bluuebunny/crossref_metadata_2025 huggingface dataset:
Inbreeding effects on mating system traits for two species ofLupinus(Leguminosae)
Authors: Karoly Keith
Published: January 2018

The consequences of inbreeding for reproductive traits were investigated for two closely related annual lupines that differ in their mating system.Lupinus bicolor (Leguminosae) is a primarily selling species whileLupinus nanusoutcrosses at intermediate rates. A controlled crossing program was used for each species to produce selfed and outcrossed progeny. These progeny were then grown in a greenhouse and scored for the date of first flower, flower morphology, and autofertility. Selfed progeny ofL. bicolorproduced significantly smaller flowers but did not differ from outcrossed progeny for the remaining traits. Selfed progeny ofL. nanusproduced flowers that significantly differed in shape and had fewer ovules than the flowers of outcrossed progeny. Selfed progeny ofL. nanusalso had significantly lower rates of autofertility in comparison to outcrossed progeny. The significant effects of inbreeding on these mating system traits may indicate the presence of directional dominance at the loci underlying these characters. The consequences of these direct effects of inbreeding on reproductive traits for plants growing in natural populations may include nonadaptive changes in the outcrossing rate between generations.
Alliin lyase localization in bundle sheaths of the garlic clove (Allium sativum)
Authors: Ellmore George S. , Feldberg Ross S.
Published: January 2018

The enzyme alliin lyase (E.C. 4.4.1.4) catalyzes formation of allicin, the parent of several sulfur‐containing compounds responsible for flavor, odor, and pharmacological properties of garlic (Allium sativum). Alliin lyase is a major product of the storage bud (clove), accounting for 10% of its total protein. Accumulation of this protein was characterized by locating alliin lyase deposits within the clove. Paraffin sections stained for general protein using aniline blue‐black reveal dense deposits within parenchymatous bundle sheaths. Deposits are most pronounced around phloem. Remaining storage parenchyma, not in contact with bundles, appears structurally uniform, with some protein accumulating in cells near the outer surface of the clove. In freehand sections of unfixed cloves, bundle sheath cells are the only ones to show green autofluorescence when excited by blue light. Such fluorescence is consistent with the presence of pyridoxal phosphate cofactor of alliin lyase. An alliin lyase activity stain, based on detecting aminocrotonate‐generating enzymes, shows activity to be restricted to bundle sheath cells in fresh material. Finally, enrichment of alliin lyase in bundle sheaths is shown by immunocytochemical staining of these areas using a polyclonal antibody generated against purified enzyme. Aliin lyase concentrates in bundle sheaths, while little if any occurs in storage mesophyll not in contact with vascular bundles. Deposits in the cloves may reflect the enzyme's role in protecting underground storage buds from decay and predation. Positioning near the phloem suggests that alliin lyase, or compounds related to its metabolism, may be translocated to and from the clove during development.
Variable reproductive output among clones of Spartina alterniflora (Poaceae) invading San Francisco Bay, California: the influence of herbivory, pollination, and establishment site
Authors: Daehler Curtis C. , Strong Donald R.
Published: January 2018

Spartina alterniflora has recently been introduced to San Francisco Bay, California, and is rapidly invading open mud flats, growing in circular patches that we found to be individual genetic clones. We collected spikelet samples from more than 200 clones and observed germination rates ranging from 0% to 59%, indicating substantial variation in reproductive output among clones. Several experiments were performed to explore the cause of variation. Pollination manipulations showed that S. alterniflora is outcrossing, but pollen supplements did not increase spikelet germination rates. Exclusion of the only insect herbivore (a phloem feeder, Prokelisia marginata) from developing inflorescences increased the proportion of spikelets containing seed, but failed to increase germinations per spikelet. Spikelets from Willapa Bay, Washington, grown free of insect herbivores, had germination rates similar to San Francisco Bay. These results suggest herbivory is not limiting reproductive output of S. alterniflora. Spikelet viability was not related to clone size; however, clones located lower in the intertidal or far up a drainage slough averaged fewer germinations per spikelet, suggesting clones in areas with lower genet density may have lower spikelet viabilities. Spikelet samples from different sections of clones growing across wide environmental ranges had similar rates of germination, suggesting some genetic influence on spikelet viability. Differential reproductive output among clones and the novel selective environment of San Francisco Bay are expected to cause gene frequency changes in this rapidly expanding population.
Pollinators of tropical dioecious angiosperms: a reassessment? No, not yet
Authors: Bawa Kamaljit S.
Published: January 2018

The association between dioecy and generalist mode of pollination suggested about 20 years ago has been recently questioned. It is argued that there is evidence to indicate that a disproportionate number of dioecious species have relatively smaller flowers and a more generalist mode of pollination than hermaphroditic taxa. This trend seems to hold at the community level as well as within genera containing dioecious and hermaphroditic species. Like other correlations among characters, correlations among dioecy, small flower size, and pollination systems provide important insights into mechanisms of plant evolution.
Evaluating the relationship of autumn buttercup (Ranunculus acriformis var. aestivalis) to some close congeners using random amplified polymorphic DNA
Authors: Van Buren R. , Harper K. T. , Andersen W. R. , Stanton D. J. , Seyoum S. , England J. L.
Published: January 2018

