGUMINOSAE)
Authors: Juncosa Adrian M. , Webster Barbara D.
Published: January 2018

Floral morphology and phenology and the timing of stigmatic receptivity and pollen viability were studied to elucidate the mechanisms by which self‐pollination in Lupinus nanus subsp. latifolius is minimized under natural conditions. Pollen germination and pollen tube growth suggest that a physiological self‐incompatibility system does not exist. Instead, self‐pollination is minimized by protandry and by a collar of peristigmatic hairs, which initially inhibit access of autologous pollen to the stigma. These hairs subsequently wilt, permitting self‐pollination of unvisited flowers. Pollen germinates in vivo one day before substantial metabolic enzyme activity can be detected. Citric acid cycle enzymes are not detectable in pollen, but those of anaerobic metabolism are. Beginning on the second day postanthesis, stigmatic secretions exude from weak areas on lateral walls of the elongate epidermal papillae, welling up in the interstices between these cells. This contrasts with the stigmas of other papilionoid legumes, in which secretions accumulate beneath the cuticle covering the stigmatic cells, and the often‐thin cuticle must be ruptured before pollen and exudate can come into contact.
IN OVULO EMBRYO DEVELOPMENT AND PLANT FORMATION FROM STENOSPERMIC GENOTYPES OF VITIS VINIFERA
Authors: Emershad Richard L. , Ramming David W. , Serpe Marcelo D.
Published: January 2018

Embryo enlargement and plant formation via in ovulo embryo culture was studied in stenospermic grapes. Genotypes, culture media and their interactions significantly affected embryo enlargement, whereas culture dates did not. Genotype P60‐58, when compared to cv. Thompson Seedless, had the greatest number of enlarged embryos after 3 months in culture. P60‐58 ovules cultured on Cain's basal medium plus L‐serine or L‐glutamine and cv. Thompson Seedless ovules cultured on Cain's basal medium plus L‐cysteine or L‐asparagine produced the greatest number of enlarged embryos. Viable embryos and morphologically normal‐appearing plants were obtained. Polyembryony was observed in cultured zygotic embryos.
A NEW SPECIES OF PICEA BASED ON SILICIFIED SEED CONES FROM THE OLIGOCENE OF WASHINGTON
Authors: Miller Charles N.
Published: January 2018

Picea eichhornii n. sp. is described from anatomically preserved seed cones. The fossils are from the Early Oligocene Jansen Creek Member of the Makah Fm. which is exposed along the northern shore of the Olympic Peninsula, Washington. The cones are at least 5.5 cm long and up to 3.5 cm in diameter. The cone axis is 4–6 mm in diameter and contains a pith made up of thick‐walled parenchyma cells. Resin canals occur in a single ring in the secondary xylem in some specimens but are absent in others. The cortex is mostly parenchymatous and contains numerous large axial resin canals that branch to supply the bract and scale. Vascular traces to each scale and its subtending bract diverge separately from the vascular cylinder of the cone axis. The bract is tongue‐shaped and keeled at its base. It is 5 mm wide and up to 9 mm long. The bract trace fades out before entering the bract base while two resin canals extend into the bract base. The ovuliferous scale is about 2.3 cm long and has a thin, probably papery, apex. Resin canals of the scale occur abaxial to the vascular tissue in the scale base, but some bend around the margins of the vascular strand to become adaxial outward. About 20 resin canals occur in the abaxial scale sclerenchyma, and this is the main anatomical feature that distinguishes these cones as a new species. There are less than 14 such canals in cones in a reference collection of 15 modern species and in the two fossil species known from anatomically preserved material. While the new species adds to our knowledge of the diversity of Cenozoic Picea, its affinities within the genus remain undetermined.
POLLEN GRAIN DEVELOPMENT AND TAPETAL CHANGES IN STRELITZIA REGINAE (STRELITZIACEAE)
Authors: Kronestedt‐Robards Eva C. , Rowley John R.
Published: January 2018

The proexine that forms within the callosic envelope before the end of the microspore tetrad period is thick (about 1 μm) and exceptionally complex. It has components equatable with tectum, columellae, and a nexine that includes lamellar zones. All these components persist in the exine although late in development they become difficult to recognize because this exine is reduced in thickness, apparently by stretching, to a maximum of 0.2 μm. Strelitzia is an example of an exine template, with receptors for sporopollenin, that is not maintained during development. The Strelitzia microspore surface changes from an exine like that on an interaperture sector to the channeled intinelike system common for the apertures of pollen grains. The exine on sterile grains gives what may be a rare view of a stabilized immature exine. The mature exine on viable pollen grains resembles this early exine only in the most impressionistic way. Tapetal cells go through at least one cycle of hyperactivity, dedifferentiation, mitosis, and then again hyperactivity before they finally decline.
MECHANICAL BEHAVIOR OF PLANT TISSUES AS INFERRED FROM THE THEORY OF PRESSURIZED CELLULAR SOLIDS
Authors: Niklas Karl J.
Published: January 2018

