bluuebunny/crossref_metadata_2025 huggingface dataset:
Nickel hyperaccumulation defends Streptanthus polygaloides (Brassicaceae) against pathogens
Authors: Boyd Robert S. , Shaw Joe J. , Martens Scott N.
Published: January 2018

The Ni‐hyperaccumulating annual, Streptanthus polygaloides, may contain as much as 16,400 ppm Ni (dry weight) in its tissues. The function of Ni hyperaccumulation is not known. We tested the hypothesis that one function of Ni hyperaccumulation in S. polygaloides is defense against pathogens. Growth of pathogenic organisms on Ni‐hyperaccumulating plants (averaging 5,630 ppm Ni, produced by growing plants on high‐Ni soil) was compared to pathogen growth on nonhyper‐accumulating plants (averaging 124 ppm Ni, produced by growing plants on low‐Ni soil). Plants containing hyperaccumulated Ni were more slowly infected by a powdery mildew (Erysiphe polygoni) than low‐Ni plants. Two strains of the bacterial pathogen Xanthomonas campestris pv. campestris (one a genetically engineered bioluminescent strain) grew in low‐Ni plants but not high‐Ni plants. Growth of X. campestris pv. campestris was markedly inhibited by Ni concentrations of 400 ppm in artificial media. Growth of the fungus Alternaria brassicicola, which was necrotrophic on S. polygaloides, also was inhibited on high‐Ni leaves relative to low‐Ni leaves. These results demonstrated negative effects of hyperaccumulated Ni on a taxonomically wide range of pathogenic organisms, supporting the hypothesis that Ni hyperaccumulation defends S. polygaloides against plant pathogens.
The reproductive biology of Anemone canadensis (Ranunculaceae): breeding system and facilitation of sexual selection
Authors: Douglas Kelly Lea , Cruden Robert William
Published: January 2018

Our data show that Anemone canadensis L. is xenogamous and has adaptations that should increase the opportunity for sexual selection and minimize interference between female and male sexual function. The flowers of plants within insect exclosures and hand self‐pollinated flowers set very few fruits compared to those that were open‐pollinated and hand crosspollinated. Examination of styles with uv‐fluorescence microscopy showed that self pollen tubes grew into the transmission tissue but rarely entered the ovary, i.e., there is a gametophytic self‐incompatibility system. A number of traits should enhance sexual selection. First, pollen grains arrived on the stigmas beginning on day 1, germinated, but the pollen tubes grew very slowly until day 4 or 5 when the transmission tissue matured. This allowed large numbers of pollen grains to reach the stigmas, presumably from a number of pollen parents. Second, basipetal maturation of the transmission tissue, which underlies the elongate stigmatic surfaces, allows pollen tubes originating near the tip of the style to initiate rapid growth prior to those lower in the style. Thus, rapidly growing pollen tubes from the top of the style were able to catch up with those lower in the style. In essence, all the pollen tubes in a style have an equal opportunity to reach the ovule. Large stigmatic pollen loads and high fruit set suggest there is minimal interference between male and female sexual function. This may be a consequence of the spatial separation of the pistils and stamens, which increases during the life of a flower. Synchrony of function among the pistils of a flower in conjunction with large and/or multipatemal pollen loads may reduce the variance in competition among developing embryos and result in fruits of equivalent size.
Structure of the stomatal complex of the monocotFlagellaria indica
Authors: Sack F. D.
Published: January 2018

The structure of the mature stomatal complex ofFlagellaria indicaL. was studied since the Flagellariaceae is reported to be one of a handful of nongrass families with a grass‐type stoma, and since relatively little is known about stomatal ultrastructure in monocots other than grasses. Both the grass guard cell and its nucleus are dumbbell‐shaped, and the walls that separate adjacent grass guard cells are perforated. Electron and fluorescence microscopy reveal that theFlagellariaguard cell lacks these features. Instead, theFlagellariaguard cell is neither dumbbellnor kidney‐shaped, its nucleus is roughly kidney‐shaped, and the end walls are thickened and imperforate. Additional structural features of the stomatal apparatus ofFlagellariainclude: 1) the subsidiary cells have a protuberance that underlies the middle of the guard cell and that forms an additional and innermost aperture of the pore; 2) guard and subsidiary cell walls are thickened differentially and are layered; and 3) organelles in both cell types appear to be confined to specific domains. AlthoughFlagellariais closely related to grasses, it does not have a grass or dumbbell‐shaped type of stomate. This suggests that the grass type of stomate may be less widespread than reported.
Nuclear DNA content of monocotyledons and related taxa
Authors: Bharathan G. , Lambert G. , Galbraith D. W.
Published: January 2018

