Some strategies for improvement of seed germination of smoke-tree (Cotinus coggygria Scop.); an endemic species of the Arasbaran Forests

Smoke-tree(Cotinus coggygria Scop.)is one of the endemic valuable shrub species of Iran which has only distributed in the Arasbaran Forests. Natural regeneration of this specie is mostly asexual with the shape of root-sucker, and its sexual reproduction is rarely possible. Considering the importance of this specie as well as difficult germination of the seeds naturally, an effort was made through the present study, for the first time in Iran, to examine the effects of several treatments on the improvement of seed germination of this specie, and to introduce the best treatment. In order to break the physical and physiological dormancies, the seeds were soaked in 98% concentration sulphuric acid for 5 and 50 minutes and cold stratified at 4°^c for 30 and 60 days. In addition, both of the mentioned treatments, soaking in 98% concentration sulphuric acid for 5, 20 and 50 minutes with cold stratified at 4°C for 60 days, were simultaneously utilized to break both physical and physiological dormancies. The experimental design was completely randomized design (CRD) with three replications in which 30 seeds were planted per replicate. The results of analysis of variance showed that the selected treatments had significant effects (p < 0.01) on all the traits including germination rate, germination speed, and seed vigor index. Furthermore, comparison of the means resulted by the Duncan tests revealed that the best results were obtained by simultaneously application of both the treatments of soaking in 98% concentration sulphuric acid for 20 minutes and cold stratification at 4°C for 60 days. Totally, the results of this study demonstrated the positive effects of the selected treatments on breaking the seed dormancies of this shrub, and the results may be considered in reforestation programs.