The mechanical behavior of plant tissues and its dependency on tissue geometry and turgor pressure are analytically dealt with in terms of the theory of cellular solids. A cellular solid is any material whose matter is distributed in the form of beamlike struts or complete “cell” walls. Therefore, its relative density is less than one and typically less than 0.3. Relative density is the ratio of the density of the cellular solid to the density of its constitutive (“cell wall”) material. Relative density depends upon cell shape and the density of cell wall material. It largely influences the mechanical behavior of cellular solids. Additional important parameters to mechanical behavior are the elastic modulus of “cell walls” and the magnitude of internal “cell” pressure.

Analyses indicate that two “stiffening” agents operate in natural cellular solids (plant tissues): 1) cell wall infrastructure and 2) the hydrostatic influence of the protoplasm within each cellular compartment. The elastic modulus measured from a living tissue sample is the consequence of both agents. Therefore, the mechanical properties of living tissues are dependent upon the magnitude of turgor pressure. High turgor pressure places cell walls into axial tension, reduces the magnitude of cell wall deformations under an applied stress, and hence increases the apparent elastic modulus of the tissue. In the absence of turgid protoplasts or in the case of dead tissues, the cell wall infrastructure will respond as a linear elastic, nonlinear elastic, or “densifying” material (under compression) dependent upon the magnitude of externally applied stress.

Accordingly, it is proposed that no single tangent (elastic) modulus from a stress‐strain curve of a plant tissue is sufficient to characterize the material properties of a sample. It is also suggested that when a modulus is calculated that it be referred to as the tissue composite modulus to distinguish it from the elastic modulus of a noncellular solid material.
INSECT‐CYCAD SYMBIOSIS AND ITS RELATION TO THE POLLINATION OF ZAMIA FURFURACEA (ZAMIACEAE) BY RHOPALOTRIA MOLLIS (CURCULIONIDAE)
Authors: Norstog Knut J. , Fawcett Priscilla K. S.
Published: January 2018

Zamia furfuracea, a cycad of Mexican origin, in cultivation is pollinated by the snout weevil, Rhopalotria mollis, also of Mexican origin. This weevil apparently is host specific, swarming upon male cones of the cycad, where mating, feeding, and oviposition occur. Sporophylls of male cones are rich in starch; those of female cones are poor in starch, and weevils feed upon male cones and are visitors to but not feeders upon or within female cones. Pollen transport to female cones occurs during such visitation. All stages of metamorphosis of R. mollis occur within male cones; larvae feed exclusively on parenchyma of microsporophylls, pupate within stalks of microsporophylls, and emerge as adults from the outer ends of microsporophylls. They do not feed on pollen and do not damage microsporangia or pollen. Toward the end of the breeding season of the weevil (and the cycad), some larvae enter diapause in thick‐walled pupal cases within microsporangial stalks of pollen‐spent cones. These remain in diapause until the next reproductive season of the cycad.
EFFECT OF CARBON DIOXIDE ENRICHMENT ON DEVELOPMENT OF THE FIRST SIX MAINSTEM LEAVES IN SOYBEAN
Authors: Leadley Paul W. , Reynolds James F.
Published: January 2018

Many conclusions concerning plant responses to CO2 enrichment have been based on assumptions of increased leaf size derived from observations of average leaf area measured at some time well into the growth period. The objectives of this study were to study the effect of elevated CO2 on 1) the timing of mainstem leaflet appearance, 2) the rate and duration of leaflet expansion, and 3) the final area of individual leaflets of soybeans (Glycine max [L.] Merr. cv. Bragg) grown from seed at 348, 502, and 645 μl 1–1 CO2 concentrations. Central leaflet areas from mainstem trifoliolates 1–6 were measured every two days from time of appearance to full expansion. Leaflets tended to appear earlier in elevated CO2 treatments; leaflets 2 through 6 appeared an average of 0.4 days earlier in the 502 μl 1–1 treatment and 1.2 days earlier in the 645 μl 1–1 treatment than in the 349 μl 1–1 treatment. Relative rates of expansion were different among leaflets in their response to elevated CO2; expansion rates of leaflets 1 and 4 were significantly higher at the highest CO2 concentration. However, final area of leaflets was not affected by CO2, or (in leaflet 5 only) was slightly smaller at the highest CO2 treatment. Apparently, higher expansion rates of leaflets 1 and 4 at high CO2 were offset by a tendency for decreased duration of expansion. It appears that there are morphological constraints on final leaflet area in soybean seedlings which limit the effects of elevated CO2 on the early development of mainstem leaf area.
GENETIC STRUCTURE OF GEOGRAPHICALLY MARGINAL POPULATIONS OF PONDEROSA PINE
Authors: Hamrick J. L. , Blanton H. M. , Hamrick K. J.
Published: January 2018

