| Summary: | During the Mesozoic and Paleogene period the northern areas of the Antarctic Peninsula were covered by diversified vegetation that included many groups of ferns and conifers. From the Cretaceous period onwards there were also angiosperms. The fall of global temperatures since the beginning of Paleogene and the gradual isolation of the continent from other southern land masses, resulted in near extinction of this vegetation and the definitive covering of the continent by ice. This work aims to present the morphology and ultrastructure of the pollen grains from the few groups of herbaceous angiosperms that today live on King George Island, in the South Shetland Islands, where are accompanied by mosses and lichens. They are represented by one Caryophyllaceae, Colobanthus quitensis (Kunth) Bartl., and two Poaceae, Deschampsia antarctica Desv. and Poa annua L. These species were registered in peat bogs dated from 4090 + 90 years B.P. and are here considered as native and relict forms. The presence of P.annua probably represents the effect of human activities in the continent or could result from animal induced dispersion by long distances. The morphologic pattern of the pollen grains is pantoporate, echinous, in C. quitensis, and porate, psilate to moderate scabrate, in D. antarctica and P. annua. Key words: Palynology, Poaceae, Caryophyllaceae, Holocene, Antarctic Peninsula, King George Island. Durante o Mesozóico e o Paleógeno, as áreas do norte da Península Antártica abrigaram uma vegetação diversificada e composta por muitos grupos de fetos, coníferas e, a partir do Cretáceo, também de angiospermas. O gradativo isolamento do continente a partir do final do Paleógeno, principal fator para sua cobertura pelo gelo, provocou o quase desaparecimento desta vegetação. Hoje, musgos e liquens e poucas angiospermas herbáceas concentram-se nas áreas mais livres de gelo, especialmente nas ilhas oceânicas periantárticas e do norte da Península. Neste trabalho, são apresentadas as características vegetativas e a morfologia e ...
|
|---|