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Medientyp:
E-Artikel
Titel:
POSICION TAXONOMICA, CITOLOGIA Y PALINOLOGIA DE TRES NIVELES DE PLOIDIA DE TURNERA SUBULATA SMITH
Beteiligte:
ARBO, MARIA M.;
FERNANDEZ, A.
Erschienen:
Facultad de Ciencias Agrarias, 1983
Erschienen in:Bonplandia
Sprache:
Spanisch
ISSN:
0524-0476;
1853-8460
Entstehung:
Anmerkungen:
Beschreibung:
<p>Turnera subulata Sm. lives in America, fr. om Panamá to Bolivia. It was introduced to Asia, where it is nowadays a common weed in India, Malasia and Indonesia. Plant and pollen morphology, and citology were studied in one diploid (2n=2x=20) accessions of Turnera subulata from Brasil. One triploid hybrid (2n=15) was obtained by espontaneous crossing of one tetraploid and the diploid strain. In the literature there are counts of four accessions from Brasil, one from India and one from Malasia, all tetraploids (2n=20). T. subulata is considered a different species of T. ulmifolia be: cause it presents a certain combination of morphological characters, constant in all three ploidy levels. Pollen sculpture is dimorphic, unlike other distylous taxa: short styled flowers have reticulate grains, with broad meshes and many free bacules within; long styled flowers have small reticulate grains, with little meshes without free bacules. Pollen fertility is 96—99% in the diploid, 86—89% in the tetraploids and 48% in the triploid. Meiotic chromosome behavior was regular in the diploid accession with 5 bivalents in every pollen mother cell (PMC). Meiosis was also studied in two tetraploid accessions, which showed a high level of quadrivalent chromosome associations. The maximum of five quadrivalents was observed in 15 and 35 percent of the PMC respectively. Three different chromosome configurations were observed in the triploid hybrid at metaphase I: 5 III in 29,5% of the PMC's, 4 III + 1 II + 11 in 45,9%, and 3 III+ 2 II + 2 I in 24,5%. These findings suggest that the 2n=20 cytotypes are autotetraploids. Turnera subulata 2n=10 and its autotetraploid dérivâtes 2n=20 constitute only one species because there is genetic continuity among them.</p>