Towards nutrients, including water. They are actually darn good at finding water. They will break through metal pipes just to get to water.
I would say you don't need to look it up, as it is fairly obvious. You understand it completely.
The problem I had with your response earlier is that you don't see turning towards the Sun the same as growing towards the Sun.
What causes a seed to actually sprout?
(Hint: again, it's not gravity)