System analysis of Phycomyces light-growth response with gaussian white-noise test stimuli

R. C. Poe, E. D. Lipson

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The light-growth response of the Phycomyces sporangiophore is a transient change of elongation rate in response to changes in ambient blue-light intensity. The white-noise method of nonlinear system identification (Wiener-Lee-Schetzen theory) has been applied to this response, and the results have been interpreted by system analysis methods in the frequency domain. Experiments were performed on the Phycomyces tracking machine. Gaussian white-noise stimulus patterns were applied to the logarithm of the light intensity. The log-mean intensity of the broadband blue illumination was 0.1 W m-2 and the standard deviation of the Gaussian white-noise was 0.58 decades. The results, in the form of temporal functions called Wiener kernels, represent the input-output relation of the light-growth response system. The transfer function, which was obtained as the Fourier transform of the first-order kernel, was analyzed in the frequency domain in terms of a dynamic model that consisted of a first-order high-pass filter, two secondorder low-pass filters, a delay element, and a gain factor. Parameters in the model (cutoff frequencies, damping coefficients, latency, and gain constant) were evaluated by nonlinear least-squares methods applied to the complex-valued transfer function. Analysis of the second-order kernel in the frequency domain suggests that the residual nonlinearity of the system lies close to the input.

Original languageEnglish (US)
Pages (from-to)91-98
Number of pages8
JournalBiological Cybernetics
Volume55
Issue number2-3
DOIs
StatePublished - Nov 1986

Fingerprint

Phycomyces
White noise
Systems Analysis
Systems analysis
Light
Growth
Transfer functions
High pass filters
Low pass filters
Cutoff frequency
Fourier Analysis
Least-Squares Analysis
Lighting
Nonlinear systems
Elongation
Dynamic models
Identification (control systems)
Fourier transforms
Damping
Experiments

ASJC Scopus subject areas

  • Biophysics

Cite this

System analysis of Phycomyces light-growth response with gaussian white-noise test stimuli. / Poe, R. C.; Lipson, E. D.

In: Biological Cybernetics, Vol. 55, No. 2-3, 11.1986, p. 91-98.

Research output: Contribution to journalArticle

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