bluuebunny/crossref_metadata_2025 huggingface dataset:
ENDOPHYTE‐HOST ASSOCIATIONS IN FORAGE GRASSES. XV. CLUSTERING OF STROMATA‐BEARING INDIVIDUALS OF AGROSTIS HIEMALIS INFECTED BY EPICHLOË TYPHINA
Authors: White James F. , Chambless Donald A.
Published: January 2018

Population studies involving the grass Agrostis hiemalis infected with the endophytic fungus Epichloë typhina were made. Grass individuals were assessed for infection state (presence or absence of fungus), number of culms and fungal stromata, and location within plot. Using clustering and ANOVA procedures available in SAS, geometric groups were identified and analyzed. The tendency of plants to bear stromata was found to be significant with respect to both the plot (P < 0.05) and the cluster (P < 0.0001) within which plants occurred. A cultural study was made of the endophytes from one of the plots. Here isolates from a cluster containing stroma‐bearing grass individuals were found to grow more rapidly than those from grass clusters without stromata on a variety of sugars naturally available in vivo. Histological studies of the host demonstrate that the endophyte is seed transmitted in a comparable fashion to endophytes in other grasses. It is suggested that the clustering of stromata‐bearing plants in Agrostis hiemalis is the result of the presence of aggressive strains of endophyte within proximally located plants.
ANGIOSPERM FLOWERS AND TRICOLPATE POLLEN OF BUXACEOUS AFFINITY FROM THE POTOMAC GROUP (MID‐CRETACEOUS) OF EASTERN NORTH AMERICA
Authors: Drinnan Andrew N. , Crane Peter R. , Friis Else Marie , Pedersen Kaj Raunsgaard
Published: January 2018

A new genus of fossil angiosperms (Spanomera gen. nov.) is established for flowers from two localities in the mid‐Cretaceous Potomac Group of Maryland, eastern North America. The type species, Spanomera mauldinensis sp. nov., from the early Cenomanian Elk Neck beds, has inflorescence units with terminal pistillate, and lateral staminate flowers. The organization of inflorescences and flowers is opposite and decussate. Staminate flowers typically have five tepals: two lateral, one posterior, and two in the anterior position. Each tepal is opposed to a stamen with a short filament, dorsifixed anther, and two pairs of pollen sacs. Stamens contain pollen comparable to the dispersed pollen species Striatopollis paraneus (Norris) Singh. Pistillate flowers have two lateral tepals and two anterior‐posterior tepals that are opposed to two carpels. Carpels are slightly fused basally along their ventral margins and are semicircular in outline with a long, decurrent, papillate ventral stigma. Frequently this stigmatic surface has abundant attached pollen of the Striatopollis paraneus type. Spanomera marylandensis sp. nov., from the late Albian Patapsco Formation, is similar to S. mauldinensis but is known only from isolated flowers and floral parts. Staminate flowers have four stamens with dorsifixed anthers and each is opposed to a tepal. Stamens contain pollen comparable to the dispersed pollen species Striatopollis vermimurus (Brenner) Srivastava. Carpels have pollen of S. vermimurus on the stigma. Spanomera provides further evidence of unisexual but probably insect‐pollinated flowers among mid‐Cretaceous, early nonmagnoliid (“higher”) dicotyledons, and is interpreted as closely related to extant Buxaceae. Characters that Spanomera shares with other taxa suggest that the Buxaceae themselves may be closely related to Myrothamnaceae and other “lower” Hamamelididae.
INVESTIGATIONS OF NORTH AMERICAN CYCADEOIDS: WELTRICHIA AND WILLIAMSONIA FROM THE JURASSIC OF OAXACA, MEXICO
Authors: Delevoryas T.
Published: January 2018

Specimens of cones of members of the family Williamsoniaceae, order Cycadeoidales, from Jurassic deposits of Oaxaca, Mexico, demonstrate the first bona fide evidence of the pollenbearing Weltrichia from the Mexican Jurassic as well as provide new information on ovulebearing Williamsonia.
MINIMAL MALE/FEMALE TRADEOFFS IN ZIZANIA PALUSTRIS, A MONOECIOUS ANNUAL GRASS
Authors: Goldman Doris Armstrong
Published: January 2018

Because a male/female resource tradeoff is a basic assumption of many models of sex allocation in cosexual plants, statistical and manipulative methods were used to look for evidence of intersexual resource conflicts in Zizania palustris. In this monoecious grass, male and female investments overlap in time within each panicle and on successive panicles, and sex allocation quickly responds to environmental changes. Nevertheless, no negative correlations were found between the numbers of florets of each sex within panicles, on consecutive panicles, or on whole plants. Removing immature fruits or florets of either sex did not significantly increase subsequent investment in the other sex. The one significant tradeoff was slightly lower total fruit production on plants with exceptionally large male investment. Wild rice, therefore, fits the tradeoff assumption of sex allocation models at the population level but rarely at the individual level.
AN EXPERIMENTAL TEST FOR REPRODUCTIVE INTERACTIONS BETWEEN TWO SEQUENTIALLY BLOOMING SAXIFRAGA SPECIES (SAXIFRAGACEAE)
Authors: Guire A. David Mc , Armbruster W. Scott
Published: January 2018