Eleven populations of ponderosa pine (Pinus ponderosa) located on an east‐west transect of the Palmer Divide of Central Colorado were studied. Within each population transects of approximately 20 × 250 m were established. In seven populations the transects represented contrasting ecological conditions such as north and south facing slopes. Within each transect 200–250 trees greater than 10 cm in height were tagged, their locations mapped, their ages determined and their diameters and heights measured. Electrophoretic analyses of mature needle tissue indicated that while most of the allozyme variation resided within transects, significant genetic heterogeneity could be found between populations and transects. Among populations consistent patterns of genetic variation were observed at only two loci. Five of the 13 loci had consistent but very small differences between transects within populations. Considerable genetic heterogeneity occurred among 20 m sections of the transects and among age classes within transects. The genetic structure of these populations can be explained by mosaic patterns of seedling recruitment characteristic of these ponderosa pine stands. Only a few maternal trees contribute to each patch of seedlings, and this localized founder effect produces the genetic structure observed in these populations.
PATTERN DETERMINATION OF THE EXINE IN CAESALPINIA JAPONICA (LEGUMINOSAE: CAESALPINIOIDEAE)
Authors: Takahashi Masamichi
Published: January 2018

Exine development in Caesalpinia japonica Sieb. et Zucc. (Leguminosae) was studied by a combination of transmission electron microscopy (TEM) and field emission scanning electron microscopy (SEM) using a freeze‐fracture method, with special attention to the initial process of exine pattern formation. The present study confirmed that the exine pattern is determined by the plasma membrane of microspores enclosed in the callose wall at the early tetrad stage. The plasma membrane, exclusive of the future apertures, invaginates and takes the form of a reticulate pattern. The reticulate pattern corresponds to the mature exine ornamentation. Protectum is the first to be laid down on the reticulate patterned plasma membrane. Probacules are initiated under the protectum and elongate basally on protruding sites of the plasma membrane. Primexine matrix is formed in coincidence with the probacules. After the protectum and probacules are completed within the callose wall, the invaginating plasma membrane becomes smooth. After the dissolution of the callose wall, endexine is organized by the accumulation of lamellated structures, and a foot layer is formed by the deposition of nonlamellated components on the developing endexine.
EVOLUTIONARY MODIFICATION IN CLARKIA. II. ROLE OF FLOWER BUD PUBESCENCE IN SECTION PHAEOSTOMA
Authors: Vasek Frank C. , Weng Vincent
Published: January 2018

Observations of the habitats and relative flowering of a Clarkia species with hairy flower buds and several with hairless flower buds led to the hypothesis that long hairs on flower buds regulate bud temperature. This hypothesis predicts that hairless buds would be warmer and develop faster than hairy buds, which would be cooler, develop more slowly, and avoid high temperature stress. The hypothesis was tested by comparing flower bud growth rates and temperatures in three genetically similar biotypes of Clarkia unguiculata and in all six species of section Phaeostoma. Flower buds of the three biotypes included hairy (HY) and hairless (HN) from the same coastal population and densely hairy (HD) from an interior locality. The six species included C. unguiculata with densely hairy buds (HD) and five related species with hairless buds. Contrary to expectations, HY buds grew more rapidly than HN buds. HD buds grew more rapidly than either and also more rapidly than the hairless buds of five related species. Again contrary to expectations, the three biotypes of C. unguiculata had equivalent temperature relations, with bud temperatures mostly somewhat below air temperatures. In a comparative experiment, bud temperatures in C. unguiculata approximated air temperatures while bud temperatures in five related species mostly fell well below air temperatures. Thus, predictions of the hypothesis were not borne out. Long bud hairs apparently have minimal effect on bud growth rates and temperatures, and we conclude that physiological adaptations are more important. Bud cooling mechanisms are discussed.
FACTORS INFLUENCING THE REPRODUCTIVE SUCCESS OF IPOMOEA PES‐CAPRAE (CONVOLVULACEAE) AROUND THE GULF OF MEXICO
Authors: Devall Margaret S. , Thien Leonard B.
Published: January 2018

