Gametophytic apomixis, asexual reproduction involving megagametophytes, occurs in many flowering-... more Gametophytic apomixis, asexual reproduction involving megagametophytes, occurs in many flowering-plant families and as several variant mechanisms. Developmental destabilization of sexual reproduction as a result of hybridization and/or polyploidy appears to be a general trigger for its evolution, but the evidence is complicated by ploidy-level changes and hybridization occurring with facultative apomixis. The repeated origins of polyploid apomictic complexes in the palaeopolyploid Maloid Rosaceae suggest a new model of evolutionary transitions that may have wider applicability. Two conjectures are fundamental to this model: (1) that as previously suggested by Rutishauser, like many sexual flowering plants the polyploid apomicts require maternal-paternal balance in the second fertilization event that gives rise to the endosperm, and (2) that the observed variation in endosperm ploidy levels relates less to flexibility late in development than to the known variation in developmental origin of the megagametophyte between mechanisms loosely categorized as diplospory and apospory. The model suggests explanations for the relative frequencies of apospory and diplospory, and for the wide but incomplete associations of apospory with a pollination requirement (pseudogamy) and of diplospory with autonomous development of the endosperm. It is suggested that pollination from other taxa may provide some adaptive advantage to pseudogamous apospory.
... complexes? Timothy A. Dickinson, a , b Eugenia YY Lo, b , * Nadia Talent, a , Rhoda M. Love... more ... complexes? Timothy A. Dickinson, a , b Eugenia YY Lo, b , * Nadia Talent, a , Rhoda M. Love c , . ... al. 1991; Asker and Jerling 1992) and in some well-studied genera from other families (eg, Ranunculus L.; Hörandl and Paun 2007). ...
Since the 1800s, natural health products that contain hawthorn (Crataegus spp.) have been used in... more Since the 1800s, natural health products that contain hawthorn (Crataegus spp.) have been used in North America for the treatment of heart problems such as hypertension, angina, arrhythmia, and congestive heart failure. Traditionally, Native American tribes used hawthorn (Crataegus spp.) to treat gastrointestinal ailments and heart problems, and consumed the fruit as food. Hawthorn also has a long history of use in Europe and China for food, and in traditional medicine. Investigations of Crataegus spp. typically focus on the identification and quantification of flavonoids and anthocyanins, which have been shown to have pharmacological activity. The main flavonoids found in Crataegus spp. are hyperoside, vitexin, and additional glycosylated derivatives of these compounds. Reviewed herein are the botany, ethnobotany, and traditional use of hawthorn while focusing on the phytochemicals that have been reported in Crataegus species, and the variation in the described chemistry between individual species.
Hawthorns (Crataegus L., Rosaceae) have well-established uses in natural health products (NHPs), ... more Hawthorns (Crataegus L., Rosaceae) have well-established uses in natural health products (NHPs), and a handful of Eurasian species have demonstrated efficacy in treating symptoms of chronic heart failure. Until recently, however, almost nothing was known about the NHP potential of native North American hawthorns, of which approximately 50 occur in Canada. We seek to lay the foundation for the agroforestry exploitation of native hawthorn species by developing methods for the analysis, traceability, and authentication of NHPs derived from Canadian hawthorn species by using DNA barcodes and microsatellite fingerprints, by deploying new methods of chemical analysis, and by developing and optimizing methodologies to aid in their production. Because little is known about either hawthorn NHP functional components or their mode of action, this project will document these aspects by seeking to (1) confirm heart and cardiovascular protective properties in an established rodent model and (2) e...
DNA barcodes can facilitate identification of organisms especially when morphological characters ... more DNA barcodes can facilitate identification of organisms especially when morphological characters are limited or unobservable. To what extent this potential is realized in specific groups of plants remains to be determined. Libraries of barcode sequences from well-studied authoritatively identified plants represented by herbarium voucher specimens are needed in order for DNA barcodes to serve their intended purpose, where this is possible, and to understand the reasons behind their failure to do so, when this occurs. We evaluated four loci, widely regarded as universal DNA barcodes for plants, for their utility in hawthorn species identification. Three plastid regions, matK, rbcLa, and psbA-trnH and the internal transcribed spacer 2 (ITS2) of nuclear ribosomal DNA discriminate only some of the species of Crataegus that can be recognized on the basis of their morphology. In part, this is because in Rosaceae tribe Maleae most individual plastid loci yield relatively little taxonomic re...
