Showing papers in "International Journal of Plant Sciences in 2009"

Time Tree of Rubiaceae: Phylogeny and Dating the Family, Subfamilies, and Tribes

Abstract: Rubiaceae are one of the largest families of plants, with ∼13,000 species. In this study, we have estimated the phylogeny for 534 Rubiaceae taxa from 329 genera with up to five different chloroplast regions by Bayesian analysis. It resulted in a highly resolved tree with many strongly supported nodes. There is strong support for the three subfamilies (Cinchonoideae, Ixoroideae, Rubioideae) and most of the 44 included tribes. A scaled‐down data set of 173 Rubiaceae taxa was used with a Bayesian approach to estimate divergence times for clades classified as tribes and subfamilies. Four fossils were used as minimum age priors, one inside each subfamily and one for Rubiaceae as a whole (Faramea‐type pollen, Scyphiphora pollen, Cephalanthus pusillus fruits, and Paleorubiaceophyllum eocenicum leaves). The estimated lineage (stem) divergence time for Rubiaceae is 90.4 Ma. The estimated lineage divergence times for the subfamilies are 84.4 (86.6) Ma for Rubioideae, 73.1 Ma for Ixoroideae, and 73.1 Ma for Cinchono...

Differentially Expressed miRNAs Potentially Involved in the Regulation of Defense Mechanism to Drought Stress in Maize Seedlings

Abstract: Maize employs complex mechanisms of gene regulation in response to drought stress. Micro‐RNAs (miRNAs) have emerged as a novel regulatory mechanism of gene expression. Drought induces upregulation and downregulation of numerous genes. However, little is known about the role of miRNAs in maize drought response. In this research, miRNA microarray hybridization showed that 34 miRNAs from 13 plant miRNA families had significantly altered expression after drought treatment. Most of the miRNA‐mediated target genes contained a cis‐acting element that responded to phytohormone (ABA) stimuli during drought stress. Drought stress–upregulated miR474 could downregulate target gene PDH, which is a negative regulator of proline accumulation, to improve osmoprotection responses to drought stress. On the other hand, drought‐downregulated miRNAs (such as miR168, miR528, and miR167) might result in accumulation of their target mRNAs (MAPK, POD, and PLD) to initiate the regulation of ABA‐induced stomatal movement and antiox...

Leaf Trait Diversification and Design in Seven Rare Taxa of the Hawaiian Plantago Radiation

Abstract: Linkages among leaf traits and environment have most often been tested across communities but infrequently within lineages. We studied seven endemic Hawaiian Plantago taxa radiated across elevations, climates, and habitats. We grew plants of six taxa in controlled conditions for 1–2 yr and collected leaves from a seventh in the field. For all taxa, we measured 46 leaf traits and tested hypotheses for trait-environment and trait-trait associations. Because of the rarity of the study plants, our study included low replication within taxa and multiple growth locations; despite these limitations, given reasonable assumptions, our analyses pointed to genetic differentiation among taxa. The leaves of bog taxa were smaller and thicker than those of woodland taxa, with higher leaf mass per area (LMA), stomatal pore area per leaf area, and carbon isotope discrimination (δ13C). Taxa from higher elevations had thicker leaves and higher LMA, as well as lower nitrogen per mass and higher adaxial stomatal distribution....

Phylogeny of the Caryophyllales Sensu Lato: Revisiting Hypotheses on Pollination Biology and Perianth Differentiation in the Core Caryophyllales

Abstract: Molecular phylogenetics has revolutionized our understanding of the Caryophyllales, and yet many relationships have remained uncertain, particularly at deeper levels. We have performed parsimony and maximum likelihood analyses on separate and combined data sets comprising nine plastid genes (∼12,000 bp), two nuclear genes (∼5000 bp), and the plastid inverted repeat (∼24,000 bp), giving a combined analyzed length of 42,006 bp for 36 species of Caryophyllales and four outgroups. We have recovered strong support for deep‐level relationships across the order. Two major subclades are well supported, the noncore and core Caryophyllales; Rhabdodendron followed by Simmondsia are sisters to the core Caryophyllales, Limeum and Stegnosperma are successive sisters to the “globular inclusion” clade, Gisekia is a distinct lineage well separated from Rivina within the “raphide” clade, and Rivina and Phytolaccaceae are disparate lineages, with Rivina sister to Nyctaginaceae. The placement of Sarcobatus and relationships ...

