bluuebunny/crossref_metadata_2025 huggingface dataset:
POLLINATION BIOLOGY OF PHYSALIS VISCOSA VAR. CINERASCENS (SOLANACEAE)
Authors: Sullivan Janet R.
Published: January 2018

Physalis viscosa var. cinerascens is a self‐incompatible, herbaceous perennial which occurs in disturbed or open habitats in the south‐central United States and eastern Mexico. The plants are low‐growing and the pendant blossoms are often obscured by the foliage. In Oklahoma the species blooms from April through October. The flowers are yellow with dark purple or brown maculations in the center and a mat of white hairs in the throat. Nectar is produced in small quantities at the base of the ovary and pollen is present in copious amounts. The pollinators are solitary bees which visit the flowers for nectar and pollen. Perdita halictoides is the primary pollinator and is oligolectic on Physalis.
AEROBIOLOGY OF SYMPLOCARPUS FOETIDUS: INTERACTIONS BETWEEN THE SPATHE AND SPADIX
Authors: Camazine Scott , Niklas Karl J.
Published: January 2018

The aerobiology of the skunk cabbage, Symplocarpus foetidus (l.) Nutt., is examined as a factor contributing to efficient pollination and temperature regulation around the spadix. Field measurements show that the compass orientation of the asymmetrical opening of the spathe is random, while wind tunnel studies reveal that similar patterns of airflow are generated around the spadix regardless of the orientation of the spathe opening to the direction of airflow. Temperature measurements within a model of the inflorescence reveal that airflow around the spathe effectively maintains heat generated by the spadix, even at airflow speeds of 1.5 m/s. These results are discussed as exaptations of the spathe for pollination and for temperature regulation in sub‐freezing weather.
POLLEN TUBE GROWTH WITHIN VEGETATIVE TISSUES OF CALLITRICHE (CALLITRICHACEAE)
Authors: Philbrick C. Thomas
Published: January 2018

Unisexual flowers of Callitriche heterophylla and C. palustris are of two types based on the degree to which they develop. Morphologically underdeveloped but functionally mature flowers occur on stems that grow completely submerged or stranded out of water. Under such conditions sexual reproduction is very unusual; pollen grains germinate in the intact anther and the pollen tubes grow down the filament, through vegetative tissue across to the pistillate flower and up into the ovary from the base. Pollen tubes may also grow through vegetative tissue to pistillate flowers across the stem at the same node, and up the stem from the staminate flowers at one node to pistillate flowers above. Morphologically mature flowers develop on stems when they reach the water surface and a floating rosette of leaves forms. In these flowers fertilization can take place via pollen tube growth through vegetative tissue as described above, or in the manner usually ascribed to angiosperms. Thus, depending upon the developmental form of the flower, fertilization takes place either with or without pollination. The current report represents the first description of pollen tubes traversing large segments of vegetative tissue within a plant to effect selffertilization.
THE EVOLUTION OF SELF‐POLLINATION IN GRANITE OUTCROP SPECIES OF ARENARIA (CARYOPHYLLACEAE). IV. CORRELATED CHANGES IN THE GYNOECIUM
Authors: Wyatt Robert
Published: January 2018

Intraspecific variation in gynoecial characters was analyzed by SEM for nine populations of Arenaria uniflora, a winter annual endemic to rock outcrops in the southeastern United States. Style lengths in self‐pollinating populations, formerly called A. alabamensis, were significantly shorter than in outcrossing populations, and style length showed a very strong correlation (r = 0.97) with outcrossing potential as assessed by degree of protandry. Selfers were also characterized by the production of fewer but longer stigmatic papillae. Papillae extended to the base of the style and diverged from all sides. Outcrossers had longer styles with dense but short papillae, mostly restricted to the upper surface of the style and lacking at its base. Styles also were observed to curl downward in outcrossers. These fine‐scale changes appear to enhance the effectiveness of plants as either outcross‐pollen or self‐pollen receivers.
ABSCISIC ACID INDUCES LAND FORM CHARACTERISTICS IN MARSILEA QUADRIFOLIA L.
Authors: Liu Bai‐Ling Lin
Published: January 2018

In aseptically cultured rhizome segments of the aquatic fern Marsilea quadrifolia, the addition of abscisic acid (ABA) to the liquid medium induced development of morphological characteristics distinctive to the land form of the plant. The land‐form characteristics induced by ABA included a change in leaf morphology, an increase in the surface area of leaflets, differentiation of stomata and trichomes, elongation of petioles and roots, development of lateral roots, shortening of rhizome, and reduction in the number of leaves and roots formed on each plant.
DEVELOPMENTAL CHANGES IN ANATOMY, MORPHOLOGY AND BIOCHEMISTRY OF LAYIA PLATYGLOSSA EXPOSED TO ELEVATED CARBON DIOXIDE
Authors: Omer Lucy St. , Horvath Steven M.
Published: January 2018

Studies investigating developmental anatomical changes in Layia platyglossa exposed to four CO2 levels—0.03, 0.07, 0.14, 0.21%—revealed significant differences in vascular tissue development in leaf and stem. Lateral root vascular structures were unchanged at the elevated CO2 concentrations. Plastochron intervals indicated higher growth rates with increasing CO2 levels. Primary differentiation of vascular and ground tissues in young stems occurred closer to the promeristem at the lower CO2 concentrations indicating less rapid growth patterns. Biochemical assays revealed that the contents of nucleic acids and chlorophyll in young leaves were unaffected while the levels of protein increased with elevated CO2 concentrations.
DEVELOPMENT OF FLOWER FORM IN AN ALLOTETRAPLOID CLARKIA AND ITS PARENTAL DIPLOID SPECIES
Authors: Smith‐Huerta Nancy L.
Published: January 2018

