PLANTS - How plants sense gravity: New look at the roles of genetics and the cytoskeleton

The general response to gravity in plants is well known: roots respond positively, growing down, into the soil, and stems respond negatively, growing upward, to reach the sunlight. But how do plants sense gravity and direct or signal their cells to grow in response to it? Although botanists understand a great deal, a recent article reveals substantial gaps in our knowledge of the molecular details and highlights new ideas for potential regulating mechanisms.

http://www.sciencedaily.com/releases/2013/02/130204154008.ht