Abstract: We studied the effect of auxin derived from inflorescence on garlic bolt elongation in Allium sativum L. The decapitation (removing inflorescence) induced the decrease of garlic bolt elongation, indicating that garlic bolt elongation was controlled by the inflorescence. After decap itation, application of exogenous either IAA or GA₃ at the excised site increased garlic bolt elongation rate significantly. Again, both exogenous IAA and GA₃ promoted elongation of excised garlic bolt segments. IAA showed a stronger p romotion effect than GA₃ in these processes. Application of 2, 3, 5-triiodobenzoic acid ( TIBA) , a polar auxin transport inhibitor, at the base of inflorescence decreased garlic bolt elongation rate. TIBA also inhibited elongation of excised
garlic bolt segments. Assay of plant hormones revealed that decapitation reduced both endogenous IAA and GA_{1+ 3} content in garlic bolt to a level of 14.00% and 13.76% of the undecapitated control, respectively,which indicated that inflorescence should be important to maintain high level of IAA and active GA in garlic bolt. Applied IAA increased GA₁₊₃ content in both decapitated garlic bolt and excised garlic bolt segments dramatically. All together, these data suggest that IAA derived from inflorescence dominate garlic bolt elongation by maintaining content of active GA in garlic bolt.

Key words: Allium sativum L., Indole-3-acetic acid ( IAA), Gibberellin (GA₃), Garlic bolt