The allotetraploid Clarkia delicata possesses a floral phenotype and breeding system intermediate to its diploid progenitors. Three patterns were observed in a comparative study of anther, sepal, and petal development using allometry and scanning electron micrographs. In Pattern 1 (e.g., anther), all three species are similar at inception and in subsequent development. Anthers of the allotetraploid mature at a size intermediate to both diploids. In Pattern 2 (e.g., sepal and petal limb), diploids exhibit divergent developmental patterns, and the allotetraploid develops similarly to one diploid. In Pattern 3 (e.g., petal size and shape), diploids exhibit divergent developmental patterns, and the allotetraploid is variously intermediate to both. In petal size (length vs. width), the diploid developmental pathways are parallel, and the allotetraploid is intermediate at all points of development. In petal shape (limb length above widest point/length below widest point vs. petal width), diploid developmental pathways intersect, and the allotetraploid is similar to one diploid at inception and the other in subsequent development.
ULTRASTRUCTURE OF ANOMALOUS POLLEN DEVELOPMENT IN EMBRYOGENIC ANTHER CULTURES OF HYOSCYAMUS NIGER
Authors: Reynolds Thomas L.
Published: January 2018

The formation of anomalous, binucleate pollen grains and their subsequent embryogenic development, induced by anther culture in Hyoscyamus niger, were analyzed by transmission electron microscopy (TEM). In culture, uninucleate pollen grains occasionally divided symmetrically giving rise to two apparently identical nuclei sharing a common cytoplasm. These nuclei divided once or twice unaccompanied by cell wall formation. After the daughter nuclei organized into cells, their subsequent division products contributed to embryoid formation. In conjunction with previous studies of pollen embryogenesis in H. niger, it appears that in contrast to the principle mode of embryogenesis (i.e., first asymmetric division forms typical two‐celled pollen grain and the generative cell acts as the embryogenic precursor), anomalous pollen show no carry‐over of gametophytic influences following embryogenic induction. This suggests that specific pathways of embryogenesis are correlated with the rate at which gametophytic gene activity is repressed following induction.
GENETIC DIVERSITY AND POPULATION STRUCTURE IN CAMELLIA JAPONICA L. (THEACEAE)
Authors: Wendel Jonathan F. , Parks Clifford R.
Published: January 2018

Camellia japonica is a widespread and morphologically diverse tree native to parts of Japan and adjacent islands. Starch gel electrophoresis was used to score allelic variation at 20 loci in seeds collected from 60 populations distributed throughout the species range. In comparison with other plant species, the level of genetic diversity within C. japonica populations is very high: 66.2% of loci were polymorphic on average per population, with a mean number of 2.16 alleles per locus; the mean observed and panmictic heterozygosities were 0.230 and 0.265, respectively. Genotypic proportions at most loci in most populations fit Hardy‐Weinberg expectations. However, small heterozygote deficiencies were commonly observed (mean population fixation index = 0.129). It is suggested that the most likely cause of the observed deficiencies is population subdivision into genetically divergent subpopulations.

The overall level of population differentiation is greater than is typically observed in out‐breeders: The mean genetic distance and identity (Nei's D and I) between pairs of populations were 0.073 and 0.930, respectively, and Wright's Fst was 0.144. Differences among populations appeared to be manifested as variation in gene frequencies at many loci rather than variation in allelic composition per se. However, the patterns of variation were not random. Reciprocal clinal variation of gene frequencies was observed for allele pairs at six loci. In addition, principal components analysis revealed that populations tended to genetically cluster into four regions representing the geographic areas Kyushu, Shikoku, western Honshu, and eastern Honshu. There was a significant relationship between genetic and geographic distance (r = 0.61; P < 0.01). Analysis of variance on allozyme frequencies showed that there was approximately four times as much differentiation among populations within regions, as among regions. It is likely that the observed patterns of population relationships result from the balance between genetic drift in small subpopulations and gene flow between them.
THE RHIZOMORPH APEX OF PAURODENDRON; IMPLICATIONS FOR HOMOLOGIES AMONG THE ROOTING ORGANS OF LYCOPSIDA
Authors: Rothwell Gar W. , Erwin Diane M.
Published: January 2018

A rhizomorph of Paurodendron with an intact apex recently has been discovered in Upper Pennsylvanian sediments of Ohio, and this provides the anatomical evidence necessary to interpret structure, ontogeny and homologies among lycophyte rooting organs. The basal meristem of Paurodendron is radial and lenticular, and produces an apical plug of parenchymatous tissue similar to a root cap. The plug is surrounded by a furrow associated with radially aligned cells that demonstrate a developmental correspondence to the furrow(s) of Isoetes. Based on external structural similarities at the rhizomorph apices of Paurodendron, Stigmaria, and young Nathorstiana, and on the anatomical similarities of Paurodendron to Isoetes, Stigmaria, Chaloneria, and Lepidocarpon embryos, all are interpreted as having a rooting organ that represents a modified shoot system that is fundamentally unlike the primary root system of seed plants. Likewise, the rootlets of rhizomorphic lycophytes are interpreted as leaves modified for rooting, and that have the equivalent of exogenous origin. As such, they are fundamentally unlike the adventitious roots of rhizomatous lycophytes like Lycopodium and Selaginella.
DEVELOPMENT OF ENDOPHYTIC FRANKIA SPORANGIA IN FIELD‐ AND LABORATORY‐GROWN NODULES OF COMPTONIA PEREGRINA AND MYRICA GALE
Authors: VandenBosch Kathryn A. , Torrey John G.
Published: January 2018

