Contributions to the pollen morphology of genus Astragalus L. (Fabaceae) and its taxonomic implications.

摘要

Pollen morphology of 13 species of genus' Astragalus distributed in Saudi Arabia was studied with light and electron microscopes. Pollen is generally 3-zonocolporate, perprolate, prolate, subprolate or prolate-spheroidal. Polar axis is ranged from 12.80 to 21.73 micro m, while the equatorial axis varies between 24.52 to 37.22 micro m. Pollen is trilobulate or triangular in polar outline, elliptic or compressed ovate in equatorial outline. Sculpturing is micro-reticulate, reticulate or rarely perforate in equatorial view (with irregular muri) and psilate, perforate or seldom scabrate (with irregular or circular perforations) in polar view. Six pollen types were recognized: Astragalus asterias pollen type, A. schimperi pollen type, A. palaestinus pollen type, A. spinosus pollen type, A. corrugatus pollen type and A. sieberi pollen type. Description of each type, a key to investigated species as well as SEM micrographs of pollen types is provided. On the other hand, numerical analysis based on UPGMA clustering, factor analysis and factor loading to pollen data has led to recognize two major clads. The second major clad separated into two branches: the first branch includes two subclads and the second branch comprises three species.