Seed germination of Lilium x Formolongi as influenced by temperature and plant growth regulators

Seed germination of L x formolongi Thunb., 'Snow Line' as influenced by presowing treatment at 5 degrees C or with plant growth regulators and constant and alternating germination temperatures was investigated to obtain uniform seedlings. Seed germination was promoted at constant 17 degrees C (test 1) or 14 degrees C (test 2) and inhibited at constant 26 degrees C (test 1) or to 29 degrees C (test 2). Pre-treatment at 5 degrees C did not overcome inhibition of seed germination induced by high temperatures. When seeds were exposed to alternating temperatures (29 degrees C for 1 week followed by 14 degrees C), germination percentage and the number of uniform seedlings was increased (Test 4). However, this response was not observed when seeds were exposed to 26 degrees C and then germinated at 17 degrees C (Test 3). Treatments with plant growth regulators did not affect germination either at 14 degrees C or 29 degrees C. To obtain uniform seedling populations, seeds should be germinated seeds at 14 degrees C with pre-treatment at 29 degrees C for 1 week. The ineffectiveness of a pre-treatment at 5 degrees C on germination and inhibition of germination at >20 degrees C suggests that L. x formolongi seeds exhibit imposed secondary dormancy by high temperatures during germination.