The blooming period of Saxifraga reflexa on south‐facing bluffs in interior Alaska precedes and slightly overlaps that of Saxifraga tricuspidata. We tested the hypothesis that reproductive interference maintains this phenological separation by measuring seed set of potted 5. reflexa during the normal and 5. tricuspidata blooming periods, with and without 5. tricuspidata nearby. During the S. reflexa blooming period we placed arrays of four pots of S. reflexa in sites with and without 5. tricuspidata. Several weeks later, during the S. tricuspidata blooming period, we repeated the experiment with potted 5. reflexa whose flowering had been artificially delayed. Seed set of 5. reflexa was decreased by retarding blooming time, but not by the presence of blooming S. tricuspidata. Although both species were visited by the same pollinators, primarily syrphid flies, the presence of S. tricuspidata did not reduce the rate of visitation to S. reflexa. In mixed plots, visitation rates by syrphid flies were much higher to 5. reflexa than to S. tricuspidata. Interspecific floral transitions by syrphid flies were uncommon. It appears that in 1986 at this site S. reflexa experienced no negative effects from flowering synchronously with, and occurring in close proximity to, 5. tricuspidata.
SECRETORY CAVITY DEVELOPMENT IN GLANDULAR TRICHOMES OF CANNABIS SATIVA L. (CANNABACEAE)
Authors: Kim Eun‐Soo , Mahlberg Paul G.
Published: January 2018

Development of the secretory cavity and formation of the subcuticular wall of glandular trichomes in Cannabis sativa L. was examined by transmission electron microscopy. The secretory cavity originated at the wall‐cuticle interface in the peripheral wall of the discoid secretory cells. During the presecretory phase in development of the glandular trichome, the peripheral wall of the disc cells became laminated into a dense inner zone adjacent to the plasma membrane and a less dense outer zone subjacent to the cuticle. Loosening of wall matrix in the outer zone initiated a secretory cavity among fibrous wall materials. Membrane‐bound hyaline areas, compressed in shape, arose in the wall matrix. They appeared first in the outer and subsequently in the inner zone of the wall. The membrane of the vesicles, and associated dense particles attached to the membrane, arose from the wall matrix. Hyaline areas, often with a conspicuous electron‐dense content, were released into the secretory cavity where they formed rounded secretory vesicles. Fibrous wall material released from the surface of the disc cells became distributed throughout the secretory cavity among the numerous secretory vesicles. This wall material was incorporated into the developing subcuticular wall that increased five‐fold in thickness during enlargement of the secretory cavity. The presence of a subcuticular wall in the cavity of Cannabis trichomes, as contrasted to the absence of this wall in described trichomes of other plants, supports a polyphyletic interpretation of the evolution of the secretory cavity in glandular trichomes among angiosperms.
CYTOLOGICAL AND INTERFERTILITY RELATIONSHIPS OF ARACHIS SECTION ARACHIS
Authors: Stalker H. T. , Dhesi J. S. , Parry D. C. , Hahn J. H.
Published: January 2018

Twenty‐nine recently introduced diploid (2n = 2x = 20) accessions of section Arachis plus an A. correntina (Burk) Krap. et Greg. nom. nud. control were hybridized to the diploid A‐genome species A. duranensis Krap. et Greg. nom. nud. (ace. 7988), the diploid B‐genome species A. batizocoi Krap. et Greg. (acc. 9484), and with two subspecies of the A‐B genome (2n = 4x = 40) A. hypogaea cultivars NC 4 and Argentine. Most attempted crosses were successful and the resulting plants were vigorous. However, A. batizocoi × accession 30008 hybrids died as seedlings and A. batizocoi × accession 30017 produced only dwarf plants. The 710 diploid F1s from A. batizocoi were generally sterile, while those from A. duranensis had fertility ranges from 5% to 84%. Meiotic chromosome relationships in diploid crosses were cytologically evaluated in 185 plants plus tester accessions. Most taxa in section Arachis have an A genome, only A. batizocoi accessions have a B genome, a D genome is represented by accessions 30091 and 30099, and two other genomic groups, represented by accessions 30011 and 30033, may be present in the section. Most cytological differentiation was found among species originally collected in southern and eastern Bolivia. On the other hand, species collected at the extremes of the distribution of section Arachis species (northern Argentina to north‐central Brazil) were cytologically very similar. Evidence is presented for speciation in Arachis being associated with both genetic differentiation and with translocated chromosomes. All taxa in the section except the D‐genome species are believed to be cross‐compatible with A. hypogaea, so germplasm introgression from most Arachis species should be possible.
DEVELOPMENTAL ANATOMY OF DIRECT SHOOT ORGANOGENESIS FROM LEAF PETIOLES OF VITIS VINIFERA (VITACEAE)
Authors: Colby Sheila M. , Juncosa Adrian M. , Stamp James A. , Meredith Carole P.
Published: January 2018

The anatomy of direct shoot organogenesis from leaf petioles of Vitis vinifera cv. French Colombard cultured in vitro was studied by light microscopy. Regenerating petiole stubs were fixed at 2‐ or 3‐day intervals and sectioned longitudinally. By day 3 on regeneration medium, new cell divisions were observed. After 6 days, three distinct regions of meristematic activity were apparent within the expanding petiole stub: the wound‐response, organogenic, and vascularization regions. In the organogenic region, rapid periclinal divisions of vacuolate outer cortical cells formed nodular bumps, many of which developed vascular strands and marginal meristems and formed adventitious leaves. Promeristems with small, densely staining cells and a distinct tunica layer also originated in the organogenic region, by cell division in the epidermal and subepidermal cell layers. With vascularization and the formation of leaf primordia, many promeristems became adventitious shoot meristems. Adventitious leaves and promeristems were initiated continuously from day 10 until day 33. Promeristems were often initiated near or upon adventitious leaves but could form either before or after the adventitious leaf developed. Adventitious leaves and shoot meristems developed vascular connections with the vascular bundles of the original expiant. The implication of this pattern of regeneration for Agrobacterium‐mediated transformation of Vitis is discussed.
ROOT PRODUCTION IN FOUR COMMUNITIES IN THE GREAT DISMAL SWAMP
Authors: Powell Susan W. , Day Frank P.
Published: January 2018

