hypothesis why parts of a plant such as the leaves are green but other parts such as the roots are not

Because roots get more water then the stem does, it absorbs at least 60% of the water, and if you use a nail that goes into water, it rusts, so that means that it's darker than others.

Explanation:

If you take a nail and place it under water, that means its getting 100% of the water, so it's the same thing with plants. Another reason that this is happening is that its a sign that a plant is unhealthy. So make sure to give it a lot of water( but not too much or it will drown) so it stays a healthy and happy plant. Hope this helps :3

there's the proffessional site that will you.

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.