Abstract:
:Welwitschiaceae, a family in the Gnetales, is known today from only one extant species, Welwitschia mirabilis. This species is distributed in the Namibian desert, along the western coast of southern Africa, about 10 km inland from the coast. Very little is known about the fossil record of this family. Lower Cretaceous megafossils of various organs, assigned to Welwitschiaceae, are presented here. These fossils include young stems with paired cotyledons attached (Welwitschiella austroamericana n. gen. et sp.), isolated leaves (Welwitschiophyllum brasiliense n. gen. et sp.), and axes bearing male cones (Welwitschiostrobus murili n. gen. et sp.). They were collected in the Crato Formation, which is dated by palynomorphs and ostracods as Late Aptian (114 to 112 million years ago). These sediments are exposed in the Araripe Basin of northeastern Brazil. This study brings together new information of the megafossil record of Welwitschia-like plants and also reports of pollen said to be similar to that of Welwitschia from Lower Cretaceous sediments.
journal_name
Am J Botjournal_title
American journal of botanyauthors
Dilcher DL,Bernardes-De-Oliveira ME,Pons D,Lott TAdoi
10.3732/ajb.92.8.1294subject
Has Abstractpub_date
2005-08-01 00:00:00pages
1294-310issue
8eissn
0002-9122issn
1537-2197pii
92/8/1294journal_volume
92pub_type
杂志文章abstract::In volume 97(2) of the American Journal of Botany (pp. 268-275), we published an article entitled "Structural, physiological, and stable carbon isotopic evidence that the enigmatic Paleozoic fossil Prototaxites formed from rolled liverwort mats". Here, we respond to a letter and a commentary on our article in the pres...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.1000172
更新日期:2010-07-01 00:00:00
abstract:PREMISE OF THE STUDY:Chloroplast microsatellites were developed in Theobroma cacao to examine the genetic diversity of cacao cultivars in Trinidad and Tobago. METHODS AND RESULTS:Nine polymorphic microsatellites were designed from the chloroplast genomes of two T. cacao accessions. These microsatellites were tested in...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.1100306
更新日期:2011-12-01 00:00:00
abstract:PREMISE:Most plants interact with mycorrhizal fungi and animal pollinators simultaneously. Yet, whether mycorrhizae affect traits important to pollination remains poorly understood and may depend on the match between host and fungal genotypes. Here, we examined how ericoid mycorrhizal fungi affected flowering phenology...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.1002/ajb2.1372
更新日期:2019-11-01 00:00:00
abstract::We assessed the effects of local environment on survival, growth, and development in six clones (genotypes) of Vallisneria americana grown at five sites in the Huron-Erie Corridor. Detrimental effects of local environment on plant performance (rate of clonal growth, leaf and root production, surface area of leaves and...
journal_title:American journal of botany
pub_type: 杂志文章
doi:
更新日期:1997-12-01 00:00:00
abstract::Phloem, as a major tissue mediating long-distance communication, has been an object of extensive research ever since its structure was first reported in 1837. Functional phloem consists of sieve elements (SEs) and companion cells (CCs). While SEs are enucleated conducting cells in the phloem, CCs are cells with intact...
journal_title:American journal of botany
pub_type: 杂志文章,评审
doi:10.3732/ajb.1400197
更新日期:2014-09-01 00:00:00
abstract:PREMISE OF THE STUDY:A total of 38 polymorphic microsatellite loci of the Indian jujube (Ziziphus mauritiana), an economically important fruit tree, were developed to evaluate genetic diversity and aid in the identification of cultivars. METHODS AND RESULTS:The 38 microsatellite markers were isolated from the Indian j...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.1100500
更新日期:2012-05-01 00:00:00
abstract:PREMISE:The ecological implications of hyperaccumulation have been investigated at the organismal level, but are poorly understood at the plant community level. Questions addressed here were: Does the presence of selenium (Se) hyperaccumulators affect Se distribution and concentration in their native soil, and do hyper...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.1002/ajb2.1500
更新日期:2020-07-01 00:00:00
abstract:PREMISE OF THE STUDY:Microsatellite markers were developed for the common wetland plant Juncus effusus to assess levels of within- and among-population genetic diversity. METHODS AND RESULTS:Using a next-generation sequencing approach we identified new microsatellite loci, from which 23 were further characterized in a...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.1100322
更新日期:2012-02-01 00:00:00
abstract::Light propagation and distribution inside leaves have been recognized as important processes influencing photosynthesis. Monochromatic light absorption across the mesophyll was measured using chlorophyll fluorescence generated from illumination of the cut edge (epi-illumination), as well as the adaxial or abaxial surf...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.92.9.1425
更新日期:2005-09-01 00:00:00
abstract::Several alpine species have outlying populations in the lowlands and lower mountains north of the Alps. These small, isolated populations are usually described as either (1) glacial relics, (2) descendants from populations living on forelands and moraines during the ice ages, or (3) populations founded by long-distanc...