Significance of Pollen Characteristics for Infrageneric Classification and Phylogeny in Quercus (Fagaceae)

Abstract: Patterns of tectum ornamentation in pollen of Quercus (oak trees, Fagaceae) are investigated using high‐resolution scanning electron microscopy. Tectum ornamentation is highly consistent at the infrageneric level and can be used to polarize character states within Quercus by comparison with other genera in Fagaceae. In particular, pollen data strongly suggest the recognition of an infrageneric Ilex group and, for the first time, allow definition of the set of taxa that comprise this group. The infrageneric Ilex group displays a relatively simple tectum ornamentation exclusively found in this group of oaks, in Fagus, and in extinct lineages related to Trigonobalanus, Colombobalanus, and Formanodendron. Such a simple type of tectum ornamentation is also known to represent an early developmental stage in infrageneric groups of Quercus that have otherwise complex ornamentation (Quercus and Lobatae). Ornamentation of the tectum in the infrageneric Cyclobalanopsis group can be derived from the plesiomorphic Ile...

Phylogeny of Opuntioideae (Cactaceae)

Abstract: Opuntioideae are a diverse subfamily of Cactaceae with significant diversity of form and habitat and wide distribution throughout the New World. Nuclear ribosomal ITS and chloroplast trnL‐trnF region DNA sequence–based phylogenetic analysis of Opuntioideae derived from Bayesian methods is presented. This analysis supports the following relationships: Opuntioideae are monophyletic; the subfamily is made up of four major lineages (Maihueniopsis‐like species, Pterocactus, other terete‐stemmed species, and flat‐stemmed species). The two deepest lineages (including most species of Maihueniopsis and all Pterocactus) are marked by diminutive, succulent, often geophytic habit and are leafless at maturity. These analyses suggest that Opuntioideae have geographic origin in west‐central South America. Generic circumscription is considered in the context of the recovered relationships. Maihueniopsis is recovered in multiple lineages. Many currently accepted genera may be para‐ or polyphyletic.

Monetianthus mirus gen. et sp. nov., a Nymphaealean Flower from the Early Cretaceous of Portugal

Abstract: Monetianthus mirus gen et sp nov is described based on a single coalified flower from the Early Cretaceous (Late Aptian‐Early Albian) Vale de Agua locality, western Portugal The flower is actinomorphic and probably bisexual, with a perianth of nine or 10 tepals, an androecium of 20 stamens, and a syncarpous gynoecium with a partly inferior ovary of 12 carpels arranged radially around a central column Phyllotaxis of tepals and stamens is uncertain Nondestructive synchrotron radiation x‐ray tomographic microscopy of internal structures documents laminar placentation with around six anatropous and ascending ovules in each locule Comparison of Monetianthus with living plants indicates a clear relationship to extant Nymphaeales in particular with the Barclaya and Nymphaeoideae clade Monetianthus thus provides evidence of crown group Nymphaeales, and probably crown group Nymphaeaceae, at a very early stage in the initial diversification of flowering plants

A Large‐Scale Phylogeny of Polygonaceae Based on Molecular Data

Abstract: Few studies have addressed the evolutionary relationships within Polygonaceae from a global perspective. The convoluted taxonomic history of Polygonaceae is a major barrier to understanding evolution in this group, and only portions of it have been included in systematic treatments. Phylogenetic studies have been limited in both taxon sampling and amount of data. Our objective is to identify clades within Polygonaceae and to provide a global estimate of phylogenetic relationships in this morphologically diverse and geographically widespread group. We include a total of 75 species representing approximately 40 of the 55 named genera in the family. We use three chloroplast regions (rbcL, matK, and ndhF) and the ribosomal internal transcribed spacer to understand the phylogenetic relationships in Polygonaceae. Maximum parsimony and maximum likelihood are used to analyze the data. Symmeria is the sister group to remaining Polygonaceae sampled, and there is strong support for this placement. Afrobrunnichia bra...