Nuclear DNA content of 62 species of angiosperms including 52 monocotyledons and ten dicotyledons has been estimated by flow cytometry using Nicotiana tabacum var. Xanthi as the internal standard. These data, considered together with previous data on diploid species, suggest the following: 1) Most families and orders of monocotyledons have small genomes. Contrary to the general impression that monocotyledons are a group characterized by large genomes, genomes of over 20 pg/2C nucleus occur only in the Liliiflorae, Commelinales, Alismatales, and Araceae. 2) Variation within families ranges from two‐ to 56‐fold, but is two‐ to fivefold in most families. Thus extraordinary variation in genome size appears to be limited to particular lineages, perhaps owing to some shared feature that facilitates such variation. 3) Endopolyploidy is not observed in the leaves of the species studied, although it has been reported to occur in the roots of several monocotyledons. This suggests that an examination of the basis for this difference between the roots and leaves of monocotyledons may provide clues to the mechanisms that regulate endopolyploidization in these organs.
Differential expression of photosynthesis genes in leaf tissue layers of Peperomia as revealed by tissue printing
Authors: Ting Irwin P. , Patel Asmita , Sipes Deborah L. , Reid Philip D. , Walling Linda L.
Published: January 2018

Peperomia has species that may be C3, show Crassulacean acid metabolism (CAM), or CAM‐cycling. Species that show CAM progress from C3 to CAM through CAM‐cycling during leaf development. In CAM and CAM‐cycling species, CAM metabolism is predominately in the upper multiple epidermis and lower spongy mesophyll, whereas C3 metabolism is localized mostly in the palisade mesophyll. Using specific protein and cDNA probes prepared from P‐enolpyruvate carboxylase (PEPc) and ribulose‐1,5‐bisphosphate carboxylase (Rubisco), we have now studied the differential distribution of photosynthetic metabolism in Peperomia leaves using the technique of tissue printing. The tissue printing studies detected Rubisco protein in leaves of C3 P. orba, but not PEPc. Young C3 leaves of P. scandens and P. camptotricha showed Rubisco protein, but not PEPc; however, the mature leaves of these two species that have CAM showed PEPc protein and RNAs in both the multiple epidermis and spongy mesophyll. In contrast, Rubisco protein and RNAs were present throughout the leaf. The tissue printing data are consistent with our previously published data showing the differential distribution of photosynthetic metabolism in leaves of Peperomia. Although the tissue printing technique is qualitative, coupled with quantitative data it has proven useful for the study of function related to structure.
Reproductive allocation in hermaphrodite and female plants of Sidalcea oregana SSP. spicata (Malvaceae) using four currencies
Authors: Ashman Tia‐Lynn
Published: January 2018

Reproductive allocation was investigated in female and hermaphrodite plants of gynodioecious Sidalcea oregana ssp. spicata. Total reproductive investment and partitioning of that investment was documented at the level of whole plants in terms of four ecologically relevant currencies: biomass, nitrogen, phosphorus, and potassium. Nutrient augmentations in the field confirmed that nutrients were limiting plant vegetative growth and propensity to flower; thus the use of these nutrients as currency was appropriate. Once the effects of plant size were removed, the sex morphs allocated similar total amounts of biomass, nitrogen, phosphorus, and potassium to reproduction, but partitioned those differentially. For any given individual size, females allocated larger proportions of their reproductive resource budgets to seeds. Hermaphrodites' reproductive investment in pollen and flowers was allocated at the expense of allocation to seeds. These data are relevant to the evolution of gynodioecy from hermaphroditism and support the hypothesis that females reallocate resources not spent on pollen to seeds.
Alliances of Muhlenbergia (Poaceae) within New World Eragrostideae are identified by phylogenetic analysis of mapped restriction sites from plastid DNAs
Authors: Duvall Melvin R. , Peterson Paul M. , Christensen Alan H.
Published: January 2018

Restriction sites for six enzymes were mapped for the plastid DNAs of 25 species of Eragrostideae, one species of Cynodonteae (Eustachys distichophylla), and one species of Pooideae. Of the 124 restriction sites observed, 67 were variably present and shared by two or more species. These data were analyzed by the parsimony method using equal and unequal weights and by bootstrap analysis. The cladistic analyses established that members of the Muhlenbergiinae, including the genera Muhlenbergia, Blepharoneuron, Bealia, Chaboissaea, Lycurus, and Pereilema, share seven restriction site mutations and are strongly supported by the data as a monophyletic subtribe. Surprisingly, Redfieldia flexuosa also clustered with the Muhlenbergiinae in the analysis, perhaps indicative of a past interspecific hybridization event. The restriction sites data also weakly support a relationship (six shared mutations) between Erioneuron, Munroa, and Dasyochloa.
Foliar anatomy of Gigantonoclea guizhouensis (Gigantopteridales) from the Upper Permian of Guizhou Province, China
Authors: Li gqi , Tian Baolin , Taylor Edith L. , Taylor Thomas N.
Published: January 2018

The present paper details the anatomy of permineralized foliar specimens of Gigantonoclea guizhouensis Gu and Zhi (Gigantopteridales) from the Upper Permian of western Guizhou Province in southwest China. In addition to reticulate venation, these fossil leaves possess a number of interesting anatomical features including: multicellular spines on the midrib, hypodermal sclerenchyma ribs, U‐ or V‐shaped xylem in the midrib and secondary veins, tracheids with various secondary wall thickening patterns, paracytic stomata on the abaxial surface, epidermal cells with sinuous anticlinal walls, and secretory cavities in the mesophyll. Based on anatomical features, a liane habit is suggested, and the systematic differences among Gigantonoclea guizhouensis, Gigantopteridium, and the North American taxon Delnortea are underscored.
Javelinoxylon, an Upper Cretaceous dicotyledonous tree from Big Bend National Park, Texas, with presumed malvalean affinities
Authors: Wheeler E. A. , Lehman T. M. , Gasson P. E.
Published: January 2018

