Spiralizations and tropisms in Arabidopsis roots.
When Arabidopsis seedlings are grown on a hard-agar plate, their primary roots show characteristic spiralling movements, apparent as waves, coils and torsions, together with a slanting toward the right-hand side. All these movements are believed to be the result of three different processes acting on the roots: circumnutation, positive gravitropism and negative thigmotropism. The basic movement of the roots is described as that of a growing right-handed helix, which, because of the root tip hitting the agar plate, is continuously switched from the right-hand to the left-hand of the growth direction, and vice versa. This movement also produces a slanting root-growth direction toward the right-hand because of the incomplete waves made by the right-handed root to the left-hand. By contrast, the torsions seen in the coils and waves are interpreted as artefacts that form as an adaptation of the three-dimensional root helix to the flat two-dimensional agar surface.
Migliaccio
F
F
Institute of Plant Biochemistry and Ecophysiology, Consiglio Nazionale delle Ricerche, Via Salaria Km 29.300, 00016 Monterotondo, Rome, Italy. fernando.migliaccio@mlib.cnr.it
Piconese
S
S
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development*; D009068:Movement / Q000502:physiology*; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development*; D018523:Tropism / Q000502:physiology*