Field‐collected nodules of Comptonia peregrina (L.) Coult. and Myrica gale L. (Myricaceae), infected by the nitrogen‐fixing actinomycete Frankia sp., were of two types: those that lacked sporangia entirely, designated spore(‐), and those that showed extensive sporangial development, designated spore(+). In spore(+) nodules of C. peregrina, sporangia began to develop after the differentiation of endophytic vesicles and the concomitant onset of nitrogenase activity. At the onset of sporangial differentiation, infected host cells appeared healthy. However, endophytic vesicles and host cell cytoplasm and nuclei began to senesce rapidly as sporangia developed. Staining of sectioned material with the fluorescent stain Calcofluor White suggested that vesicles, hyphae and young sporangia were enclosed within a host‐derived encapsulation layer, but mature sporangia were no longer encapsulated. In both C. peregrina and M. gale, vesicles were more short‐lived in spore(+) than in spore(‐) nodules. Field‐collected spore(+) M. gale nodules exhibited a pronounced seasonality of sporangial formation. Sporangia began to differentiate in June, after the formation of vesicles and became more prominent in late summer. Inter‐ and intraspecific cross‐inoculations suggest that the ability to form sporangia in the symbiotic state is controlled by endophytic strain type rather than host genotype or host/endophyte combination. The host may, however, influence the number and seasonal appearance of sporangia formed.
PREDATION IN INSULAR PLANT DYNAMICS: AN EXPERIMENTAL ASSESSMENT OF POSTDISPERSAL FRUIT AND SEED SURVIVAL, ENEWETAK ATOLL, MARSHALL ISLANDS
Authors: Louda Svaťa M. , Zedler Paul H.
Published: January 2018

We studied predation upon the fruits of four common terrestrial plant species of atolls by excluding: 1) all predators; 2) large predators only; and 3) no predators. Each of these treatments was located within the vegetation at three distances from the shore: beach edge of fringing thicket; middle of the thicket; and inner forest. The plants were Terminalia catappa, Messerschmidia argentea, Scaevola taccada, and Guettarda speciosa. Predation loss over the year was significant (P > 0.01) for all four species. Location contributed significantly only for S. taccada. Amount of loss and predominant type of seed predator for a plant species were related to size and conspicuousness. The largest fruits, those of the widespread tree T. catappa, were destroyed completely at all sites; the damage was done by both insects and terrestrial crabs. The large fruits of G. speciosa were destroyed by insects inland and by crabs at the beach edge. The small fruits of M. argentea, a plant which is common along the beach, tended to have greater losses away from the beach edge; those losses were caused primarily by insects. For S. taccada, which occurred at the beach edge, fruit survival was highest in the middle of the fringe thicket; average damage and disappearance were high and caused primarily by large predators. In sum, the experiment demonstrated that predation by widespread, omnivorous large animals and insects on an atoll island was important in survival of fruits and enclosed seeds. We conclude that this interaction could have a significant influence on the dynamics of plants on atolls.
FLORA OF THE LOWER CRETACEOUS CEDAR MOUNTAIN FORMATION OF UTAH AND COLORADO. PART III: ICACINOXYLON PITTIENSE N. SP
Authors: Thayn G. F. , Tidwell W. D. , Stokes W. L.
Published: January 2018

Icacinoxylon pittiense, a new species of angiospermous wood from the Lower Cretaceous Cedar Mountain Formation of Utah is described and compared with similar fossil and modem woods. It is distinguished from other species of Icacinoxylon by its thick‐walled fiber‐tracheids with their walls making up at least 50% of the total diameter of the cells, conspicuous bordered pits with obliquely crossing extended apertures on both the tangential and radial walls of its fiber‐tracheids, scalariform perforation plates with as few as four or greater than 30 bars, transitional opposite to scalariform pitting on its vessel walls, thick‐walled ray cells, and distinct sheath or border cells in its rays. Icacinoxylon pittiense is the first species of this genus to be reported from Cretaceous sediments. This wood is of special interest because very few angiosperm woods have been reported from lower Cretaceous strata.
EFFECTS OF CLIPPING AND FOUR LEVELS OF NITROGEN ON THE GAS EXCHANGE, GROWTH, AND PRODUCTION OF TWO EAST AFRICAN GRAMINOIDS
Authors: Wallace L. L. , McNaughton S. J. , Coughenour M. B.
Published: January 2018

Kyllinga nervosa and Themeda triandra plants were subjected to different clipping and nitrogen availability regimes. Following an extended period of growth under these conditions, total biomass, gas exchange and several morphological parameters were measured. Kyllinga nervosa showed compensatory growth to moderate levels of clipping whereas any clipping reduced the total biomass of T. triandra. Unclipped plants of either species were unable to respond to increased levels of nitrogen. Clipped plants responded in an ambiguous fashion, with increased allocation to offtake (material removed by clipping) in both species. Total biomass of K. nervosa was highest at 15 mM nitrogen levels which are equivalent to field levels. Both photosynthesis and respiration rates were unaffected by nitrogen treatments. Photosynthesis was significantly reduced by the most severe clipping regime of K. nervosa, but was unaffected by clipping of T. triandra.
VEGETATIVE PROPAGATION OF CHENOPODIUM QUINOA BY SHOOT TIP CULTURE
Authors: Burnouf‐Radosevich M. , Paupardin C.
Published: January 2018