Genetic Diversity and Gene Exchange in Pinus oocarpa, a Mesoamerican Pine with Resistance to the Pitch Canker Fungus (Fusarium circinatum)

Abstract: Eleven highly polymorphic microsatellite markers were used to determine the genetic structure and levels of diversity in 51 natural populations of Pinus oocarpa across its geographic range of 3000 km in Mesoamerica. The study also included 17 populations of Pinus patula and Pinus tecunumanii chosen for their resistance or susceptibility to the pitch canker fungus based on previous research. Seedlings from all 68 populations were screened for pitch canker resistance, and results were correlated to mean genetic diversity and collection site variables. Results indicate that P. oocarpa exhibits average to above‐average levels of genetic diversity ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} ewcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcomma...

The Birds and the Bees: Using Selective Exclusion to Identify Effective Pollinators of African Tree Aloes

Abstract: Bees are frequent visitors to plants that, on the basis of floral traits, would be expected to be specialized for bird pollination We conducted bird exclusion experiments to establish the contribution that bees make to the female component of pollination success of five “ornithophilous” Aloe species in the succulent‐rich subtropical thicket vegetation in southeastern South Africa Experiments showed that all five aloes are genetically self‐incompatible and require cross‐pollination for seed set Seed set in flowers exposed to both bird and bee visitors was generally severalfold higher than in flowers exposed to bee visitors only The magnitude of this effect varied greatly among species and was affected by floral traits and bee behavior In three aloes where the relatively short corolla tubes are blocked by exserted filaments, bees made a negligible contribution to seed production However, in two aloes with long tubular flowers and included filaments, bees often crawled into the perianth tube to obtain

Effects of genetic variation and inbreeding on volatile production in a field population of horsenettle.

Abstract: Plant volatiles mediate numerous interactions between plants and insects, yet few studies have examined variation in volatile production within plant populations or the genetic and environmental causes of this variation. Here we document the effects of inbreeding and maternal family on volatile production by horsenettle Solanum carolinense L. (Solanaceae). We collected volatiles from ramets (clones) of each of 12 genets (genotypes) of horsenettle grown in four agricultural fields with natural levels of herbivory. The 12 genets included self‐ and cross‐pollinated progeny from six maternal plants. We found that inbreeding reduced total volatile production relative to that of outcrossed plants. We also found a breeding‐by‐family interaction for the total amount and blend of volatiles, indicating genetic variation among families for inbreeding depression. Analysis of outcrossed plants alone (a random sample from the population) revealed a genet effect on the total amount and blend of volatiles released, indic...

Phylogeny, Biogeography, and Character Evolution in Mediterranean, Asiatic, and Macaronesian Helichrysum (Asteraceae, Gnaphalieae) Inferred from Nuclear Phylogenetic Analyses

Abstract: The genus Helichrysum has 500–600 species in Africa, Madagascar, the Mediterranean basin, Macaronesia, western and central Asia, and India. The aims of this study are to confirm the exclusion of Castroviejoa from Helichrysum, to elucidate the origin of the Macaronesian endemics, to confirm the monophyly of the Mediterranean‐Asiatic group, and, within this group, to contrast molecular data with sectional classification and to provide insight into trends in character evolution and biogeography. To address these issues, ITS and ETS sequences were used in phylogenetic analyses. Results show that Castroviejoa is excluded from Helichrysum. The phylogeny obtained suggests a southern African origin for Helichrysum and several subsequent migrations throughout the African continent. The species from the Canary Islands do not form a monophyletic clade, suggesting that at least two independent colonization events occurred. Helichrysum makranicum, from Oman and southern Iran, is the closest relative of a clade consist...

