The effect of various scarification methods, He-Ne laser and sodium nitroprusside on seed dormancy breaking and the growth of myrtle (Myrtus commnius L.) seedlings

Myrtus communis is a medicinal plant that its seeds have primary dormancy. Therefore, in current study, firstly effect of various types of scarification (treatment with H2SO4 70 or 90% or sand paper for 5 and 10 min, blade and soaking in hot water for 10, 20 min) were evaluated on seed dormancy breaking. Results showed that without scarification, seed germination was very low, whereas various types of scarification significantly increased final seed germination. Among various levels of treatments, the highest seed germinatin obtained by soaking in hot water for 20 min (33%), treatment with  H2SO4  90% for 5 min (59%), sand paper for 10 min (63%) and blade (65%). The next experiment showed that myrtle seeds were photoblastic and He-Ne laser more than white or red light increased germination of scarified seeds by above methods. He-Ne laser irradiation reached seed germination of scarified seeds by sand paper and blade to 80%. Results of the last experiment also showed that application of concentrations of 0.5% KNO3 and 100 µM sodium nitroprusside (SNP as a NO donor) also increased seed germination, seedling length and vigor of seedlings grown from all scarified seeds and seed germination of scarified seeds by sand paper and blade achieved to 80%. These results showed that myrtle seeds have combination of physical and physiological dormancy that can be attenuated with scarification by sand paper and treatment with SNP or He-Ne laser irradiation.