bluuebunny/crossref_metadata_2025 huggingface dataset:
A NOVEL PATTERN OF APICAL CELL POLYPLOIDY, SEQUENTIAL POLYPLOIDY REDUCTION AND INTERCELLULAR NUCLEAR TRANSFER IN THE RED ALGA POLYSIPHONIA
Authors: Goff Lynda J. , Coleman Annette W.
Published: January 2018

Nearly a century ago, Rosenvinge published a now‐classic paper reporting nuclear transfer between cells ofPolysiphoniaduring secondary pit connection (SPC) formation. While reinvestigating this phenomenon, we discovered that the uninucleate apical cell, which is the progenitor of all cells in the plant, has many times (ca. 64–128 ×) the level of nuclear DNA characteristic of nuclei of gametes or mature pericentral cells. Via a regular sequence of cell divisions, the polyploid apical cell gives rise to tiers of cells, each composed of a number of pericentral cells which surround a single central cell. A large proportion of the nuclear divisions are not accompanied by DNA replication. Thus, as the number of nuclei within elongating pericentral cells increases, the DNA level of nuclei in these cells “cascades” down to the DNA level expected for the particular life history generation (i.e., gametophyte or tetrasporophyte). In mature pericentral cells, the number of nuclei is proportional to the volume of the cell. The pattern of nuclear division, reduction in ploidy level and the timing of intercellular nuclear transfer via SPC formation is regular and characteristic of a species. Nuclei transferred from one cell to an adjacent cell participate in the further nuclear divisions of the recipient cell. The degree of polyploidy in apical cells may determine the number of cells in a “determinant” branch or even the number of cells in “indeterminant” axes. In addition, the highly polyploid state of the germinating spore and its pattern of development may provide for the rapid initial growth so characteristic of this taxon.
BRANCHING PATTERNS OF COLUMNAR CACTI: INFLUENCES ON PAR INTERCEPTION AND CO2 UPTAKE
Authors: Geller Gary N. , Nobel Park S.
Published: January 2018

Field measurements and a computer model were used to determine how stem shape and arrangement of stems in space affect interception of photosynthetically active radiation (PAR) and CO2 uptake under otherwise optimal conditions for four species of columnar cacti (Carnegiea gigantea, Lophocereus schottii, Pachycereus pringlei, and Stenocereus thurberi). In simulations where the number of widely spaced stems was increased from 1 to 19 but plant volume remained constant, surface area and PAR interception increased, leading to 3‐fold increases in whole‐plant CO2 uptake. Increasing the distance between stems from 0 cm to infinity decreased self‐shading and increased predicted CO2 uptake 4‐fold. Stem length, diam, ribbing characteristics, and spine coverage also influenced PAR interception. The model indicated that the observed higher frequency of branches on the south side of the trunk of C. gigantea had only a slight, though positive, effect on CO2 uptake for single‐branched plants. Because of its greater surface area (A), a five‐stemmed plant of C. gigantea typical for a field site near Tucson, Arizona was predicted to have 52% more CO2 uptake than a single‐stemmed plant of the same volume (V). Although large A/V decreases water storage per unit transpiring area, whole‐plant CO2 uptake can be increased when A/V is increased by branching for these constant‐volume plants. However, the stems must be arranged to avoid excessive self‐shading and thus keep the area below PAR compensation small.
MORPHOLOGICAL CHANGES ACCOMPANYING THE TRANSITION FROM JUVENILE (ATMOSPHERIC) TO ADULT (TANK) FORMS IN THE MEXICAN EPIPHYTE TILLANDSIA DEPPEANA (BROMELIACEAE)
Authors: III William W. Adams , Martin Craig E.
Published: January 2018

Two distinct morphological forms characterize the ontogenetic development of the epiphytic bromeliad Tillandsia deppeana. Juveniles are characterized by a non‐impounding rosette of small, linear leaves covered with elaborate trichomes possessing a 4 + 8 + 16 + 64 shield cell pattern. The broader transitional leaves, which form an impounding rosette prior to the initiation of true adult leaves, also possess trichomes with the 4 + 8 + 16 + 64 cell pattern. Adult individuals have large, broad leaves with overlapping, sheathing bases which impound water and debris. These leaves have trichomes with shields exhibiting a 4 + 8 + 32 cell pattern. Trichome density is fairly uniform in the juvenile leaves with trichomes covering 100% of leaf surfaces, whereas in the adult leaves density is high at the base and diminishes significantly toward the apex. Stomatal density of both juvenile and adult leaves increases from the base to the apex, although this is most pronounced in the adults. Stomata in the adults are also arranged in longitudinal series parallel and abaxial to parallel rows of mesophyll tissue. The results of this study indicate that juveniles of T. deppeana are more similar morphologically to adult atmospheric‐type tillandsioid species than to the tank‐forming adults into which they eventually develop.
GRAFT INCOMPATIBILITY BETWEEN PEAR AND QUINCE: THE INFLUENCE OF METABOLITES OF CYDONIA OBLONGA ON SUSPENSION CULTURES OF PYRUS COMMUNIS
Authors: Moore Randy
Published: January 2018

