Can you tell us what kind of plant it is? The picture isn't quite sharp enough, if you can try to re-take with a piece of white paper behind it the camera may focus more on the leaf. From the current image my suggestion would be to look at pictures of "edema" on Google, you may need to add the word leaf or leaves to the search box so that you don't get medical pictures. Here's one result of such a search:
http://www.ipm.iastate.edu/ipm...
