How Do Plants Know Which Way Is Up And Which Way Is Down?:
Think of a seed buried in a pot (…) It’s dark down there in the potting soil. There’s no light, no sunshine. So how does it know which way is up and which way is down? It does know. Seeds routinely send shoots up toward the sky, and roots the other way. Darkness doesn’t confuse them. Somehow, they get it right…
As the resident expert on gravitropism, I had several friends send me this link, excited that they “knew all about this”. Krulwich takes this example from David Chamovitz’s new book, What a Plant Knows. He goes on to explain in words and drawings the concept of the starch-statolith theory of gravity sensing in plants. It’s an old concept that continues bearing fruitful research, as demonstrated by our recent work studying gravitropism in a starchless mutant.
Gravitropic 