The reproductive biology of Ipomoea pes‐caprae, a pantropical beach morning glory, was studied at five sites around the Gulf of Mexico. The primary pollinators were Xylocopa species (carpenter bees) which dispersed pollen up to 90 m. Exclusion experiments demonstrated that ants feeding on extrafloral nectaries increased seed set but did not protect seeds from predation by the bruchid beetle Megacerus. The water‐dispersed seed and long‐range dispersal of pollen may function to counter the sporophytic incompatability mechanism of the plant; populations exhibit a large neighborhood size. Key reproductive factors in the life cycle of I. pes‐caprae are the long‐range pollen flow and mass germination of water‐dispersed seeds.
DETERMINATE (det) MUTANT OF PISUM SATIVUM (LEGUMINOSAE: PAPILIONOIDEAE) EXHIBITS AN INDETERMINATE GROWTH PATTERN
Authors: Singer Susan R. , Hsiung Linda P. , Huber Sarah C.
Published: January 2018

Inflorescence ontogeny and morphology of the det mutant of Pisum sativum L. were investigated using scanning electron microscopy. This mutation causes the production of a limited number of axillary flowers followed by the formation of an apparent terminal flower slightly offset from the vertical. Our study indicates that the apparent terminal flower arises from an axillary meristem. The terminal meristem senesces and differentiates hairs, forming a rudimentary stub in the same manner as axillary meristems of conventional (Det) and det plants. Thus the dramatic effect of the det gene on inflorescence architecture results from early apical arrest rather than conversion of the terminal meristem to a flower as implied by the symbol det. This mutant will be valuable in elucidating regulation of apical arrest.
XYLEM ANATOMY AND HYDRAULIC CONDUCTANCE OF COSTA RICAN BLECHNUM FERNS
Authors: Veres John S.
Published: January 2018

Hydraulic conductivities of stems, stipes, and elongate leaf stipes were determined for greenhouse‐grown Blechnum (B. fraxineum, B. fragile, B. buchtienii, B. sprucei) and Salpichlaena (S. volubilis) plants collected in tropical rain forests of Costa Rica. Organ conductivity was examined in relation to morphology and tracheid characteristics in order to gain an understanding of factors influencing water flow. Hydraulic conductivity of plant organs was determined by measurement of transpiration rates, leaf areas, and water potential gradients. Erect stemmed species develop larger whole plant water potential gradients than elongate stemmed species for a similar transpiration rate. Elongate leaves develop even smaller water potential gradients for a given transpiration rate. Stems have larger hydraulic conductivities but smaller leaf‐specific conductivities (LSCs) than stipes. Small conductivities and small LSCs are associated with short, erect stems. Elongate structures have large conductivities and large LSCs. Of the tracheid characteristics examined, the most important characteristics determining the magnitude of organ hydraulic conductivity are diameter, pit aperture area between tracheids, taper length, and cell length. Large conductivities of S. volubilis climbing leaf stipes are associated with very large‐diameter tracheids (some > 200 μm), large tracheid number, exceptionally long tracheids (some > 4 cm), large pit aperture area between tracheids, short tracheid taper, and smooth tracheid lumen walls. Hagen‐Poiseuille estimates of hydraulic conductivity range from 1.1 to 3.3 times the measured values. Conductivity of stipes is highly correlated with leaf area supplied by stipes. Conductivities of stems and elongate leaf stipes also correlate with leaf area supplied by these structures. Estimated hydraulic conductivities of field‐grown Blechnum and Salpichlaena demonstrate that larger conductivities are associated with larger plants. This study contributes toward our knowledge of fern water relations and extends previous growth form/hydraulic architecture characterizations by providing a more comprehensive comparison of closely related species. In addition, this study provides evidence for the relative importance of tracheid characteristics in determining the magnitude of organ hydraulic conductivity.
SOMATIC EMBRYOGENESIS OF CARROT IN HORMONE‐FREE MEDIUM: EXTERNAL pH CONTROL OVER MORPHOGENESIS
Authors: Smith David L. , Krikorian Abraham D.
Published: January 2018

