THE CYTOPLASMIC STREAMING RESPONSE OF TOMATO ROOT HAIRS TO AUXIN - OBSERVATIONS OF CYTOSOLIC CALCIUM LEVELS

Cytoplasmic streaming velocity in tomato root hairs was strongly influ enced 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 1-2 min. The transplasmamem brane electrical potential difference was rapidly depolarised by IAA. Measurements of cytoplasmic calcium concentrations, using the fluoresc ent dyes fura-2 and indo-1, indicated that in some, but by no means al l, cells auxin application was followed by a small slow increase in [C a2+](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.