The fresh weights of suspension cultures of pear (Pyrus communis) and quince (Cydonia oblonga) increased exponentially for 30 to 40 days after subculturing. Transferring pear cultures to media in which quince cultures had grown for 10 days resulted in a 70% inhibition of callus growth. Transferring quince cultures to media in which pear cultures had grown for 10 days resulted in less than a 20% inhibition of growth. Addition of the cyanogenic glycosides amygdalin and prunasin (as 50 ppm CN _) killed pear cultures, while growth of quince cultures was inhibited by only approximately 50%. Addition of 50 ppm CN‐ severely inhibited growth of both cultures. These results indicate that 1) suspension cultures of quince release factor(s) that significantly inhibit growth of pear cultures, 2) quince cultures are relatively unaffected by metabolites released by pear cultures, 3) the severe inhibition of pear growth by quince metabolites is mimicked by the addition of cyanogenic glycosides ubiquitous to vegetative portions of quince, 4) direct cellular contact is not necessary to elicit incompatibility between pear and quince, and 5) incompatibility between pear and quince need not be associated with any particular stage of graft development.
COMPARATIVE REPRODUCTIVE BIOLOGY OF ALPINE BIENNIAL AND PERENNIAL GENTIANS (GENTIANA: GENTIANACEAE) IN CALIFORNIA
Authors: Spira Timothy P. , Pollak Oren D.
Published: January 2018

Reproductive characteristics of three sympatric species of Gentiana exhibiting perennial and non‐perennial life histories were studied in alpine meadows of the White Mountains of California during three consecutive years. High fruit and seed set and the production of a relatively large number of seeds characterized the alpine biennials, Gentiana tenella and G. prostrata. In contrast, fruit and seed set were considerably reduced and yearly seed production was relatively low in the alpine perennial, G. newberryi. Successful seed production in the biennial species was a result of low rates of flower predation, self‐pollination, and the allocation of a comparatively high proportion of biomass to reproductive structures. Seed production in the perennial species was limited by high rates of flower predation, insufficient amounts of pollen reaching stigmas, an unusually late flowering period, and by the relatively small proportion of biomass allocated to reproduction.
ULTRACYTOCHEMICAL AND BIOCHEMICAL STUDIES OF PLASMA MEMBRANE ATPASE IN THE INDIVIDUAL PARTS OF THE MATURE, DORMANT SEED OF PISUM SATIVUM
Authors: Pollak Peggy E. , Mogensen H. Lloyd
Published: January 2018

The location and activity of a K+‐ATPase in mature, dormant peas were investigated using two ultracytochemical techniques, as well as biochemical assays of plasma membrane fractions from separate seed parts. Both the Wachstein and Meisel (1957) and the Ernst (1972) cytochemical methods showed plasma membrane‐associated reaction product located primarily on the exterior surfaces of the entire pea embryo, except for the stem apex and tip‐most cells of the radicle. No plasma membrane‐assocated reaction product was found in the seed coat, which typically consists of cells with degenerating protoplasts. Biochemical results showed the highest specific K+‐ATPase activity in the radicles (775 nmol Pi/mg protein/hr), followed by epicotyls (168 nmol Pi/mg protein/hr) and cotyledons (147 nmol Pi/mg protein/hr). It is proposed that the entire pea embryo may function in the active absorption of nutrients during the initial phases of germination. Additional functions of the enzyme may include cell wall loosening prior to cell elongation, regulation of cytoplasmic pH, and the generation of turgor.
GENETIC VARIATION AND ESTIMATES OF GENE FLOW IN CLARKIA SPECIOSA SUBSP. POLYANTHA (ONAGRACEAE)
Authors: Soltis Pamela S. , Bloom William L.
Published: January 2018

Estimates of interpopulational gene flow and the levels and distribution of genetic variation in Clarkia speciosa subsp. polyantha were obtained using enzyme electrophoresis. Eight enzymes encoded by 17 loci were analyzed. Nei's mean genetic identity was 0.96, indicating little genetic divergence among populations. Gene diversity statistics also suggest little heterogeneity among populations. Interpopulational gene flow, estimated according to Slatkin (1985), was fairly high, Nm = 3.9, probably accounting for the lack of differentiation among populations.
STRUCTURALLY PRESERVED FOSSIL PLANTS FROM ANTARCTICA: II. A PERMIAN MOSS FROM THE TRANSANTARCTIC MOUNTAINS
Authors: Smoot Edith L. , Taylor Thomas N.
Published: January 2018

An anatomically preserved moss from the late Permian of Antarctica is described. The fossils include delicate, unistratose leaves and axes with numerous rhizoids preserved in a silicified peat. Leaves exhibit a multi‐layered midrib of thick‐walled cells, and a lamina of rhomboidal cells that become more elongate toward the margin. The axes consist entirely of parenchyma with a central column of slightly smaller diam cells. Rhizoids are attached to the outer layer of the cortex and surround all the axes. These Permian fossils represent the oldest anatomically preserved bryophytes yet described from Gondwanaland and compare most closely with modern members of the Bryidae.
CHARRED WOOD STIMULATED GERMINATION OF TWO FIRE‐FOLLOWING HERBS OF THE CALIFORNIA CHAPARRAL AND THE ROLE OF HEMICELLULOSE
Authors: Keeley Sterling C. , Pizzorno Marie
Published: January 2018

Germination of the fire‐following chaparral herbs, Emmenanthe penduliflora (Hydrophyllaceae) and Eriophyllum confertiflorum (Asteraceae), previously has been shown to be stimulated by charred wood from the widespread chaparral shrub Adenostoma fasciculatum (Rosaceae). A series of investigations undertaken to clarify this effect gave the following results. Light is not required, but may enhance the response. The effect is not limited to A. fasciculatum but is produced by a wide variety of chaparral and non‐chaparral woods. Charring is not necessary; wood heated to 175 C for 30 min produced the same germination stimulation. The stimulatory compound is water soluble, effective within 24 hr exposure and active at 0.04 g/50 cc soil. Germination was stimulated by heated xylan, a hemicellulose, and by heated glucuronic acid, a common side chain of xylan and other hemicelluloses. Heating produced changes in the color and consistency of xylan and glucuronic acid. An oligosaccharin‐type molecule is postulated to be produced by heating xylan or other hemicelluloses with glucuronic acid side chains. Previously described oligosaccharins are derived from galactouronic acid and xyloglucan which are structurally and functionally related to compounds tested here.
FORMATION OF 2N MEGAGAMETOPHYTES IN DIPLOID TUBER‐BEARING SOLANUMS
Authors: Stelly David M. , Peloquin Stanley J.
Published: January 2018

