ABSTRACT
Morphology of pollen grains of each species is based on specimens selected at random. Proposed characters i.e. grain, shape of pollen grain, equatorial view, polar view, equatorial diameter [E], polar diameter [P], P/E ratio, length of colpus, exine surface, exine thickness, number of spines between colpi in each species were recorded for comparison. At species level, micro-morphological differences and distribution of surface pattern, shape and size of pollen have been found to exist. The pollen grains are consistently echinate, trizonocolporate. This study demonstrates the potential of pollen studies in distinguishing some taxonomic groups in the Asteraceae. The present research project is confined to the palynological studies of some of the problematical medicinal plants of Pakistan. Sixteen different genera: acacia, Agrimonia, Allium, Anthemis, Asparagus, Berberis, Centella, Colchicum, Cotula, Delphinium, Gentiana, Lactuca, Matricaria, Nigella, Phyllenthus, Viola have been examined in this study. Matricaria chamomilla, Anthemis nobilis, and Cotula aurea have been differentiated with the help of palynology. The palynological studies of Lactuca dissecta [with white flowers] and Lactuca dissecta [with purple flowers] showed many characteristic differences