Autumn buttercup, an endangered endemic of wet, saline meadows in Garfield County, Utah, is treated differently in various taxonomic references now in use in the region. The taxon is currently listed as endangered by the United States Fish and Wildlife Service under the name Ranunculus acriformis var. aestivalis L. Benson. Others treat it as R. acris var. aestivalis (L. Benson) Welsh. In an attempt to resolve the taxonomical disagreements and to quantitatively describe the genetic uniqueness of this taxon, putative close relatives of the autumn buttercup, namely R. occidentalis (Nevada County, CA), R. acris (introduced from Europe and now growing wild in Rich and Cache counties, UT), R. acriformis var. montanensis (Lincoln County, WY), R. acriformis var. acriformis (Emery and Sanpete counties, UT), and R. acriformis var. aestivalis were collected and analyzed using random amplified polymorphic DNA (RAPD) genetic markers amplified from total cellular DNA extracts. Twenty‐three decanucleotide primers of arbitrary sequence were used for DNA amplification; over 350 markers were generated. The genetic marker data were analyzed using similarity coefficients and parsimony. Based on the results of those analyses and on a review of ecological and morphological characteristics, we have elevated the autumn buttercup to species rank as Ranunculus aestivalis (Benson) Van Buren & Harper.
A comparison of leaf physiology and anatomy ofQuercus(sectionErythrobalanus‐Fagaceae) species in different light environments
Authors: Ashton P. M. S. , Berlyn G. P.
Published: January 2018

Physiological and anatomical attributes of leaves were examined of three species ofQuercussectionErythrobalanus.All three species occur in moist temperate deciduous forests of eastern North America. Seedlings of each species were grown in different light conditions for comparison. The attributes measured were net photosynthesis, stomatal conductivity, blade and cuticle thickness, stomatal density, thickness of upper and lower epidermis, and thickness of palisade mesophyll. The results generally demonstrate the close association between anatomical adaptations and efficiency of physiological processes; they also elucidate the distribution patterns of the threeQuercusspecies across the forest topography in southern New England. The most drought‐tolerant and light‐demanding species,Q. velutina(Lam.), exhibited the greatest leaf anatomical plasticity, the highest net photosynthesis in the different light conditions, and the lowest stomatal area per unit area of leaf. The most drought‐intolerant species,Q. rubra(L.), exhibited the least leaf anatomical plasticity, the lowest net photosynthesis in the different light conditions, and the highest stomatal area per unit area of leaf.Quercus coccinea(Muenchh.) usually exhibited values that were intermediate betweenQ. rubraandQ. velutina.
Inflorescence development in a perennial teosinte: Zea perennis (Poaceae)
Authors: Orr Alan R. , Sundberg Marshall D.
Published: January 2018

The ontogeny of tassels and ears in a perennial Mexican teosinte, Zea perennis (Hitchc.) Reeves and Mangelsdorf, was examined using scanning electron microscopy and light microscopy. Ear development follows a pattern previously described for two annual teosintes, Z. mays subsp. mexicana and Z. mays subsp. parviglumis var. parviglumis (race Balsas), and for the bisexual mixed inflorescence in a diploperennial teosinte, Z. diploperennis; it differs from that described for the ear of Z. diploperennis plants grown at the latitudes of Iowa and Wisconsin. Common bud primordia of the ear are initiated in the axil of distichously arranged bracts along the ear axis. These common primordia bifurcate to form paired pedicellate and sessile spikelet primordia. Development of the pedicellate spikelets in the ear is arrested leaving the sessile spikelets, along with the adjoining rachis segment, to form solitary grains enclosed within cupulate fruitcases. The organogenesis of the central spike of the tassel is similar to that previously described in other Zea taxa. This developmental study supports the hypothesis that both femaleness and maleness are derived from and expressed on a common background; it is consistent with the view that the maize ear was derived from the central spike of a male inflorescence terminating a primary branch of the main axis of the inflorescence.
Leaf structure and patterns of photoinhibition in two neotropical palms in clearings and forest understory during the dry season
Authors: Araus José L. , Hogan Kevin P.
Published: January 2018

We studied the leaf structural, water status, and fast fluorescence responses of two palms, Socratea exorrhiza and Scheelea zonensis, under natural dry season conditions in a clearing (high light [HL] palms) and the forest understory (low light [LL] palms) on Barro Colorado Island, Panama. HL‐Socratea leaves were more shade‐adapted, less xeromorphic, and more strongly affected by drought than HL‐Scheelea. Fv/Fm (the ratio of variable to maximum chlorophyll fluorescence) and t½ (the half‐rise time of Fm) was lower in HL‐leaves of both species, indicating photoinhibition. In HL‐Scheelea, the light‐induced reduction of Fv/Fm was much less than in HL‐Socratea, and Fv/Fm recovered completely overnight. Patterns of relative water content, specific leaf dry weight, stable carbon isotope composition, and leaf conductance suggest that increased drought resistance in Scheelea reduces susceptibility to photoinhibition. An increase in Fo indicated the inactivation of PSII reaction centers in HL‐Socratea. The very low chlorophyll a/b ratio and alterations in chloroplast ultrastructure in HL‐Socratea are consistent with photoinhibition. Under LL, the species showed no appreciable interspecific differences in chlorophyll fluorescence. Excess light leads to low values of Fv/Fm in HL‐plants relative to LL‐plants on both leaf surfaces, particularly on the lower surface, due to a decrease of Fm in both surfaces and an increase in F., of lower surface. For both species, Fo for the lower surfaces of HL‐plants was higher and t½ was markedly lower than for the upper surface, as is typical for shade‐adapted leaves. Xeromorphic leaf structure may reduce susceptibility to photoinhibition during the dry season. Drought‐enhanced photoinhibition could limit the ability of some species to exploit treefall gaps.
Systematics of Mielichhoferia (Bryaceae: Musci). III. Hybridization between M.elongata and M.mielichhoferiana
Authors: Shaw A. Jonathan
Published: January 2018

