For tutorials & tests on this topic from ‘skoool’ go here and scroll down to 49 onwards.

Click here for Plants for Food (Scientific Eye), a 19m 48s video.

Plants are not just for food though. Here are two fab videos from Twig World:

http://youtu.be/1JbTuGt8o28?list=PL_5OKef10sqdjt8yvtjVeK4xLS7lInZjj

http://youtu.be/OzqqEJBazx4?list=PL_5OKef10sqdjt8yvtjVeK4xLS7lInZjj