EFFECT OF 6-BENZYLAMINOPURINE ON STEM FORMATION AND FLOWER BUD INITIATION IN RUDBECKIA BICOLOR PLANTS OF DIFFERENT AGES UNDER NON-INDUCTIVE CONDITIONS

Rudbeckia rosette long-day plants of different ages (1,5 – 4,5 months) were treated with BA solutions (0,1 – 100 mg/l) every day for some weeks under non-inductive SD conditions. High concentrations of BA (10 – 100 mg/l) induced the formation of dwarf stems and the abundant appearance of stem axillary buds as well as flower bud formation. Most of the adult (4,5 months) plants produced flowers. All young leaves had some morphological abnormalities, being wrinkled and not very green. The cessation of BA application resulted the cessation of flower bud transition to flowers. The BA-sensivity was higher in the more adult plants. However, even in 1,5-month-old plants, BA treatment induced the commencement of stem elongation. The differentiation of stem apices was examined, The possibility of cytokinin participation as a complementary phytohormone in the induction of the transition to flowering is discused.