Evolutionary relationships in ephedra (gnetales), with implications for seed plant phylogeny

Abstract: Evolutionary relationships in Ephedra are difficult to resolve, mainly because there are few informative characters in investigated loci and long distances to outgroups. We address these problems by using a large data set that includes information from seven plastid and nuclear loci and 204 vascular plants. The deepest divergences in Ephedra are weakly supported and differ by analytical method, but they indicate a basal grade of species distributed in the Mediterranean area. New World species are monophyletic, with a South American clade possibly nested within a North American clade. A mainly Asian clade comprises several well‐supported subgroups, of which some are endemic to restricted geographic regions in East or Central Asia; others have a broad distribution that may extend into Europe (E. distachya, E. major) and/or Africa (E. pachyclada–E. somalensis). Ephedra laristanica and E. somalensis are nested within other species, whereas the recognition of E. milleri as a separate species is supported. Our ...

A PHYLOGENY OF SETARIA (POACEAE, PANICOIDEAE, PANICEAE) AND RELATED GENERA BASED ON THE CHLOROPLAST GENE ndhF

Abstract: The genus Setaria is the largest genus in the so‐called bristle clade, a monophyletic group of panicoid grasses distinguished by the presence of sterile branches, or bristles, in their inflorescences. The clade includes both foxtail millet and pearl millet, the latter an important cereal crop in dry parts of the world. Other members of the clade are weeds that are widespread agricultural pests. Previous molecular phylogenetic studies have suggested that Setaria might not be monophyletic but did not have a large enough sample of species to test this rigorously. In addition, taxonomic studies have suggested a close relationship between Setaria and Paspalidium, with some authors combining them into a single genus, but molecular studies included too few Paspalidium accessions for a meaningful conclusion. Accordingly, we have produced 77 new sequences of the chloroplast gene ndhF for 52 species not in previous analyses. These were added to available sequences for 35 species in 10 genera of the bristle clade an...

Pollination biology of hydnora africana thunb. (hydnoraceae) in namibia: brood-site mimicry with insect imprisonment

Abstract: Hydnora africana is a root holoparasite of southern Africa that emerges only to flower. The trimerous flowers of H. africana have androecial and gynoecial chambers and attract floral visitors with putrid odors emitted from prominent osmophores. We observed floral phenology and insect visitation for H. africana at two sites in southern Namibia and evaluated the insect imprisonment mechanism with beetle addition and pollen viability assays. Flowers are putatively protogynous for 3 d. We observed 18 floral visitors, including 10 coleopteran species imprisoned by the smooth inner surface of the androecial chamber. The hide beetle Dermestes maculatus (Tenebrionidae) accounted for 76.9% of the imprisoned insects, with a density of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} ewcomma...

Correlated evolution of leaf shape and physiology in the woody sonchus alliance (asteraceae: sonchinae) in macaronesia

Abstract: The Sonchus alliance represents an oceanic island radiation that includes six genera and 31 species of herbs, shrubs, and trees occurring in diverse habitats ranging from cool, upland cloud forests to hot, dry, exposed cliff faces and coastal deserts To investigate the role of photosynthetic adaptations during radiation into diverse habitats, we measured leaf morphological and physiological traits and relationships among 15 representative species of the woody Sonchus alliance grown under uniform conditions Correlated evolution was observed between photosynthesis per mass with leaf size and specific leaf area and between photosynthesis per area with dark respiration per area and stomatal conductance In general, species from exposed habitats exhibited smaller, more dissected leaves with greater photosynthetic rates compared with those of species native to relatively shaded pine and laurel cloud forest We also observed that sister taxa in contrasting habitats can develop substantially divergent leaf form

Congruent Climate‐Related Genecological Responses from Molecular Markers and Quantitative Traits for Western White Pine (Pinus monticola)

Abstract: Analyses of molecular and quantitative genetic data demonstrate the existence of congruent climate‐related patterns in western white pine (Pinus monticola). Two independent studies allowed comparisons of amplified fragment length polymorphism (AFLP) markers with quantitative variation in adaptive traits. Principal component analyses were conducted on seedling traits in common gardens collected from 58 sites; principal coordinate analyses were conducted on AFLP data from 15 sites. Collection site eigenvector means were regressed on 35 climate variables to produce a genecological prediction for each data set. Both predictions explained a large percentage (>70%) of the genetic variation from the first eigenvector from similar predictors involving the interaction growing season precipitation and temperature. Both predictions were significant ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \u...