A sequential coring approach was used to measure root biomass and production over 1 year in four different communities within the Great Dismal Swamp. A second method, an implanted bag technique, was also used to measure root production, and values were generally lower using this technique. On all sites, fine roots were the most dynamic root component. Both biomass (1,887 g/m2) and production (354–989 g m 2 yr‐1) were highest on the mixed hardwood site, the least flooded site, and second highest on the cedar site, the site with the longest duration of soil saturation (1,033 g/m2 and 274–366 g m‐2 yr‐1). The maple‐gum (696 g/m2 and 59–91 g m‐2 yr‐1) and cypress (824 g/m2 and 68–308 g m‐2 yr‐1) sites had similarly low amounts of biomass and rates of production. Environmental parameters that influenced production include frequency and duration of flooding, and soil type. Peaks in belowground production were observed on the most productive sites (mixed hardwood and cedar) in summer and late fall‐winter; the other two sites exhibited little seasonal variability. The least flooded stand appears to allocate a greater percentage of net primary production belowground than the more extensively flooded stands. The ratio of above‐ and belowground allocation appears to change in response to a flooding gradient. This has major implications for ecosystem functions as carbon allocation patterns determine the array of litter types generated (leaves vs. roots) which affect decomposition rates and nutrient availability.
POLLINATOR LIMITATION IN THE FACULTATIVELY AUTOGAMOUS ANNUAL, LUPINUS NANUS (LEGUMINOSAE)
Authors: Karoly Keith
Published: January 2018

The importance of pollinator visitation for determining both maternal reproductive success and outcrossing rates was investigated in the facultatively autogamous annual, Lupinus nanus. Sixty plants in each of two adjacent sites were assigned to either a pollinator‐exclusion, pollen‐augmentation, or open‐pollinated (control) treatment. Flower, fruit, and seed production were recorded for each plant, and outcrossing rates were determined for plants in all three treatments at each site. Pollinator‐exclusion reduced the reproductive success of plants at Site 1, but had no effect on reproduction for plants at Site 2. Pollen‐augmentation increased fruit production by 22% and seed production by 45% at Site 2, but had no effect on reproduction for plants at Site 1. Plants in the open‐pollinated, control treatment outcrossed at intermediate rates at both sites, with plants at Site 2 (outcrossing rate, t = 0.66) outcrossing at a significantly higher rate than plants at Site 1 (t = 0.40). The pollen‐augmentation treatment increased the outcrossing rate for plants at both sites (Site 1, t = 0.72; Site 2, t = 0.78). These results indicate that pollinator availability can limit maternal reproductive success for this facultatively autogamous plant species. Additionally, the intermediate outcrossing rates observed in nature for this species are not a consequence of plant characters alone, but instead result from plant characters combined with the local pollination ecology.
DISPERSION OF SEEDLINGS OF THE PRAIRIE COMPASS PLANT, SILPHIUM LACINIATUM (ASTERACEAE)
Authors: Pleasants John M. , Jurik Thomas W.
Published: January 2018

Although the dispersal of seeds around individual plants (the seed shadow) has frequently been characterized, the dispersion of seedlings around plants (the seedling shadow) has rarely been examined. We mapped 101 and 149 seedlings of the prairie compass plant (Silphium laciniatum) that appeared in our study area in 1987 and 1990 following mass flowering in 1986 and 1989. We also mapped the locations of flowering stems which appeared in 1986 and 1989 and recorded the number of flowerheads at each stem location. The frequency distributions of distance between a seedling and the nearest flowering stem were identical in the 2 years, with a median distance of 1.0 m. The large size and lack of wind‐dispersal structures of compass plant seeds (achenes) are responsible for their limited dispersal. From estimates of the total seed production in the study area in 1986 and 1989, we calculated that about 1% of seeds became seedlings in each year. Flowering stem locations with a higher number of flowerheads had a significantly higher density of seedlings around them. This indicates that recruitment to compass plant populations is not a “lottery”; individual plants that produce more seeds produce, on average, more seedlings.
REVERSIBLE ANTHER OPENING IN LILIUM PHILADELPHICUM (LILIACEAE): A POSSIBLE MEANS OF ENHANCING MALE FITNESS
Authors: Edwards Joan , Jordan James R.
Published: January 2018

Studies of Lilium philadelphicum on Isle Royale National Park, Lake Superior, show that thecae (pollen‐containing sacs) of dehisced anthers close in the rain, thus protecting the pollen and prolonging the pollen donor phase of the flower. To our knowledge, this is the first report of anthers with longitudinal dehiscence reclosing after opening. Individual flowers of L. philadelphicum are long lived (8–11 d), do not shorten their flowering period in response to successful fertilization of the ovules, and are primarily pollinated by butterflies. Butterflies do not forage in the rain and may first visit a flower several days after anthesis. Under such circumstances, strong selection may exist to protect pollen during unfavorable weather conditions in order to prolong the pollen donor phase. Flowers with long pollen donor phases are likely to contribute more offspring to the next generation than flowers with short pollen donor phases.
GRAFTING AND ROOTING OF LEAVES OF GUAREA (MELIACEAE): EXPERIMENTAL STUDIES ON LEAF AUTONOMY
Authors: Fisher Jack B.
Published: January 2018

