The method to regulate the heat environment in the root zones of crops by the establishment of heating equipment in soil is used widely.
This paper is concerned with the dimensionless term (HTF) corresponding to heat transfer coefficients on soil surface which affect the temperature distribution in a ridge. The results of discussion are as follows.
1) It shows that the values of HTF on soil surface have a tendency, that is, 3 (HTF at the middle of ridge surface) : 3/2 (end of ridge surface) : 1 (top of ridge surface) .
2) HTFs are calculated from natural convection and radiation classifying the heat transfer phenomena. From the results, it is proved that HTF by radiation is greater than by natural convection.
3) Noctural radiation calculated using HTF by radiation is roughly in accord with measurement in field.
4) It brings the HTF of the ridge top closer to the sum of HTF by natural convection and by radiation.
5) As the evaporation of soil surface water has an effect on the heat transfer, a term of evaporation should be added to the heat transfer coefficient.

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In this paper, electronic measurements of water content in plants with high sensitive impedance meter were discussed and dynamic characteristics of stemwater in tobacco plants by step input of environmental elements were made clear.
1) By step input of light (0lux to 30, 000 lux and 30, 000lux to 0lux) at the air temperature of 25°C and the air humidity of 60% RH, the variations of capacitance in the stem were about 1 pF and the time constant was about 30 min.
2) By step input of relative humidity (60% RH to 80% RH and 80% RH to 60% RH) at the air temperature of 25°C and light intensity of 30, 000 lux, the variations of capacitance in the stem were about 1pF and the time constant was 1 min to 10 min.
3) By step input of temperature (25°C to 30°C and 30°C to 25°C) at the air humidity of 60% RH and light intensity of 30, OOOlux, the variations of capacitance in the stem were about 0.5pF and the time constant was about 10 min.
4) By step inputs of light and relative humidity, the variations of capacitance in the stem were about 3 pF at maximum. Effects of complex inputs on dynamic characteristics of capacitance of the stem were examined.
5) Reliability of these values was examined on digital simulation.

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This paper reports the study on the effects of daylength and light intensity on the growth of seedlings and the flower formation in egg-plant.
Egg-plant seedlings were grown under 4-, 8-, 12- and 15-16-hr in the first experiment, and under 6-, 8-, 10-, 12- and 14.5-15.5-hr day-lengths in the second experiment. The seedlings were exposed to high light intensity of natural daylight in all the daylengths.
The longer the day-length, the more vigorous the growth of seedlings and the earlier the date of flower bud differentiation, resulting in the decrease in the number of leaves to the first flower, and in the increase in the number of flowers.
The seedlings were grown unde 4-, 8-, 12-, 16-, 20and 24-hr in the third experiment, and under 8-, 16and 24-hr day-length in the fourth experiment. The day-lengths longer than 8 hr were supplemented by low intensity lighting of incandescent lamps.
The longer the day-length up to 8-12 hr, the more vigorous the growth of seedlings, being followed with the earlier flower bud differentiation with the decrease in the number of leaves to the first flower. The daylength longer than 8-12 hr, on the other hand, induced the more vigorous growth of seedlings, but did not affect the flower formation.
The seedlings were exposed to the natural daylight for 8 hr f rom 6 : 00 a.m. to 2: 00p.m., from 8: 00a.m. to 4: 00p.m. and 10: 00 a.m. to 6: 00p.m. daily, respectively.
Delayed exposure to the daylight restricted the growth of seedlings and retarded the flower bud differentiation, resulting in the increase in the number of leaves to the first flower and in the decrease of number of flowers.
The seedlings were grown at four different light intensities (100, 75, 50 and 25 per cent of natural day light), and three different light intensities (100, 60 and 20 per cent of natural day light) .
The higher the light intensity, the more vigorous the growth of seedlings, being followed with the earlier flower bud differentiation with the decrease in the number of leaves to the first flower, and the increased number of flowers.

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In the course of investigations on photosynthesistranpiration-CO₂ concentration relations, cyclic changes of transpiration rate with approximately 30 minute periods were found under conditions of 0.75 cal⋅cm^-2⋅ min^-1 light intensity, 25°C air temperature and 65% relative humidity in normal CO₂ concentration of air. The amplitude of oscillation was affected by wind speed and increased with increase of wind speed. The average transpiration rate increased with increase of wind speed and showed the maximum value at 150 cm·sec^-1 wind speed.
In high CO₂ concentration, the period and the amplitude of oscillation became longer and narrower respectively and the cyclic changes disappeared at about 3, 000 ppm, but when air temperature was raised to 30°C, the cyclic changes continued up to 20, 000 ppm.
The average transpiration rate reduced with increase of CO₂ concentration and showed minimum value at about 1, 000 ppm. Over that concentration, the transpiration rate increased up to approximately 20, 000 ppm, and also in darkness, the transpiration rate increased over 1, 000 ppm. This phenomenon depended on air temperature, i.e., the depression of transpiration rate disappeared when air temperature was raised to 35°C. Similar phenomena were observed on pet-sai (Brassica pekinensis PUPR), cabbage (Brassica oleraces L., var. capitata L.), turnip (Brassica ropa var. Mana) and radish (Raphanus sativus L.) .
The causes of increase of the transpiration rate in high CO₂ concentration were not clarified, but the transpiration rate was reduced by spraying ABA solution on the plants. This means that CO₂ causes the stomata to open again in high CO₂ concentration.

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