Allozyme variation in mixed populations of Mielichhoferia elongata and M. mielichhoferiana was investigated to determine if interspecific hybridization occurs when these two closely related species grow together. Previous research has shown that M. elongata and M. mielichhoferiana can be distinguished by three diagnostic isozyme loci (Gpi‐1, Mdh‐2, and Mdh‐3) at which the two species do not share alleles in 32 allopatric populations from North America and Europe. The present study shows that in five populations from Colorado, Norway, and Sweden, gametophytes resulting from interspecific hybridization can be recognized by recombinant genotypes combining alleles of the otherwise diagnostic loci. A total of 32 multilocus genotypes was found among the 111 individuals sampled, of which 13 were recombinants. The frequency of recombinants ranged from 12% to 35% within populations, and all but one population contained both parental species. Moreover, recombinant genotypes could be accounted for by the allelic constitution of sympatric parents. In two of the populations, more than one hybridization event was necessary to account for the diversity of recombinant genotypes. Twenty‐nine of the 32 genotypes detected in this study were restricted to one population each, two occurred in two Swedish populations separated by approximately 14 km, and one occurred in both Sweden and Norway.
Effects of fire season and soil fertility on clonal growth in a pyrophilic forb, Pityopsis graminifolia (Asteraceae)
Authors: Brewer J. Stephen , Platt William J.
Published: January 2018

We experimentally manipulated fire season in a longleaf pine sandhill community in north Florida in 1990 and 1992. We determined the size and demography of shoots, rhizomes, and clones of Pityopsis graminifolia from late 1990 to early 1993. In addition, we examined shoot responses to seasonal variation in canopy/litter removal and soil fertility in 1992. May fires caused a higher short‐term rate of increase in shoot density than did either January fires or August fires. The combination of canopy/litter removal and mineral nutrient addition as part of the clipping experiment revealed a similar effect on shoot density in May. Fire season influenced clone structure. May fires resulted in greater numbers of shoots/clone than did January or August fires. January‐burned plots had clones and rhizomes that contained larger (but fewer) shoots than did May‐burned or August‐burned plots. We suggest that such variation in clone structure may indicate a greater capacity of clones to grow laterally following May fires than following either January or August fires. This capacity is positively associated with the likelihood that longleaf pine savannas will be burned by lightning fires at different times during the year.
Influence of light level on the growth and morphology of saplings in a panamanian forest
Authors: King David A.
Published: January 2018

Leaf spacing and aboveground growth were monitored in saplings of ten species in a range of light environments in a Panamanian lowland humid forest. One‐ to 2‐m‐tall individuals of the chosen species had intermediate to large leaves on stems with few or no branches. Saplings in high light environments grew faster in height and produced more biomass per unit leaf area than shaded saplings for all species. These growth responses involved morphological plasticity with greater extension per unit biomass increment increasing the height growth rate of gap‐grown saplings and greater biomass allocation to leaves decreasing the whole plant light compensation point in shade. The relative performance of the species also varied across the light gradient and was related to differences in leaf lifespan and specific leaf mass. Light‐demanding species grew as rapidly in shade as shade‐tolerant species, but the shorter leaf lifespan of the former necessitates higher production rates to maintain a given leaf area, largely excluding light‐demanders from shaded understory locations. Height growth rate was positively correlated with leaf spacing for each species, and differences between species in the height growth rate‐internode length relationship were related to interspecific differences in specific leaf mass. Thus, sapling growth histories may be inferred from their morphologies.
Comparative ecophysiology of a rare and a widespread species ofEchinacea(Asteraceae)
Authors: Baskauf Carol J. , Eickmeier William G.
Published: January 2018

Among various potential causes of rarity, one explanation could be that a rare species has more narrow physiological tolerances to important environmental variables than does a widespread species. To test this hypothesis photosynthetic performance as a function of irradiance and temperature was compared for the rare cedar glade endemicEchinacea tennesseensisand its widespread prairie congenerE. angustifoliafollowing various light and soil moisture preconditioning regimes. Although the species differed in some morphological characteristics such as specific leaf area, both species demonstrated similar photosynthetic light‐response curves on a leaf area basis, with low to moderate photosynthetic capacity. Thus no photosynthetic differences were found that could account for the contrasting geographic distributions of the endemic species and its widespread congener.
Comparison of leaf morphology among submersed species of Myriophyllum (Haloragaceae) from different habitats and geographical distributions
Authors: Gerber D. Timothy , Les Donald H.
Published: January 2018

