effects of various chemical and non-chemical treatments to break seed dormancy in silybum marianum l. gaertner

milk thistle (silybum marianum l. gaertner) is an annual or biannual plant of the asteraceae family. this species is important not only as a medicinal plant traditionally, but also as an endemic plant to protect vegetative and natural resources in iran. this experiment was carried out to find the most effective treatments to break milk thistle seed dormancy and improve its cultivation in vast scales and/or restoration of its natural habitats. experimental factors were: potassium nitrate (0.2%), hot water (70 and 90 °c for 15 min), tap water (for 24 and 48 h), pre-moist chilling (at 4°c for 5, 10 and 15 days) and sulphuric acid (75%  for 5 and 15 min). the results showed that the maximum percent germination (58%) can be obtained by applying potassium nitrate for 24 h. although, tap, hot water and pre-moist chilling treatments significantly increased the seed germination but had still lower effects in comparison to potassium nitrate to break seed dormancy (38, 30 and 27%, respectively) in milk thistle. sulphuric acid could not break seed dormancy in this plant.