Ultrasonic thermometer for Phytotron was designed. Block-diagram of this instrument is shown in Fig.2. Received level and phase changes are shown in Fig. 1. Calibration curve of temperature vs. resonance frequency is shown in Fig.4. Characteristic of this instrument is shown in Figs.5 and 6. Measurements of temperature in Phytotron are shown in Figs.9 and 10.
This work was partially supported by the Grantin-Aid from the Ministry of Education.

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In this paper, the analog simulation of temperature control system of Phytotron is discussed. Phenomena in temperature control system of Phytotron so strongly depend on desired value of temperature and condition of external fresh air that the steady-state and transient characteristic of temperature control can not be made clear from data of several experiments. So, analog simulation is necessary approach to temperature control system of Phytotron.
For this simulation, time constant, time lag, control action, initial condition of control in Phytotron and meteorologic condition of external air should be set from data of experiments.
In this simulation, time constant is set 5-10 min, time lag is set 1-2 min, PI-action is adopted in control action of heater and 3-value on-off control action is adopted in control action of cooler. As a result of the analog simulation, following three points are concluded.
1. Optimal adjustment of control system
This is concerned with desired value of temperature, thermal load, parameter of controlled system (L/T) and parameter of control action. Characteristic of adjustment of control system is shown in Figs. 6-8. For example, stability of control is good for small value of (L/T), (1/20>1/10>1/5) . Stability of P-action is good, but off-set upon P-action is not desirable. I-action is effective to decrease off-set, but stability of I-action is bad. So, optimal adjustment of control action should be decided from graphical inspection under consideration of desired value of temperature, thermal load and parameter of controlled system (L/T) .
2. Relative-humidity characteristic effected by temperature control system
This is important problem in the transient control of temperature. Dynamic-characteristic of relative-humidity in the case of changes in temperature on t-x chart, for example 5°C/step, is indespensable thema to be made clear. Humidifying dynamic-characteristic on the condition of winter and dehumidifying dynamic-characteristic on the condition of summer have been obtained.Especially, humidifying dynamic-characteristic on setting of temperature of spray-water and program control and dehumidifying dynamic-characteristic caused. by on-off action of cooler are obtained only from this simulation on analog-computer. For example, relation between dehumidifying lower limit upon on-off action of cooler in several setting point of program control and amplitude of changes in relative-humidify is shown in Fig.19.
3. Non-linear element
Limit-cycle caused by on-off control is obtained from this simulation.

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To confirm a photorecepter in the embryo having a concern in embryonic diapause induction in next generation. First of all, effects of different wavelength on diapause formation in the silkworm, Bombyx mori, irradiated for 17 hr daily during incubation period of egg at 18-19°C, were examined with those races, J106 × Daizo and (w2 × Daizo) × W₂.
(1) It was found that lower light intensity limits for the production of moths laying diapause eggs were below 1.3 μW·cm^-2 at the wave-length of both 483 nm and 503 nm, and between 0.0084 and 0.039 μW·cm^-2 at 525 nm.
(2) It was also found that higher limits for non-diapause eggs were beyond 13 μW·cm^-2 at both 483 nm and 503 nm, and between 3.9 and 17.8 μW·cm^-2 at 525 nm.
(3) From the examination on the effects of light of wave-length from 356 nm to 687 nm at equal light intensities of 10 or 13 μW·cm^-2, it became evident that longer wave-length than 640 nm had no effect upon the production of diapause eggs, likewise in darkness, while shorter wave-length than this showed a distinct effect upon it, as the white light did.

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In order to analyze the interference of uncontrolled factors of environment with the temperature effect on plant growth and other plant responses, the effect of soil temperature on the hypocotyl elongation of cucumber seedlings was analyzed at respective air temperatures in the growth cabinet. The soil temperature was controlled 5°C higher and 5°C lower than respective air temperatures of 15, 20, 25, 30 and 35°C, and also controlled at the same temperatures as the respective air temperatures, with the use of the water bath system. Cucumber seeds were sown in the stainless pots filled with burnt chaff, and one day after germination, the seedlings were cultured under respective soil temperatures.
At air temperatures of 20 and 25°C, the hypocotyl elongations were promoted under higher temperature of soil, but inhibited under lower temperature of soil. At air temperature of 35°C, the hypocotyl elongation was promoted under lower temperature of soil, but inhibited under higher temperature of soil. The differences among the hypocotyl elonga-tions under respective soil temperatures were not significant at air temperatures of 15°C and 30°C.
In the phytotron glass rooms, the soil temperature was greatly affected by solar irradi-ation, and the maximum temperature of soil became 33.8°C even under air temperature of 25°C. Under this condition of the glass room, appreciable differences were found be-tween the respective hypocotyl elongations under the soil temperatures controlled and uncontrolled.
From these results, it is clear that the soil temperature remarkably interferes with the temperature effects on the hypocotyl elongation. This fact indicates that the control of soil temperature is necessary for the adequate analyses of the temperature effects on the plant growth and other plant responses.