Cultures of preglobular stage proembryos (PGSPs) were initiated from mechanically wounded mature zygotic embryos of carrot, Daucus carota, on a hormone‐free, semisolid medium. These PGSPs have been maintained and multiplied for extended periods without their progression into later embryo stages on the same hormone‐free medium containing 1 mM NH4+ as the sole nitrogen source. Sustained maintenance of cultures comprised exclusively of PGSPs was dependent on medium pH throughout the culture period. Best growth and multiplication of PGSP cultures occurred when the pH of unbuffered, hormone‐free medium fell from 4.5 to 4 over a 2‐week period or when buffered medium was titrated to pH 4. If the hormone‐free medium was buffered to sustain a pH at or above 4.5, PGSPs developed into later embryo stages. Maintenance with continuous multiplication of PGSPs occurred equally well on medium containing NH4+ or NH4+ and NO3−, but growth was poor with NO3− alone. Additional observations on the effects of medium components such as various nitrogen sources and levels, sucrose concentration, semisolid supports, type of buffer, borate concentration, activated charcoal, and initial pH that permit optimum maintenance of the PGSPs or foster their continued developmental progression into mature embryos and plantlets are reported. The influence of the pH of the hormone‐free medium as a determinant in maintaining cultures as PGSPs or allowing their continued embryonic development are unequivocally demonstrated by gross morphology, scanning electron microscopy, and histological preparations.
ALLOZYME DIFFERENTIATION AND GENETIC STRUCTURE IN ISLAND AND MAINLAND JAPANESE POPULATIONS OF CAMPANULA PUNCTATA (CAMPANULACEAE)
Authors: Inoue Ken , Kawahara Takayuki
Published: January 2018

Allozyme variation was investigated in 17 Japanese populations of Campanula punctata, ten from the Izu Islands and seven in the mainland (Honshu). The data indicate that there are two groups, a mainland group and an island one, and that the systematically problematic Oshima Island (northernmost Izu island) populations are closely related to those of the other islands. Nei's genetic identity values among islands and among mainland populations were 0.95 and 0.97, respectively, while the value between island and mainland populations was 0.84, suggesting that the island populations are an independent species. Total genetic variation was nearly the same among island and mainland populations. However, the apportionment of variation within and among populations was considerably different; 14% of gene diversity exists among mainland populations, while 31% of the diversity exists among island populations. Mean outcrossing rates of self‐incompatible mainland and Oshima populations are 0.62–0.79, supporting xenogamy; those in self‐compatible island populations are 0.37–0.57 in the northern islands, indicating a mixed mating system, and 0.16–0.25 in southern ones, indicating dominant inbreeding. Total genetic diversity in each island population decreased with distance from the mainland. Genetic and geological data suggest that the ancestors of insular populations were founded on northern islands in a relatively ancient period and that they dispersed progressively to the southern ones. Chromosome number (2n = 34) and isozyme numbers indicate gene duplications in this species, which suggests it is an ancient polyploid.
ROLE OF COROLLA ABSCISSION IN DELAYED SELF‐POLLINATION OF MIMULUS GUTTATUS (SCROPHULARIACEAE)
Authors: Dole Jefferey A.
Published: January 2018

Corollas of Mimulus guttatus are shed 1–9 days post‐anthesis, and autofertility is often high. The possibility that corolla shedding causes self‐pollination in the absence of pollinators was examined. In one experimental population 82% of seed produced under conditions of pollinator exclusion were due to corolla abscission. Corolla abscission, in the absence of pollinators, is a mechanism of delayed self‐fertilization in this taxon.
EMASCULATION EFFECTS ON FILAMENT GROWTH IN IPOMOEA NIL (CONVOLVULACEAE)
Authors: Kiss Helen Guiragossian , Koning Ross E.
Published: January 2018

Filament growth in the morning glory Ipomoea nil is promoted by gibberellic acid (GA3) and inhibited by ethylene production during the earlier stages in development (Koning and Raab, 1987). The effects of anther removal on filament growth were examined in I. nil. Three‐quarters of the calyx and corolla tissues were removed in order to emasculate the stamens. This removal caused filament growth to be inhibited in the intact stamens (69 hr before anthesis) as well as the emasculated stamens (69 to 21 hr before anthesis). When the ethylene biosynthesis inhibitors CoCl2 and aminoethoxyvinylglycine (AVG) were applied in separate experiments (to eliminate wound ethylene generated by the damaged tissues), filament growth was promoted to control levels observed in intact flower buds (69 hr before anthesis). Our data suggest that the wounding effect from the calyx and corolla tissues and subsequent reduction in filament growth override any observable effects with anther removal on filament growth. Apparently, the removal of the calyx and corolla tissues severs a normal hormonal relationship between these floral organs and the developing filament.
GEOGRAPHIC VARIATION IN REPRODUCTIVE BEHAVIOR AND SIZE STRUCTURE OF THE AUSTRALIAN CYCAD MACROZAMIA COMMUNIS (ZAMIACEAE)
Authors: Ornduff Robert
Published: January 2018