An in vitro procedure is described for vegetative propagation of two varieties of Chenopodium quìnoa. Shoot tips of seedlings and adult plants were stimulated to produce multiple shoots by axillary branching in a B5 medium modified by decreasing sucrose (10 g/l), increasing nitrate (2,700 mg/l) and phosphate (315 mg/l) salts, and to which glycine was added (4 mg/l). This modified medium was supplemented with benzyladenine (0.22 mg/l) and naphthaleneacetic acid (0.018 mg/l). These conditions allowed development of more than twice the average number of shoots per culture as did the non‐modified B5 medium. Absence of exogenous growth substances stimulated shoot elongation and rooting more effectively than auxins or gibberellic acid added to the medium. Rooted plants, transferred to a greenhouse, grew to 2 m at the flowering stage.
PLASTOCHRON INDICES FOR JUVENILE AND MATURE FORMS OF HEDERA HELIX L. (ARALIACEAE)
Authors: Cordero Robert E. , Murray John R. , Hackett Wesley P.
Published: January 2018

English ivy (Hedera helix) plants were assessed for the applicability of the plastochron index (PI). Juvenile ivy satisfied all requirements for the use of the PI and showed a plastochron of 4.23 days. Mature ivy grown under long day conditions flowered after 11–12 leaves. Two distinct groups of leaves were produced with different plastochrons (0.83 and 3.2 days, respectively) and leaf morphologies. Long‐day‐grown ivy did not satisfy the requirements for the use of the PI. Short‐day‐grown mature ivy continued production of leaves beyond the 12th leaf. Vegetative growth was perpetuated for at least 25 plastochrons. By 19 plastochrons (ca. 41 days after budbreak) a linear PI vs. time relationship was established with a plastochron of 3.16 days. This newly acquired ability to maintain vegetative growth in mature ivy plants may allow a direct comparison with the vegetative indeterminant juvenile in order to assess possible anatomical factors responsible for phase stability and phase change using the PI as a basis for comparison.
A NEW SPECIES OF COREOCARPUS (COMPOSITAE: HELIANTHEAE) FROM SAN PEDRO NOLASCO ISLAND, MEXICO
Authors: Smith Edwin B.
Published: January 2018

A new species of Coreocarpus endemic to San Pedro Nolasco Island, Mexico, C. sanpedroensis, is described and illustrated.
FLORAL FLAVONOIDS AND ULTRAVIOLET PATTERNS IN VIGUIERA (COMPOSITAE)
Authors: Rieseberg Loren H. , Schilling Edward E.
Published: January 2018

Variation occurs among species of Viguiera series Viguiera for ultraviolet (uv) absorption/reflection patterns of ligules. Floral flavonoids that cause uv absorption occur in epidermal papillae. Flavonoids are further localized to the proximal portion of the ligule in the seven taxa that have only proximal uv absorption. Floral flavonoids involved in uv absorption consist of flavone, flavonol, and anthochlor (chalcone/aurone) glycosides. Quercetin 3‐methyl ether glycosides characterize the ligules of 10 taxa occurring in Baja California, Mexico, and nearby areas, and these taxa appear to form one taxonomic group. The anthochlor pair, marein/maritimein, characterizes V. dentata, and the lack of ligule flavonoids distinguishes V. potosina from the remaining taxa. The presence of the anthochlor pair, marein/maritimein, only in V. dentata and the lack of ligule flavonoids in V. potosina concur with other data to indicate that these species are not correctly placed with each other or with the other species currently included in series Viguiera.
PALYNOLOGY AND SYSTEMATICS OF THE LYTHRACEAE. I. INTRODUCTION AND GENERA ADENARIA THROUGH GINORIA
Authors: Graham Alan , Nowicke Joan , Skvarla John J. , Graham Shirley A. , Patel Varsha , Lee Sangtae
Published: January 2018

A palynological survey, including LM, SEM, and TEM, is presented for 10 genera of the Lythraceae s.s. (plus Alzatea to be assigned separate family status): Adenaria, Ammannia, Capuronia, Crenea, Cuphea, Decodon, Didiplis, Diplusodon, Galpinia, and Ginoria. Discussion of the results is deferred until the survey is complete, but already information of taxonomic interest is available for the 11 genera studied. The pollen data, consistent with results from cytology, anatomy, and embryology, suggest the current subgeneric classification into the Tribes Lythreae and Nesaeeae based on complete or incomplete septation of the ovary is not valid. The pollen of Alzatea is a generalized type and lacks the morphological features most characteristic of the Lythraceae (pseudocolpi, sculptured exine). The genus is being described as a separate family, and the pollen morphology is consistent with this treatment. The pollen of Cuphea is more diverse and shows little similarity to other genera in the family. It also has a unique combination of floral characters and lipid chemistry that suggests a separate category within the developing subfamilial classification of the Lythraceae.
SECONDARY SEX CHARACTERISTICS IN SPINACIA OLERACEA L.: QUANTITATIVE EVIDENCE FOR THE EXISTENCE OF AT LEAST THREE SEXUAL MORPHS
Authors: Vitale Jeffrey J. , Freeman D. Carl
Published: January 2018

