The Phototropic Responses ofAvenaColeoptiles

Abstract

Macleod, K., Firn, R. D. and Digby, J. 1986. The phototropic responses of Avena coleoptiles.—J. exp. Bot. 37: 542–548. A number of studies of the elongation rate changes causing phototropism have been made but the findings of different groups have not been entirely Consistent. Studies of oat coleoptile phototropism in response to first-positive and second-positive doses indicate that no single pattern of elongation rate changes causes phototropism even in a single species. The relative effect of phototropic stimulation on the elongation rate at the shaded or the illuminated side of coleoptiles subject to unilateral illumination depends on physiological state of the cell-for instance its position in the elongation zone or whether it has been given red light recently. Models of phototropism will have to account for such a diversity of phototropic responses. The importance of making full elongation rate measurements has once again been demonstrated.