An image analysis system was used to calculate the surface area and volume of the submerged leaves of seven species of Myriophyllum. We separated the species into two categories based on their distribution and habitat differences and compared their surface area, volume, dry mass, specific leaf area, and surface to volume ratios. The geographic location and habitat of the species explained the greatest percentage of total variance for these variables when compared by analysis of variance. A leaf shape analysis was performed by regressing surface area with volume for each species. Interspecific comparisons of leaf shape were made using analysis of covariance. Fundamental interspecific differences in submerged leaf shape, associated with differences in their geographic distributions and habitats, are explained as adaptations for different nutrient uptake regimes.
Gibberellic acid (GA3)‐induced enhancement of α‐amylase activity in the aleurone of Shrunken‐2 maize kernels
Authors: Sanwo Monica M. , DeMason Darleen A.
Published: January 2018

The aleurone of RB‐3 shrunken‐2 (sh2) maize kernels is deficient in α‐amylase activity during germination, but exogenous applications of gibberellic acid (GA3) (0.001–10 μm) induced low levels of activity. The highest activity was measured in the aleurone of kernels treated with 10 μm GA3 (14,600 ± 945 units), but was lower than untreated Starchy (Su) aleurone tissues (35,280 ± 5,010 units). On isoelectric focusing gels, no α‐amylase isozymes were detected in the untreated sh2 aleurone using starch zymograms or immunoblots, but the 1.0 and 10 μmmm GA3 treatments induced nearly all the isozymes (eight to ten) present in the Su aleurone. There was a very low level of α‐amylase mRNA in the untreated sh2 aleurone, an intermediate level in the 1.0 μm GA3‐treated sh2 aleurone, and the highest level in the untreated Su aleurone. On the confocal microscope, the 1.0 μm GA3‐treated aleurone cells had enhanced levels of cytoplasmic membranes and RNA compared to untreated sh2 aleurone cells. The 1.0 μm GA3 treatment also induced shoot elongation in the sh2 seedlings. The data demonstrate that the sh2 aleurone is deficient in its function to produce α‐amylases, and exogenous GA3 can partially restore cell function in the sh2 kernels.
Anatomy of the Muhlenbergia Montana complex (Poaceae)
Authors: Herrera‐Arrieta Yolanda , Grant William F.
Published: January 2018

Leaf anatomical data from 13 taxa of the Muhlenbergia montana complex were surveyed, and 18 critical characters were found. Results obtained from the phenetic analysis of anatomical data have given independent data to compare with the morphological, phytogeographical, and flavonoid data (previously reported) in determining the relationships of the species. An anatomical dendogram illustrates a close corroboration. Leaf anatomy clearly supports the recognition of a close relationship among the two taxa — M. virescens and M. quadridentata—as has been suggested in previous reports. Therefore, a change of level is suggested in which M. quadridentata (H.B.K.) Kunth is proposed here as M. virescens (H.B.K.) Kunth ssp. quadridentata (H.B.K.) Herrera (comb. nov.).
Genetic diversity and mating system in a tropical tree, Carapa guianensis (Meliaceae)
Authors: Hall Pamela , Orrell Lelia C. , Bawa Kamaljit S.
Published: January 2018

Carapa guianensis Aublet. (Meliaceae) is an abundant, canopy tree species often exported as fine wood products. The populations in the Atlantic coastal plain of Costa Rica have undergone a wide variety of human‐induced changes in distribution and abundance, including isolation due to deforestation. Using protein electrophoretic analysis of seeds, we investigated the genetic variability and population differentiation of nine populations and the outcrossing rate in two populations that differed in density by a factor of 50%. Average polymorphism (35%) and heterozygosity (0.12) across populations were relatively low in comparison with other tropical tree species. Only 4.6% of the total genetic variability could be attributed to population differentiation even though populations were separated by as much as 70 km. However, genetic differentiation did increase with distance between pairs of compared populations. There were no apparent differences in genetic variation between logged and unlogged forests. The outcrossing rate for each population was not significantly different from 1.0, but there was evidence of nonrandom mating in the lower density population. High levels of gene flow are probably maintained by seed dispersal as seeds travel well throughout flooded forests and rivers. High population density and synchronous flowering also contribute to high outcrossing rates. These genetic characteristics suggest that Carapa guianensis is a good candidate for natural forest management where it occurs at high density. However, current management practices need to account for the rapid rate of deforestation occurring around managed natural forest sites that will result in the elimination of intervening populations.
A molecular phylogeny of Arceuthobium (Viscaceae) based on nuclear ribosomal DNA internal transcribed spacer sequences
Authors: Nickrent Daniel L. , Schuette Kevin P. , Starr Ellen M.
Published: January 2018