Dispersal syndromes in North American Ephedra.

Abstract: Ephedra (Gymnosperma, Gnetales, Ephedraceae) includes 13 species in the arid American Southwest that have three morphological types of propagules. We performed field and laboratory experiments on five species (E. torreyana, E. antisyphilitica, E. viridis, E. funerea, and E. nevadensis) that represent the three morphological types (dispersal syndromes) and two intermediate forms. Ephedra torreyana has large, winged cone bracts and small seeds that are largely ignored by animals and that are dispersed by the wind. Ephedra antisyphilitica has succulent cone bracts that are eaten by birds that disperse the seeds in their feces. Ephedra viridis has large, conspicuous seeds that are attractive to some rodents, which gather the seeds and scatter hoard them in soil. Ephedra funerea and E. nevadensis are also dispersed by seed‐caching rodents but share traits with wind‐dispersed and bird‐dispersed species, respectively. Most North American species of Ephedra are dispersed by seed‐caching rodents, and this mode of ...

Key morphological alterations in the evolution of leaves.

Abstract: Evolution of plant form proceeds through sequential alterations in the development of plant organs. Leaves (or fronds) are organs that have diagnostic characteristics, including definite arrangement on a stem, bilateral symmetry (abaxial/adaxial identity), and determinate growth. Evolution of those diagnostic characteristics represents a series of critical steps in plant evolution that resulted from specific developmental alterations. The fossil record reveals a transformational series in leaf evolution that highlights steps that have occurred in parallel but independently in both leptosporangiate ferns and seed plants, resulting in superficially similar frond morphologies. In this study, the fronds of the most ancient fossil fern, Psalixochlaena antiqua, and the most ancient reconstructed seed plant, Elkinsia polymorpha, are characterized and compared with leaves of modern plants in order to identify the sequence in which features of leaves in two distinct clades of euphyllophytes arose. While both frond...

Reproductive ecology of the endangered enigmatic Mauritian endemic Roussea simplex (Rousseaceae).

Abstract: Roussea simplex is the sole member of the endemic family Rousseaceae from Mauritius. Once widespread and locally common on Mauritius, today R. simplex is critically endangered, with 85–90 known remaining individuals in a few scattered populations. We documented the unusual flowering and fruiting phenology and studied the pollination and seed dispersal ecology of R. simplex in the accessible flowering and fruiting populations. Endemic diurnal Phelsuma cepediana geckos were the only pollinators and the only animals eating the pulp and dispersing the tiny seeds. In experiments with captive geckos, we confirmed that geckos ingest the seeds and pass them apparently unharmed. This makes R. simplex one of the few known plants that use the same animal species for both pollination and seed dispersal. However, none of the seeds from fruits or gut‐passed seeds germinated, highlighting the large gap that remains in our understanding of the germination and regeneration of R. simplex. Conservation management must addre...

Effects of De‐ and Rehydration in Desiccation‐Tolerant Liverworts: A Cytological and Physiological Study

Abstract: Liverworts are probably the earliest‐diverging group of green land plants, but in contrast to mosses and vascular plants, there has been only limited information on the physiology of desiccation tolerance and none on the cytological consequences of de‐ and rehydration in this group. We explore the physiological and cytological effects of drying and rewetting in several desiccation‐tolerant liverworts and examine parallels with and differences from vascular plants and mosses. Observations were made of water‐stress responses and recovery using infrared gas analysis and modulated chlorophyll fluorescence, and structural and ultrastructural changes were observed with light and electron microscopy. Dehydration elicits profound cytological changes: fragmentation of the vacuole, rounding of the chloroplasts and mitochondria with thylakoids, and cristae becoming rearranged but remaining undamaged. These changes closely parallel those seen in mosses and desiccation‐tolerant vascular plants, as does recovery of the...