Well‐preserved petrified woods from the Maastrichtian of Big Bend National Park, Texas, with a combination of characters seen in the Malvales are described asJavelinoxylon multiporosumgen. et sp. nov. One log is over 70 cm in diameter and is riddled with termite galleries; this specimen provides additional documentation for the occurrence of dicotyledonous trees in the Late Cretaceous. These woods have structure different from any other known Cretaceous dicotyledonous wood and are advanced in the Baileyan sense as vessel elements are relatively short, perforations are exclusively simple, vessels are commonly in long radial multiples, and rays are storied. This is the earliest record for woods with storied structure. The occurrence of large dicotyledonous trees with advanced wood structure in Big Bend suggests there were differences between the Late Cretaceous vegetation of the northern Rocky Mountains and the Big Bend region.
Morphology of the perennial ryegrass (Lolium perenne; Poaceae) coleorhiza and emerging radicle with continuous or discontinuous hydration
Authors: Debaene‐Gill Susan B. , Allen Phil S. , Gardner John S.
Published: January 2018

This study was conducted using scanning electron microscopy to characterize morphological changes in the maturing perennial ryegrass (Lolium perenne L.) coleorhiza and emerging radicle during continuous hydration or hydration interrupted by dehydration. With continuous hydration, coleorhizae emerged and cell expansion led to a progressive increase in tissue size. Coleorhiza cells developed extensions like epidermal root hairs. Although coleorhiza cells appeared undamaged by radicle emergence, they began deteriorating when the radicle had reached a length of approximately 2 mm. In response to dehydration, coleorhiza cells shrank but did not rupture. If dehydration was initiated during an early stage of coleorhiza development, greater tissue shrinkage occurred at ‐150 MPa than at ‐4 MPa; otherwise, coleorhizae showed no differential response due to dehydration water potential. Upon rehydration, coleorhizae dehydrated at ‐4 MPa regained cell turgor within 24 hr, while coleorhizae dehydrated at ‐150 MPa did not. Loss of the coleorhiza (due to desiccation) did not preclude radicle emergence, which occurred upon rehydration. Radicles up to 2 mm in length were more tolerant of dehydration than were coleorhizae. These results suggest that the coleorhiza may be an expendable tissue during germination, as its likely protective and absorptive roles are lost following a single harsh dehydration event.
Historical biogeography of Asplenium adiantum‐nigrum (Aspleniaceae) in North America and implications for speciation theory in homosporous pteridophytes
Authors: Ranker Tom A. , Floyd Sandra K. , Windham Michael D. , Trapp P. Genie
Published: January 2018

Theories of plant speciation have generally recognized the importance of allopatry as a potential precursor to the genetic divergence of populations. The relative importance of long‐distance dispersal vs. vicariance events in leading to allopatry, however, has been debated. We examined isozymic variability in highly disjunct populations of allotetraploid Asplenium adiantum‐nigrum to test alternative hypotheses on their mode of origin. In addition, we assessed the genetic distinctness of the population from Boulder County, Colorado, which had been proposed as a separate species, A. andrewsii. Our results revealed that samples from all continental U.S. populations were isozymically identical and, with the exception of two samples from Boulder, displayed no intrapopulational variability. Continental U.S. populations were most similar to those from Hawaii, whereas both of these sets of populations were considerably more divergent from samples from Mexico and the Caucasus. The distribution of alleles and genotypes support the hypothesis that populations from different geographical regions had unique origins, resulting from at least several independent hybridization and polyploidization events followed by long‐distance dispersal. These results have implications for speciation theory of pteridophytes in documenting the effectiveness of long‐distance dispersal in the establishment of disjunct populations which may set the stage for allopatric speciation. In addition, the data suggest that the Boulder population is not sufficiently distinct to be considered a separate species.
Allelopathic effect of Pluchea lanceolata (Asteraceae) on characteristics of four soils and tomato and mustard growth
Authors: Inderjit  , Dakshini K. M. M.
Published: January 2018

The effect of the leachate of the noxious weed Pluchea lanceolata was explored using mustard and tomato seedling growth bioassays of four soil types (sandy loam, clay loam, silty loam, and sand). The objectives of the present study were: 1) to determine how soil chemistry changes after addition of leachate and leaves of the weed; 2) to determine what level of input to the soil does not cause significant differences from those of weed‐associated soils under field conditions; and 3) to determine whether soil texture affects bioassay results. Leaf leachates of the weed were added to four soil types in different dilutions, and soils were analyzed for pH, electrical conductivity, organic matter, Cl, PO4, exchangeable Cu+ +, Zn+ +, Na+, K+, Mg+ +, and Ca+ +, and total phenolics. These results indicated that the leachates of the weed altered chemical characteristics of each soil type. Concentration of phenolics in treatment of each soil type was dilution‐dependent. Leachates were more inhibitory on sandy loam and clay loam than on silty loam and sand. Present study indicated that in allelopathic bioassays, amended soils that are nonsignificantly different from weed‐associated soils should be taken. Further, present investigations confirmed the significance of good control soil with nonsignificantly altered chemical characteristics from those of natural soils, as well as soil texture to establish allelopathy of ecological relevance.
Reproductive consequences of interactions between Yucca glauca (Agavaceae) and Tegeticula yuccasella (Lepidoptera) in Colorado
Authors: Dodd Rhea Jean , Linhart Yan B.
Published: January 2018

