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At least 991 records · Page 55Linked to original sources
PubMed2007

Endosperm formation in aposporous Crataegus (Rosaceae, Spiraeoideae, tribe Pyreae): parallels to Ranunculaceae and Poaceae.

Apomixis in Crataegus is primarily aposporous and requires pollination. The embryo sac is of the Polygonum type. A combination of meiotically unreduced embryo sacs with apparently reduced pollen would violate the usual requirement for a 2 : 1 ratio of maternal to paternal contributions to the endosperm. We therefore investigated the origin of endosperm in seeds of sexual diploids and apomictic polyploids of the sister genera Crataegus and Mespilus. Flow-cytometric DNA measurements from embryo and endosperm in mature seeds were converted to ploidy levels using leaf-tissue information. The diploids had triploid endosperm. In c. 60% of seed from polyploids, one sperm apparently contributes to the endosperm, while 25% or more may involve two sperm. Additional results suggest that trinucleate central cells also occur. Fertilization of meiotically unreduced eggs is indicated. The ratio of maternal to paternal contributions to the endosperm in these apomictic Crataegus is not constrained to 2 : 1. They thus resemble some Sorbus (Pyreae) and very distantly related Ranunculus (Ranunculaceae). It is suggested that Paspalum (Poaceae) may have similarly flexible endosperm ploidy levels.

Crataegus↗
PubMed2002

A variable minisatellite sequence in the chloroplast genome of Sorbus L. (Rosaceae: Maloideae).

The chloroplast genome is now known to be more variable than was once thought. Reports of RFLP (restriction fragment length polymorphism) and sequence variation, as well as variation in chloroplast microsatellites, are common. Here, data are presented on the variability of a minisatellite sequence in the chloroplast genome of Sorbus species. RFLP analysis of a PCR product comprising the region between the trnM and rbcL genes of nine Sorbus species identified seven size variants. Sequencing revealed the observed size polymorphism to be due to differences in the number of copies of an imperfect 9-bp motif. A more intensive survey of the variability of the minisatellite was undertaken in populations of Sorbus aucuparia. The potential uses of such regions in chloroplast DNA are discussed and a possible mechanism for the evolution of the minisatellite is presented.

Base Sequence↗
PubMed1992

The occurrence of long chain polyprenols in leaves of plants of Rosaceae family and their isolation by time-extended liquid chromatography.

The long chain polyprenols composed of 30 and more isoprene units from leaves of plants belonging to the genera Potentilla and Rosa have been described. They occur in the form of fatty acid esters. The composition of polyprenol mixture was species dependent and its content reached ca. 0.5% wet weight. Large scale preparation of individual polyprenols from a natural polyprenol mixture was performed using time-extended liquid chromatography on the hydrophobic gel Lipidex-5000.

Chromatography, Liquid↗
PubMed1999

Allozyme and morphological variation in two subspecies of Dryas octopetala (Rosaceae)in Alaska.

The Alaskan endemic shrub Dryas octopetala ssp. alaskensis and its circumpolar conspecific ssp. octopetala are adapted to closely adjacent habitats in alpine areas of Alaska. These alpine areas form geographically disjunct "islands" among which there are limited opportunities for gene flow. Allozyme electrophoresis and a common garden experiment were used to examine genetic variation between subspecies and among disjunct populations of each subspecies. Overall, allozyme variation in D. octopetala is low with little differentiation among populations or between subspecies. Morphological differences, however, are greater between subspecies than among populations within subspecies. Divergence for a few morphological and life-history characters has apparently occurred in response to strong selection, but without divergence at allozyme loci. The ancestors of both subspecies of D. octopetala in Alaska were isolated during the Pleistocene in the glacial refugia of Alaska and Yukon, which may explain low overall variation. Dryas. o. alaskensis is thought to be a Pleistocene derivative of ssp. octopetala, which may account for the low allozyme divergence between subspecies. Recent restriction to alpine areas may explain the low differentiation among disjunct populations.

Journal Article↗
PubMed2000

Dissecting the causes of variation in intra-inflorescence allocation in a sexually polymorphic species, Fragaria virginiana (Rosaceae).

In this study we dissect the causes of variation in intra-inflorescence allocation in a sexually polymorphic species, Fragaria virginiana. We separated out the effects of resource competition during flowering from those of inflorescence architecture, as well as identified the effects of sex morph and genotype. We found position-based variation in petal length, ovule, pollen, and flower number to be influenced more by architecture than by our resource manipulations during flowering. We also found both genotype- and sex-specific intra-inflorescence patterns. Furthermore, our data indicate that the sex morph-specific intra-inflorescence patterns result from architectural modifications of the basic pattern. In fact, sex-differential intra-inflorescence patterns suggest that fitness through male and female function may be maximized by different resource distribution patterns within the inflorescence and may have been modified by past selection. Specifically, females invested heavily in ovules at positions where fruit set was most likely (primary and secondary), at the expense of flower number and allocation per flower at more distal positions. Whereas functional males invested minimally in ovules at all flower positions and produced the most abundantly flowered inflorescences, hermaphrodites, on the other hand, showed intermediate patterns, implying a compromise between sex functions. We suggest that consideration of intra-inflorescence allocation and inflorescence architecture may reveal the mechanism underlying sexual dimorphism in flower allocation and number.

Journal Article↗
PubMed2000

Megagametophyte development in Potentilla nivea (Rosaceae) from northern Swedish Lapland.