A Continent-Wide Clone: Population Genetic Variation of the Invasive Plant Hieracium Aurantiacum (Orange Hawkweed; Asteraceae) in North America

Abstract: We investigated the population genetic structure of the invasive plant Hieracium aurantiacum (Asteraceae), a facultative apomict. We generated amplified fragment length polymorphism fingerprints for H. aurantiacum samples from across its invasive range in North America (N ¼ 226) and from six other North American native and invasive Hieracium species (N ¼ 60). Almost no genetic variability was found in the North American H. aurantiacum across locations from Alaska and Oregon to Pennsylvania and Ontario (clonal diversity ¼ 0:035). In contrast, other Hieracium species showed a range of clonal diversities (range ¼ 0:154‐1:0). The single H. aurantiacum genotype that dominated the North American invaded range was identical to a sample from the native range (Czech Republic), where low genetic diversity has also been reported. However, we did find evidence of hybridization between H. aurantiacum and at least one other nonnative Hieracium species in North America, indicating that the generation of novel hybrid genetic combinations may be an important factor in this invasive group of Hieracium taxa. Our findings suggest that sexual recombination and genetic diversity are not essential for successful plant invasion and that phenotypic plasticity alone may provide the flexibility necessary for the establishment of H. aurantiacum in diverse habitats.

Diversity and Lability of Floral Phyllotaxis in the Pluricarpellate Families of Core Laurales (Gomortegaceae, Atherospermataceae, Siparunaceae, Monimiaceae)

Abstract: Floral phyllotaxis of Laurales (Magnoliidae) is poorly and sometimes conflictingly documented, especially in the pluricarpellate families of the core Laurales (Gomortegaceae, Atherospermataceae, Siparunaceae, Monimiaceae). In this study four types of floral phyllotaxis were recovered: Fibonacci spiral, simple-whorled (decussate), complex-whorled, and irregular. Whorled and spiral phyllotaxis co‐occur in all families except Gomortegaceae and even vary within a species in some Mollinedioideae (Monimiaceae). Complex‐whorled floral phyllotaxis with two or more organs in a position where only one is expected and changes in merism are especially prominent in Atherospermataceae and Monimiaceae. The most elaborate complex‐whorled phyllotaxis pattern (leading to 8‐merous whorls) is present in flowers with a flat floral base. Presence of a hyperstigma is correlated with double positions in the perianth. Flowers with low organ number commonly have simple‐whorled phyllotaxis; flowers with high organ number have compl...

Secondary Growth in Vertebraria Roots from the Late Permian of Antarctica: A Change in Developmental Timing

Abstract: Permineralized Vertebraria roots from the late Permian of the Central Transantarctic Mountains, Antarctica, are investigated to understand the unusual vascular anatomy of the genus. The specimens range from ∼1 mm to several centimeters in diameter and illustrate all the stages of secondary growth. Our observations confirm previous hypotheses on the development of these roots and suggest that their unique anatomy is the result of a change in developmental timing. Vertebraria is characterized by a vascular cambium that remains discontinuous through several growth seasons, leading to the formation of lacunae alternating in cross section with wedges of secondary vascular tissues. The bifacial nature of the cambium is confirmed by the presence of well‐developed secondary phloem composed of longitudinally elongated cells and uniseriate parenchymatous rays. In some of the largest specimens, a continuous vascular cylinder is formed by the differentiation of cambium from parenchymatous cells bordering the lacunae....

Cordaitalean Seed Plants from the Early Permian of North China. II. Reconstruction of Cordaixylon tianii

Abstract: From a single Early Permian locality in the Taiyuan Formation of northern China, a new whole‐plant cordaitalean is reconstructed and named Cordaixylon tianii (B. Tian and S.‐J. Wang) S.‐J. Wang and J. Hilton sp. nov. The reconstruction is based on pairs of plant organs found in organic attachment, supplemented with cases where two or more co‐occurring morphospecies share distinctive anatomical features. Stems have sympodial primary vascular architecture with endarch primary xylem maturation of the cauline bundles, which surround a septate pith. Leaf traces are endarch, most diverging from the pith margin as double bundles (less frequently singly) and bearing leaves in 3/8 and 5/13 phyllotaxis. Leaves are long and straplike, resembling those of the previously reconstructed Cordaixylon dumusum Rothwell and S. Warner, but with a geniculate posture that justifies their segregation as Cordaites tianii S.‐J. Wang and J. Hilton sp. nov. Both male and female cones are compound, borne irregularly as epicormic bran...