For over 100 years the association between Yucca (Agavaceae) and Tegeticula (Lepidoptera: Incurvariidae) has been accepted as a quintessential example of an obligate mutualism. The yucca moth is purported to be the sole pollinator of Yucca, while Yucca flowers provide courtship and mating arenas, and Yucca seeds provide food for developing Tegeticula larvae. We studied Yucca glauca in northern Colorado, comparing the reproductive ecology and breeding systems of Yucca in plains populations, the “preferred” habitat of Yucca, with “marginal” sites at the edge of the local elevational distribution. Tegeticula are abundant at plains sites, and fruit set is significantly higher than in the foothills, where fruit set is limited by the paucity of moths. The low frequency of moths at high elevation, coupled with behaviors of adult female Tegeticula which lead to self‐pollination, failure to pollinate, and periodic overloading of fruits with eggs, may help explain why Yucca glauca appears to maintain alternative pollinators. Some fruits lack evidence of Tegeticula infestation, suggesting that larvae die before completing development, or that fertilization of Yucca sometimes occurs without the intervention of Tegeticula. Biochemical analyses of nectar and observations of floral visitors revealed that it is highly likely that the fly Pseudocalliope sp. nov. (Lauxaniidae), which congregates and mates on Yucca glauca blossoms, acts as a secondary pollinator. Autogamy appears to occur infrequently in natural populations. We therefore propose that the yucca‐yucca moth symbiosis be viewed as a facultative mutualism.
Growth and photosynthetic responses of field‐grown sweetgum (Liquidambar styraciflua; Hamamelidaceae) seedlings to UV‐B radiation
Authors: Sullivan Joe H. , Teramura Alan H. , Dillenburg Lucia R.
Published: January 2018

Very few studies have evaluated the effects of UV‐B radiation on trees. especially deciduous species. In this study we evaluate the effects of supplemental UV‐B radiation on the growth and photosynthetic capacity of sweetgum (Liquidambar styracifluaL.). Sweetgum seedlings were grown for 2 years in the field under either ambient or supplemental UV‐B radiation. Artificial UV‐B radiation was supplied by fluorescent lamps at a maximum daily supplementation of either 3.1 or 5.0 kJ of biologically effective UV‐B radiation. Over the 2‐year period, supplemental UV‐B radiation had little effect on total plant biomass or photosynthetic capacity. However, subtle changes in leaf physiology, carbon allocation, and growth were observed. Supplemental UV‐B radiation reduced photosynthetic capacity only during the first year, while leaf area and biomass were reduced in the second year. Alterations in carbon allocation included an increase in branch number and root to shoot ratio. While these data do not indicate that the productivity of sweetgum would likely be compromised by an increase in solar UV‐B radiation, they do suggest that the UV‐B portion of the solar spectrum contributes to the regulation of sweetgum growth and development. Therefore the possibility of significant consequences to sweetgum due to possible increases in UV‐B radiation cannot be ruled out.
Effects of atmospheric CO2 enrichment on regrowth of sour orange trees (Citrus aurantium; Rutaceae) after coppicing
Authors: Idso S. B. , Kimball B. A.
Published: January 2018

Sixteen sour orange tree (Citrus aurantium L.) seedlings were grown out‐of‐doors at Phoenix, Arizona, in eight clear‐plastic‐wall open‐top enclosures maintained at four different atmospheric CO2 concentrations for a period of 2 years. Over the last year of this period, the trees were coppiced five times. The amount of dry matter harvested at each of these cuttings was a linear function of the atmospheric CO2 concentration to which the trees were exposed. For a 75% increase in atmospheric CO, from 400 to 700 microliter per liter (μL liter 1), total aboveground biomass rose, in the mean, by a factor of 3.19; while for a 400 to 800 μL liter 1 doubling of the air's CO2 content, it rose by a factor of 3.92. The relative summer (mean air temperature of 32.8 C) response to CO2 was about 20% greater than the relative winter (mean air temperature of 16.4 C) response.
Reproductive biology and relative male and female fitness in a trioecious cactus, Pachycereus pringlei (Cactaceae)
Authors: Fleming Theodore H. , Maurice Sandrine , Buchmann Stephen L. , Tuttle Merlin D.
Published: January 2018