The pinnately compound, indeterminate leaves of G. glabra and G. guidonia were air layered, detached from their original shoots, and grown on their own adventitious root systems for up to 58 mo and 26 mo, respectively. The detached leaves grew in the same indeterminate manner and reached sizes similar to attached leaves. Although detached leaves grew autonomously, they never produced shoot buds. Leaves of both species were grafted onto their own stems and cut free of their original leaf bases. Leaf scions survived and grew for up to 29 mo and 20 mo, respectively, similar to ungrafted leaves. Axillary branches were grafted onto subtending leaves. Branch scions grew on their leaf stocks for over 30 mo and 24 mo, respectively, after being cut free from the branch bases. Secondary growth of the leaf axis (petiole) was promoted, and vascular tissues of leaf and branch axes were continuous. However, the unlignified basal region of the leaf, including the abscission zone, remained unchanged after grafting. The results indicate that proximity of roots and bypassing the abscission zone did not enhance leaf longevity or pinna production. The presence of a growing branch on a leaf did not modify the structure of the abscission zone, which suggests that the zone is strongly committed or developmentally fixed.
DISTRIBUTION AND INHERITANCE OF INCONSTANT SEX FORMS IN NATURAL POPULATIONS OF DIOECIOUS BUFFALOGRASS (BUCHLOE DACTYLOIDES)
Authors: Huff David R. , Wu Lin
Published: January 2018

Variations of sex inconstancy were examined for vegetative and seed samples from eight natural populations of buffalograss located along two east‐west transects crossing the shortgrass prairies of Oklahoma, New Mexico, and Texas. Each of the eight populations was found to contain inconstant (monoecious) sex forms. Sex form distributions ranged from the Guymon vegetative sample, having no inconstant sex forms, to the Chillicothe seed sample in which the frequency of inconstant sex forms was nearly 70%. Frequencies of inconstant sex forms were generally higher for seed samples than for vegetative samples. Male to female sex ratio of constant (dioecious) sex forms generally did not differ from 1:1 expectations. Inconstant sex forms were more common among peripheral populations where buffalograss vegetation coverage was sparse than for more central populations having a higher concentration of buffalograss vegetation. Quantitative measures of sex inconstancy from artificial crosses were significantly (P < 0.001) correlated with the additive linear model of general combining ability, suggesting that sex determination in buffalograss has high heritability. The possible selection forces affecting the frequency of monoecious sex forms among natural populations are discussed.
HERITABILITY OF CARBON ISOTOPE DISCRIMINATION IN GUTIERREZIA MICROCEPHALA (ASTERACEAE)
Authors: Schuster William S. F. , Phillips Susan L. , Sandquist Darren R. , Ehleringer James R.
Published: January 2018

The carbon isotope composition (13C/12C) of C3 plant tissues provides a long‐term, integrated measure of photosynthetic metabolism. Quantitative genetic methods were used to study the inheritance of carbon isotope composition and several morphological characters in Gutierrezia microcephala, a short‐lived desert perennial. Open‐pollinated seed was collected from a population located near Lee's Ferry, Arizona, in an area that was disturbed approximately 20 years ago. Seeds were germinated and seedlings grown in a common greenhouse environment. Carbon isotope discrimination (Δ) and all morphological characters varied significantly among maternal families. Heritability of Δ was estimated as 81% in the greenhouse and as 92% using the regression of family mean Δ on parent Δ from field samples. Using both field and greenhouse data, we estimated a lower bound for heritability in nature of 54%. Offspring size and biomass both showed significant, positive correlations with Δ. The corresponding genetic correlations were similar in magnitude and direction, but did not differ significantly from zero. These results imply the existence of heritable differences in physiology associated with carbon assimilation and water loss within populations, and the potential for microevolutionary change through natural selection.
A LOCAL FLORA AND THE BIOLOGICAL SPECIES CONCEPT
Authors: Mayr Ernst
Published: January 2018

Up to the end of the 19th century the typological species concept was universally accepted, in which degree of morphological difference was the species criterion. This concept was increasingly replaced (particularly in zoology) beginning around 1900 by the biological species concept because the criterion of morphological distinctness broke down in the case of sibling species and of highly distinct intrapopulational variants. The yardstick for the recognition of biological species is the noninterbreeding of coexisting species in a local situation. This yardstick can be applied to isolated populations only by inference. It is discussed whether the making of such inferences is too arbitrary to be acceptable. A local flora is analyzed to determine whether polyploidy, apomixis, hybridization, and other deviations from regular sexual reproduction are sufficiently frequent in plants to make the biological species concept illusory. It is found that the number of difficulties is small, validating use of the sympatric situation as yardstick for the ranking of allopatric populations.
HEAT INJURY DURING FLORAL DEVELOPMENT IN COWPEA (VIGNA UNGUICULATA, FABACEAE)
Authors: Ahmed Faisal E. , Hall Anthony E. , DeMason Darleen A.
Published: January 2018

