Palynological Study of Cheilanthes and Astrolepis (Pteridaceae) Species from Northwestern Argentina

Abstract

The spore morphology of Cheilanthes and Astrolepis species from northwestern Ar- gentina was analyzed using light microscopy and scanning electron microscopy. Three patterns of sporoderm structure were found: two exclusive and different structures in A. sinuata and the C. squamosa group, and a typically cheilanthoid structure with diverse sculptures in the rest of the species of Cheilanthes, i.e., C. bonariensis, C. buchtienii, C. cf. cucullans, C. obducta, and C. volcanensis. Sporophytic features such as hairs with tongue and groove wall cells and dixylic vascular strands are also mentioned in C. obducta. Similar spore characteristics are correlated with sporophyte morphology in some of the recognized groups. Spore-size differences, abnormal- ities in spore type, abortion and number of spores per sporangium (16, 32) suggest polyploidy and/or apogamy in some specimens of C. buchtienii, C. obducta, and C. squamosa, and in all samples of A. sinuata and C. bonariensis. The present paper is the second in a series of studies on cheilanthoid ferns preliminary to an ongoing project, Atlas of Spores of Pteridophyta of North- western Argentina (Morbelli, in prep.). Perispore structure and stratification offer some interesting substructures and variations. Previous papers (Ranker, 1989; Tryon and Lugardon, 1991) have shown that detailed analysis of the exospore and perispore can provide valuable information in cheilanthoid ferns. The aim of these papers is to characterize each species of the region from the palynological point of view and to assess whether spore morphology is useful in the systematics of the group. When necessary, sporophytic features are included for comparative analysis of species groups.