Gravity affects the ecology and evolution of every living organism. In plants, the general response to gravity is well known: their roots respond positively, growing down, into the soil, and their stems respond negatively, growing upward, to reach the sunlight. But how do plants sense gravity and how do they direct or signal their cells to grow in response to it? Although botanists understand a great deal about how this works, a recent article in the recent issue of the American Journal of Botany reviews what we know so far, from mechanical to genetic approaches; it reveals that there are still substantial gaps in our knowledge of the molecular details and highlights new ideas for potential regulating mechanisms.
One of the most constant environmental stimuli that a plant encounters is gravity. Elison Blancaflor, author of the article and a Professor in the Plant Biology Division at the Samuel Roberts Noble Foundation, Oklahoma, is particularly interested in the effects that gravity has on plant development, and especially in its pivotal role in the evolution of a plant's sensory and signaling system.
"Although the process of gravitropismdefined as the downward growth of the plant root so it can explore the soil better for nutrients and water and the upward growth of the plant shoots to maximize light absorptionappears to be a simple plant response that we observe here on earth, the biological processes that control it are rather complex," notes Blancaflor.
Indeed, Blancaflor explains in his review article that gravitropism requires the coordinated activity of different cell and tissue types. In plants, the area where gravity is sensed is often spatially distinct from the area of growth. So how do these two discrete areas communicate with each other and direct the plant to where it should grow?
To date, gravity sensing i
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American Journal of Botany