This is a project to use green plants as inexpensive detectors for explosives. The plants will sense explosives using computer designed receptors and transmit this information to the nucleus via a synthetic signal transduction system. The trigger genetic circuitry will be constructed by producing a feedback system of repressors that are quantitatively analyzed. Specifically, because naturally occurring components have widely varying kinetic characteristics, mathematical modeling of genetic circuits, will be employed to produce a functional trigger circuit in plants.