THE ROLE OF ENDOGENOUS AUXIN IN ROOT INITIATION .2. SENSITIVITY, AND EVIDENCE FROM STUDIES ON TRANSGENIC PLANT-TISSUES

This paper is the second part of a review which considers evidence for the involvement of auxin in root initiation. Part II examines the res earch being carried out with transformed plant tissues. Agrobacterium rhizogenes causes abundant root initiation at the site of inoculation. Ri plasmid T-DNA contains several genes which encode enzymes involved in the biosynthesis and metabolism of indole-3-acetic acid. Transfer of various fragments of the Ri plasmid has also been reported to confe r increased sensitivity to auxin upon plant cells. Controlled expressi on of these genes in the plant genome potentially offer an insight for developmental plant physiologists into the role of plant growth subst ances in the process of root initiation. The importance of absolute le vels of IAA in the stimulation of root initiation is discussed.