Ribosomal DNA (rDNA) internal transcribed spacer (ITS) and 5.8S rDNA sequences were obtained from 22 species of dwarf mistletoes (Arceuthobium — Viscaceae) to test phylogenetic relationships. Interspecific distances ranged from 0 to 21.4% between New World species, values two to five times higher than those measures for the ITS region in other plants. One Old World species (A. oxycedri) and one New World species (A. abietis‐religiosae) were remarkably similar to each other but exhibited up to 41% sequence divergence from the remaining species. Minimum length trees support the concept of a verticillately branched subgenus Arceuthobium; however, interspecific distances indicate this group is extremely heterogeneous. Subgenus Vaginata, Section Vaginata, is centered in Mexico and encompasses all the taxa previously placed in this group but is expanded to include several species previously classified in Section Campylopoda (e.g., A. divaricatum, A. rubrum, and A. strictum). The sister group relationship between A. divaricatum and A. douglasii, first seen following isozyme analysis, is supported by ITS sequence data. Section Campylopoda s. s. is now composed of 13 mainly U.S. species that show a high degree of morphological and genetic similarity. The eastern dwarf mistletoe, A. pusillum, is not closely related to A. douglasii but rather with A. bicarinatum from Hispaniola, which suggests that these taxa represent highly modified relicts that shared an ancestor in the early Tertiary. Two endemic species from Mexico and Central America (A. guatemalense and A. pendens) formed a sister group and have been placed in a new Section (Penda). Rapid molecular evolution in Arceuthobium may be associated with the adaptive radiation of this genus on numerous conifer hosts.
The effects of white fluorescent light, far‐red light, darkness, and moisture on spore germination of Lygodium heterodoxum (Schizaeaceae)
Authors: Pérez‐García Blanca , Orozco‐Segovia Alma , Riba Ramón
Published: January 2018

Spores of Lygodium heterodoxum Kunze were stored in dry and fully water‐imbibed conditions in darkness at 23–25 C. Spores stored in dry conditions lose viability faster than those stored fully water‐imbibed. After 1 year, less than 1% of the spores stored in dry condition germinated, while about 40% of the stored water‐imbibed spores still germinated. The spores do not germinate in darkness, but they do germinate under white and far‐red light.
Variation in the mating system of Sitka spruce (Picea sitchensis): evidence for partial assortative mating
Authors: Chaisurisri Kowit , Mitton Jeff B. , El‐Kassaby Yousry A.
Published: January 2018

Five allozyme polymorphisms were used to analyze the mating system in a Sitka spruce seed orchard in Saanichton, British Columbia. Allelic frequencies differed between the pollen and maternal pools at three of the five loci, with alleles rare in the maternal pool being even rarer in the effective pollen pool. Minor differences in pollen allelic frequencies were observed in the upper vs. lower crown. The multilocus outcrossing rate of the upper crown (tm = 0.909) exceeded that of the lower crown (tm = 0.764). Single‐locus estimates of the outcrossing rate were significantly heterogeneous, with the lowest estimate of outcrossing, t = 0.773, observed for PGM‐2 locus. Analyses of the mating system for the three maternal PGM‐2 genotypes revealed heterogeneous pollen allelic frequencies and heterogeneous outcrossing rates, possibly due to assortative mating at this locus.
Comparisons among biomass allocation and spatial distribution patterns of some vine, pteridophyte, and gymnosperm shoots
Authors: Niklas Karl J.
Published: January 2018

The interspecific allometry of leaf, stem, and reproductive biomass distal to stem diameter was determined for a total of 12 angiosperm vine, gymnosperm, and pteridophyte species to compare allocation patterns to vegetative and reproductive shoot organs. The allometry of stem diameter in terms of the distance from shoot apices also was determined to quantify the manner in which vines, gymnosperms, and pteridophyte stems tapered along their length. The stems of vine species were found to weigh more than those of arborescent gymnosperm species distal to any point of equivalent stem diameter. Vine species also distribute more of their stem mass to shoot length as opposed to girth than gymnosperm species. Vine stems also supported proportionally larger leaf and reproductive biomass in comparison to gymnosperm stems of equivalent diameter, yet partitioned their total shoot biomass more or less equally between leaf and stem biomass in the same manner as the gymnosperm species examined. The allometry of vine as well as gymnosperm leaf biomass with respect to stem biomass appeared to be slightly anisometric and negative, suggesting that more massive stems had proportionally less leaf biomass than their smaller, less massive counterparts. Vine stems could be approximated as very slender cones; the shape and geometry of gymnosperm stems complied with those of stubby, truncated cones whose top diameter (for those examined), on the average, equaled 28% of the basal diameter. In general terms, the interspecific allometry of vines was most similar to that of pteridophytes. Collectively, these data refute the commonly held notion that vine stems are simply more slender than those of species with self‐supporting stems.
Genetic differentiation in endemic Silene (Caryophyllaceae) on the Hawaiian Islands
Authors: Westerbergh Anna , Saura Anssi
Published: January 2018

