The Effect of Salinity on Seed Germination and Seedling Growth of Four Medicinal Plant Species

To study the effect of salinity stress on seed germination and seedling growth of four medicinal plants, Nigella sativa L., Cannabis sativa L., Trigonella foenum graecum and Cynara scolymus L. an experiment was conducted in the botany laboratory of Islamic Azad University, Birjand branch. A completely randomized design (CRD) with 3 replications was used as separately for each species. Treatments were consisted of six salinity (NaCl) concentrations (0, 4, 8, 12, 16 and 20 dS m-1). The measured traits were root, shoot and seedling length, dry and fresh weight of seedling, germination rate and percent, seed vigor index, seedling water content and root/ shoot ratio. Salinity stress reduced significantly shoot, root and seedling length of the species. Increasing of salinity stress declined dry and fresh weight of Trigonella foenum and Nigella sativa L. and dry weight of Cannabis sativa L.. Seedling water content and root/ shoot ratio of Nigella sativa L. increased in salinity treatments. Increasing of salinity stress declined germination rate and percent in Nigella sativa L., but in other species (Cannabis sativa L., Trigonella foenum graecum and Cynara scolymus) only germination rate decreased. Trigonella foenum graecum germinated completely (%100) in all salinity treatments. Increasing of salinity until 16 dS m-1 reduced seed germination of Nigella sativa. Seed germination of Nigella sativa did not occurred in the highest salinity stress (20 dS m-1). Totally the results showed that in the germination stage, Trigonella foenum graecum and Cannabis sativa were relatively tolerate to salinity stress but Nigella sativa L. was the most sensitive on