حمیرا سلیمی - Weed Research Dept., Plant Pests & Diseases Research Institute, P. O. Box ۱۴۵۴, Tehran ۱۹۳۹۵, Iran
فریدون ترمه - Dept. of Botany, Plant Pests & Diseases Research Institute, P. O. Box ۱۴۵۴, Tehran ۱۹۳۹۵, Iran

       Seed dormancy has an important role in resistance and survival mechanisms of plants. Finding of some information about the range of primary dormancy and effective factors in dormancy breaking and optimal conditions of seed germination are necessary for weed control and other research purposes.  In this research, the seeds of ۱۰ species of grass weeds in Tehran province fields (Echinocloa crus-galli, Bromus tectorum, B. dantoniae, Hordeum glaucum, Setaria viridis, S. glauca, S. verticillata, Elymus repens, Phalaris minor and Sorghum halepense) have been studied. The results showed that seeds of all the species had high viability. The effects of some chemical, mechanical and temporal factors on seed dormancy breaking have been studied. Light had an inhibitory effect only in seed germination of Bromus spp. and H. glaucum and promoted germination in other species. Main factor of dormancy in all the species was in seed coat and pericarp. Of course there was a little of dormancy in embryo in some of them but  B. dantoniae, S. halepense, E. repens  and  S. viridis specially had deep dormancy in embryo. Two different collected  types of Ph. minor, had different primary dormancy in their seeds. 

seed, dormancy, germination, Gramineae