Subject: Why do roots grow down no matter what position the seed is in?

 My 1st grade class was studying seeds and found that no matter which 
way we placed a seed the root always grew down. Since we used seeds 
in a clear glass with a wet paper towel, we decided that it had 
nothing to do with avoiding sunlight. We hypothized that it had to do 
with seeking more moisture. Or perhaps, affects of gravity.

Re: Why do roots grow down no matter what position the seed is in?