Development of megaspores and megagametophytes was analyzed for several diploid potato clones (Solanum spp.) that exhibit either high (HI) or low (LO) seed set when crossed as female with the tetraploid cultivated potato S. tuberosum Group Tuberosa. The objectives were to determine the relationship between ploidy and diam of nuclei and nucleoli, and to determine the mechanism(s) and frequencies of 2n megagametophyte formation. Sizes of nuclei and nucleoli were found to depend on ploidy. For HI clones, the distributions of sizes indicated that doubling occurred during meiosis, and that 30 to 50% of the megaspores and megagametophytes were 2n rather than haploid. Omission of the second meiotic division led to formation of second division restitution (SDR) 2n megagametophytes. Only one HI clone had abnormal meiosis I, in addition to omission of meiosis II in some meiocytes; this clone seemed to produce not only 1n and 2n, but also 4n megagametophytes. The results indicated that high crossability of the HI clones as female with tetraploids largely was due to formation of SDR 2n megagametophytes, a finding strongly supporting the hypothesis that sexual polyploidization is the driving force behind polyploidization of Solanums. The results contribute to increasing evidence that meiotic mutants and abnormalities play an important role in angiosperm evolution.
REPRODUCTIVE ECOLOGY OF JEFFERSONIA DIPHYLLA (BERBERIDACEAE)
Authors: Ronsheim Margaret L. , Swartz Kathryn R.
Published: January 2018

The reproductive ecology of Jeffersonia diphylla (L.) Pers. (Berberidaceae) was investigated by studying its breeding system, ovule production, seed set, seed dispersal by ants and seed predation by rodents. This species flowers early in the spring and is facultatively autogamous. In a typical year fruit and seed set is high (90%), however, freezing temperatures from late spring frosts in 1983 and 1985 resulted in low fruit set (7% and 20%, respectively), and reduced seed set in those flowers that produced fruit. No differences in seed set between selfed and outcrossed flowers were observed over a two‐yr period (1983–84). Ovule number per capsule increased with plant size as measured by leaf number. Seed set and seed wt were unaffected by leaf number unless leaves were removed after flowering was initiated. Jeffersonia diphylla is myrmecochorous. Ants removed seeds faster when seeds were placed in areas where J. diphylla plants were absent, suggesting that dispersal within J. diphylla populations is ant limited. Moreover, fresh (1 day old) seeds were removed by ants faster than 3 day old seeds. Seed predation by rodents prior to dehiscence from capsules is heavy in large populations (85–90%), and apparently negligible in small populations. Predation of seeds that are released from capsules is heavy (approx. 66%), particularly at night. Overall, seed predators consume about 96% of the seed crop in well established populations, but probably much less in small young populations. Hence, seedling recruitment is likely to be higher in small populations, whereas ramet production from rhizomes is the primary mode of propagation in large ones. The evolution of autogamy, early flowering, and myrmecochory are discussed in light of the results of this study.
GENE EXCHANGE IN LOBLOLLY PINE: THE RELATION BETWEEN POLLINATION MECHANISM, FEMALE RECEPTIVITY AND POLLEN AVAILABILITY
Authors: Greenwood Michael S.
Published: January 2018

The pollination process in loblolly pine has been examined over several years, both in the field (seed orchards) and experimentally on greenhouse‐grown material. Female strobili are receptive to pollination for periods of a wk or more. Initially, background pollen from outside the seed orchard is the main source of pollen but as peak receptivity approaches, pollen from the stand itself predominates especially in older orchards. Consequently, strobili can receive pollen both from outside the orchard as well as from within. The pollen lands on the micropylar horns where it is transferred through the micropyle onto the nucellus by either rainfall or the pollen drop, whichever comes first. Since the pollen drop does not occur until the latter part of the receptive period, rainfall is the most likely transfer agent and pollen flotation is vital if rain occurs. Early arriving pollen does not appear to have an advantage over later arriving pollen for uptake onto the nucellus, even if rain follows the first pollination immediately. Therefore, total pollination of the strobilus can result from both distant and nearby pollen sources.
GENETIC POLYMORPHISM IN THE MORPHOLOGICALLY REDUCED DWARF MISTLETOES (ARCEUTHOBIUM, VISCACEAE): AN ELECTROPHORETIC STUDY
Authors: Nickrent Daniel L.
Published: January 2018

Arceuthobium is a well defined genus of obligate parasites of conifers. Assessment of taxonomic and phylogenetic relationships in this group is difficult owing to morphological reductions and complex host relationships. In the present study, genetic relationships within and among 19 taxa were examined using starch gel electrophoresis of triploid seed endosperm tissue. Allelic frequency data for eleven polymorphic loci were derived from analysis of 40 natural populations collected from the U.S. and Mexico. The genus showed remarkably high levels of genetic diversity: averaged across the 19 taxa, 66.7% of the loci were polymorphic with an average of 2.23 alleles per locus. This level of polymorphism is approximately double the average value reported for many dicotyledons and stands in contrast to the overall uniform morphology of these parasites.

