Regulation of Plant Growth and Differentiation by Automatic Program Control of Environmental Factors with the Use of a Computer

The hypocotyl elongation was regulated by the automatic program control of temperature with the use of a computer system.The hypocotyl length was measured in time course under the constant temperatures of 10, 15, 20, 23, 25, 27 and 30°C, respectively, and the hypocotyl elongation curves at respective constant temperatures were formularized. On the basis of the equation of the relations between the temperature and hypocotyl elongation, the temperature required for the desired hypocotyl elongation, was computed by each of the two methods: In the first method, the temperature (Ti) corresponding to an equation curve which satisfies the desired hypocotyl length (yi) at an optional time (xi) was computed from the equations of the relations between time (x) and hypocotyl length (y) at respective constant temperatures (T) . In the second method, the temperature (Ti) corresponding to an equation curve which has the same inclination as that of the desired hypocotyl elongation line at an optional time (xi) was computed from the equations of the relations between time (x) and hypocotyl length (y) at respective constant temperatures (T) . The computed temperature was exchanged into voltage value and led into the temperature controller of the growth cabinet to control the temperature on line in real time. Two of the desired values of the hypocotyl elongation were given as follows; 1) y=7.5.x+10 (0≤x≤4) and 2) y=5.04x+10 (0≤x<2), y=0.71x+18.66 (2≤x≤4) .When the temperature was computed by the second method, the hypocotyl elongation conformed to the desired values. However, when the temperature is computed by the first method, the hypocotyl elongation could not coincide with the desired value. From these results, it could be estimated that the temperature should be computed on the basis of the elongation rate, and further, it is suggested that computation of environmental factors should be made on the basis of the growth rate for the regulation of the plant growth.