High night temperatures during floral development induce male sterility in cowpea (Vigna unguiculata [L.] Walp.). The objectives of this study were to determine: the possible causes of the male sterility; the stage of floral development when damage due to heat stress occurs; and whether specific tissues are damaged during the period of sensitivity to heat. Plants were grown under controlled temperatures in both greenhouses and growth chambers in separate experiments. Floral development was normal under a night temperature of 20 C, whereas flowers developed under high night temperature (30 C) set no pods due to low pollen viability and anther indehiscence. Anthers developed under 33/30 C day/night temperatures did not exhibit endothecial formation, whereas anthers developed under 33/20 C day/night temperatures exhibited normal development of the endothecial layer. Reciprocal transfers of plants between chambers with high or optimum night temperature demonstrated that the stage of floral development most sensitive to heat stress occurs 9 to 7 d before anthesis. Anthers developed under either optimal or high night temperatures were compared cytologically. Development was similar through meiosis, but after tetrad release, which occurred 8 d before anthesis, the tapetal layer degenerated prematurely under high night temperature. Premature degeneration of the tapetal layer and lack of endothecial development may be responsible for the low pollen viability, low anther dehiscence, and low pod set under high night temperatures.
PHYSIOLOGICAL BASIS OF ACHENE DORMANCY IN POLYGONUM CONVOLVULUS (POLYGONACEAE)
Authors: Metzger James D.
Published: January 2018

Germination of dormant achenes of wild buckwheat (Polygonum convolvulus L.) was promoted at 25 C if they were stratified at low temperatures. Preincubation at either 2 C or 10 C promoted subsequent germination at 25 C equally, although the period of time to reach maximum germination was shorter for the 2 C treatment. Moreover, a preincubation treatment of a daily alternating cycle 2 C for 20 hr and 10 C for 4 hr promoted germination at 25 C more than either temperature alone. Removing portions of the hard pericarp and testa did not promote germination of dormant achenes at 25 C except when the portion of those structures covering the tip of the radicle was removed. This suggests that the structures covering the embryo do not prevent germination by restricting the movement of water or gases but rather restrict growth mechanically. Complete removal of the pericarp promoted germination, but much higher germination was obtained when the testa was also removed, indicating that the pericarp may not be the main factor in dormancy. Thus the role of low temperature in the loss of dormancy in wild buckwheat achenes may be to promote the production of hydrolytic enzymes that lower the mechanical resistance of pericarp and testa and/or increase the embryo growth potential beyond some threshold level and thereby enable the radicle to overcome the resistance to growth imposed by the structures covering the embryo.
CYTOLOGICAL DIFFERENCES BETWEEN A CYTOPLASMIC MALE STERILE TOBACCO CYBRID AND ITS FERTILE COUNTERPART DURING EARLY ANTHER DEVELOPMENT
Authors: Pollak Peggy E.
Published: January 2018

Ultrastructural differences were detected between a cytoplasmic male sterile tobacco cybrid (Nicotiana sp.) formed by protoplast fusion and normal, fertile tobacco. Cell structure was compared between anther primordia from normal, fertile tobacco and anther primordia from the cybrid using stereological methods. Particular emphasis was placed on the ultrastructure of mitochondria because of their known relationship to cytoplasmic male sterility in this cybrid and other plants. The volume density of mitochondria in cybrid anther primordia (6.3%) was significantly lower than in normal, fertile anther primordia (10.1%), although mitochondria from both plants contained similar amounts of cristae and profiles were of similar relative area. Dictyosomes and vacuoles also differed in volume density but not at a statistically significant level. Although the volume density of plastids did not differ, a larger amount of starch was stored within plastids in cybrid anther primordia than in normal, fertile anther primordia. These results are compatible with the hypothesis that an abnormally low rate of mitchondrial replication, and the resultant limit on adenosine triphosphate production, could contribute to cytoplasmic male sterility in the cybrid.
ALLOZYME DIVERSITY WITHIN AND DIVERGENCE AMONG FOUR SPECIES OF ROBINSONIA (ASTERACEAE: SENECIONEAE), A GENUS ENDEMIC TO THE JUAN FERNANDEZ ISLANDS, CHILE
Authors: Crawford Daniel J. , Stuessy Tod F. , Haines David W. , Cosner Mary Beth , O. Mario Silva , Lopez Patricio
Published: January 2018

Enzyme electrophoresis was employed to assess genetic diversity within and divergence among four species of Robinsonia (R. evenia, R. gayana, R. gracilis, R. thurifera), a genus endemic to the Juan Fernandez Islands, Chile. The genus consists of treelike perennial plants, and all species are dioecious. Morphological diversity within the genus is reflected by recognition of two subgenera, with three sections in one subgenus. Total gene diversity is highest in the two species (R. gayana and R. gracilis) that are most common and have the largest population sizes. Robinsonia evenia has only half and the rare R. thurifera only 20% of the diversity detected in the other two species. The diversity measured in R. gayana and R. gracilis is comparable to the values typical of continental species of flowering plants with similar life history attributes. The genetic identities between species range from 0.560 to 0.706, which is similar to or below many values for congeneric species, but much lower than most reports for congeners on oceanic islands. The higher diversity within and divergence among species of Robinsonia compared to many insular endemics may result from several factors. The genus probably arose from selfincompatible plants of the genus Senecio, which means that several to perhaps many colonizers carried considerable allozymic variation to the Islands. Large population sizes and obligate outcrossing are additional factors that would account for higher diversity. Sorting of alleles during radiation and the process of mutation probably combined to produce divergence among the species. Estimated divergence times calculated for the species from allozyme data range from 1.7 to 5.5 million years depending on the assumptions made in the calculations; the age of the island (Masatierra) on which these four species are confined is approximately 4.0 million years. The electrophoretic data suggest that Robinsonia arrived early in the archipelago, and radiated and speciated rapidly after colonization.
INTERFERENCE POTENTIAL OF PLUCHEA LANCEOLATA (ASTERACEAE): GROWTH AND PHYSIOLOGICAL RESPONSES OF ASPARAGUS BEAN, VIGNA UNGUICULATA VAR. SESQUIPEDALIS
Authors: Inderjit  , Dakshini K. M. M.
Published: January 2018

