The Cytoplasmic Streaming Response of Tomato Root Hairs to Auxin; Observations of Cytosolic Calcium Levels

Abstract

Cytoplasmic streaming velocity in tomato root hairs was strongly influenced by the addition of IAA to the bathing medium. Concentrations of IAA above 10-6 M were inhibitory, while concentrations between 10-7 and 10-8 M stimulated streaming within 1–2min. The transplasmamembrane electrical potential difference was rapidly depolarised by IAA. Measurements of cytoplasmic calcium concentrations, using the fluorescent dyes fura-2 and indo-1, indicated that in some, but by no means all, cells auxin application was followed by a small slow increase in [Ca2+]cyt. We were unable to detect changes in [Ca2+]cyt as rapid as those in cytoplasmic streaming or membrane potential. The experiments reported also illustrate some of the problems of using the dyes fura-2 and indo-1.