Spinacia oleracea L. was grown hydroponically across an experimental salinity gradient with treatments of 0.0, 1.5, 3.0, 4.5, and 6.0 grams of NaCl/liter of nutrient medium. Plant height, root biomass, vegetative biomass, fruit morphology, average fruit weight, and fruit mass: volume ratio were examined in each treatment to determine if differences other than primary sex characteristics exist between male, female, and monoecious plants. Average fruit weight was the only parameter examined that was not useful as a secondary sex characteristic. Orthogonal contrasts examining plant height, vegetative biomass, and root biomass of plants were distinct from one another across the salinity gradient. Similarly, female and monoecious plants differed significantly from one another in terms of root biomass and the average mass: volume ratio of the fruit each sexual morph produced, as well as the proportion of smooth to wrinkled fruit produced. The data indicate that male, female, and monoecious plants are three distinct sexual morphs.
SPORE GERMINATION AND EARLY DEVELOPMENT OF THE GAMETOPHYTE OF SCHIZAEA PUSILLA
Authors: von Aderkas Patrick , Raghavan V.
Published: January 2018

During germination of the spore of Schizaea pusilla, the first division of the protoplast was perpendicular to the polar axis and resulted in the formation of the rhizoid. The next division parallel to the polar axis of the spore gave rise to the protonemal initial. Following this “Vittaria”‐type germination, the protonema that developed was characterized by an extensive branching to produce uniseriate filaments and rhizoidophores.
LEAF CAVITY SIZE DIFFERENTIATION AND WATER RELATIONS IN CAREX ELEOCHARIS
Authors: Veres John S. , Williams George J.
Published: January 2018

Carex eleocharis leaves contain large intercellular cavities that traverse the length of the leaf above rows of stomata and are roughly constant in size throughout a leaf. Semithin sections (1–2 μm) demonstrate that the substomatal chambers are directly continuous with the intercellular cavities. Leaves of plants inhabiting moist swale regions of the shortgrass steppe, in northeastern Colorado, were found to have larger cavities as compared to leaves of plants inhabiting dry hilltops. Plants collected from a common hilltop site were grown in a controlled environment chamber, and, by manipulating the watering schedule, we obtained water potentials similar to those in the field. Leaves of “well‐watered” plants were found to have larger intercellular cavities as compared to “water‐stressed” plants. Leaf mesophyll cell sizes did not differ significantly between “well‐watered” and “water‐stressed” plants, suggesting that cavity size differences are not the result of developmental differences. Leaf cavities were shown to contain gases and to occur along the leaf length above rows of stomata. Additionally, the cavities in unstressed plants were continuous with substomal chambers. It is proposed that the reduction of cavity size is a mechanism to reduce water loss from the leaves during periods of plant water stress.
EXPERIMENTAL EVIDENCE FOR HOST RACES IN MISTLETOE (PHORADENDRON TOMENTOSUM)
Authors: Clay Keith , Dement David , Rejmanek Marcel
Published: January 2018

In order to test the hypothesis that mistletoes (Phoradendron tomentosum) are differentially adapted for the host species that they occur on, mistletoe seeds from the three most common hosts in central Texas (hackberry, Celtis occidentalis, elm, Ulmus crassifolia, and mesquite, Prosopsis glandulosa) were planted onto different individuals of each of the three hosts. Germination of seeds and formation of haustorial disks by seedlings were followed in the subsequent 17 months. Germination of seeds was very high for all nine combinations of maternal (source) and seed (experimental) hosts (range 82%–98%). There were no significant differences in seed germination between the two groups when source and experimental hosts were the same species and when they were different species. In contrast, development of haustorial disks when source and experimental hosts were the same species was significantly greater than when experimental host and source host species were different. The data suggest that populations of mistletoes are genetically differentiated such that early seedling development is greatest when there is correspondence between maternal and seedling host species.
BRANCHING IN PSILOPHYTON: A NEW SPECIES FROM THE LOWER DEVONIAN OF NEW BRUNSWICK, CANADA
Authors: Trant Charles A. , Gensel Patricia G.
Published: January 2018

A new species of Psilophyton is described from serial peels of permineralized axes in terms of vasculature, cortical histology, and branching. The axes bear small, multicellular emergences, and wound tissue occurs on several of them. Anatomical changes associated with branching are analyzed and five different patterns described, some of which are new for the genus. Particularly noteworthy is the apparent lack of correlation of axis and stelar diameters in some branching sequences. This information adds to our knowledge of anatomy and variability within the genus Psilophyton and allows for closer comparison of Psilophyton to other plant groups.
REPRODUCTIVE BIOLOGY OF SEVERAL BROMEGRASSES (BROMUS): BREEDING SYSTEM, PATTERN OF FRUIT MATURATION, AND SEED SET
Authors: McKone Mark J.
Published: January 2018

Five species of Bromus were tested for self‐fertility when bagged. Bromus inermis was self‐incompatible. Bromus tectorum, B. kalmii, B. ciliatus, and B. latiglumis were capable of self‐fertilization. Further evidence from flowering behavior suggested that B. tectorum almost always self‐pollinated and that the remaining self‐fertile species sometimes outcrossed. Florets in different positions on a spikelet varied in the proportion that set seed. Open‐pollinated B. inermis plants had lower seed set than the self‐fertile species, in agreement with the pattern in a variety of hermaphroditic plants.
LEAF DIMORPHISM IN THE AQUATIC ANGIOSPERM CALLITRICHE HETEROPHYLLA
Authors: Deschamp Paula A. , Cooke Todd J.
Published: January 2018

