POSICION TAXONOMICA, CITOLOGIA Y PALINOLOGIA DE TRES NIVELES DE PLOIDIA DE TURNERA SUBULATA SMITH

Resumen

Turnera subulata Sm. lives in America, from 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).

1. 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 m any 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 acces- sion 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 máximum of five qua- drivalents 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 + 1 I in 45,9%, and 3 III + 2 II +21 in 24,5%. These findings sug- gest that the 2n=20 cytotypes are autotetraploids.

Tumera subulata 2n=10 and its autotetraploid derivates 2n = 20 constitute only one species beeause there is genetic continüity among them.