Unweighted pair group cluster analysis (UPGMA) of genetic similarity measures was conducted for all sampled populations and the results compared to a phenetic system of classification for the genus. Similarities between the two studies include the recognition of two subgenera based upon the segregation of the verticillately branched Arceuthobium americanum from the remainder of the taxa examined. Analysis of isozyme data supported a grouping of six taxa: A. vaginatum ssp. cryptopodum, A. vaginatum ssp. durangense, A. gillii, A. rubrum, A. divaricatum, and A. douglasii. The placement of the latter three taxa in other groups by phenetic criteria provides evidence for molecular divergence not seen using morphological features. The Campylopodum group of taxa comprised eleven members that were linked at similarity values of 80% or greater. Populations were not unambiguously grouped according to species as defined by the phenetic study or at similarity levels comparable to other well defined species in this study. This group is either not reproductively isolated or molecular differentiation is cryptic due to rapid adaptive radiation onto numerous host tree species.
POLLEN TETRADS IN STENOMESSON ELWESII (AMARYLLIDACEAE)
Authors: Meerow Alan W. , Dehgan Nancy B. , Dehgan Bijan
Published: January 2018

Pollen tetrads within Amaryllidaceae are reported for the first time for Stenomesson elwesii. Tetrads were examined with light and scanning and transmission electron microscopy. The tetrads are tetragonal in shape. Tetrad‐members are rounded‐triangular in equatorial view and elliptic in polar view. Average polar diam is 50.1 μm; average longest equatorial diam is 62.5 μm. Morphology of the aperture is monosulcate. Exine sculpturing of the intectate pollen is gemmate. Systematic implications are briefly discussed.
SEM COMPARISON OF FRUITS OF A SEAGRASS, HALODULE (CYMODOCEACEAE), FROM AUSTRALIA AND TEXAS
Authors: Bragg Louis H. , McMillan Calvin
Published: January 2018

Fruits of Halodule were collected from marine sediments in Shark Bay, Western Australia, and in Laguna Madre, Texas, and compared using scanning electron microscopy. The fruits of the Australian collection had a more deeply furrowed wall surface, and the fruits of the Texas collection had a more prominent stylar beak. The fruits of both collections had walls that were composed of irregularly interlocking cells, each with multilayered, concentric cell walls. The fruit wall separates into nearly equal halves along a cleavage line composed of cells that are not interlocked. The seed coats are composed of flattened cells with annular thickenings and the oblong hypocotyls are composed of large, polygonal cells that contain starch grains. The cotyledon and plumule are folded into a hypocotylary invagination along the line of wall separation. A radicle hump or short radicle develops during germination in seawater. Although the taxonomy of Halodule has been based on a vegetative feature, the leaf tips, fruit differences may be of diagnostic value.
INDETERMINATE GROWTH OF LEAVES IN GUAREA (MELIACEAE): A TWIG ANALOGUE
Authors: Steingraeber David A. , Fisher Jack B.
Published: January 2018

Leaves of seed plants are generally characterized as organs of determinate growth. In this regard, Guarea and related genera seem unusual in that the pinnately compound leaves of these plants contain a bud at their tip from which new pinnae expand from time to time. Previous studies (based upon superficial examinations of leaf‐tip buds) have produced contradictory conclusions regarding how long the leaf apex remains meristematic and produces new pinna primordia. In order to determine whether leaf development in Guarea is truly indeterminate, we microscopically examined leaf‐tip buds of G. guidonia and G. glabra. In both species, the leaf apex remains meristematic and continues to produce new pinna primordia as the leaf ages. Unexpanded leaves of G. guidonia contained an average of 23 pinna primordia, while the oldest leaves we examined had initiated an average of 44 total pinnae. In G. glabra, unexpanded leaves contained 8 pinnae, whereas an average of 28 pinnae had been initiated on the oldest leaves. These results indicate that leaf development in Guarea is truly indeterminate. Periodic examination of individual intact leaves indicated that the leaves commonly continue their growth for 2 or more years (observed maximum = 51 months). As new leaflets are initiated at the shoot apex (and subsequently expand in rhythmic flushes), older (basal) leaflets may abscise. In addition, the petiole and rachis of the leaf thicken and become woody as a result of the activity of a vascular cambium. Guarea leaves therefore seem to function as the analogue of a typical twig (stem) in general habit as well as in their indeterminate apical growth and secondary thickening.
GENETIC EVIDENCE FOR DIPLOIDY IN EQUISETUM
Authors: Soltis Douglas E.
Published: January 2018

Sporophytes and gametophytes of Equisetum arvense, E. laevigatum, and E. telmateia were analyzed using enzyme electrophoresis to estimate isozyme number. Despite their uniformly high chromosome numbers (2n = 216), these three species exhibited isozyme numbers typical of diploid seed plants for the enzymes AAT, ADH, ALD, GDH, [NADP]IDH, LAP, MDH, [NADP]ME, PGI, PGM, SkDH, and 6PGDH. All three species exhibited an additional isozyme for TPI. There is, therefore, no genetic evidence for low base numbers such as x = 9 and x = 12 suggested for Equisetum. Intact chloroplasts were isolated from E. arvense and the chloroplast extract compared electrophoretically to whole plant extracts. The single enzymes observed for LAP, GDH, [NADP]IDH, and [NADP]ME were absent from the chloroplast extract. Isozymes AAT‐1, ALD‐2, MDH‐3, PGI‐1, PGM‐2, SkDH‐2, 6PGDH‐2, TPI‐2, and TPI‐3 were active in the chloroplast fraction; 6PGDH‐1, PGI‐2, PGM‐1, and TPI‐1 were lacking from the chloroplast fraction and were considered cytosolic. Isozymes AAT‐2, MDH‐1, MDH‐2, MDH‐4, and SkDH‐1 were also lacking from the chloroplast fraction but because AAT, MDH, and SkDH have been reported from several subcellular compartments, their localization is unknown. These findings indicate that isozymes in Equisetum species are subcellularly compartmentalized as has also been demonstrated for homosporous ferns, gymnosperms, and angiosperms.
SCANNING ELECTRON MICROSCOPY OF THE UREDINIAL STAGE OF PUCCINIA CANALICULATA ON YELLOW NUTSEDGE, CYPERUS ESCULENTUS (CYPERACEAE)
Authors: Wetzstein Hazel Y. , Phatak Sharad C.
Published: January 2018

