Palynological Studies of Some Species in the Genus Astragalus L. (Leguminosae) in Egypt PDF

Keywords

pollen, morphology, evolution

Abstract

Pollen grains of twenty seven species of Egyptian Astragalus were studied, using LM, SEM and TEM. Pollen morphology of Astragalus tends to be rather uniform. The majority of species have tricolporate grains of medium size, with a micro reticulate exine. Evolutionary trends within the genus have been observed. One trend is from subprolate to prolate and another shows increase in pollen size. The present results show also a correlation between pollen morphology and habitat. Xerophytic species usually have a thick tectum with narrow lumina. In addition to this, the pores are covered by thick apertural membranes in the form of bridges or plugs. On the other hand, mesophytic species have a thinner tectum and thin pore membranes. By plotting P/E again P, four pollen types can be distinguished. These types can be related to established taxonomic groupings.