http://cuip.uchicago.edu
http://en.wikipedia.org
http://www.foodsubs.com
Leaves: Where food is made by photosynthesis. These contain chlorophyll which converts carbon dioxide and water to simple glucose sugars in the presence of sunlight.
http://mohammedkassem.edublogs.org
Stems: give support to leaves and flowers. They help carry water and food from the leaves
travelling through stems down to the roots.
http://science.howstuffworks.com
Roots: parts of a plant found below the surface of the soil. Water and minerals are being absorb by the roots from the ground in order to prevent erosion of the soil.