SYSTEM ANALYSIS OF PHYCOMYCES LIGHT-GROWTH RESPONSE.

Two methods of nonlinear system identification have been applied to the transient light-growth response of the fungus Phycomyces. These methods, both in the framework of the Wiener theory, use Gaussian white noise and a sum of sinusoids, respectively, as test stimuli. The resulting Wiener kernels represent the input-output relation of the system. Analyses of a family of single and double mutants that are affected in eight genes associated with the light-growth response and phototropism indicate extensive interactions among the gene products. A dynamic nonlinear model of the light-growth response has been developed for wild type mutants and applied to analyze the mutant responses.