journal_title:American journal of botany
pub_type: 杂志文章
doi:
更新日期:2000-04-01 00:00:00
abstract:PREMISE OF THE STUDY:Hybridization and polyploidization (allopolyploidy) are ubiquitous in the evolution of plants, but tracing the origins and subsequent evolution of the constituent genomes of allopolyploids has been challenging. Genome doubling greatly complicates genetic analyses, and this has long hindered investi...
journal_title:American journal of botany
pub_type: 杂志文章,评审
doi:10.3732/ajb.1100395
更新日期:2012-02-01 00:00:00
abstract::After 120 yr of burial in moist, well-aerated sand, 23 seeds of Verbascum blattaria and two seeds of a Verbascum sp. germinated and produced normal plants (50% germination for Verbascum). After a 6-wk cold treatment, a single seed of Malva rotundifolia germinated also, producing a normal plant (2% germination). Plants...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.89.8.1285
更新日期:2002-08-01 00:00:00
abstract::The direct and indirect effects of vegetative herbivory on the mating system of Impatiens capensis were analyzed through a survey of herbivory in natural I. capensis populations and manipulation of leaf damage in the field. Across 10 wild populations of I. capensis proportion of cleistogamous flowers had a significant...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.91.7.1046
更新日期:2004-07-01 00:00:00
abstract:PREMISE:The genus Arisaema (Araceae) has rapidly diversified in Japan, and multiple species often coexist in the field. Although Japanese Arisaema species hybridize from artificial crossing, hybrid individuals are rare in mixed populations; suggesting the presence of effective pre-pollination barriers. We examined the ...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.1002/ajb2.1389
更新日期:2019-12-01 00:00:00
abstract::Senna (Leguminosae) is a large, widespread genus that includes species with enantiostylous, asymmetric flowers and species with extrafloral nectaries. Clarification of phylogenetic relationships within Senna based on parsimony analyses of three chloroplast regions (rpS16, rpL16, and matK) provides new insights on the ...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.93.2.288
更新日期:2006-02-01 00:00:00
abstract:PREMISE OF THE STUDY:One explanation for the evolution of selfing, the drought escape hypothesis, proposes that self-fertilization may evolve under conditions of intensifying seasonal drought as part of a suite of traits that enable plants to accelerate the completion of their life cycle, thereby escaping late-season d...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.1400557
更新日期:2015-06-01 00:00:00
abstract::Self-incompatibility (SI) is an effective method for limiting self-fertilization in flowering plant species, but there are circumstances in which an otherwise functional SI system may fail. One of the most intriguing of these is the induction of selfing by mixed loads of self and heterospecific pollen (the mentor effe...