Macrozamia communis is a common cycad that occurs in eastern New South Wales, Australia, where it forms an understory in various forest or woodland communities. Leaf number of reproductive individuals as well as of nonreproductive ones, taken as an indication of size class, varies clinally from north to south, with reproductive individuals in southern populations having mean leaf numbers about 12 times greater than those at the northern end of the range of this species. Female cone size and mature ovule weight appear to vary also along this gradient. Using leaf number as a predictor of sexual maturity, from 37 to 100% of the individuals present in a population were judged to be mature. The percent of mature individuals participating in the 1987 coning episode ranged from none in three southern populations to 68% elsewhere. In 9 of 10 samples more males than females participated in the 1987 coning episode, with a collective sex ratio slightly male biased for all populations sampled. In three population samples average cone numbers for male and female plants were equal. In two samples males produced more cones per plant than females. Leaf numbers of males and females in individual populations were equal. Few individuals producing cones in 1987 showed evidence of recent prior cone production, suggesting that successive cone production by both sexes is separated by an interval of several years. The periodicity with which fire is used as a fire suppression method may affect the frequency of cone production in some populations, perhaps preventing it entirely. The apparent absence of recruitment in some populations may result from long‐term seed collection by humans for horticultural purposes as well as the very poor seed dispersal that appears to characterize this cycad throughout its range. The weevil Tranes internatus was observed occupying the internal tissues of female cones; this insect may be involved in the pollination of M. communis.
EMBRYOLOGICAL STUDY OF HERMINIUM MONORCHIS (ORCHIDACEAE) USING CONFOCAL SCANNING LASER MICROSCOPY
Authors: Fredrikson Margit
Published: January 2018

The embryology of Herminium monorchis (Orchidaceae) was studied using confocal scanning laser microscopy (CSLM), a new technique for embryological studies. This technique may contribute new information to plant embryology. Herminium monorchis has a monosporic embryo sac development. The mature embryo sac is 8‐nucleate. Two integuments, both 2‐layered, are formed, but only the inner takes part in formation of the micropyle. Double fertilization takes place. The primary endosperm nucleus does not divide, but remains alive at least at the 3‐celled stage of embryo development. The three antipodals do not show any sign of degeneration at this stage.
CHARACTERIZATION OF STARCH GRAINS IN THE NONARTICULATED LATICIFER OF EUPHORBIA PULCHERRIMA (POINSETTIA)
Authors: Spilatro Steven R. , Mahlberg Paul G.
Published: January 2018

Starch grain morphology in laticifer amyloplasts of Euphorbia pulcherrima Willd. (poinsettia) was examined for evidence of starch metabolism in vegetative and flowering plants. Laticifer starch grains in vegetative plants were rod shaped with lengths ranging from 3 to 60 μm. Average grain size was significantly larger in stems than leaves, and in older than younger tissues. Starch grain length frequency was unimodal and approximated a normal probability distribution in stems, but was skewed positively toward smaller grains in leaves. Frequency distributions were shifted toward larger grains in older tissues. Under short‐day photoperiod (flowering) conditions, round starch grains formed in latex of stems, and the average length of rod‐shaped grains decreased in latex of stems and leaves. Round grains did not occur in laticifers of leaves or bracts. Round starch grains often occurred in aggregates of two or more subunits. Changes in size and shape of latex starch grains indicate that amyloplasts in fully differentiated laticifers metabolize starch. Identification of metabolically active amyloplasts in differentiated laticifers suggests that the function of these organelles may involve starch mobilization under certain physiological conditions.
REPRODUCTIVE ECOLOGY OF CARYA (JUGLANDACEAE): PHENOLOGY, POLLINATION, AND BREEDING SYSTEM OF TWO SYMPATRIC TREE SPECIES
Authors: McCarthy Brian C. , Quinn James A.
Published: January 2018

Observations and experiments on both shagbark (Carya ovata; 2n = 32) and mockernut (C. tomentosa; 2n = 64) hickories in a New Jersey forest were performed over a 2‐year period to determine the mechanisms operating both to maintain reproductive fidelity and to regulate fruit initiation. Phenological observations indicated significant differences between the species for almost all vegetative and reproductive characters examined; however, a large amount of overlap was also observed. Pollination experiments indicated that pollen limitation is not a significant factor in reducing fruit set in these anemophilous species. Pollen‐ovule ratios ranged from 1 to 25 × 106. Pollen was 80–90% viable at time of shedding. The large surface area of vegetative structures (e.g., leaves) at the time of pollination may retard the flow of pollen into and out of the canopy and thus increase self‐pollination. A full diallel cross, replicated 5 times, was made among 8 trees (4 trees of each species) to characterize combining ability and compatibility relationships. All trees were found to be both geitonogamous and xenogamous to varying degrees. A high frequency of putative interploidal cross‐compatibility was also observed. Fruits from these interspecific crosses were found to be germinable. Observations on individual trees suggested that dichogamy may help to reduce selfing and promote outcrossing in this breeding system. While most trees exhibited a temporal separation of genders, the trait was found to be quite plastic (i.e., trees switched between protogyny and protandry between years). Pistillate flowers were receptive for all trees within a species during the same general time period; however, pollen shedding varied considerably among trees and between years. Both species appear to be utilizing a broad array of mechanisms in order to maintain reproductive fidelity and adequate fruit set.
CORRELATES OF LEAF OPTICAL PROPERTIES IN TROPICAL FOREST SUN AND EXTREME‐SHADE PLANTS
Authors: Lee David W. , Bone Richard A. , Tarsis Sara L. , Storch David
Published: January 2018