We describe the breeding system of an autotetraploid trioecious cactus, Pachycereus pringlei, provide estimates of the fitnesses of males and females relative to that of hermaphrodites, and discuss the role played by pollinators in the maintenance of three sexual morphs. Relatively high frequencies of females (45%) and males (26%) exist in coastal desert populations around Bahia Kino, Sonora, Mexico. They differ from hermaphrodites in flower size (females only), initiation of the flowering season, number of flowers produced per night and per season, sucrose content of nectar, and, in females, number of fruits produced per season under open pollination and in response to hand‐pollination. Major similarities between the sex classes include overall plant size, nectar volume per flower, percent fruit set in open‐pollinated flowers of females and hermaphrodites, seed mass and number of seeds per fruit, and pollen mass per flower in males and hermaphrodites. Hermaphrodites are self‐compatible, and the selfing rate is high (65%). Levels of inbreeding depression in selfed fruits and seeds appear to be low. Fruit set is strongly pollinator‐dependent in females but much less so in hermaphrodites. Relative fitness of males and females, as measured by annual production of pollen or seeds, is at least 1.5 times higher than that of the corresponding sex function in hermaphrodites. Given the high selfing rate and apparent lack of inbreeding depression, these fitness differences are insufficient to explain the occurrence of trioecy in this species.
Development and ultrastructure of the primary phloem in the shoot of Ephedra viridis (Ephedraceae)
Authors: Cresson Ruth A. , Evert Ray F.
Published: January 2018

Sieve cell differentiation in the primary phloem of Ephedra viridis is first indicated by an increase in thickness of the wall, which begins in the corners of the cell, and next by the proliferation of smooth tubular endoplasmic reticulum (ER). As differentiation proceeds, cisternae of rough ER form stacks along the wall, losing their ribosomes in the process. Concomitantly, all of the mitochondria, plastids, and ER become parietal in distribution, and the vacuoles collapse. Nuclear degeneration is pycnotic and accompanied by the formation of tubular invaginations of the nuclear envelope into the peripheral chromatin. At maturity, an anastomosing network of smooth ER borders the plasmalemma, interconnecting aggregates of smooth tubular ER located primarily opposite the sieve areas. In addition to ER, the mature sieve cell contains mitochondria, plastids, and remnants of the degenerate nucleus, all of which are parietal in distribution. P‐protein is lacking at all stages of sieve cell development. Sieve pore and compound median cavity development is similar to that reported for the sieve cells of conifers. Albuminous cells are associated with the sieve cells of the metaphloem throughout the shoot but with sieve cells of the protophloem only in the node. Among their cytoplasmic components are broad bundles of microfilaments spatially associated with a complex system of rough and smooth ER.
The significance of allozyme variation and introgression in the Liriodendron tulipifera complex (Magnoliaceae)
Authors: Parks Clifford R. , Wendel Jonathan F. , Sewell Mitchell M. , Qiu Yin‐Long
Published: January 2018

Fifty populations of Liriodendron tulipifera were sampled and scored for electrophoretic variation at 23 loci. The level of genetic polymorphism and population differentiation is greater in L. tulipifera than is usual for an outbreeding species. Since this species exhibits a cline of morphological and ecological variation from north to south, the 50 populations were divided into seven geographically defined regional groupings: three from the Appalachian uplands, three from the southeastern coastal plains, and one from the Florida peninsula. Nei's genetic identity, I, was calculated for all within‐ and among‐population and region comparisons. The populations from the upland regions clustered closely together while the coastal plain populations were similar but measurably separated from the upland ones. The populations from the Florida peninsula were markedly divergent. A principal components analysis of the same data set revealed a nearly identical pattern of population clustering. Two hypotheses were explored to explain the pattern observed: 1) post‐Pleistocene differentiation and migration from a single refugium and; 2) sympatry of two previously isolated taxa during glacial maxima, followed by introgression and migration. The weight of evidence best supports the introgression hypothesis which is explained in terms of plant migration events during Pleistocene time. The level and distribution of electrophoretic variation in L. tulipifera is compared to that of other woody taxa in which historical events of the Pleistocene may have contributed to modern levels and patterns of variation.
Systematic implications of chloroplast DNA VARIATION IN Jaltomata and selected physaloid genera (Solanaceae)
Authors: Mione Thomas , Olmstead Richard C. , Jansen Robert K. , Anderson Gregory J.
Published: January 2018

Chloroplast DNA restriction site data were used to assess relationships among the solanaceous genera Jaltomata, Hebecladus. Old and New World Physalis, Chamaesaracha, Leucophysalis, Margaranthus, Nicandra, and Saracha, and to assess interspecific relationships within Jaltomata. Cladograms rooted with Nicotiana tabacum were constructed with Wagner and Dollo parsimony. Strict consensus trees indicate that Hebecladus originated from within Jaltomata; together these genera are monophyletic and constitute the recently circumscribed genus Jaltomata. There are two primary clades in Jaltomata: one a morphologically diverse group confined to western (largely Andean) South America, the Greater Antilles, and the Galapagos Islands; and the other a morphologically homogeneous group widely distributed from the southwestern United States to Bolivia. The controversial Leucophysalis viscosa, formerly treated as Jaltomata viscosa, is related to Leucophysalis, Physalis, Chamaesaracha, and Margaranthus; it does not group with any of the sampled species of Jaltomata. Physalis appears to be polyphyletic since P. alkekengi of the Old World branches off prior to a clade including Chamaesaracha, Margaranthus, and the two New World Physalis species sampled.
Variance for water‐use efficiency among ecotypes and recombinant inbred lines of Arabidopsis thaliana (Brassicaceae)
Authors: Nienhuis James , Sills Gavin R. , Martin Bjorn , King Gretchen
Published: January 2018

