| Abstract: | Effects of exogenous growth regulators are related to the histologicalevents in adventitious root initiation in hypocotyls of Pinusradiata D. Don. Indolebutyric acid (IBA) is required both forthe pre-initiative and post-initiative phases in root development.Kinetin has a marked inhibitory effect over the pre-initiativephase, with escape from inhibition following establishment ofmeristemoids. Gibberellic acid (GA3) has three distinct effectsdepending on time of application. While inhibitory during thepre-initiative phase, it strongly enhances rooting if appliedat a time coincident with the first observable stage of rootinitiation. If applied following establishment of meristemoids,GA3 inhibits root formation. |
