Seed germination response to temperature and salinity stress in Lilium longiflorum and L. formosanum

Seed germination response to different degree of thermal and salinity treatments for two closely related, but ecologically distinct bulbous species, Lilium longiflorum and L. formosanum was investigated, in order to clarify optimum temperature for seed germination and whether the tolerance to salinity stress is different between the species. Among seven constant thermal treatments for seeds collected from two natural populations of L. longiflorum and one of L. formosanum, treatments of 25 and 30°C significantly reduced the final germination percentage approximately less than 80 and 10%, respectively, of the treatments below 20°C. Treatment exposed to 17.5 or 20°C allowed the maximum germination rate and percentage, irrespective of the seed source populations. By exposure to 1 and 2% NaCl at 17.5°C, 97 and 93% of the seeds, respectively, were germinated in L. formosanum. The values were comparable to or greater than the highest values obtained from L. longiflorum. Both the species could little germinate in 3% NaCl treatment. The results indicate that L. formosanum is not physiologically distinct from L. longiflorum in terms of salinity tolerance. It is concluded that salinity stress, which is one of the major abiotic environmental stresses specific to habitats of L. longiflorum, cannot work as a factor of habitat isolation between the two species.