Endemic Hawaiian Silene colonize new lava flows and are outcompeted as the ground ages. They illustrate the genetic processes operating in the evolution of pioneering island plants. The volcanic history of the Hawaiian Islands allows an estimation of the age of these plant populations. In this study, populations of S. struthioloides from Maui and the older part of the island of Hawaii, and S. hawaiiensis from the youngest volcanoes of the island of Hawaii were analyzed by enzyme electrophoresis. The genetic structures of these populations were placed in a geographic and geologic context. Silene is much more polymorphic on the older island, Maui. Genetic variation appears to have been lost in the colonization of the youngest island, Hawaii. Interestingly, some loci for populations on the younger volcanoes of the island of Hawaii are monomorphic for alleles not found in populations on the older part of Hawaii. Recurrent colonizations are accompanied with founder effects, and restricted gene flow among populations has led to isolation and genetic drift. This has resulted in genetic and morphological differentiâtion of Silene populations on the youngest volcanoes.
Genetic control of B chromosome transmission in Aegilops speltoides (Poaceae)
Authors: Cebria Antonio , Navarro Maria Luisa , Puertas Maria J.
Published: January 2018

The transmission of B chromosomes in Aegilops speltoides was studied in 1B and 3B plants. 1B plants tend to lose the B, while the Bs are accumulated in 3B plants with respect to Mendelian expectation. The experimental conditions permitted us to deduce the number of Bs transmitted in the egg cells. The quantitative character “mean number of Bs transmitted in the egg cells” shows a large variation in both types of plants. We have carried out a mass selection experiment, selecting those plants with the highest and the lowest values for this character. A genetic component of such variation was demonstrated because significant selection gain was obtained for high transmission rate in 1B plants, and low transmission rate in 3B plants. We have also estimated some fitness variables and their relationship with B transmission by the egg cell. We found that vigor variables are not correlated with B transmission variation. However, in 3B plants there is a significant negative correlation between B transmission rate and fertility, measured as grains per plant and grains per spikelet. It seems that natural selection acts at this level, balancing the strength of the drive and preventing the excessive increase of B number.
Cladode development forOpuntia ficus‐indica (Cactaceae) under current and doubled CO2concentrations
Authors: North Gretchen B. , Moore T. Lin , Nobel Park S.
Published: January 2018

Morphological and anatomical changes for first‐order daughter cladodes (flattened stem segments) of a prickly pear cactus, Opuntia ficus‐indica, were monitored to determine the effects of a doubled atmospheric CO2 concentration on their development and mature form. For daughter cladodes developing in controlled environment chambers for 60 d, maximal elongation rates were similar under a photosynthetic photon flux density (PPFD) of 6 mol m−2 d−1 and a CO2 concentration of 370 μl liter−1, an increased PPFD (10 mol m−2 d−1), and an increased PPFD and a doubled CO2 concentration. These maximal rates, however, occurred at 20, 15, and 12 d, respectively. The maximal relative growth rate under the doubled CO2 concentration was about twice that under the other conditions. For cladodes at 60 d as well as after 4 and 16 mo in open‐top chambers, doubling the CO2 concentration had no effect on final length or width. At 4 mo, cladodes under doubled C02 were 27% thicker, perhaps allowing the earlier production of second‐order daughter cladodes. The chlorenchyma was then 31% thicker and composed of longer cells. At 16 mo, the difference in cladode thickness diminished, but the chlorenchyma remained thicker under doubled CO2, which may contribute to greater net CO2 uptake for O. ficus‐indica under elevated CO2 concentrations. Two other persistent differences were a 20% lower stomatal frequency and a 30% thicker cuticle with more epicuticular wax for cladodes under doubled CO2, both of which may help reduce transpirational water loss.
Higher‐level systematics of Acanthaceae determined by chloroplast DNA sequences
Authors: Scotland Robert W. , Sweere Jennifer A. , Reeves Patrick A. , Olmstead Richard G.
Published: January 2018

Parsimony analyses of ndhF chloroplast gene sequences were undertaken for 15 species of Acanthaceae and nine representative outgroup species. In addition, parsimony analyses of rbcL sequences were undertaken for 12 species of Acanthaceae and the same nine outgroup species as for ndhF. The results indicate that ndhF provides more informative characters and greater systematic resolution at this hierarchical level than rbcL. The ndhF analyses demonstrate that Elytraria and Thunbergia are successive sister taxa to all Acanthaceae taxa that have retinacula and explosive fruits. These data also demonstrate that taxa with both retinacula and explosive fruits can be subdivided further into two monophyletic groups that correspond to taxa with and without cystoliths. Within the group with cystoliths three putatively monophyletic groups correspond to taxa possessing quincuncial, left contort, and ascending‐cochlear corolla aestivation patterns. The results of the rbcL analysis provide less systematic resolution than ndhF but do contain several congruent arrangements of taxa within Acanthaceae.
Postfertilization causes of differential success of pollen donors inErythronium grandiflorum (Liliaceae): nonrandom ovule abortion
Authors: Rigney Lisa P.
Published: January 2018