The water‐soluble compounds synthesized by the weed, Pluchea lanceolata, and released by it into the soil significantly reduced seed germination, number of nodes, internode length, shoot and root lengths, nodule number and weight, and Chl a and b and Chl a/b ratio of asparagus bean plants. The pattern of accumulation of nutrients in shoot and root of asparagus bean was also affected. In contrast, the net photosynthetic rate and stomatal conductance of fully expanded leaves were higher in plants grown with treated soil. The concentrations of Mg++, Zn++, and PO43‐ were higher and K+ was lower in shoots of plants grown with treated soil as compared to those grown with the control soil. Also, roots of plants grown with treated soil showed greater accumulation of Mg++ and NO3‐. Shoot/root ratio of nutrients in plants grown with control soil were higher for Zn++, Na+, Ca++, and NO3‐, whereas plants grown with treated soil had higher ratios for PO43‐. These results provide evidence for allelopathic interference by P. lanceolata to the growth of asparagus bean.
FLOWERS, FRUITS, AND POLLEN OF FLORISSANTIA, AN EXTINCT MALVALEAN GENUS FROM THE EOCENE AND OLIGOCENE OF WESTERN NORTH AMERICA
Authors: Manchester Steven R.
Published: January 2018

Compressed flowers and fruits of Florissantia (Lesquereux) comb. nov. from the latest Eocene of Colorado and Montana and from the middle Eocene to early Oligocene of Oregon were reinvestigated using the type material and more recently collected specimens. Two additional species, Florissantia quilchenensis (Mathewes & Brooke) comb. nov. from the middle Eocene of British Columbia and Washington and F. ashwillii sp. nov. from the middle Eocene to early Oligocene of Oregon, are also recognized on the basis of differences in perianth and anther morphology. Florissantia flowers are borne on long (up to 3 cm) pedicels and possess a large (2.3‐5.3 cm diam), shallowly campanulate, five‐lobed, persistent gamosepalous calyx. The fertile parts include a superior, pentagonal ovary, a single style with five stigmas, and a cycle of five stamens with bifurcate filaments topped by stout anthers or half anthers. Pollen removed from the anthers is oblate, 20‐32 μm equatorial diam, 3(‐4)‐colporate, with short colpi and reticulate ornamentation. Although formerly placed in Porana (Convolvulaceae) and Holmskioldia (Verbenaceae), the newly recognized characters of floral and pollen morphology demonstrate that the genus belongs within the Malvales as an extinct genus possessing features found today in Tiliaceae, Bombacaceae, and Sterculiaceae. Recognizing that there is much overlap among extant genera of these families, and that the circumscription of these families is in need of systematic revision, the fossil is tentatively placed in the Sterculiaceae. Florissantia flowers exhibit a syndrome of features suggestive of insect or bird pollination, while the fruits, provided with a large, persistent, membranous calyx, appear to be well adapted for wind dispersal. Dismissal of this and other purported verbenaceous fossils from the Verbenaceae casts doubt on the presence of Verbenaceae in the early Tertiary of North America.
PETAL APPENDAGES IN BROMELIACEAE
Authors: Brown Gregory K. , Terry Randall G.
Published: January 2018

The Bromeliaceae were surveyed for petal appendage morphology using light and scanning electron microscopy. Three general morphological types were recognized, each loosely correlating with one of the three subfamilies. Petal appendage elaboration and variation were greatest in the Bromelioideae, while subfamilies Pitcaimioideae and Tillandsioideae exhibit more simplified, consistent morphologies. All Pitcaimioideae examined with petal appendages possessed a single appendage per petal, as opposed to two appendages per petal for the Bromelioideae and Tillandsioideae. Analyses of floral ontogenetic sequences revealed that, in all cases, petal appendage initiation is a late developmental event with petal appendages being the last formed external multicellular structures. There has been an overemphasis in the use of the presence of petal appendages in the circumscription of generic limits in the Bromeliaceae, and especially in the Tillandsioideae (e.g., Tillandsia vs. Vriesea).
CHLOROPLAST DNA RESTRICTION SITE VARIATION IN THE FERN GENUS PELLAEA: PHYLOGENETIC RELATIONSHIPS OF THE PELLAEA GLABELLA COMPLEX
Authors: Gastony Gerald J. , Yatskievych George , Dixon Colleen K.
Published: January 2018