Knowledge of natural variation among ecotypes and recombinant inbred lines of Arabidopsis thaliana L. Heynh for season‐long water‐use efficiency (WUE, moles of carbon accumulated per mole of water used) is useful in the design of experiments to understand the genetic control of this phenomenon. Water‐use efficiency among 31 container‐grown Arabidopsis ecotypes ranged from a high of 2.40 to a low of 1.86 mg/g (grams of dry aerial biomass per gram of water used). Genetic variance for WUE was observed among 80 F5 recombinant inbred lines (RILs) derived from a cross between the highest (Lip‐0) by the lowest (Edi‐0) ecotype. The heritability of WUE was calculated as 0.18 ± 0.07. The mean WUE for the ten highest and ten lowest RILs was 2.42 and 1.05 mg/g, respectively. A significant difference was observed in the composition of stable isotopes of plant carbon (δ13C) between the mean of the ten highest (‐31.23±) and the mean of the ten lowest (‐31.96±) RILs based on WUE. Characterization of the 80 RILs provides a structured population for further genetic and physiologic study of WUE.
Patterns of isozyme variation in relation to population size, isolation, and phytogeographic history in royal catchfly (Silene regia; Caryophyllaceae)
Authors: Dolan Rebecca W.
Published: January 2018

The distribution of genetic variation within and among plant populations is influenced by both contemporary and historical factors. I used isozyme analysis of band phenotypes to examine genetic structure in the rare prairie forbSilene regia.Relationships between current‐day population size, isolation, and phenotypic variation were assessed for 18 populations in two regions with differing postglacial history. Western populations from unglaciated southern Missouri and Arkansas were more genetically diverse based on the Shannon‐Weaver index (H) and a polymorphic index than were more eastern populations. These differences may be due to loss of variation with repeated founding of new populations in previously glaciated sites in Indiana and Ohio. Within the western region, population size was not significantly correlated with genetic variation. In the east, size was correlated with Shannon‐Weaver diversity. There was no relationship between variation and isolation in either region, but eastern populations were slightly more differentiated. Greater among‐population differentiation and the demonstrated connection between population size and variation in the eastern sites may reflect lower levels of interpopulation gene flow in the fragmented remnant prairies of Indiana and Ohio.
Fly pollination of Linum lewish (Linaceae)
Authors: Kearnsaf1> Carol Ann , Inouye David W.
Published: January 2018

This study examines the reproductive biology of Linum lewisii Pursh. (Linaceae), a polyphilic species visited by small bees and generalist flies in montane Colorado. L. lewisii plants growing at different sites experience large temporal and spatial variations in pollinator visits. Their ability to attract both dipteran and hymenopteran pollinators allows pollination under varying conditions as pollinator pool composition changes. Although L. lewisii is self‐compatible, hand‐pollination studies indicate that insects are required for seed production. The relative effectiveness of fly and bee pollinators is assessed in terms of per‐visit pollen deposition. Insect visitation patterns are combined with per‐visit effectiveness data to evaluate the relative importance of different pollinator groups. Overall, bees tend to be more effective than flies in depositing pollen. However, in many instances flies appear to be responsible for more pollen deposition due to their higher visitation rates.
Genetic structure and mating systems in wild and cultivated populations of Phaseolus coccineus and P. vulgaris (Fabaceae)
Authors: Escalante Ana María , Coello Gerardo , Eguiarte Luis E. , Piñero Daniel
Published: January 2018

We present a study of the genetic variation, genetic structure, and outcrossing rate of two wild populations of Phaseolus coccineus ssp. formosus (both from Central Mexico), two cultivated populations of P. coccineus ssp. coccineus (one from Central Mexico, the other from Chiapas), and one cultivated population of P. vulgaris (from Central Mexico), using seven electrophorectic loci. All the populations of P. coccineus showed high and similar levels of genetic variation, without differences among wild and cultivated populations (H ranged between 0.187 to 0.271). In contrast, P. vulgaris has low levels of genetic variation (H = 0.041). The three P. coccineus populations from Central Mexico were genetically similar, while the cultivated P. coccineus from Chiapas and the cultivated P. vulgaris from Central Mexico were very different. In all the loci and all the populations for both species, the fixation indices (F) were positive and differed significantly from random mating expectation in 59% of the cases for P. coccineus. The highest F was the estimated for P. vulgaris. For P. coccineus, the multilocus outcrossing rate estimates ranged from 0.592 to 0.698, and these did not differ significantly among populations. For P. coccineus, we also estimated the outcrossing rate for each of 60 different families, showing great variation, with a majority of families with a t between 0.8 and 1, but a substantial fraction of the families with a t as low as 0.12–0.20. The domestication process has neither eroded the levels of genetic variation of the cultivated populations of P. coccineus nor changed its mating system.
Inflorescence bracts of fossil and extant Tilia in North America, Europe, and Asia: patterns of morphologic divergence and biogeographic history
Authors: Manchester Steven R.
Published: January 2018

