Dear Angelina,

I do not have experience on this type of molecular work, but from a biochemical and metabolic standpoint the use of BAP should be preferable. Trans-zeatin undergoes catabolization and conjugation (to yield a cytokinin nucleotide or N- or O-glycosylated products), along with the other metabolic transformations and transport. BAP should be much less prone to metabolic reactions, therefore it should be more effective and the effects of your treatments should be more reliable and repeatable.

All the best,

Carlo