Abstract

Much of the data to support the involvement of endogenous IAA in root initiation is circumstantial. Measurement of the levels of endogenous IAA in the rooting zone of propagules and micropropagules should provide further evidence towards the role of IAA in adventitious root initiation. The aim of this ongoing study is to analyse the levels of endogenous IAA cuttings of differing rooting abilities from seedlings, and form in vitro shoot cultures of Eucalyptus globulus. GC-MS analysis using a stable isotope of IAA (13C IAA) as an internal standard has been employed to measure endogenous IAA. In 14 day old hypocotyl cuttings for example, the first cell divisions take place within 35 hours, well developed root primordia are visible within 60 hours and roots emerge after 100 hours. Elevated levels of IAA occur in the rooting zone over the first 25 hours following cutting excision, but decline before the first cell divisions take place. No such rise was detected in parts of the