journal_title:American journal of botany
pub_type: 杂志文章
doi:
更新日期:1998-06-01 00:00:00
abstract::Recent molecular phylogenetic studies of Solanaceae have identified many well-supported clades within the family and have permitted the creation of a phylogenetic system of classification. Here we estimate the phylogeny for Iochrominae, a clade of Physaleae sensu Olmstead et al. (1999), which contains 34 Andean specie...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.93.8.1140
更新日期:2006-08-01 00:00:00
abstract::The eudicot order Malpighiales contains ∼16000 species and is the most poorly resolved large rosid clade. To clarify phylogenetic relationships in the order, we used maximum likelihood, Bayesian, and parsimony analyses of DNA sequence data from 13 gene regions, totaling 15604 bp, and representing all three genomic com...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.0800207
更新日期:2009-08-01 00:00:00
abstract::Perennial crops represent important fresh and processed food sources worldwide, but advancements in breeding perennials are often impeded due to their very nature. The perennial crops we rely on most for food take several years to reach production maturity and require large spaces to grow, which make breeding new cult...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.1400143
更新日期:2014-10-01 00:00:00
abstract:PREMISE OF THE STUDY:Previous studies have shown that polyploidy has pronounced effects on photosynthesis. Most of these studies have focused on synthetic or recently formed autopolyploids, and comparatively little is known about the integrated effects of natural allopolyploidy, which involves hybridity and genome doub...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.1100465
更新日期:2012-01-01 00:00:00
abstract:PREMISE OF THE STUDY:Areas lacking dominant plants, or gaps, can support high diversity and specialist species. Previous chronosequence research in Florida rosemary scrub showed indistinct gap area patterns with fire and the dependence of certain species on gaps. We hypothesized that fire and gap size would affect exti...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.1700175
更新日期:2017-12-01 00:00:00
abstract::In spite of the ecological and economic importance of temperate bamboos, relatively little is known about their population biology or evolutionary history. Recently, hybridization has emerged as a potential source of diversity in this group, as well as an underlying cause of taxonomic problems. As part of a broader ph...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.0900244
更新日期:2010-03-01 00:00:00
abstract:PREMISE OF THE STUDY:Expressed sequence tag (EST)-derived microsatellite markers were developed for Elaeocarpus photiniifolia, an endemic taxon of the Bonin Islands. METHODS AND RESULTS:Initially, a complementary DNA (cDNA) library was constructed by de novo pyrosequencing of total RNA extracted from a seedling. A tot...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.1100391
更新日期:2012-02-01 00:00:00
abstract::Natural recruitment of oaks appears to be declining throughout the northern hemisphere. Summer drought poses a potentially important barrier to oak recruitment in southern California. To evaluate this barrier, we grew evergreen Quercus agrifolia and deciduous Q. lobata from seeds near parental trees. We measured water...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.0800247
更新日期:2009-04-01 00:00:00
abstract:PREMISE OF THE STUDY:Giant cacti species possess long cylindrical stems that store massive amounts of water and other resources to draw on for photosynthesis, growth, and reproduction during hot and dry conditions. Across all giant cacti taxa, stem photosynthetic surface area to volume ratio (S:V) varies by several fol...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.1002/ajb2.1166
更新日期:2018-10-01 00:00:00
abstract:PREMISE OF THE STUDY:Autopolyploidy, or whole-genome duplication within a species, leads to closely related cytotypes in one geographic location. One hypothesized mechanism by which autopolyploids become established is climatic niche divergence from their diploid progenitor. Here we tested this hypothesis in diploid, t...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.1002/ajb2.1161
更新日期:2018-10-01 00:00:00
abstract:PREMISE OF THE STUDY:Robust markers are required (inter alia) for assessing origins of Calophyllum inophyllum populations on the Bonin Islands, Japan. Therefore, informative expressed sequence tag (EST)-based microsatellite or simple sequence repeat (SSRs) markers in the species were sought. METHODS AND RESULTS:Using ...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.1100299
更新日期:2012-01-01 00:00:00
abstract:PREMISE OF THE STUDY:Permineralization provides the most faithful known mode of three-dimensional preservation of the morphology and cellular anatomy of fossil plants. Standard optical microscopic documentation of such structures can provide only an approximation of their true three-dimensional form and is incapable of...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.1300027
更新日期:2013-08-01 00:00:00
abstract::In the alpine landscape most plant populations are spatially isolated due to extreme patchiness and strong natural fragmentation. We used RAPD-PCR (randomly amplified polymorphic DNA polymerase chain reaction) for a study of the genetic diversity within and among 20 populations of Geum reptans, an outcrossing clonal p...
journal_title:American journal of botany
pub_type: 杂志文章
doi:10.3732/ajb.91.12.2013
更新日期:2004-12-01 00:00:00