While experimentation, why do you think it is difficult to assign any effect seen to any single hormone?
Plant hormones mostly work together, complementary to each other. Plant hormones can have both synergistic and antagonistic interactions which affect the plant tissues. A single hormone can have multiple effects, while multiple hormones can target and aim to achieve just one effect. Therefore it can be exceedingly difficult to identify one single hormone according to the particular effect in plant metabolism and system. Moreover, plant hormones function in the presence of a lot of extrinsic factors which are needed for the reaction. Thus, it is difficult to assign any effect seen to any single hormone.