In Arabidopsis thaliana, the cytokinin signal is perceived by

three sensor histidine kinases, AHK2, AHK3, and CRE1/AHK4. AHK2,3,4 

function in shoot growth, leaf senescence, leaf longevity, seed

size, germination, and root development. AHK3  controls cytokinin-mediated leaf longevity through a specific phosphorylation of the response regulator, ARR2.

Hi Naveed,

Studies have showed that AHKs have functions on abiotic stress. A paper (see link below) demonstrates the results from authors using ahk mutants as materials for the study.

Part of paper abstract:

"Overall, our examination of ahk mutants found specific phenotypes associated with AHK2 and AHK3 as well as a general function of cytokinin signaling in proline accumulation and low water potential induction of P5CS1 and NCED3 expression. These results show the stress physiology function of AHKs at a new level of detail."

http://onlinelibrary.wiley.com/doi/10.1111/ppl.12290/abstract;jsessionid=96F4303F629CE219386CBA39CA20B484.f01t01?systemMessage=Subscribe+and+renew+is+currently+unavailable+online.+Please+contact+customer+care+to+place+an+order%3A++http%3A%2F%2Folabout.wiley.com%2FWileyCDA%2FSection%2Fid-397203.html++.Apologies+for+the+inconvenience.

Thanks for guiding me  Yuan-Yeu Yau and K.Suresh Naidu