The effect of different seed dormancy breaking treatments on germination and primary functions of of Betula pendula

Birch regeneration in natural habitats of species in Iran has been faced with severe problems and they are disappearing. This study was carried out in laboratory aiming to determine the best treatment to break surface dormancy in germination and primary function of Betula pendula seeds. Seeds were collected from Siahmarzkooh habitat (Golestan province) and treated with seed soaking for 24 hours in water, hormone gibberlic acid (50, 100, 150 ppm), potassium nitrate (0.1, 0.2, 0.25 %), stratification for 3, 6 and 9 weeks at 3 to 5°c in sterile sand and a control group (only light). Then the germination characteristics (germination rate, germination value, mean daily germination, germination energy, germination speed) and seedling growth characteristics (root length, shoot length, seedling length and weight of biomass) were obtained. Results showed that at the level of 99%, there were significant differences between treatments. It appears that the birch seeds just need the sun light to relieve seed dormancy and germination but to achieve higher germination and better growth characteristics, treating 50 ppm gibberellic acid may helpful because the best germination rate (71%), energy (22), speed (5.15) and the highest seedling growth characteristics including shoot length (4.39), root length (4.63), weight of biomass (0.18), seedling length (8.85) was achieved in this treatment after three months.