Thirteen shade‐adapted rain forest species were compared with twelve sun‐adapted tropical forest species for correlates to leaf optical properties (described previously in Amer. J. Bot. 73: 1100–1108). The two samples were similar in absorptance of quanta for photosynthesis, but the shade‐adapted taxa: 1) had significantly lower specific leaf weights, indicating a more metabolically efficient production of surface for quantum capture; 2) synthesized less chlorophyll per unit area; and 3) used less chlorophyll for capturing the same quanta for photosynthesis. The anatomical features that best correlate with this increased efficiency are palisade cell shape and chloroplast distribution. Palisade cells with more equal dimensions have more chloroplasts on their abaxial surfaces. This dense layer of chloroplasts maximizes the light capture efficiency limited by sieve effects. The more columnar palisade cells of sun‐adapted taxa allow light to pass through the central vacuoles and spaces between cells, making chloroplasts less efficient in energy capture, but allowing light to reach chloroplasts in the spongy mesophyll. Pioneer species may be an exception to these two groups of species. Three pioneer taxa included in this study have columnar palisade cells that are extremely narrow and packed closely together. This layer allows little penetration of light, but exposure of the leaf undersurface may provide illumination of spongy mesophyll chloroplasts in these plants.
RELATIONSHIPS BETWEEN FLOODING TOLERANCE, LIFE HISTORY, AND SHORT‐TERM COMPETITIVE PERFORMANCE IN THREE SPECIES OF POLYGONUM
Authors: Carter Mark F. , Grace James B.
Published: January 2018

The objective of this study was to compare the growth and short‐term (single season) competitive performance of three species of Polygonum known to differ in flooding tolerance and life history. Polygonum amphibium is a perennial with low sexual reproductive effort and a relatively high degree of flooding tolerance, P. lapathifolium is an annual species with a high sexual reproductive effort and a low tolerance to flooding, and P. hydropiperoides is intermediate to the other two in terms of sexual reproductive effort and flooding tolerance. In order to determine the relative growth and competitive abilities of these species, mixtures and monocultures of plants were grown in pots and maintained under three flooding regimes: 1) flooded, 2) partially drained, and 3) well drained. Both P. hydropiperoides and P. amphibium grew best under flooded and partially drained conditions with reduced growth in the drained treatment. Polygonum lapathifolium, in contrast, grew as well in the drained treatment as in the more flooded treatments. Results from competition experiments were consistent in showing the relative competitive abilities to be P. lapathifolium > P. hydropiperoides > P. amphibium regardless of flooding regime. Thus, short‐term competitive performance was found to trade off with flood tolerance rather than with sexual reproductive effort.
ORGANIZATION OF GENETIC DIVERSITY WITHIN AND AMONG POPULATIONS OF GLEDITSIA TRIACANTHOS (LEGUMINOSAE)
Authors: Schnabel Andrew , Hamrick J. L.
Published: January 2018

This study describes levels of allozyme diversity and patterns of genetic structure within and among populations of honey locust (Gleditsia triacanthos L.). Using data from starch gel electrophoresis, honey locust was found to have high genetic diversity within populations (HME = 0.198), and low, but significant genetic differentiation among populations (ΓST = 0.059). Temporal and spatial substructuring were also investigated in two populations from eastern Kansas. Few genetic differences were found among nine age classes in one population and between juveniles and adults in the second population. Separate autocorrelation analyses of juveniles and adults revealed significant spatial substructuring in both age classes. Three conclusions were reached from these analyses. First, even small amounts of clonal growth can cause large increases in the amount of substructuring in populations. Second, spatial genetic substructuring among juveniles at both sites most likely represents the presence of family groups. Last, the overall level of spatial genetic substructuring at both sites was somewhat greater in the juvenile classes than in the nonclonal adult classes. This latter conclusion is consistent with theoretical studies suggesting that limited gene movement causes a steady increase in spatial structure from generation to generation.
EFFECTS OF TREE AGE ON SECONDARY XYLEM AND PHLOEM ANATOMY IN STEMS OF GREAT BASIN BRISTLECONE PINE (PINUS LONGAEVA)
Authors: Connor Kristina F. , Lanner Ronald M.
Published: January 2018