An investigation of the embryology of Potentilla nivea was carried out using a confocal laser scanning microscope. The crassinucellate nature of the ovule as well as the presence of a multicellular archesporium was confirmed. A "nucellar cap" builds up as the result of mitotic divisions in the parietal cell tissue and the nucellar epidermis. Earlier reports that several mature megagametophytes are present in each ovule was confirmed. The processes of megasporogenesis and megagametogenesis in Potentilla turned out to differ from descriptions in previous reports, and we propose a reinterpretation. Most importantly, the "archesporium" of previous authors is here considered to be parietal cells, whereas the "chalazal cells" are here interpreted as the archesporium. Meioses commonly occur, giving rise to tetrahedral tetrads. Cytologically unreduced megagametophytes arise from generative tissue (archesporial cells or megasporocytes) only and are diplosporous. Apospory does not occur. The megagametophyte is monosporic and five-nucleate; the three antipodal nuclei normally present in eight-nucleate megagametophytes are missing.

Journal Article↗
PubMed2000

Molecules and morphology in concert: tests of some hypotheses in arctic Potentilla (Rosaceae).

We developed a combined molecular and morphological approach to unravel complex variation at low taxonomic levels, exemplified by some arctic members of Potentilla. Twenty-one populations from Svalbard were analyzed for random amplified polymorphic DNAs (RAPDs) and 64 morphological characters to test the hypotheses that (1) the P. nivea complex (section Niveae) consists of three taxa (P. chamissonis, P. insularis, and P. nivea), (2) three "eco-morphotypes" in P. pulchella (section Multifidae) should be considered different taxa, and (3) P. insularis originated as an intersectional hybrid (Niveae × Multifidae). Twenty-two RAPD multilocus phenotypes were observed in the 136 plants analyzed based on 35 markers. Three fairly distinct groups of RAPD phenotypes were identified in the P. nivea complex based on multivariate analyses and an analysis of molecular variance (AMOVA; 77.6% among-group variation). The variation within the P. nivea complex was more or less continuous in multivariate analyses of the morphological data. We identified, however, several individual morphological characters that separated unambiguously among the three groups of RAPD phenotypes, revealing that these groups correspond to the previously hypothesized taxa. Many identical RAPD multilocus phenotypes were observed in the "eco-morphotypes" of P. pulchella, suggesting that its conspicuous morphological variation is caused by plasticity or by genetic variation at a small number of loci. The hypothesis of the hybrid origin of P. insularis was not supported by the RAPD data. Overall, very little RAPD variation was observed within populations of the four taxa (2.1-16.7% in AMOVA analyses; average genotypic diversity, D, was 0.10-0.30). We conclude that detailed, concerted analysis of molecules and morphology is a powerful tool in low-level taxonomy.

Journal Article↗
PubMed2000

Evidence of sexuality in European Rubus (Rosaceae) species based on AFLP and allozyme analysis.

Reproduction of polyploid Rubus species is described as facultatively apomictic. Pollination is needed for seed set, but most seedlings are produced asexually by pseudogamy. Although sexual processes may occur, clonal diversity can be extremely low. We performed a pollination experiment to investigate the breeding system and used allozyme and AFLP markers to analyze genetic variation among and within seed families in R. armeniacus and R. bifrons. Pollination either with self or outcross pollen was necessary to trigger seed set. Outbreeding marginally increased the number and quality of seeds compared with selfing. The enzyme PGI revealed some genetic variation within seed families. Seven other enzyme systems were monomorphic. The more detailed AFLP analyses with five primer pairs detected the same rate of genetic variation (14-17% of seedlings were genetically distinct) and confirmed the allozyme results for the same individuals. No genetic variation was found between the seed families from within a species collected in widely separated populations, but clear species-specific differences were observed. The results support the view that polyploid Rubus species are pseudogamous apomicts with low genetic diversity among and within seed families. However, sexual reproduction occasionally occurs and contributes to the maintenance of genetic variation within natural populations.

Journal Article↗
PubMed2001

Preformation, architectural complexity, and developmental flexibility in Acomastylis rossii (Rosaceae).

The duration of preformation and the seasonal pattern of development were studied in the architecturally complex alpine perennial Acomastylis rossii. Each leaf and inflorescence requires 3 yr to progress from initiation through structural and functional maturity to senescence. As a consequence, three cohorts of preformed organs, initiated in successive years, are borne simultaneously by each individual plant. The oldest cohort matures immediately following snowmelt, after which no additional leaves are matured until the following spring. A second cohort remains below ground in the apical bud and continues development, while a third cohort is initiated. Initiation and development of primordia proceed below ground throughout the summer and continue for at least 2.5 mo after aboveground structures have senesced. Acomastylis rossii maintains numerous dormant vegetative buds containing preformed leaf primordia in the axils of senesced leaves. Developmental preformation has been widely reported in arctic and alpine tundra environments and has been theorized to severely constrain rapid responses to environmental variation. The presence of many such preformed structures may mitigate some of the constraint on plant response to environmental variation imposed by the long developmental trajectories of leaves and inflorescences in apical buds.

Journal Article↗
PubMedDate not supplied

Triterpenes and sterols in the flowers and leaves of Prunus spinosa L. (Rosaceae).

From the flowers of Prunus spinosa L. a mixture of alpha- and beta-amyrine, a mixture of ursolic and oleanolic acids, ursolic acid, a mixture of beta-sitosterol, gamma-sitosterol and stigmasterol and beta-sitosterol 3-O-beta-D-glucopyranoside were isolated. Their structure was determined by spectroscopic methods (GC/MS, IR, 1H and 13C NMR). Chromatographic methods (GC, HPLC, TLC) were employed to determine the presence of the listed compounds in the leaves. Also, the content of beta-sitosterol, ursolic and oleanolic acids in the leaves and flowers of blackthorn was determined by GC/MSD method.

Phytosterols↗