Depending on the position of the shoot tip relative to the water surface, the aquatic angiosperm Callitriche heterophylla produces either ovate land‐form or linear water‐form leaves. This paper is concerned with the developmental basis for the leaf dimorphism of this species. Little significant difference is observed between the apical meristems of submerged vs. emergent shoots; moreover, land‐form and water‐form primordia undergo similar, if not identical, patterns of initial development until they attain a length of 350 to 400 μm. These findings are interpreted to mean that the divergent leaf forms result from the marked sensitivity of the primordia to their respective environments rather than from the mode of their inception. Subsequent growth of the young water‐form leaf emphasizes longitudinal extension, while the immature land‐form leaf continues balanced expansion in both longitudinal and lateral directions. The lateral growth of the land‐form primordium is accomplished in part by a more persistent marginal meristem, but the morphological difference between the two leaf forms is mostly attributable to the difference in the predominant direction of intercalary expansion. In addition, certain anatomical features, such as vasculature, stomates, and cuticle, are much more prominent in mature land‐form leaves than in water‐form leaves. These anatomical differences seem to represent structural adaptations of each leaf form to the specific physiological requirements of its environment.
STRUCTURALLY PRESERVED FOSSIL PLANTS FROM ANTARCTICA. I. ANTARCTICYCAS, GEN. NOV., A TRIASSIC CYCAD STEM FROM THE BEARDMORE GLACIER AREA
Authors: Smoot Edith L. , Taylor Thomas N. , Delevoryas T.
Published: January 2018

Silicified stems with typical cycadalean anatomy are described from specimens collected from the Fremouw Formation (Triassic) in the Transantarctic Mountains of Antarctica. Axes are slender with a large parenchymatous pith and cortex separated by a narrow ring of vascular tissue. Mucilage canals are present in both pith and cortex. Vascular tissue consists of endarch primary xylem, a narrow band of secondary xylem tracheids, cambial zone, and region of secondary phloem. Vascular bundles contain uni‐ to triseriate rays with larger rays up to 2 mm wide separating the individual bundles. Pitting on primary xylem elements ranges from helical to scalariform; secondary xylem tracheids exhibit alternate circular bordered pits. Traces, often accompanied by a mucilage canal, extend out through the large rays into the cortex where some assume a girdling configuration. A zone of periderm is present at the periphery of the stem. Large and small roots are attached to the stem and are conspicuous in the surrounding matrix. The anatomy of the Antarctic cycad is compared with that of other fossil and extant cycadalean stems.
LEAF DISPLAY, CANOPY STRUCTURE, AND LIGHT INTERCEPTION OF TWO UNDERSTORY PALM SPECIES
Authors: Chazdon Robin L.
Published: January 2018

The implications of leaf size, leaf display, and crown size for whole‐plant light interception were investigated in Geonoma cuneata and Asterogyne martiana, two understory palm species native to Central American rain forests. Adults of A. martiana had longer leaves, more leaves per plant, and greater total leaf area than G. cuneata adults. Geometric measurements within whole crowns were used to calculate light interception efficiency, a leaf‐based measure of the proportion of total incident light that is intercepted by a crown. Light interception efficiency was higher in adult G. cuneata than in adult A. martiana; seedlings of the two species did not differ significantly in light interception efficiency. Decreased efficiency of adult A. martiana crowns was largely due to an increased proportion of pendent leaves. Compared to G. cuneata, adults of A. martiana had greater light interception capacity (the product of light interception efficiency and total leaf area), but they also had higher biomass costs of light interception. Lower biomass costs of light interception in adult G. cuneata enable this species to exploit successfully the most deeply shaded microsites in the rain forest understory.
C‐BAND HETEROCHROMATIN AND DNA CONTENT IN ZEA MAYS
Authors: Rayburn A. Lane , Price H. James , Smith J. D. , Gold John R.
Published: January 2018

The number of mitotic chromosomal C‐bands, the percent of the genome comprised of C‐band heterochromatin, and genome size (4C DNA content) were determined for 22 North American inbred and open‐pollinated lines of Zea mays. The number of C‐bands ranged from 0 in Tama Knobless Flint to 18 in Zapolate Grande. The percent C‐band heterochromatin ranged from 0% in Tama Knobless Flint to 16.9% in Tx601. Genome size varied over 23%: Gaspe Flint had the lowest DNA content (9.82 pg), and Zapolate Grande had the highest (12.12 pg). Genome size and the amount of heterochromatin were significantly correlated.

The corn lines were assigned to five maturity zones encompassing a south‐to‐north range from Mexico to Canada. Significant negative correlations were detected between the amount of C‐band heterochromatin and maturity zones, and between DNA content and maturity zones among the lines.

It is speculated that the simultaneous selection by man for earlier maturation and plant size may be related to the lower DNA content of corn varieties adapted to higher latitudes. Such selection for larger plants may have been achieved through selection for more cells, which could result from the shorter mitotic cycle time that correlates with reduced DNA amount.
RESPONSE OF ANDROPOGON GERARDII (POACEAE) TO FIRE‐INDUCED HIGH VS. LOW IRRADIANCE ENVIRONMENTS IN TALLGRASS PRAIRIE: LEAF STRUCTURE AND PHOTOSYNTHETIC PIGMENTS
Authors: Knapp Alan K. , Gilliam Frank S.
Published: January 2018

Photosynthetic pigments and several structural characteristics were measured in leaves of Andropogon gerardii from tallgrass prairie populations in an unburned, low‐irradiance site and a burned, high‐irradiance site to determine if these species displayed sun/shade differences similar to those documented in forest species. Early in the growing season, leaves of A. gerardii in the low‐irradiance, unburned site had significantly lower stomatal density, pore length, and conductance, as well as specific leaf mass and thickness than leaves from the high‐irradiance, burned site. Moreover, the chlorophyll a:b ratio, carotenoid content, and bundle sheath‐vascular complex area were significantly lower, but chlorophyll content (mass/mass) was greater in leaves in unburned vs. burned sites. These differences are consistent with sun/shade adaptations reported for forest understory plants and may contribute to the low productivity of A. gerardii in unburned tallgrass prairie.
NONFRUITING HERMAPHRODITIC FLOWERS OF CALOCHORTUS LEICHTLINII (LILIACEAE): POTENTIAL REPRODUCTIVE FUNCTIONS
Authors: Holtsford Timothy P.
Published: January 2018

