Recently, it was reported the gene expression pattern observed as a spatio-tempral pattern using bioluminescence technology for a clock gene. The travelling wave patterns, including spiral wave, were observed. In this study, a dynamics of observed phenomena as a spatio-tempral pattern in the experiment were investigated numerically. As a model, a reaction-diffusion equation was used. These results suggest that the reaction-diffusion system may be useful for studying the self-organization phenomenon of plants.

A method for early diagnosis of plant productivity using a luciferase bioluminescence assay at the early stage of cultivation was developed for transgenic Arabidopsis thaliana carrying the CCA1::LUC construct, in which the promoter of the CCA1 clock gene had been fused to a modified firefly luciferase (LUC) gene. Because the intensity of luciferase bioluminescence is proportional to the CCA1 promoter activity and the expression level of LUC, the dynamics of both can be investigated by measuring the bioluminescence. In this paper, plant biomass was considered a measure of plant production and LUC protein a measure of foreign protein production. The leaf area and bioluminescence of seedlings at the early stage of cultivation were investigated as indexes for early diagnosis of productivity leaf area was a reflection of morphological information, and bioluminescence, molecular information. Bioluminescence showed higher correlation to productivity based on biomass and LUC protein than the leaf area under various growth conditions, indicating that bioluminescence is a better index for early diagnosis. In addition, we developed a general statistical method for selecting superior seedlings based on this early diagnosis and a general theory for determining an optimal parameter set for maximizing profit. This early diagnostic methodology appears suited to enhance the quality of the products in plant factories.

Departmental Bulletin Paper

The photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated at an asymmetrically illuminated gap, which was drawn using computer software and then projected on a filter paper soaked with BZ solution using a liquid-crystal projector. The probability of the chemical wave passing through the gap with asymmetric illumination was different from that through its mirror image. The location at which the wave disappeared and the time delay of the chemical wave passing through the gap changed depending on the velocity of chemical wave propagation. The experimental results were qualitatively reproduced by a theoretical calculation based on the three-variable Oregonator model that included photosensitivity. These results suggest that the photosensitive BZ reaction may be useful for studying spatiotemporal development that depends on the geometry of excitable fields.

(2009)

(2009)

We report the vectorial transport of a material object to a desired location by chemical waves generated in an excitable medium (Belousov-Zhabotinsky reaction). The transportation route is determined by the excitable waves induced at a certain point on the excitable medium. This study realized direct coupling between a chemical reaction and vectorial motion; such transduction of energy is generally found in biological motility but has been difficult to achieve in artificial model systems. We discuss the future possible application of these findings to the fabrication of a chemical machine that works under the self-management of motion in response to external stimuli.

The photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated on a circular ring, which was drawn using computer software and then projected on a film soaked with BZ solution using a liquid-crystal projector. Under the initial conditions, a chemical wave propagated with a constant velocity on the black ring under a bright background. When the background was rapidly changed to dark, coexistence of the oscillation on part of the ring and propagation of the chemical wave on the other part was observed. These experimental results are discussed in relation to the nature of the photosensitive BZ reaction and theoretically reproduced based on a reaction-diffusion system using the modified Oregonator model.

Both the direction and distance of the wave source of an excitable wave were detected on excitable media in both an experiment and a numerical simulation. By detecting the time-difference between two inputs, we were able to calculate the trajectory of wave propagation. The position of the wave source was then evaluated by considering two different trajectories that depended on a time-difference.

The propagation of chemical waves in the photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated using an excitable field in the shape of a circular ring or figure "8" that was drawn by computer software and then projected on a film soaked with BZ solution using a liquid-crystal projector. For a chemical wave in a circular reaction field, the shape of the chemical wave was investigated depending on the ratio of the inner and outer radii. When two chemical waves were generated on a field shaped like a figure "8" (one chemical wave in each circle) as the initial condition, the location of the collision of the waves either was constant or alternated depending on the degree of overlap of the two circular rings. These experimental results were analyzed on the basis of a geometrical discussion and theoretically reproduced on the basis of a reaction-diffusion system using a modified Oregonator model. These results suggest that the photosensitive BZ reaction may be useful for creating spatio-temporal patterns depending on the geometric arrangement of excitable fields.

Living organisms process information without any central control unit and without any ruling clock. We have been studying a novel computational strategy that uses a geometrically arranged excitable field, i.e., "field computation." As an extension of this research, in the present article we report the construction of a "direction detector" on an excitable field. Using a numerical simulation, we show that the direction of a input source signal can be detected by applying the characteristic as a "coincidence detector" embedded on an excitable field. In addition, we show that this direction detection actually works in an experiment using an excitable chemical system. These results are discussed in relation to the future development of "field computation."

Living organisms process information without any central control unit and without any ruling clock. We have been studying a novel computational strategy that uses a geometrically arranged excitable field, i.e., “field computation.” As an extension of this research, in the present article we report the construction of a “direction detector” on an excitable field. Using a numerical simulation, we show that the direction of a input source signal can be detected by applying the characteristic as a “coincidence detector” embedded on an excitable field. In addition, we show that this direction detection actually works in an experiment using an excitable chemical system. These results are discussed in relation to the future development of “field computation.”. © 2004 The American Physical Society.