While experimentation , why do you think it is difficultto assign any affect seen to any single hormone?

Explanation

Phytohormones are synthesised by plant cells itself and individually . These are auxin GA, ABA ethylene and cytokinin. There is not a separate system of their tansloctin in plants . So their effects on plnats are also inter mixed e.g many effects of suxins Ga shown the same function. similarly ethylene and ABA support each other for many roles i plants secondaly effects of phytohormone in virtro and in vivo will also be different .