Understanding phototropism: from Darwin to today.

Few individuals have had the lasting impact on such a breadth of science as Charles Darwin. While his writings about time aboard the HMS Beagle, his study of the Galapagos islands (geology, fauna, and flora), and his theories on evolution are well known, less appreciated are his studies on plant growth responses to a variety of environmental stimuli. In fact, Darwin, together with the help of his botanist son Francis, left us an entire book, 'The power of movements in plants', describing his many, varied, and insightful observations on this topic. Darwin's findings have provided an impetus for an entire field of study, the study of plant tropic responses, or differential growth (curvature) of plant organs in response to directional stimuli. One tropic response that has received a great deal of attention is the phototropic response, or curvature response to directional light. This review summarizes many of the most significant advancements that have been made in our understanding of this response and place these recent findings in the context of Darwin's initial observations.