The breeding system, flowering display, and fruiting pattern of Calochortus leichtlinii Hook. (Liliaceae) was studied in the eastern Sierra Nevada. This species is capable of both autogamy and insect‐mediated outcrossing. Either of these two means of pollination alone could affect full seed set; the populations studied were not pollination limited in 1983. Most individuals produced two flowers but set only one fruit. Flowers are not selectively matured on the basis of the quantity or purported quality of the pollen they receive; the first flower to open was matured in all experiments. Nonfruiting flowers have at least three potentially important reproductive functions: disseminating pollen, allowing plants to produce more seeds in response to an abundance of soil moisture, and setting seeds if the first flower fails to develop fruit.
POLLEN TUBE COMPETITION AND SELECTION FOR METAL TOLERANCE IN SILENE DIOICA (CARYOPHYLLACEAE) AND MIMULUS GUTTATUS (SCROPHULARIACEAE)
Authors: Searcy Karen B. , Mulcahy David L.
Published: January 2018

An experiment was conducted to test whether metal tolerance expressed in pollen would provide a competitive advantage during pollen tube growth and fertilization. Copper or zinc was introduced into the pistil by growing metal tolerant plants of Silene dioica or Mimulus guttatus in a nutrient solution to which metals were added. Flowers from treated and control plants were pollinated with either metal tolerant or metal sensitive pollen. The rate of pollen tube growth, the number of seeds set, and the number of viable seeds produced were measured. In general, no effects were found on the rates of pollen tube growth. However, the number of fertilizations and viable seeds were affected. When toxic metals were present, the relative success of pollen from the nontolerant parent was reduced.
DEVELOPMENTAL CHANGES IN ENERGY (ATP AND ADP) AND NUTRIENT LEVELS PRIOR TO SENESCENCE IN PODDED AND DEPODDED PEA PLANTS
Authors: Omer Lucy St. , Horvath Steven M. , Setaro Frank
Published: January 2018

Energy (ATP and ADP) levels in stem apices of depodded pea plants (Pisum sativum L. cv. Little Marvel) were significantly higher than those of podded plants during the pod‐filling stage before whole plant senescence. This difference in energy content appeared before decreases in leaf chlorophyll and soluble proteins occurred in plants of both treatments. In contrast, the mineral nutrient levels (N, P, K, Ca, Mg, Fe, and Mn) in stem apices of plants from both treatments were similar. Energy levels in reproductive leaves from podded and depodded plants were similar. The mineral nutrients in leaves with fruits in their axils and similar leaves of depodded plants were comparable except for nitrogen. Plant growth measurements—dry weight, leaf area, leaf dry weight, root/shoot ratio—were significantly higher in depodded than podded plants. Whole plant senescence occurred significantly earlier in podded than in depodded pea plants.
DISTRIBUTION OF CALCIUM OXALATE CRYSTAL IDIOBLASTS IN LEAVES OF TARO (COLOCASIA ESCULENTA)
Authors: Sunell Leslie A. , Healey Patrick L.
Published: January 2018

Cleared leaves of taro (Colocasia esculenta) were examined microscopically to determine changes in the distribution of both druse and raphide idioblasts during a late developmental process—leaf unfurling and expansion. Druse crystal idioblasts are small spherical cells found throughout the lamina, mostly in subepidermal areas. Two types of raphide idioblasts were observed in taro leaves: the nondefensive raphide idioblasts, which are elongated cells usually found embedded in tissues of the leaf margins; and the defensive raphide idioblasts, also elongated cells, but usually found suspended between mesophyll cells in leaf airspaces. The densities of both druse and raphide cells were highest at the fully furled stage and least in the mature, unfurled stage, after substantial leaf expansion. During leaf unfurling, the raphide cells showed a bilaterally symmetrical distribution during all stages from fully furled to mature, unfurled leaves. The distribution of druse cells was bilaterally symmetrical during the fully furled and unfurled stages, but, during unfurling, when one half of the lamina is unfurled and the other half is still tightly furled, up to 80% of the druse cells were found on the unfurled half of the lamina.
CHROMOSOME RELATIONSHIPS OF DIPLOID SPECIES OF GRINDELIA (COMPOSITAE) FROM COLORADO, NEW MEXICO, AND ADJACENT AREAS
Authors: Dunford Max P.
Published: January 2018

Previous studies of chromosome relationships of Grindelia species recognized three basic genomes designated Oxylepis, Hallii, and Havardii. Differences are based on different end arrangements of the chromosomes resulting from reciprocal translocations. This report will review and give additional information about the genomes and interrelationships of 17 species. All of the species are diploids (2n = 12) and show six bivalents at meiosis. Species in this study that have the Oxylepis genome are G. oxylepis var. eligulata, G. fastigiata, G. inornata, G. revoluta, and G. squarrosa. Species that have the Havardii genome included G. havardii, G. grandiflora, G. lanceolata, G. littoralis, and G. texana. The Hallii genome is present in G. camporum var. davyi and G. procera. Hybrids of species with the same genome have six bivalents at meiosis. Hybrids between species with the Oxylepis genome and those having the Havardii genome have four bivalents and one quadrivalent at meiosis. Likewise for Oxylepis x Hallii hybrids. A new genome is presented for G. subalpina which would explain the configurations of two bivalents and two quadrivalents observed in G. subalpina x G. havardii and G. subalpina x G. fastigiata hybrids. This is designated the Subalpina genome. Species tested but with genomes as yet undetermined are G. acutifolia, G. arizonica, G. nana, and G. scabra.
GERMINATION AND GROWTH OF BIRD‐DISPERSED PLANTS: EFFECTS OF SEED SIZE AND LIGHT ON SEEDLING VIGOR AND BIOMASS ALLOCATION
Authors: Piper Jon K.
Published: January 2018