Seed paternity in Erythronium grandiflorum does not fully reflect the proportion of pollen on the stigma. When two types of pollen are simultaneously applied to the stigma, outbred seeds are produced over inbred, and seeds from more distant donors are produced over seeds from donors nearby. I looked for postfertilization causes of these previously reported patterns of differential success of pollen donors. I simultaneously pollinated stigmas with pollen from two donors and observed ovule development through a window sliced in the ovary. Pollen donor pairs were self and cross, donors 1 and 100 m from the recipient, and two donors each 100 m from the recipient. Since one donor was always the alternate homozygote from the recipient at the malate dehydrogenase locus, I could determine the paternity of developing seeds. When it appeared that ovules were aborting, I removed them and determined their paternity using starch gel electrophoresis. Ovules fertilized by self pollen were more likely to abort than ovules fertilized by cross pollen, and ovules fertilized by nearby donors were more likely to abort than ovules fertilized by distant donors. Ovules fertilized by donors 100 m from the recipient were equally likely to abort. There was not a significant relationship between the proportion of ovules fertilized by a pollen donor and the probability of those fertilized ovules developing into seeds. There was no relationship between ovule position within a fruit and ovule abortion. I manipulated available resources by removing leaves and by permitting only one fruit to develop per plant. Decreasing the amount of resources increased the proportion of aborted ovules. Abortion of ovules of lesser quality appears to release resources that can then be used to develop other offspring.
Organization of the vascular system in the stems ofDiplaziumandBlechnum (Filicales)
Authors: White Richard A. , Weidlich Wayne H.
Published: January 2018

Detailed analysis of the three‐dimensional vascular organization in species of Diplazium and Blechnum indicates that these ferns possess reticulate (dictyostelic) vascular systems that closely reflect the helical phyllotaxis of the shoot. In each species, the vascular pattern shows a specific relationship to the phyllotaxis, so that the phyllotactic fraction can be determined by examination of the number of cauline vascular bundles (meristeles) in cross section of the stem. The number of meristeles in a cross section equals the denominator of the phyllotactic fraction, i.e., the number of foliar orthostichies on the stem. The same numerical relationship also exists in the eusteles of seed plants between the number of axial (sympodial) stem bundles and the phyllotaxis. There is a further parallel between the three‐dimensional reticulate pattern of fern dictyosteles and the reticulate patterns that characterize some herbaceous dicotyledons. However, the hypothesized separate origins of seed plant eusteles and fern dictyosteles from protostelic precursors preclude any direct homologies between these similar patterns. The parallel evolution of presumably more physiologically efficient reticulate systems in herbaceous seed plants and in ferns that have only a primary plant body is noteworthy. The similar relationships between the primary stem vascular patterns and phyllotaxy in both ferns and seed plants further emphasize the likely similarity of the morphogenetic events that occur at the shoot apex in these taxonomically disparate groups.
Pollen quantity and quality as explanations for low seed set in small populations exemplified byEupatorium (Asteraceae)
Authors: Byers Diane L.
Published: January 2018

As plant populations decrease in size, reduced seed set may contribute to their ultimate extirpation. In this study, effects of pollen quantity and compatibility relationships (quality) on seed set were investigated in a rare species (Eupatorium resinosum) and a closely related common species (E. perfoliatum). The impact of pollen quantity was studied through pollen supplementation experiments in two populations of each species. Addition of pollen increased seed set only in the smaller population of E. resinosum. Compatibility relationships (pollen quality) were investigated in a diallel crossing experiment using ten genotypes from the same populations. Plants from the smaller population of E. resinosum were found to be 40% cross‐incompatible, which was higher than the larger population of E. resinosum and the two populations of E. perfoliatum, the latter showing signs of self‐compatibility in some individuals. In addition the variance in number of compatible matings per individual was higher in the smaller population of E. resinosum. These results are consistent with a computer simulation model that investigated the effect of small population size on S‐allele diversity. Sufficient pollination accompanied by a partial breakdown of the incompatibility system may account, in part, for the relative success of E. perfoliatum.
Accumulation of the ZRP3 mRNA in the root and coleorhiza of germinating maize (Zemays, Poaceae)
Authors: Wang Huiqing , Colbert James T. , Wurtele Eve Syrkin
Published: January 2018

The evolutionary origin of the coleorhiza of species of Poaceae is unclear. The zrp3 gene, which codes for a protein of an as yet unknown function, is expressed in the roots of maize early in development. The sequence of zrp3 is similar to the sequences of three other genes isolated from dicot species. The pattern of accumulation of ZRP3 mRNA was examined in embryos of maize. No ZRP3 mRNA can be detected in the dry seeds; however, 1.5 d after inhibition, ZRP3 mRNA accumulated in both the roots and the coleorhiza of the embryo but not in other regions of the seed. In the roots, ZRP3 mRNA accumulates specifically in the cortical ground meristem and the pro‐pith tissues. In the coleorhiza, ZRP3 mRNA accumulates in the parenchymal cells but not in the epidermal cells, thus distinguishing two tissue types in this organ. The accumulation of ZRP3 mRNA in the coleorhiza as well as in the root is molecular evidence consistent with the homology of these two organs.
Reaction norms ofArabidopsis (Brassicaceae). III. Response to nutrients in 26 populations from a worldwide collection
Authors: Pigliucci Massimo , Schlichting Carl D.
Published: January 2018

