Studies directed at understanding those processes by which plants control the level of the phytohormone, indole-3-acetic acid (IAA), are complicated by multiple problems associated with experimental designs using terrestrial plants as study organisms. To avoid many of the difficulties, a system using the aquatic plant Lemna gibba has been developed for the selection of metabolic mutants and their subsequent biochemical evaluation. Studies of IAA metabolism will be continued using these techniques and a previously generated unique germplasm. Specifically, inbred lines of Lemna will be mutagenized to obtain additional mutants. Various screening procudures will be used on the resulting mutant population to obtain lines altered in several different aspects of IAA metabolism. Furthermore, the biochemical and genetic characteristics of mutants already in hand and those recently selected will be defined. Indole-3-acetic acid occurs in minute amounts in higher plants where it is thought to function hormonally to control a variety of events during plant development. By acting through hormone messengers, a plant is able to control its orderly growth and development. It is implicit that if hormones are to regulate plant processes, then the concentration of the bioactive compound must itself be requlated. This research provides an in-depth study of the events that regulate the synthesis and activity of the enzymes or other regulators involved in the metabolism of IAA.