The cheilanthoid ferns have long resisted efforts to circumscribe well‐defined, phylogenetically natural generic and infrageneric groups, presumably because of homoplastic morphologies associated with their xeric habitats. This cladistic analysis of phylogenetically informative chloroplast DNA restriction site data from 14 enzymes and seven taxa in the cheilanthoid genus Pellaea provides new insights into the phylogenetic relationships of the P. glabella complex. It also assesses the congruence of results based on restriction site data at inter‐ and intraspecific levels in these sexually and apogamously reproducing ferns with those of earlier morphological and isozyme analyses of the same group. Wagner parsimony yielded a single most parsimonious tree of 187 steps and 11% homoplasy, based on a data matrix of 166 restriction sites of which 66 were phylogenetically informative. Phylogenetic analysis based on user‐defined stepmatrix character‐state weighting of site gains over losses produced an identical single most parsimonious tree. Dollo parsimony yielded two most parsimonious trees, one of which was topologically identical to the Wagner tree. Specific and infraspecific relationships in the P. glabella complex determined by the completely independent restriction site and isozyme data sets are identical. This lends confidence to the ongoing use of restriction site data in a broader study of Pellaea and other cheilanthoid taxa and to the present conclusions that P. atropurpurea is sister to the P. glabella complex, whereas P. breweri, previously considered the closest relative of this complex, is actually more distantly related to it than are the other taxa in this study.
CARBON INTEGRATION IN TWO PLANTAGO SPECIES
Authors: Lacey Elizabeth P. , Marshall C.
Published: January 2018

We measured the pattern of export of 14C‐assimilate from reproductive spikes and leaves subtending spikes in Plantago aristata and P. virginica. In P. arislata, little 14carbon was exported to any other reproductive metamer (leaf + associated spike) from the leaf subtending a flowering spike. In P. virginica a large amount was exported. Thus, like clonal species, rosette species can vary in patterns of carbon integration among the repeated morphological subunits comprising an individual. When considered in the context of other studies, these data suggest that comparisons of carbon integration in species differing in morphological complexity would be useful in trying to understand the evolution of patterns of carbon integration in plants.
CHARACTERIZATION OF TISSUE CULTURE INITIATION AND PLANT REGENERATION IN SPOROBOLUS VIRGINICUS (GRAMINEAE)
Authors: Straub Peter F. , Decker Debra M. , Gallagher John L.
Published: January 2018

Tissue cultures of the halophytic saltmarsh grass Sporobolus virginicus were initiated from unemerged immature inflorescence tissue. Typical graminaceous embryogenic and nonembryogenic callus and cell types were noted. Embryogenic callus was compact golden yellow. Histological evidence indicated that proliferation of the ovary tissue of the immature pistil was the source for embryogenic callus. Plants regenerated after first reducing and then eliminating auxin from the culture medium. Regeneration was observed both through the concerted development of bipolar meristems from somatic embryos and by the formation of multiple shoot meristems that were either connected through callus tissue to root meristems or which later adventitiously rooted. The main mode of regeneration appeared to be somatic embryogenesis with additional multiple shoot formation probably due to precocious germination of somatic embryos. Plants recovered from culture were acclimated to soil, grown up in a greenhouse, and planted in field plots with saline irrigation to ensure stability of salt tolerance.
REPRODUCTIVE PHENOLOGIES IN LOBELIA INFLATA (LOBELIACEAE) AND THEIR ENVIRONMENTAL CONTROL
Authors: Kelly Carol A.
Published: January 2018

Flowering and fruiting phenologies of individual plants and flowers of Lobelia inflata, a North American summer annual, were studied in the field and greenhouse to determine whether onset of flowering and fruit maturation were correlated, and the degree to which these reproductive phenologies were influenced by the environment. Within each of two field populations, larger plants flowered earlier and produced more flowers than smaller plants. Onset of flowering was positively correlated with onset of fruit maturation but not perfectly so. Two factors decreased the intensity of this correlation. First, at the flower level, the earlier a flower bloomed, the longer the resulting fruit took to develop. Second, fruit development times varied significantly among individual plants. In the greenhouse, individuals watered more frequently attained greater size and flowered earlier than individuals watered less frequently. Nutrient additions did not affect plant size or onset of flowering. These results indicate that for the summer annual Lobelia inflata, reproductive phenologies are phenotypically correlated, and that timing of reproduction is resource and size dependent, as it is for other monocarpic plant species.
IRREGULAR FLORAL DEVELOPMENT IN CALLA PALUSTRIS (ARACEAE) AND THE CONCEPT OF HOMEOSIS
Authors: Lehmann Naida L. , Sattler Rolf
Published: January 2018

About two‐thirds of the more than 100 genera in the Araceae lack tepals and their absence is considered derived. Unlike most of these atepalate genera, Calla palustris has about twice as many stamens per flower. Using epi‐illumination microscopy, we studied floral development in Calla to see if the supernumerary stamens form in positions corresponding to tepal positions in perigonate Araceae. If so, this would be an example of homeosis—in this case, the replacement of tepals with stamens—in the evolution of this genus. We found the positions of stamen primordia in many floral buds too irregular to conclude that they replace tepals positionally. However, in more regular floral buds the first formed stamens do form in what correspond to tepal sites in related genera. If the immediate ancestor to Calla had tepals, as is generally assumed, stamen positions in the more regular flowers, at least, support a homeotic interpretation. There is no evidence that the supernumerary stamens arise by dédoublement, but since morphogenesis in Calla is only partly comparable to other aroids, and the phylogeny in the family is not well understood, further studies are needed to resolve the interpretation of the flower in Calla. With regard to systematics and evolution, the absence of tepals in Calla may not be homologous with atepaly in other members of the family, as has been assumed for the past century.
PHYLOGENY OF THE RUBIACEAE AND THE LOGANIACEAE: CONGRUENCE OR CONFLICT BETWEEN MORPHOLOGICAL AND MOLECULAR DATA?
Authors: Bremer Birgitta , Struwe Lena
Published: January 2018