Phylogenetics of Dilleniaceae Using Sequence Data from Four Plastid Loci (rbcL, infA, rps4, rpl16 Intron)

Abstract: Dilleniaceae are an angiosperm family consisting of 10–14 genera and ∼500 described species, with a pantropical distribution extending into temperate Australia. This study addresses the infrafamilial relationships of Dilleniaceae with nucleotide sequence data from the plastid loci rbcL, infA, rps4, and the rpl16 intron. Analyses of these data using maximum parsimony and Bayesian methods resolve Tetracera, the only pantropical genus in the family, as sister to all other Dilleniaceae. Within the clade of Dilleniaceae exclusive of Tetracera, the New World endemic genera form a clade that is sister to a clade composed of the Old World endemic genera. The latter contains two major subclades: (1) a clade containing Acrotrema, Dillenia, and Schumacheria and (2) a clade containing Hibbertia and its satellite genera, Adrastaea and Pachynema, which are embedded within Hibbertia. Ancestral‐state reconstructions of six morphological characters of both biological and taxonomic significance within Dilleniaceae suggest ...

Plant–Mycorrhizal Fungus Interactions Affect the Expression of Inbreeding Depression in Wild Strawberry

Abstract: The influence of biotic interactions on the expression of inbreeding depression has received only modest investigation; however, these interactions may be important in determining the magnitude and/or variation of inbreeding depression seen in the wild and invoked in models of mating and sexual system evolution. We present the first experimental test of the effects of plant–mycorrhizal fungus interactions on the expression of inbreeding depression. We inoculated selfed and outcrossed seedlings from eight hermaphrodite genotypes of wild strawberry (Fragaria virginiana) with mycorrhizal fungal spores and determined the effect on vegetative growth and sexual and asexual reproduction. We found that inoculated plants grew at rates similar to those of control plants but produced fewer flowers and more plantlets than controls. However, some of these effects varied with maternal genotype and cross type. As a consequence, mycorrhizal fungal inoculation had variable and trait‐dependent effects on the expression of ...

Patterns of DR5::GUS Expression in Organs of Pea (Pisum sativum)

Abstract: The recent availability of DR5 reporter constructs to visualize regions of auxin response allows us to examine the role of auxin in developmental processes. In Arabidopsis, DR5::GUS is sensitive to auxin pools in a dosage‐dependent manner and has been used extensively to visualize areas of high auxin concentration. We transformed pea (Pisum sativum) with DR5::GUS. Several lines, originating from independent events, have shown stable expression through T5. In pea, GUS expression occurred in embryos, root tips, developing flowers, procambium, and pollen. In root primordia, GUS expression was most abundant in the peripheral root cap cells, protoderm, and protoxylem. In leaf primordia, dark blue staining occurred in the distal tip of the primordium from plastochrons P0 through P4–5. Lateral tendril primordia and tendril tips stained more intensely blue and for more plastochrons than leaflet primordia and tips. Blue (GUS) staining in floral organs during initiation and development also revealed specific, shift...

Physiological characterization of transgenic alfalfa (Medicago sativa) plants for improved drought tolerance.

Abstract: WXP1 is an ethylene‐responsive element‐binding transcription factor that has been shown to lead to improved drought tolerance and increased wax accumulation when overexpressed in transgenic alfalfa under the control of the CaMV35S promoter. In this study, alfalfa was transformed with the WXP1 gene, driven by the epidermis‐specific promoter CER6. The transgenic CER6::WXP1 alfalfa plants and a previously tested CaMV35S::WXP1 line were subjected to water stress for 3 d and then rewatered. Gas exchange, chlorophyll fluorescence, relative water content, and water potential were measured. Compared with the controls, the transgenic lines showed higher net photosynthetic rate, transpiration rate, and stomatal conductance and higher efficiency of photosystem II, quantum yield of photosystem II, coefficient of photochemical quenching, and apparent electron transport rate under water stress and after rewatering. The transgenic lines also showed higher relative water content and leaf water potential under water defic...