Gibberellin induces shoot growth and flowering in nonprecooled derooted bulbs of tulip (Tulipa gesneriana L.)

Abstract

Effect of gibberellic acid (GA3) at a concentration of 200 mgl1 on shoot growth and flowering in nonprecooled derooted tulip bulbs cvs. Gudoshnik and Apeldoorn was investigated. In control nonprecooled derooted bulbs flower bud blasting occurred and no growth of stem was observed. GA3 greatly induced shoot growth and flowering. The stimulatory effect of gibberellin on shoot growth and flowering in nonprecooled derooted bulbs was much stronger than in case of nonprecooled rooted bulbs (previously published results). GA3 stimulated also stem growth after excision of flower bud with upper part of leaves and scales. It is probable that excision of all roots in nonprecooled bulbs decreases the level of abscisic acid and exogenous gibberellic acid is more effective in comparison to nonprecooled rooted bulbs. Or it is also possible that better penetration and uptake of gibberellin take place after removal of roots. It seems that gibberellin can substitute for cold requirement and that interaction of exogenous gibberellin with endogenous auxin controls stem growth.