Xylem and phloem tissue samples were collected from various‐aged Great Basin bristlecone pine (Pinus longaeva D. K. Bailey) stems in southern Utah and southeastern California to determine whether the vascular cambia of older trees produce fewer xylem rays, shorter‐lived xylem and phloem ray cells, fewer phloem sieve cells, and a thinner phloem. Increment cores were examined to determine whether ‘aged’ cambia produced narrower tracheids that might reduce water translocation. Sapwood thickness was measured and sapwood growth layers were counted on these cores. Regression and Classification and Regression Tree (CART) analyses of sample data found no age‐related changes in cambial products. Phloem and xylem production appeared normal at all ages, with no evidence of cambial malfunction.
MEIOSIS WITH TELOMERIC PAIRING IN A HAPLOID OF TRITICUM MONOCOCCUM (x = 7)
Authors: Jackson R. C. , Nguyen Henry T. , Shang X. M.
Published: January 2018

In the microsporocytes of a haploid of Trilicum monococcum (x = 7), foldback and other nonhomologous pairing was observed at pachytene. At the diplotene equivalent stage of meiosis, nonhomologous chromosomes were connected by their telomeres in associations involving two to seven chromosomes. Telomeric connections were Feulgen‐positive for DNA and were disjoined by metaphase I. These connections may have resulted from earlier base‐pairing of repeated sequences of guanine‐rich telomere overhangs of nonhomologous chromosomes. Recent molecular studies of several widely divergent organisms have shown that all telomeres of nonhomologous chromosomes in a genome are identical, and telomere structure is conserved among widely divergent eukaryotes. Chromosome distribution at anaphase I fitted theoretical expectations of random movement of each of the seven chromosomes to one or the other of the two poles as did pollen fertility (stainability) resulting from such distribution. A single bivalent in 3.78% of the metaphase I cells provided evidence for a duplication in the genome of Triticum monococcum.
VARIATION OF NUCLEAR DNA CONTENT IN HELIANTHUS ANNUUS (ASTERACEAE)
Authors: Michaelson Martin J. , Price H. James , Johnston J. Spencer , Ellison John R.
Published: January 2018

Nuclear 2C DNA content was determined by laser flow cytometry for 13 diploid (2n = 34) lines (cultivated varieties and inbred lines) of Helianthus annuus. Mean DNA amount of second leaf nuclei varied from 6.01 to 7.95 pg (32%) among lines. Mean DNA content varied up to 19% within lines. Variability in mean DNA content exceeding 27% and 48% was detected among leaves from different nodes of plants of the open‐pollinated variety, Californicus, and the inbred line, RHA 299, respectively. The root tip and shoot tip nuclei of H. annuus have been reported to consist of a mixture of aneuploid (17 to 33 chromosomes) and diploid (34 chromosomes) cells, a condition called aneusomaty. Chromosome counts of root tips and an analysis of the distribution of DNA content of large numbers of nuclei from leaves indicate that aneusomaty either does not occur, or is not common, among the lines investigated. The intraspecific, intraline, and intraplant variation in DNA content in H. annuus support the concept that a sizable portion of a plant genome is unstable and subject to rapid changes in DNA amount.
A NEW SPECIES IN SECTION ARACHIS OF PEANUTS WITH A D GENOME
Authors: Stalker H. T.
Published: January 2018

Arachis glandulifera Stalker is a diploid (2n = 2x = 20) taxon in section Arachis native to eastern Bolivia. Plants of A. glandulifera have longer lateral branches than other taxa of section Arachis, an upright mainstem, prostrate lateral branches, and larger flowers and seeds than other wild species in the section. The pods are greatly reticulated. Glandular trichomes are present on vegetative plant parts and the peg. Intraspecific hybrids among four accessions are fertile and uniformly have ten bivalents in pollen mother cells. Three accessions had nearly identical karyotypes, while a fourth had subtelocentric chromosomes 6 and 9. Hybrids between A. glandulifera and two other diploid species of section Arachis were male‐sterile, and chiasmata frequencies ranged between 5.8 and 12.1 per cell. Attempts to hybridize the species with A. hypogaea failed. A new species description and D genomic classification are proposed for A. glandulifera, which is different from previously described A and B genomes of section Arachis.