Gibberellins (GAs), as one of the most important phytohormones, control different aspect of plant growth and development including seed germination, stem elongation and flower induction. Among more than a hundred and thirty GAs identified from plants, fungi and bacteria only a small number of them, such as GA1, GA3, GA4, GA5, GA6 and GA7, are thought to function as bioactive hormones. Therefore, many non-bioactive GAs exist in plants as precursors or deactivated metabolites.