After learning plant basics you are ready to advance to more complex plant systems. You'll find there's still plenty of great material online.
First, check out Exploratium's site for these very cool activities:
The neoK12 site has about 20 different short videos on everything from photosynthesis to reproduction. For some reason we can't link to each video separately, but look for the following ones in the plant video menu. (they're really good).
world's strangest plants
plant growth time lapse
root growth time lapse