Ethylene is the smallest and lone gaseous plant growth regulator. For evaluating impact of ethylene on whatever plant system you want, you need to design special chambers that will not allow leakage of this gas. Accordingly, use of ethylene would be expensive and moreover, such a experimental setup can induce some or some other kind of stress. Therefore, use of 2-chloroethylphosphonic acid (i.e. ethephon or etherel) is better in all respects. This can penetrate into plant cells easily and under cellular pH, it releases ethylene (accordingly you will see ethylene effect).

How can we prepare the ethephon or etherel solution for treatment ? either to solve that into distilled water or some other buffer solution P. Pardha-Saradhi

Distilled water would be good. Etherel/Ethephon release ethylene generally at pH above 7.0.

Thanks for comment Sir P. Pardha-Saradhi