Stem elongation and flowering response of Tulipa cultivars as influenced by bulb cooling. Growth regulators and light quality

Stem elongation and flowering response of Tulipa cultivars as influenced by cold treatment duration, plant growth regulator application, and light quality during tulip forcing, were studied. The flowering percentage of 'Apeldoorn' and 'Golden Apeldoorn' was more than 90%, regardless of low temperature and GA(3) treatments. Flowering in both cultivars was accelerated by gibberellins (GA(3) and GA(4+7)) Or Promalin injected into bulb-scale tissue and the flower bud after bulbs had been stored at 5 degrees C for 6-12 weeks. Total stem length was shorter after injection of bulbs and flower buds with GA than in control plants. For 'Apeldoorn', flower stem length was slightly reduced when GA(3), GA(4+7) or Promalin were injected into bulb-scale tissue. Blue and far-red light, as well as darkness increased the length of the 1(st) and 2(nd) internode in 'Apeldoorn' tulips when compared with control plants or other light treatments. Growth of the last internode was stimulated by darkness and by red and blue light treatments.