The enlarged inflorescence bract diagnostic of extant Tilia has an extensive Tertiary fossil record in the Northern Hemisphere. Diversity of bract morphology, and the extent of adnation between peduncle and bract, is reviewed for fossil and extant species of Tilia. An extinct type of bract with an orbicular outline and palmate venation is documented by the fossil species Tilia circularis (Chaney) comb. nov. from the early Oligocene of Oregon and is designated Type A. Living species of the genus have elongate bracts with predominately pinnate venation that are borne in two basic configurations: Type B, with the peduncle fused only to the extreme base of the bract lamina, as in extant Tilia endochrysea Hand.‐Mzt. of southern China; and Type C with the peduncle fused medially along the basal one‐third of the bract lamina, as in most extant species. Bracts of Type B were widely distributed in the Tertiary of western North America (late Eocene to Miocene) and Europe (early Miocene to Pliocene), while those of Type C are known in the fossil condition only from the middle and late Tertiary of Asia and Pliocene of Europe. The bracts of T. circularis, like those of type B, are borne on relatively long stalks and have the peduncle fused only at the extreme base. The fossil record supports recognition of the following characters as apomorphic in Tilia bract evolution: bracts sessile, peduncle adnate to the upper surface of the bract, and pinnate bract venation.
Seed size and dispersal potential of Acer rubrum (Aceraceae) samaras produced by populations in early and late successional environments
Authors: Peroni Patricia A.
Published: January 2018

In order to determine if red maple dispersal potential or seed size change during secondary succession, samaras were collected from five populations located in early successional environments and five populations located in late successional environments. Wing loading ratios (samara mass—mg/samara area—cm2), which are inversely proportional to dispersal ability, were computed for all samaras, and seeds were excised from each samara and weighed. Samaras from the early successional red maples showed slightly but significantly lower wing loading ratios than those from the late successional environments. This result corresponds with the conclusions reached by several theoretical investigations of seed dispersal evolution that predict that recently founded populations will show greater dispersal abilities than more established populations. The earlier successional populations had slightly heavier seeds than the later successional populations, which suggests that the changes in community composition and dynamics that occur during this successional sequence do not select for heavier seeds in older red maple populations. Coefficients of variation for wing loading and seed size showed no consistent trends with successional stage, which indicates that variation in these characters does not decrease as succession proceeds.
Floral color change: a widespread functional convergence
Authors: Weiss Martha R.
Published: January 2018

Ontogenetic color changes in fully turgid flowers are widespread throughout the angiosperms, and in many cases are known to provide signals for pollinators. A broad survey of flowering plants demonstrates that such color changes appear in at least 77 diverse families. Color‐changing taxa occur commonly within what are considered derived lineages, and only rarely in early or primitive groups. The pattern of distribution of floral color change across orders, families, genera, and species demonstrates that the occurrence of the phenomenon within a group is not simply a result of phylogenetic history. Color changes can affect the whole flower or they can be localized, affecting at least nine floral parts or regions. The scale of color change (localized or whole‐flower) is broadly correlated with the type of pollinator that characteristically visits the plant. Color changes can come about through seven distinct physiological mechanisms, involving anthocyanins, carotenoids, and betalains. Color changes due to appearance of anthocyanin are the most common, occurring in 68 families. Floral color change has clearly evolved independently many times, most likely in response to selection by visually oriented pollinators, and reflects a widespread functional convergence within the angiosperms.
The influence of nectar production on hawkmoth behavior, self pollination, and seed production inMirabilis multiflora (Nyctaginaceae)
Authors: Hodges Scott A.
Published: January 2018

Nectar is the most common floral reward that plants produce to attract pollinators. To determine the effect of nectar production on hawkmoth behavior, pollen movement, and reproductive success in Mirabilis multiflora, I manipulated nectar volumes and observed the subsequent foraging behavior of the hawkmoth Hyles lineata and the resulting pollen movement patterns. Individual hawkmoths visited significantly more flowers on plants with more nectar. The increase in flower visits significantly increased pollen deposition on stigmas and pollen removal from anthers when nectar volume was raised to twice the highest level found in nature. As hawkmoths visited flowers consecutively on a plant, the proportion of self pollen deposited on stigmas increased significantly and rapidly. Based on simulated hawkmoth visits, seed set was significantly reduced for flowers later in a visit sequence. A simple model combining these results predicts that the form of selection on nectar production varies depending on pollinator abundance. Using a multiple regression analysis a nearly significant (P < 0.08) effect of stabilizing selection was detected during a single season as predicted by the model for the prevailing hawkmoth abundance. Although increased nectar production may indirectly affect plant fitness by reducing resources available for other plant functions, the direct effect of high nectar production on pollinator behavior and self pollination may generally limit floral nectar production.
Pollen and ovule development inArabidopsis thalianaunder spaceflight conditions
Authors: Kuang Anxiu , Musgrave Mary E. , Matthews Sharon W. , Cummins Denyse B. , Tucker Shirley C.
Published: January 2018

The development of pollen and ovules in Arabidopsis thaliana on the space shuttle ‘Endeavour’ (STS‐54) was investigated. Plants were grown on nutrient agar for 14 days prior to loading into closed plant growth chambers that received light and temperature control inside the Plant Growth Unit flight hardware on the shuttle middeck. After 6 days in spaceflight the plants were retrieved and immediately dissected and processed for light and electron microscope observation. Reproductive development aborted at an early stage. Pistils were collapsed and ovules inside were seen to be empty. No viable pollen was observed from STS‐54 plants; young microspores were deformed and empty. At a late stage, the cytoplasm of the pollen contracted and became disorganized, but the pollen wall developed and the exine appeared normal. The tapetum in the flight flowers degenerated at early stages. Ovules from STS‐54 flight plants stopped growing and the integuments and nucellus collapsed and degenerated. The megasporocytes appeared abnormal and rarely underwent meiosis. Apparently they enlarged, or occasionally produced a dyad or tetrad, to assume the form of a female gametophyte with the single nucleus located in an egglike cell that lacks a cell wall. Synergids, polar nuclei, and antipodals were not observed. The results demonstrate the types of lesions occurring in plant reproductive material under spaceflight conditions.
Patterns of ontogenetic evolution in perianth diversification ofBesseya (Scrophulariaceae)
Authors: Hufford Larry
Published: January 2018

