I have an article directory..........if I get back links for only home page then would it help in optimizing inner pages also?
There isn't much difference between optimisting for inner pages of a site and the homeapage, you still need to get the meta tags right, get quality links pointing to the inner page ... the short answer to your question is that yes, if the article you got a link from is of good quality, the link will boost the inner page you point the link from the article to.
Well if you want to pinpoint an individual keyword to an individual page of your directory then yes you can use the inner links. But judging you have an article directory there would probably be many. So pointing links to the homepage is still as good.
I agree 100% above -((((( individual keyword to an individual page____))))) that's way optimize out of play ----- all your sub pages must have a separate title tag description and keyword listing that sells described a webpage titled --------- If you want Google to send their spiders to crawl your sub pages a must add the domain name at the end of your title tag --------------- that would be a smart idea in my opinion ------ and that is where you can use the inner links........ to help boost your search engine ranking for that article directory .....