the application to roots during  2 h found the effect, but it is not very long.

It need regularly applicate ABA for effect on leaves.

See the expriment of Darwin, 

good day

You should apply ABA to roots in hydroponics. The effect on the plant depends on the manifestation (growth? leaf discoloration?). The quickest response within one hour or less is on stomatal closure. ABA concentration matters. Try several: 10-3, 10-4 and 10-5M.

thank you @Marpha and @Abraham for suggestions. i want to apply 100uM ABA to plant roots in hoagland solution and check some ion movement to roots. so in this case what will be your suggestions about ''after application how much time should i wait to check Ion movement?''  

Dear Haider,

I strongly agree with Mr. Blum recommendations. In any case, have you thought about doing several timepoints? 

Here I also attach a link to a paper that might help you:

http://www.sciencedirect.com/science/article/pii/S0176161710004852