Tu, Yicheng, M.S., Purdue University, December, 2000. Endogenous Gibberellins in Developing Apple Seeds in Relation to Biennial Bearing. Major Professor: Peter M. Hirst. It is believed that Gibberellins (GA) produced in apple seeds act as an inhibitory signal to flower induction in the neighboring buds. As an exception, GA4 is not inhibitory and sometimes found to be promotive to apple flowerin...