Phylogenetic analyses of 33 genera of Rubiaceae were performed using morphological and a few chemical characters. Parsimony analysis based on 29 characters resulted in eight equally parsimonious trees, with a consistency index of 0.40 and a retention index of 0.69. These results were compared to a phylogenetic analysis of the same genera based on chloroplast DNA restriction site data. There are discrepancies between the two analyses, but if we consider groupings reflected in the present classification there is much congruency. With the exception of four genera, all the genera are positioned in the same group of taxa in the two analyses. Clades of taxa representing three of the four subfamilies (~the Antirheoideae, ~the Rubioideae, and the ~Ixoroideae) are monophyletic, while the fourth subfamily Cinchonoideae is shown to be paraphyletic. Both analyses support a widened tribe Chiococceae, including the former subtribe Portlandiinae (Condamineeae). Furthermore, in both analyses the tribe Hamelieae is placed outside the subfamily Rubioideae where it is now housed. In search for the most plausible sister group to the Rubiaceae, the genus Cinchona (Rubiaceae) was analyzed together with 13 genera of the Loganiaceae, Nerium (Apocynaceae), and Exacum (Gentianaceae). Cornus (Comaceae), Olea (Oleaceae), and these two genera together were used as outgroups. The analysis, including 25 characters, 16 taxa, and with Cornus and Olea together as an outgroup, resulted in four equally parsimonious trees, with a consistency index of 0.53 and a retention index of 0.62. The non‐Loganiaceae taxa Cinchona (Rubiaceae), Nerium (Apocynaceae), and Exacum (Gentianaceae) were all found to have their closest relatives within the Loganiaceae indicating that the Loganiaceae are paraphyletic and ought to be reclassified. As a result of the morphological data the most plausible sister group to the Rubiaceae is the tribe Gelsemieae of the Loganiaceae.
SEED DISPERSAL OF METROSIDEROS POLYMORPHA (MYRTACEAE): A PIONEER TREE OF HAWAIIAN LAVA FLOWS
Authors: Drake Donald R.
Published: January 2018

Wind dispersal of seeds of Metrosideros polymorpha, the dominant tree of rain forests and the main pioneer of volcanic substrates in Hawaii, was measured on a 20‐yr‐old lava flow downwind of a M. polymorpha forest. Seed rain was concentrated in December and January, when 74.5% of the annual total was dispersed. Annual seed rain at the forest edge was 63,893 seeds/m2, of which 5,580 (8.7%) contained embryos and were potentially viable. Beyond the forest edge, the density of embryo‐containing seed decreased to 363, 137, 37, 25, and 20/m2 at distances of 25, 50, 100, 150, and 250 m, respectively. In contrast, the density of established M. polymorpha seedlings remained relatively constant beyond 25 m, a fact suggesting that the density of safe sites for germination and establishment was also constant over the same distance. It was concluded that colonization of the lava flow was limited by the density of safe sites, i.e., conditions for establishment, rather than by seed rain, i.e., dispersal, which was more than sufficient to saturate the available safe sites.
FUNGI FROM THE LOWER DEVONIAN RHYNIE CHERT: CHYTRIDIOMYCETES
Authors: Taylor Thomas N. , Remy Winfried , Hass Hagen
Published: January 2018

Several different chytridiomycetes are described from the Lower Devonian (Siegenian) Rhynie chert. Included are both eucarpic and apparently holocarpic forms that occur in Palaeonitella, Aglaophyton, Lyonophyton, Horneophyton, and clusters of algal cells, as well as in the surrounding chert matrix. Holocarpic types consist of endobiotic sporangia, each characterized by one discharge tube. Sporangia can be traced from the thallus stage to the discharge of zoospores. Monocentric and polycentric eucarpic chytrids are associated with the miospores of Aglaophyton and various thick‐walled fungal spores. In these forms the sporangia are variable in size and shape ranging up to 30 μm. Most appear to be inoperculate and there is evidence that the sporangium ruptured on the distal surface. Some contain zoospores with flagella. One operculate eucarpic form had parasitized the cellular gametophyte emerging from the proximal surface of an Aglaophyton spore. Several of the Rhynie chert chytrids are comparable with a number of extant forms (e.g., Olpidiaceae and Spizellomycetaceae), while others possess features that encompass several groups. These fossil fungi are discussed in the context of their interactions with other organisms in this Lower Devonian freshwater paleoecosystem.
EFFECT OF SILICON SUPPLY ON GROWTH, FERTILITY, AND MINERAL COMPOSITION OF AN ANNUAL BROME, BROMUS SECALINUS L. (GRAMINEAE)
Authors: Gali Hala U. , Smith Christopher C.
Published: January 2018

A study of the effects of three levels of silicon nutrition, representing low, intermediate, and high levels, shows that silicon does not enhance the vegetative growth of Bromus secalinus (cheat), yet it increases the rate of seed development and the efficiency of seed set. Grasses supplied with silicon have a higher percent of viable seeds compared to those grown in very low levels of silicon. Silicon supply, however, is not an absolute requirement for cheat reproduction, since grasses growing in low silicon levels set flowers and seeds, and the average weight of individual seeds or the mean number of inflorescences per plant are not influenced by silicon nutrition. Concentrations of silicon in tissues of cheat increase over time and with higher levels of silicon supply. Considerable differences are found in the silicon content of various vegetative and reproductive parts of cheat. Among vegetative parts, levels of silicon are lowest in stems and highest in green and senescent leaf blades. Among reproductive parts, silicon is most highly concentrated in the husks (glumes, lemmas, and paleas) surrounding filled seeds and is almost nonexistent in the seed itself. Mechanisms influencing silicon deposition and the ecological significance of the present findings are discussed.