Circumnutation and gravitropism cause root waving in Arabidopsis thaliana

Arabidopsis thaliana roots grow in a wavy pattern on inclinedagar plates. This waving behaviour has been interpreted as representinga gravitropism-dependent thigmotropic response. We argue insteadthat this root waving represents primarily a flattened spiralgrowth pattern resulting from circumnutation and gravitropism. Key words: Arabidopsis, circumnutation, gravitropism, roots, thigmotropism