The ultrastructure of the uredinial stage of the rust fungus, Puccinia canaliculata (Schw.) Lagerh., on yellow nutsedge (Cyperus esculentus L.) is described using scanning electron microscopy. This rust has been proposed as a potential biological control agent against this serious weed species. Urediniospores are ellipsoid to ovoid, and echinulate with the spines distributed over the surface except at basal portions. Spines are in circular depressions, encircled by annuli. Germination is through one of two equatorial germ pores. Germ tube growth is primarily perpendicular to the longitudinal orientation of epidermal cells. Appressoria completely cover stomata. Uredinia develop within linearly aligned intercellular cavities in substomatal regions. Uredinia become erumpent, exposing pedicellate urediniospores and smooth paraphyses scattered throughout the sori. Uredinia are nonperidiate.
QUANTITATIVE ULTRASTRUCTURAL CHANGES IN TUNICA AND CORPUS CELLS OF THE SHOOT APEX OF NICOTIANA TABACUM DURING THE TRANSITION TO FLOWERING
Authors: Kanchanapoom Malee L. , Thomas Judith F.
Published: January 2018

Very distinct ultrastructural differences in organelle composition in the cells of tunica and corpus layers in the central part of shoot apices of the quantitative short‐day plant, Nicotiana tabacum L. cv. NCTG‐22, were observed during the 17‐day transition period from vegetative to reproductive growth. Under short‐day conditions, changes in the tunica layer included the eventual reduction in cross sectional areas of cells, nuclei, vacuoles, and proplastids, while mitochondrial cross sectional area increased throughout the course of the induction period. From the measurable changes of several of the organelles, tunica cells appeared to respond to induction sooner than corpus cells. After one exposure the relative volume of tunica cell nuclei in short‐day plants was larger than in long‐day controls, but thereafter became smaller than controls. Enlargement of nuclei profiles in corpus cells in response to induction did not occur until after seven exposures, subsequently decreasing below control values. In addition, after one inductive exposure, vacuolar density was reduced in the tunica cells of induced meristems, yet at the same time in corpus cells vacuole density increased slightly and decreased only much later. An early increase in proplastid density in tunica cells of induced meristems was a further indication that these cells responded sooner than corpus cells to the photoperiodic stimulus. The changes in organellar composition of tunica and corpus cells, including nuclei, vacuoles, and proplastids, suggests that each layer was independent in readjustment of rate of growth towards the new pattern of development. That tunica cells seemed to respond sooner than corpus cells to the inductive signal may indicate that, at least in this species, the epidermis (i.e., tunica) plays a dominant role in controlling the initial morphogenetic change.
CHLOROPLAST DNA VARIABILITY AMONG LINUM SPECIES
Authors: Coates David , Cullis Christopher A.
Published: January 2018

We have compared the chloroplast DNA maps of a selection of Linum species, using recombinant DNA probes derived from L. usitatissimum chloroplast DNA. The heterologous probes have allowed us to construct physical maps for seven other Linum species. The chloroplast DNAs from two other species, L. flavum and L. tenuifolium, were so divergent that restriction maps could not be derived by this method. Analysis of the differences between the chloroplast DNAs has produced a phylogeny separating the species into two groups. These groups are coincident with previous taxonomic groupings and consist of L. perenne‐related and non‐related species. The major difference between the chloroplast DNAs of the two groups is a 13‐kilobase pair segment near an inverted repeat/large single copy region boundary, which is present in the perenne‐group species and absent from the non‐perenne group species. In addition, we have identified a mutational hotspot analogous to that found in Nicotiana species chloroplast DNAs (Tassopulu and Kung, 1984). Among the species examined, the amount of base pair substitutions approaches 14% for the sites examined.
STRUCTURE OF CLONES OF NORTHERN PRICKLY ASH (XANTHOXYLUM AMERICANUM)
Authors: Reinartz James A. , Popp James W.
Published: January 2018

Clones of northern prickly ash (Xanthoxylum americanum) were excavated to expose their horizontal root structure and pattern of vegetative spread; stems and horizontal roots were mapped. Most of the root system was very shallow (< 10 cm deep). Stems and roots were aged from annual rings. The four clones studied ranged in age from 26 to 33 yrs. All root connections between shoots were maintained for the life of the clone. Clones were found to be single individuals in a physical as well as a genetic sense. There was virtually no overlap of adjacent clones; horizontal roots turned away or stopped growing when the border of another clone was encountered. No differences were found between male and female clones in above‐ or below‐ground morphology. There was, however, a great deal of intrasexual variation among clones.
EFFECT OF SOIL SURFACE TOPOGRAPHY AND LITTER COVER ON THE GERMINATION, SURVIVAL, AND GROWTH OF MUSK THISTLE (CARDUUS NUTANS)
Authors: Hamrick J. L. , Lee Janet M.
Published: January 2018

