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Shoot tips from in vitro plants of four rose species were cryopreserved by the droplet vitrification method. Optimized conditions involved exposure to loading solution for 20 min, then treatment with plant vitrification solution (PVS2) for 20 min (Rosa agrestis, R. canina and R. dumalis) or 30 min (R. rubiginosa) followed by freezing in liquid nitrogen. Survival rate ranged from 78.3 to 95.1%, depending on the species. Regrowth rate of shoot tips was 50.5% for R. agrestis, 63.2% for R. rubiginosa, 71.4% for R. dumalis and 78% for R. canina. The preculture of donor plants in a medium with 0.25 цЫ sucrose facilitated the isolation of shoot tips and increased regrowth rate after cryopreservation. Plant regeneration was carried out in Murashige and Skoog medium with 1 цЫ 6-benzylaminopurine, 1.5 цЫ gibberellic acid and 0.087 M sucrose. Plants regenerated from cryopreserved shoot tips did not display morphological alterations in comparison with non-cryopreserved shoot tip - derived plants.
The variability of pollen grains of 16 species from genus Rosa L. was studied (i.e. Rosa agrestis, R. canina, R. dumalis, R. gallica, R. inodora, R. jundzillii, R. kostrakiewiczii, R. majalis, R. micrantha, R. mollis, R. pendulina, R. rubiginosa, R. sherardii, R. tomentosa, R. villosa, and R. zalana). The material came from 107 native localities of those species in Poland. The measurements are based on at least 30–50 randomly selected mature pollen grains per specimen. In total, 3510 pollen grains were examined. They were analysed for 8 quantitative features, i.e. length of polar axis (P), length of equatorial axis (E), exine thickness on the pole (Exp), exine thickness at the equator plane (Exe), length of ectocolpi (Le), P/E ratio, and relative thickness of exine (Exp/P and Exe/E ratio). Statistically significant differences were found among the examined species with regard to all analysed pollen features. The pollen and ectocolpi dimensions (P, E and Le) were largest in R.gallica (35.9, 28.1, and 28.0 μm, respectively) and smallest in R. majalis (27.0, 20.2, and 21.2 μm, respectively). The mean coefficients of variability of the pollen features measured can be used to arrange the examined rose species from the least to the most variable as follows: R. pendulina, R. villosa, R. jundzillii, R. inodora, R. canina, R. rubiginosa, R. dumalis, R. gallica, R. agrestis , R. micrantha, R. zalana, R. tomentosa, R. sherardii, R. majalis, R. kostrakiewiczii and R. mollis. The obtained data failed to confirm fully both the division of the Rosa genus currently in force in taxonomy into sections as well as relationships among the examined species from the Caninae section. In addition, values of morphological characters of the same species may differ considerably from one another. The extent of these differences indicated that it was necessary to measure large numbers of pollen grains in order to obtain accurate biometric data.
The morphology of pollen grains of 16 species from the Rosa L. genus were studied (i.e. R. agrestis, R. canina, R. dumalis, R. gallica, R. inodora, R. jundzillii, R. kostrakiewiczii, R. majalis, R. micrantha, R. mollis, R. pendulina, R. rubiginosa, R. sherardii, R. tomentosa, R. villosa, and R. zalana). The material came from 16 native localities of those species in Poland. The measurements are based on at least 30-50 randomly selected, fully developed pollen grains per specimen. In total, 500 pollen grains were examined. They were analysed for 13 quantitative features of pollen grains and exine sculpturing and the following qualitative traits: outline, shape, "operculum" structure. The diagnostic features of pollen grains of studied species were: length of polar and equatorial axes and length of ectocolpi. The above-mentioned pollen grain morphological features make isolation of one species possible: R. gallica. R. gallica is distinguished for its highest values of the length of polar and equatorial axes, and the length of ectocolpi. The obtained analytical results of operculum and exine sculpture features, considered as diagnostic, corroborated only slightly their priority significance for the isolation of the examined species and sections. The collected data failed to confirm fully the current taxonomical division of the Rosa genus into sections (only section Gallicanae from R. gallica is isolated) as well as consanguinity relationships between the examined species from the Caninae section. On the dendrogram, both species closely related with each other as well as those from other developmental lines were found in the same group. These equivocal results are by no means surprising because the Caninae section is the most polymorphic group in the Rosa genus, and contemporary Caninae are of the nature of a swarm of R. canina hybrids as a link combining all taxons of the section.
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