Additional Evidence for Separable Responses to Auxin in Soybean Hypocotyl

Abstract

Additional evidence for 2 separable responses to auxin is presented. The average of 24 control experiments indicated lag times of 12.4 and 35.4 min, and maximum rates of 0.57 and 0.54 mm .cntdot. h-1, for the 1st and 2nd response, respectively. The auxin analog 4-azido-2-chlorophenoxyacetic acid increased the lag time of the 2nd response (but not the 1st), resulting in the temporal separation of the 2 responses. Plots of elongation rates against time, taken from the literature, allowed the characterization of the 2 responses in monocotyls and dicotyls. Study of published rate-time elongation curves showed that the maximum rate of the 1st response was frequently greater than the maximum rate of the 2nd response; the maximum rate of the 2nd response had not yet been shown to exceed the maximum rate of the 1st response.