In natural populations of musk thistle (Carduus nutans L.) germination occurs over several months in the fall and spring. To better understand the physical environmental mechanisms that influence this pattern of germination, a greenhouse experiment was established consisting of ten treatments in which soil surface topography and the amount and consistency of litter cover was varied. Significant differences occurred among the treatments for germination percentage, levels of mortality and individual growth rates. Optimum levels of germination, survival and growth occurred in treatments that provided microhabitats with reduced evaporation. Treatments with cracks or moderately irregular surface topographies provided the best conditions. A light covering of litter benefited establishment and growth but thick layers of litter prevented seeds from reaching the soil surface and reduced germination and establishment. These results were consistent with what is known about the germination ecology of musk thistle in natural populations.
DEVELOPMENTAL ANATOMY OF THE STEM OF WELFIA GEORGII, IRIARTEA GIGANTEA, AND OTHER ARBORESCENT PALMS: IMPLICATIONS FOR MECHANICAL SUPPORT
Authors: Rich Paul M.
Published: January 2018

Changes in stem anatomy with radial position and height were studied for the arborescent palms Welfia georgii, Iriartea gigantea, Socratea durissima, Euterpe macrospadix, Prestoea decurrens, and Cryosophila albida. Vascular bundles are concentrated toward the stem periphery and peripheral bundles contain more fibers than central bundles. Expansion and cell wall thickening of fibers within vascular bundles continues throughout the life of a palm, even in the oldest tissue. Within individual vascular bundles, the fibers nearest the phloem expand first and fiber cell walls become heavily thickened. A front of expanding fibers moves outward from the phloem until all fibers within a vascular bundle are fully expanded and have thick cell walls. Peripheral vascular bundles differentiate first and inner bundles later. In the stem beneath the crown, vascular bundles and ground tissue cells show little or no size increase, but marked cell wall thickening during development for Welfia georgii. Beneath the crown, diameters of peripheral vascular bundles increase more than twofold for Iriartea gigantea, while diameters of central bundles do not increase. In Iriartea stems, ground tissue cells at the periphery elongate to accommodate expanding vascular bundles and cell walls become thickened to a lesser degree than in fibers; central ground tissue cells elongate markedly, but cell walls do not become thickened; and large lacunae form between central parenchyma cells. For Iriartea, Socratea, and Euterpe, sustained cell expansion results in limited, but significant increases in stem diameter. For all species, sustained cell wall thickening results in dramatic increases in stem stiffness and strength.
ROLES OF POLLEN AND OVARY AGE IN FOLLICLE PRODUCTION OF THE COMMON MILKWEED ASCLEPIAS SYRIACA
Authors: Morse Douglass H.
Published: January 2018

Using cross‐pollination experiments, pollinia viability of the common milkweed Asclepias syriaca L. (Asclepiadaceae) did not change significantly over the five‐day life of the flowers, but stigma receptivity decreased over threefold over this period. During most of the season pollinators inserted over 90% of their pollinia into flowers during the first two days following anthesis. However, pollinators were scarce during the first few days of flowering, and they inserted over 60% of their pollinia into flowers three or more days old. This behavior potentially decreased outcrossing success and increased the relative male contribution of the flowers. Pollinator visitation patterns may play an important role in determining the functional sexuality of these plants.
STRUCTURE OF THE EUGLENOID STORAGE CARBOHYDRATE, PARAMYLON
Authors: Kiss John Z. , Vasconcelos Aurea C. , Triemer Richard E.
Published: January 2018

Paramylon, the euglenoid storage carbohydrate, was studied by transmission electron microscopy (thin sectioning, negative staining, and freeze‐etching) and scanning electron microscopy in order to develop a three‐dimensional model of paramylon structure. The paramylon granule is a membrane‐bound crystal composed of two types of segments, rectangular solids and wedges. The segments meet in the central region of the crystal. Both the segments and the granule as a whole are composed of several layers. Fibers traverse the paramylon granule in an overall concentric pattern. These fibers appear to be composed of bundles of microfibrils, which measure 4.0 nm in diameter and are similar to cellulose elementary microfibrils.
MORPHOLOGY, INHERITANCE, AND EVOLUTIONARY SIGNIFICANCE OF SEX REVERSAL IN TRIPSACUM DACTYLOIDES (POACEAE)
Authors: Dewald C. L. , Burson B. L. , de Wet J. M. J. , Harlan J. R.
Published: January 2018

Inflorescences of Tripsacum dactyloides (L.) L. (Andropogoneae) are characterized by single female spikelets at one to several basal nodes and paired male spikelets at several nodes above them on each raceme. Female spikelets are one‐flowered and male spikelets are two‐flowered. A sex form variant was found in a wild population in north central Kansas and classified as T. dactyloides (L.) L. forma prolificum Dayton et Dewald. The variant of this native distant relative of maize (Zea mays L. spp. mays) differs from the normal form by having both pistillate and perfect rather than staminate spikelets in the terminal (tassel) portion of the inflorescence and by having two functional pistillate florets in the basal spikelets instead of one. A recessive major gene at a single locus regulates the change of the inflorescence from monoecious to gynomonoecious.
WOOD ANATOMY OF THE AMERICAN FRANKENIAS (FRANKENIACEAE): SYSTEMATIC AND EVOLUTIONARY IMPLICATIONS
Authors: Whalen Molly A.
Published: January 2018