Species of Besseya have perianth diversity centered largely in meristic variation, extreme corolla diminution, and corolla tube loss. Flowers of Besseya differ from those of their closest relative Synthyris in having a bilabiate corolla. The avenues of ontogenetic evolution that were important in creating these aspects of perianth diversity were explored by optimizing developmental transformations on cladograms. Three different evolutionary transformations were important in the diversification of calyx ontogenies in Besseya, including the derived reciprocal substitution of ontogenetic states in B. bullii, labile abaxial lobe expression in B. wyomingensis, and a heterotopic novel substitution in B. oblongifolia. The bilabiate corolla of Besseya arose via fractionation and localization of the zonal growth expressed in the more plesiomorphic Synthyris. Besseya plantaginea, B. ritteriana, and B. oblongifolia form a group characterized by diminished expression of the anterior corolla lobe. Four alternative scenarios equally explain the ontogenetic transformations underlying extreme corolla diminution and corolla tube loss. Corolla tube loss has been considered rare or impossible among angiosperms, but some alternative scenarios in Besseya demonstrate how this may have occurred via fractionation of zonal growth. Corolla tube loss may have arisen only indirectly from the sympetalous ancestors of Besseya following extreme corolla diminution and the reestablishment of a “full‐size” corolla which had a novel developmental pattern that did not include the distribution of zonal growth present in ancestors.
Floral ontogeny ofZippelia begoniaefoliaand its familial affinity: Saururaceae or Piperaceae?
Authors: Han‐Xing Liang , Tucker Shirley C.
Published: January 2018

Zippelia begoniaefolia Bl., a monotypic species having characteristics of both Piperaceae and Saururaceae, has racemes of about 20 small flowers lacking a perianth, each with six free stamens and a four‐carpellate syncarpous gynoecium. The inflorescence apical meristem initiates bracts acropetally and helically, each of which subtends a later initiated single floral apex; there are no “common” primordia. The six stamens are initiated as two lateral pairs and two solitary successive primordia, the latter two opposite in median sagittal positions. Four carpel primordia are initiated as a lateral pair and two successively initiated in the median sagittal plane. This order of organ inception is unique among Piperaceae and Saururaceae. Intercalary growth below carpellary attachment raises them up on a common cylindrical base that becomes the syncarpous ovary, covered with unique glochidiate hairs and containing a single basal ovule. The free portions of the carpels become the reflexed papillate stigmas. The floral vascular system has a single bundle at base that branches to supply the bract and flower traces. The floral vasculature is similar but not identical to that of Saururus (Saururaceae) and some Piper species (Piperaceae). Plesiomorphic character states of Zippelia that are shared with Saururus include hypogyny, free stamens, cleft stigma, and a similar floral groundplan. Synapomorphies, derived shared character states that unite Zippelia with Piperaceae, include syncarpy, solitary ovule, basal placentation, fused ventral carpellary bundles, and a double vascular cylinder in the stem. Cladistic analysis aligns Zippelia with Piperaceae because they share apomorphies, and because Zippelia shares only plesiomorphies with Saururus.
Chlorella vulgaris (Chlorellaceae) does not secrete autoinhibitors at high cell densities
Authors: Mandalam Ramkumar K. , Palsson Bernhard O.
Published: January 2018

Filtrates (conditioned medium) from high‐density Chlorella vulgaris cultures in photobioreactors were obtained and tested for autoinhibitory activity under different conditions. Exponentially growing cells were inoculated at low initial cell concentration (2 × 105 cells/ml) in 90% conditioned medium (CM) supplemented with 10% fresh medium (FM) at low (atmospheric) CO2 levels. The time sequence of DNA histograms of cells in CM cultures showed that there is an accumulation of cells with two and four DNA equivalents in the culture over a period of time, signifying a blockage of cells at the division stage of the cell cycle. Examination of the chemical composition of CM showed the presence of high concentrations (> 10 mM) of bicarbonate. Adding similar bicarbonate concentrations to FM were found to have similar effects as CM cultures, causing blockage of cell division, though the intensity of the blocking effect was lower. The bicarbonate‐free CM did not show any cell cycle modulating or inhibitory activity. The growth of cells cultivated at high (5%) CO2 levels in 90% CM supplemented with 10% FM was comparable to 10% FM cultures, indicating nutrient limitation in 90% CM culture. When the 90% CM culture was supplemented with 100% nutrients, the growth rate and final cell concentration was similar to 100% FM culture. Based on these results we conclude that C. vulgaris does not secrete any autoinhibitor(s) or cell cycle modulating compound(s) under the conditions from which the CM was obtained.