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In order to estimate the temperature-control system of Phytotron, spectrum analysis with temperature and air-flow has been carried out.
So, how to measure fluctuation of temperature, how to process data of time series and how to adapt spectrum analysis to Phytotron are discussed.
As a result, it is concluded that characteristic of temperature-distribution in Phytotron is given by power spectrum density function of temperature and that spectrum analysis with air-flow (input) and temperature (output) is good approach to estimate the temperature-control system of Phytotronunder consideration of system-linearity.

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To analyze the light characteristics of lamps and to develop a methodology of artificial light irradiation in a contolled environment, the growth of spinach plant (Spinacea oleracea L.“Ujyo”) was examined under the same light intensities which were adjusted to equal illuminance of 10, 000lux and also adjusted to equal irradiance of 2.5 mW/cm², using an incandescent lamp, an incandescent lamp equipped with infrared-absorption filter, a daylight fluorescent lamp and a ballastless mercury lamp with 13 hr photoperiod.
At equal illuminance of 10, 0001ux, plant height, fresh weight and flower-bud formation were scarcely affected. However, significant differences in length between the cotyledonary node and the shoot apex at day 38 were found among the various light conditions; the increase in length greatly inhibited under the incandescent lamp.
At equal irradiance of 2.5 mW/cm², increases in plant height and in fresh weight were promoted under the fluorescent lamp, but were inhibited under the ballastless mercury lamp. Increases in length between the cotyledonary node and the shoot apex under the fluorescent lamp or the incandescent lamp with an infrared-absorption filter were much more pronounced than that under the ballastless mercury lamp.
Thus, different light conditions produced different plant responses, even under equal light intensities. Furthermore, the effects of light on plant growth appeared to differ with the methods used for measuring light intensity.
From these results, it was assumed that the selection and combination of lamps are important for artificial light irradiation in a controlled environment and also that development of a method to measure light intensities, which should satisfy requirements of biological experiments, is necessary for the adequate analysis of plant responses to environmental factors in an artificial light room.

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1) Red light irradiated for a relatively short time to Pharbitis plants grown under continuous green, blue, or far-red lights and in darkness just before a 16 hr dark treatment always initiated flowering induction, but far-red light given in the same way to red light grown plants inhibited flowering induction.
2) The effectiveness of red light given to plants grown under green light before a 16 hr dark treatment to induce photoperiodic sensitivity was compared between fluorescent light obtained from colored fluorescent lamps and spectral light beams from a grating spectrograph.
3) The effectiveness in inhibiting flowering induction of far-red light, obtained through an IR-1 filter and radiant heat cut glass from incandescent lamps, was also compared with that of spectral light beams from the far-red region by irradiating to plants grown under red light for a short time before the dark period.
4) Total energy values required for inducing 100% flowering by red light were about 37×10⁶ erg/cm² and 8.9×10⁶erg/cm² in fluorescent and spectral light, respectively.Those required for complete inhibition of flowering were 8.6×10⁶ erg/cm² and 9.9×10⁴ in filtered far-red light and spectral light, respectively.
The present experiment indicates that the total energy required for the same photoresponse are apt to be larger in colored fluorescent lights or filtered lights than in spectral light beams.This fact must be considered in photobiological experiments using monochromatic light other than spectral light beams.
5) The regions effective for flowering induction are roughly the three regions with wavelengths of about 550-600 nm, 620-640 nm and 650-675 nm, and those for inhibition of flowering induction range from about 710 nm to 770nm.
6) Experimental conditions for light and temperature were examined in detail. Reasons for the difference in total energy values between fluorescent light and spectral light were discussed.

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