Results of a comparative wood anatomical survey of the American frankenias are presented. The eleven species examined are woody perennials occurring almost exclusively in arid and semiarid regions and on saline and gypseous soils. The secondary xylem of all species is highly specialized and is characterized by libriform fibers, vessel elements with simple perforation plates, and the absence of rays. Axial elements of all species are quite small. A number of unusual features, e.g., anomalous secondary growth and formation of interxylary cork, were observed in some species. Nonfibrous woods have evolved independently in two species of reduced stature and contrast markedly with the highly fibrous woods of most species. Woods of the American frankenias are compared with those of the Tamaricaceae. The systematic and evolutionary implications of interspecific variation in both qualitative and quantitative features are discussed. There is a general tendency for dimensions of the axial wood elements to be positively associated and to decrease with decreasing plant height. In general, differences in wood anatomy more strongly reflect differences in plant growth form and size than phylogeny.
FLORAL DEVELOPMENT IN MANGROVE RHIZOPHORACEAE
Authors: Juncosa Adrian M. , Tomlinson P. B.
Published: January 2018

The flowers of mangrove Rhizophoraceae (tribe Rhizophoreae) are adapted to three different pollination mechanisms. Floral development of representative species of all four genera suggests that the ancestral flower of the tribe was unspecialized, with successively initiated whorls of separate sepals, petals, antisepalous stamens, and antipetalous stamens; at its inception, the gynoecium had a united, half‐inferior ovary and separate stigmatic lobes. This developmental pattern is found in Rhizophora mangle (wind‐pollinated) and Ceriops decandra (insect‐pollinated). In Kandelia, all floral organs distal to the sepals are initiated simultaneously, and there has apparently been an evolutionary amplification in the number of stamens to about six times the number of petals. Explosive pollen release evolved independently in C. tagal and in Bruguiera. In the former, all stamens belong to one whorl and arise simultaneously upon a very weakly differentiated androecial ring primordium. In Bruguiera, the androecial ring is pronounced, and two whorls of stamens arise upon it; the primordia of the antisepalous whorl arise first but are closer to the center of the apex than the antipetalous stamen primordia. The antisepalous stamens bend toward and are enclosed by the petals early in development. In all genera, the inferior ovary develops by zonal growth of receptacular tissue; additional intercalary growth above the placenta occurs in Bruguiera. In general, floral specialization is accompanied by an increase in the width of the floral apex compared to the size of the primordia, increasing fusion of the stylar primordia, and decreasing prominence of the superior portion of the ovary. Apparent specializations of petal appendages for water storage, including the presence of sub‐terminal hydathodes (previously unreported in any angiosperm), were found in two species in which flowers remain open during the day but were absent from two species normally pollinated at night or at dawn. Distinctive tribal characteristics that may aid in phylogenetic analysis include the mode of development of the inferior ovary; the aristate, bifid, usually fringed petals that individually enclose one or more stamens; the intrastaminal floral disc; and the initially subepidermal laticiferous cell layer in the sepals and ovary.
ASSESSMENT OF THE GENOMIC SYSTEM OF CLASSIFICATION IN THE TRITICEAE
Authors: Baum Bernard R. , Estes James R. , Gupta Pushpendra K.
Published: January 2018

We have made an assessment of the genomic system of classification recently proposed for the Triticeae as a whole by Löve and for perennial Triticeae by Dewey. Limitation of genomes as a measure of similarity were discussed using examples where pairing may fail even between highly similar genomes and where morphology is a better indicator of evolutionary relationships. We found that only two of the 41 characters extracted from Löve's descriptions were described for 36 of the 37 genera, and most characters were described for less than half of the genera. Thus the descriptions were incomplete. This was further illustrated when a data matrix was created using 15 most frequent characters. A majority rule consensus tree was computed using the program BOOTM in Felsenstein's PHYLIP package, and we found that many operational taxonomic units or OTUs (the genomically defined genera) could not be resolved on the tree; homoplasy occurs throughout the tree, synapomorphies were parallel in many branches, and only one character (flowers, perfect/rudimentary) was an apomorphy leading to Elymus. We recommended that all the attributes be considered a priori with equal weight without attributing supremacy to genome, thus enabling the genera to be described, circumscribed, and arranged in a meaningful system of classification.
INDUCED POLLEN TUBE DIRECTIONALITY
Authors: Mulcahy Gabriella Bergamini , Mulcahy David L.
Published: January 2018

Pollen grains placed within longitudinal cuts in styles germinate and produce pollen tubes which grow equally well towards the stigma or the ovary. If there are simultaneous stigmatic pollinations, the growth of the intrastylar pollen tubes toward the stigma is significantly impeded. This observation indicates the presence of an influence which may or may not be related to pollen tube tropism, one which is inducible rather than constitutive.
EFFECTS OF SINGLE AND MULTIPLE EXPOSURES OF FERULIC ACID ON THE VEGETATIVE AND REPRODUCTIVE GROWTH OF PHASEOLUS VULGARIS BBL‐290
Authors: Waters Elizabeth R. , Blum Udo
Published: January 2018