The study of phenotypic plasticity, the ability of a given genotype to express different phenotypes as environments change, is becoming a central focus of ecological genetics and evolutionary theory. To help address the most pressing questions about plasticity (its genetic control, ecological relevance, and macroevolutionary consequences) we advocate the use of Arabidopsis thaliana (and eventually other related species of the same genus) as a model system. In this study we present experimental data concerning: (a) the extent of reaction norm variation to two levels of nutrients in a worldwide collection of 26 A. thaliana populations; and (b) the existence of multivariate associations among key phenotypic characters, and their reaction to changes in the environment. We found significant among‐population genetic variation for eight of the nine traits measured, as well as plasticity in four traits. Five traits showed significant differences in genetic variation between the two environments. The multivariate association of the nine traits defines four major groups of covarying characters, each of which may be plastic or not, depending on the particular population. The use of populations that can be easily obtained by any researcher, because they are part of a worldwide collection, implies that it will be easy to build on our results during future investigations of phenotypic plasticity in this species.
PHOTOSYNTHESIS AND CARBON ALLOCATION IN TIPULARIA DISCOLOR (ORCHIDACEAE), A WINTERGREEN UNDERSTORY HERB
Authors: Tissue David T. , Skillman John B. , McDonald Evan P. , Strain Boyd R.
Published: January 2018

Seasonal patterns of photosynthesis and carbon allocation were determined for Tipularia discolor, a summer‐deciduous wintergreen orchid of the southeastern United States, to assess the effects of environmental conditions and leaf age on carbon acquisition and allocation patterns. There was no shift in the optimum temperature for photosynthesis (Topt) on a seasonal basis and Topt (≈26 C) was at least 10 C higher than daily maximum air temperature during most of the growing season. Lack of photosynthetic adjustment in Tipularia to seasonal fluctuations in temperature and light suggested that the photosynthetic characteristics of this wintergreen were more similar to those of spring ephemerals than to those of evergreens and summer‐active herbs. The decline in photosynthetic capacity during the winter growing season for Tipularia, largely due to leaf age effects, gradually reduced net photosynthetic rates in the field despite more favorable light and temperature conditions. Photosynthesis in the field was primarily limited by environmental conditions in early‐ and mid‐season and by photosynthetic capacity in late‐season. A 14CO2 labelling experiment demonstrated that patterns of carbon allocation to vegetative structures were affected by the season of photosynthetic carbon fixation, whereas reproductive structures received 21% of the recovered labelled carbon regardless of the period of labelling. Carbon acquired and stored during all periods of the growing season was used to produce new vegetative and reproductive structures.
PHENOTYPIC CONSEQUENCES OF FORCING GERMINATION: A GENERAL PROBLEM OF INTERVENTION IN EXPERIMENTAL DESIGN
Authors: Fox Gordon A. , Evans Ann S. , Keefer Christopher J.
Published: January 2018

Many evolutionary and ecological studies of plants with seed dormancy are plagued by design problems related to seed germination. On the one hand, traits of interest, especially life history traits like early growth rate or time to flowering, may not be independent of dormancy phenotype. On the other hand, germination‐inducing treatments are likely to affect these traits of interest. Consequently, researchers often have had to use confounded designs without information about the consequences. To examine this problem, we studied how early growth in California poppy (Eschscholzia californica) is affected by treating seeds with giberellic acid (GA) to stimulate germination. The dose used was sufficient to slightly but significantly advance emergence time in treated seeds, but it appeared to cause variable growth responses among treated seeds. Experiments using GA to stimulate germination may thus be misleading, at least for the populations and dose studied. Perhaps more importantly, the experimental and statistical approach we used can be employed to study the effects of this confounded design for other doses and species.
Spatial genetic structure of a tropical understory shrub, PSYCHOTRIA OFFICINALIS (RuBIACEAE)
Authors: Loiselle Bette A. , Sork Victoria L. , Nason John , Graham Catherine
Published: January 2018

Analyses of fine‐scale and macrogeographic genetic structure in plant populations provide an initial indication of how gene flow, natural selection, and genetic drift may collectively influence the distribution of genetic variation. The objective of our study is to evaluate the spatial dispersion of alleles within and among subpopulations of a tropical shrub, Psychotria officinalis (Rubiaceae), in a lowland wet forest in Costa Rica. This insect‐pollinated, self‐incompatible understory plant is dispersed primarily by birds, some species of which drop the seeds immediately while others transport seeds away from the parent plant. Thus, pollination should promote gene flow while at least one type of seed dispersal agent might restrict gene flow. Sampling from five subpopulations in undisturbed wet forest at Estación Biologíca La Selva, Costa Rica, we used electrophoretically detected isozyme markers to examine the spatial scale of genetic structure. Our goals are: 1) describe genetic diversity of each of the five subpopulations of Psychotria officinalis sampled within a contiguous wet tropical forest; 2) evaluate fine‐scale genetic structure of adults of P. officinalis within a single 2.25‐ha mapped plot; and 3) estimate genetic structure of P. officinalis using data from five subpopulations located up to 2 km apart. Using estimates of coancestry, statistical analyses reveal significant positive genetic correlations between individuals on a scale of 5 m but no significant genetic relatedness beyond that interplant distance within the studied subpopulation. Multilocus estimates of genetic differentiation among subpopulations were low, but significant (Fst = 0.095). Significant Fst estimates were largely attributable to a single locus (Lap‐2). Thus, multilocus estimates of Fst may be influenced by microgeographic selection. If true, then the observed levels of IBD may be overestimates.