SELL OF PROPERTY WITHOUT CO APPLICANT

Presumably you are referring the terminology for "co-owner" and erronously mentioned in your post as "co-applicant",  is it so ?

If so, she may authorise, grant and appoint you as her attorney by executing a Power of Attorney.   

You have not posted the complete facts. How is that the mother is the joint holder of the property.

Yes, what Mr Basis the says is correct. By virtue of being attorney holder, you can transfer your mother's share too. Even you can transfer your share in the property subject  local amendment of Indian Registration Act does not stipulate any precondition for  its registration. Or else, you can transfer what ever right you have in the property. If property has not been divided by  metes and bound, the purchaser may do it later with your mother.