Gametophytic apomixis, asexual reproduction involving megagametophytes, occurs in many flowering-... more Gametophytic apomixis, asexual reproduction involving megagametophytes, occurs in many flowering-plant families and as several variant mechanisms. Developmental destabilization of sexual reproduction as a result of hybridization and/or polyploidy appears to be a general trigger for its evolution, but the evidence is complicated by ploidy-level changes and hybridization occurring with facultative apomixis. The repeated origins of polyploid apomictic complexes in the palaeopolyploid Maloid Rosaceae suggest a new model of evolutionary transitions that may have wider applicability. Two conjectures are fundamental to this model: (1) that as previously suggested by Rutishauser, like many sexual flowering plants the polyploid apomicts require maternal-paternal balance in the second fertilization event that gives rise to the endosperm, and (2) that the observed variation in endosperm ploidy levels relates less to flexibility late in development than to the known variation in developmental origin of the megagametophyte between mechanisms loosely categorized as diplospory and apospory. The model suggests explanations for the relative frequencies of apospory and diplospory, and for the wide but incomplete associations of apospory with a pollination requirement (pseudogamy) and of diplospory with autonomous development of the endosperm. It is suggested that pollination from other taxa may provide some adaptive advantage to pseudogamous apospory.
... complexes? Timothy A. Dickinson, a , b Eugenia YY Lo, b , * Nadia Talent, a , Rhoda M. Love... more ... complexes? Timothy A. Dickinson, a , b Eugenia YY Lo, b , * Nadia Talent, a , Rhoda M. Love c , . ... al. 1991; Asker and Jerling 1992) and in some well-studied genera from other families (eg, Ranunculus L.; Hörandl and Paun 2007). ...
Since the 1800s, natural health products that contain hawthorn (Crataegus spp.) have been used in... more Since the 1800s, natural health products that contain hawthorn (Crataegus spp.) have been used in North America for the treatment of heart problems such as hypertension, angina, arrhythmia, and congestive heart failure. Traditionally, Native American tribes used hawthorn (Crataegus spp.) to treat gastrointestinal ailments and heart problems, and consumed the fruit as food. Hawthorn also has a long history of use in Europe and China for food, and in traditional medicine. Investigations of Crataegus spp. typically focus on the identification and quantification of flavonoids and anthocyanins, which have been shown to have pharmacological activity. The main flavonoids found in Crataegus spp. are hyperoside, vitexin, and additional glycosylated derivatives of these compounds. Reviewed herein are the botany, ethnobotany, and traditional use of hawthorn while focusing on the phytochemicals that have been reported in Crataegus species, and the variation in the described chemistry between individual species.
Hawthorns (Crataegus L., Rosaceae) have well-established uses in natural health products (NHPs), ... more Hawthorns (Crataegus L., Rosaceae) have well-established uses in natural health products (NHPs), and a handful of Eurasian species have demonstrated efficacy in treating symptoms of chronic heart failure. Until recently, however, almost nothing was known about the NHP potential of native North American hawthorns, of which approximately 50 occur in Canada. We seek to lay the foundation for the agroforestry exploitation of native hawthorn species by developing methods for the analysis, traceability, and authentication of NHPs derived from Canadian hawthorn species by using DNA barcodes and microsatellite fingerprints, by deploying new methods of chemical analysis, and by developing and optimizing methodologies to aid in their production. Because little is known about either hawthorn NHP functional components or their mode of action, this project will document these aspects by seeking to (1) confirm heart and cardiovascular protective properties in an established rodent model and (2) e...
DNA barcodes can facilitate identification of organisms especially when morphological characters ... more DNA barcodes can facilitate identification of organisms especially when morphological characters are limited or unobservable. To what extent this potential is realized in specific groups of plants remains to be determined. Libraries of barcode sequences from well-studied authoritatively identified plants represented by herbarium voucher specimens are needed in order for DNA barcodes to serve their intended purpose, where this is possible, and to understand the reasons behind their failure to do so, when this occurs. We evaluated four loci, widely regarded as universal DNA barcodes for plants, for their utility in hawthorn species identification. Three plastid regions, matK, rbcLa, and psbA-trnH and the internal transcribed spacer 2 (ITS2) of nuclear ribosomal DNA discriminate only some of the species of Crataegus that can be recognized on the basis of their morphology. In part, this is because in Rosaceae tribe Maleae most individual plastid loci yield relatively little taxonomic re...
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