I examined germination and seedling growth in nine species of fleshy‐fruited plants from Washington and Idaho to assess their relative responses to sun and shade. I allowed seeds to germinate over a period of 500 days, and grew the seedlings in a greenhouse for 35 days prior to harvest. Cumulative percentage germination of six species approximated logistic curves. Species with larger seeds were more shade‐tolerant, which resulted largely from greater biomass allocation to roots by these species. Seedlings of Rosa gymnocarpa, Sorbus scopulina, Symphoricarpos albus, Clintonia uniflora, and Streptopus amplexifolius grew larger in open sun than in shade (35% open sun), whereas those of Actaea rubra, Disporum trachycarpum, Smilacina racemosa, and Smilacina stellata showed no differences. Percentage root biomass was higher in sun than in shade for R. gymnocarpa, S. scopulina, S. albus, C. uniflora, and S. amplexifolius, but lower for S. stellata. In C. uniflora, S. racemosa, and S. stellata, seeds from unripe fruits failed to germinate. The results suggest that light gaps resulting from periodic disturbance of canopy influence recruitment of bird‐dispersed species differentially and thereby contribute to maintaining high species richness and diversity in understories of temperate coniferous forests.
CHROMOSOME PAIRING AND POLLEN FERTILITY IN INTERSPECIFIC HYBRIDS OF SPECIES OF PARTHENIUM (ASTERACEAE)
Authors: Hashemi Ahmad , West Jan E. , Waines J. Giles
Published: January 2018

Meiotic analyses and pollen viability tests were performed on F, hybrids between diploid guayule (Parthenium argentatum Gray 2n = 36), P. rollinsianum Rzedowski (2n = 36), P. alpinum var. tetraneuris Barneby (2n = 36), and P. alpinum var. alpinum Nutt. (2n = 36). Parthenium chromosomes are small and karyomorphologically similar, and meiotic analysis is difficult because of chromosome clumping. However, cytogenetic studies at metaphase I indicated univalents can be seen in a lateral view of the metaphase plate. Chromosome pairing and the number of univalents varied within and between the interspecific hybrids, with an average univalent number of 1.54 for the P. rollinsianum hybrids, 2.36 for the P. alpinum var. tetraneuris hybrids, and 2.46 for the P. alpinum var. alpinum hybrids. Pollen viability tests for the parental species and the hybrids were conducted by germination of pollen grains on stigmas. The percent of viable pollen recorded for the diploid guayule hybrids with P. rollinsianum, P. alpinum var. tetraneuris, and P. alpinum var. alpinum are 21.94, 13.47, and 11.17, respectively. The degree of chromosome pairing and pollen viability is striking because there are many morphological differences between the parents. The chromosome homology of these species based on their pairing behavior allows for the design of a backcross breeding program that would permit the transfer of the desirable characteristics from these species into diploid guayule.
GROWTH CORRELATIONS WITHIN THE SEGMENT IN THE ARACEAE
Authors: Ray Thomas S.
Published: January 2018

The segment is defined as an internode and the associated petiole and lamina. In many climbing members of the family Araceae, there is great variation in the relative sizes and shapes of the three component parts of the segment. In Syngonium standleyanum Bunting, it was found that the form of the internode may be characterized by its length and diam, the petiole by its length, and the lamina by its wt and its shape (the ratio of central lobe wt to lamina wt). The sizes and shapes of the various components of the segment were found not to be allometrically related, with three exceptions: the internode diam is allometrically related to the segment wt, petiole wt, and lamina shape. In the four species of Araceae studied, the strong correlation between the diam of the internode and the wt of the entire segment results in a trade‐off between making a large leaf or a long internode. For an internode of a given diam, the total dry wt of the segment is fixed, but may be proportioned in virtually any manner between the leaf and internode, from 95% of the wt in a large leaf, to 98% of the wt in a long internode. The complete form of the segment may be defined by just two variables. A suitable pair of variables is internode diam, and the ratio of internode diam to internode length.
MATING SYSTEM IN NATURAL POPULATIONS OF JEFFREY PINE
Authors: Furnier Glenn R. , Adams W. T.
Published: January 2018

The mating system and allozyme variation at 20 loci in three Klamath Mountains and two Sierra Nevada populations of Jeffrey pine (Pinus jeffreyi Grev. & Balf.) were investigated. On average, multilocus estimates of the proportion of viable progeny due to outcrossing (tm) were high in all populations (mean tm = 0.935, range 0.881 to 0.971). Despite differences in stand structure, tm did not differ (P > 0.05) between the Klamath (mean tm = 0.933) and Sierra Nevada (mean tm = 0.937) populations. At all but one locus in one population and at two in another, genotype frequencies fit (P > 0.05) Hardy‐Weinberg expectations. Mean estimates of observed heterozygosity in Klamath (0.182) and Sierra Nevada (0.327) populations were comparable to values reported for other conifers.