Effect of Gibberellic Acid on the Elongation Rate of Agrostis alba Root Hairs

Abstract The influence of gibberellic acid over a wide range of concentrations on the rate of elongation of root hairs of redtop grass was investigated. The rate of root hair elongation was increased by GA over the concentration range of 10−7 to 10−12 M inclusive, with peak stimulation occurring at 10−6 M. Although root hair growth was slightly accelerated by 10−6 M GA, this concentration damaged many root hairs and caused some to stop growing altogether. Rate of root hair elongation was reduced to less than 84% of the control by 10−5 M GA.