Phaseolus vulgaris BBL‐290 plants were grown in growth chambers in the Southeastern Plant Environment Laboratory and exposed to either single (at seedling, flower, or podfill) or multiple (biweekly or weekly) treatments of ferulic acid (FA). In the first experiment, plants were harvested one week after FA treatment (0, 1.0, 2.0 mM) and at final harvest (56 days old). FA delayed leaf expansion during the seedling and flowering stages. The total plant leaf area and the plant dry weight of plants treated with 1.0 and 2.0 mM FA as seedlings were reduced one week after treatment by 38–48%. The total plant leaf area and the plant dry weight of plants treated at flowering with 2.0 mM FA were reduced by 25% one week after treatment. Treatment with 2.0 mM FA at podfill caused the senescence and abscission of older leaves and reduced total plant leaf area, plant dry weight and mean pod dry weight by 54, 40, and 48%, respectively, one week after treatment. The plants treated at the seedling and flowering stages recovered by final harvest. In a subsequent experiment, FA (0, 0.50, 1.0, 1.5 mM) reduced total plant leaf area at the seedling and flowering stages but not at podfill. The youngest expanding leaves were most sensitive to FA at flowering. The leaf area of these leaves was reduced by 35 and 25%, one and two weeks after treatment, respectively. Their absolute growth rates were reduced from 31 to 56% one week after treatment at flowering. Their relative growth rates were reduced by 50% one week after treatment. Growth rates then recovered within two weeks after treatment. In the final experiment, biweekly exposures of FA (0.25, 0.50, 0.75, 1.0) reduced total plant leaf area but did not affect any other growth parameters. Weekly exposures of FA (0.25, 0.50, 0.75, 1.0) reduced total plant leaf area up to 34%, absolute growth rate up to 58%, leaf number up to 31% and pod number up to 58%. As the frequency of exposure to FA increased, the concentration necessary to affect bean plant growth and development decreased.
A WOODY LYCOPSID STEM FROM THE NEW ALBANY SHALE (LOWER MISSISSIPPIAN) OF KENTUCKY
Authors: Cichan Michael A. , Beck Charles B.
Published: January 2018

A lycopsid axis from the New Albany Shale (Sanderson Formation) of Kentucky is described. The stem, which branches dichotomously, is 45 mm in diameter and is characterized by a relatively narrow parenchymatized protostele, a 3.0 mm‐thick cylinder of secondary xylem, a tripartite cortex, and a periderm that is more than 5.0 mm thick. The secondary xylem is composed of uniseriate and biseriate vascular rays and narrow tracheids with scalariform wall thickenings on both radial and tangential walls. The periderm is characterized by elongate, thick‐walled cells, some of which broaden tangentially in the outer part of the tissue forming zones that appear wedge‐shaped in cross section. Surface features of the axis, including leaf bases, are not preserved. The stem is tentatively regarded as a member of the Lepidodendrales in accordance with the numerous anatomical characters that it shares with more recent representatives of the order. Because the external morphology is not known, however, the possibility exists that the axis corresponds to a protolepidodendralean taxon currently known only from compression and/or impression remains or some other nonlepidodendralean plant that produced secondary xylem. The extremely narrow profile of the secondary xylem tracheids (relative to other arborescent lycopsids) is interpreted as evidence that the plants grew in a habitat that was substantially drier than the Upper Carboniferous coal swamps.
DEVELOPMENT OF OMNIAPERTURATE POLLEN IN TRILLIUM KAMTSCHATICUM (LILIACEAE)
Authors: Takahashi Masamichi
Published: January 2018

Ultrastructural changes during omniaperturate pollen development in Trillium kamtschaticum Pall, was examined using transmission electron microscopy. The pollen mother cells are not enveloped within a thick callosic wall. The microspores resulting from successive meiosis are divided by scanty deposition of callosic wall in the tetrad. A primexine/exine template is not recognizable within the tetrad during formation of exinous components. Preexinous globules, originating from vesicles in the callosic wall, accumulate electron‐dense materials and develop into exinous globules. The preexinous globules have ca 10 nm wide contacts with tilted and invaginated plasma membrane of the microspore within the callosic wall. After dissolution of the callosic wall, the microspores separate and mitosis subsequently leads to the formation of a generative cell and vegetative cell encased in a loose aggregation of developing exinous globules. When the generative cell is at the pollen grain surface, the channeled zone is initiated at the opposite side of the microspore on the surface of the vegetative cell. Just before pollen maturity, a new layer develops under the channeled zone. Thus, development of the omniaperturate pollen grains of T. kamtschaticum involves some processes that are distinct from those of Canna and Heliconia and some that are similar.
ANALYSIS OF EXTENSION AND CURVATURE DURING THE GRAVIRESPONSE IN LEPIDIUM ROOTS
Authors: Selker Jeanne M. L. , Sievers A.
Published: January 2018

Intact roots of Lepidium sativum were photographed at 1.5‐ to 6‐min intervals before and after being tilted from a vertical to a horizontal position. Relative extension rates were calculated for segments of the root by measuring the rate of movement of charcoal particles on the surface of the root. Curvature was measured at points separated by 0.8 mm, from the tip to the root hair zone. For the first hour after the root was tilted to a horizontal position, the relative extension rate for the side of the root producing the outer side of the curve is higher than that during straight growth. The relative rate for the inner side falls to near zero during the first hour in the horizontal position. There is thus a positive gradient in extension rate from the inner to the outer side of the curve. For most of the second hour, the two sides have approximately equal relative rates of extension. In the last 12 min of the second hour, as the root tip is moving the final distance to a vertical position, the rate on the inner side shows a high extension rate. The gradient in extension rate from the inner to the outer side of the curve has thus become negative during the second hour. This reversal in the extension gradient is necessary to prevent the root from continuing to grow in a circle past the point where the root tip is vertical. Curvature reaches maximal values of 0.7 mm‐1 to 1.2 mm‐1 for the inner side and 0.5 mm‐1 to 0.7 mm‐1 for the outer side. (Units express reciprocals of the radius of curvature in mm.) Two locations where curvature is highest are separated by a flatter region. The charcoal particles marking specific locations on the root surface move away from the tip at the same rate as the features of the curvature pattern.