Pollen of circumpolles - An enigma or morphotrends showing evolutionary adaptation
Abstract
An unusual combination of pollen characters imparts a unique identity to the Mesozoic Circumpolles: the absence of sacci, the tetrad or dyad configuration, heteropolarity marked by the aperturoid thinnings, a distal pore fortified by an endo-annulus, the occurrence of exinal filaments and spherules, the development-transition-diminution of supratectal sculpture, tectal complexity, grades of columellar complexity, the presence of lamellate nexine and the development, multiplication and disappearance of endoridges. Analogous or homologous pollen characteristics in other taxa belonging to various plant groups, as well as the functional significance of important features and their conjectured evolutionary trends and adaptive values are discussed. Characters such as tetrad or dyad configuration, exinal filaments and tectal complexity partly comparable with those in extant angiosperms, are not encountered in living gymnosperms.
- Publication:
-
Review of Palaeobotany and Palynology
- Pub Date:
- 1990
- DOI:
- 10.1016/0034-6667(90)90069-U
- Bibcode:
- 1990RPaPa..65..179P