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EFFECTS OF SEED DISPERSAL UNIT AND THE POSITION OF SEED RELATIVE TO SUBSTRATE ON GERMINATION OF THREE COMPOSITES

ABDUL WAJID AND S. SHAHID SHAUKAT

Abstract: Diaspore morphology has long been assigned a role for dispersal byvarious mechanisms. An experiment was designed to investigate the effect of dispersal unit and the position of seed relative to substrate on germination of three composites (Iphonia grantioides, Tridax procumbens and Sonchus arvensis). Seed morphology of the three species was studied and pappus appeared to influence the overall germination percentage. Diaspore having attached pappus and lying horizontally on the surface of the soil showed maximum germination compared to other positions. Diaspore having detached pappus and lying horizontally on the soil surface showed lower germination percentage than the seed with attached pappus. The angle of contact with soil is also important besides pappus which presumably regulates water absorption by seed and consequently the rate and overall germinat}on percentage.

Department of Botany, University of Karachi, Karachi-75270, Pakistan.