Several thermomodules were selected from the family of miniature thermo-electric heat pumps in modular form, to investigate their performance to condense water from laboratory room air by cooling.
The efficiency to get condensed water was mainly restricted by the low heat conversion at the cooling surface (Fig. 7) . The highest efficiency was obtained when the cold surface temperature was set about 8°C cooler than the dew point (Fig. 5) .
The dew point control using a thermomodule was also studied on a model house, composed of vinylfilm and wood frames of 61 cm in hight, 45 cm in width, 45 cm in length.
Dew point and house temperature were measured in the center of the house containing a plant pot from which the evapotranspiration was fed with the rate of 0.5-2 cm³per hour at the temperature of 23-27°C.
A simple on-off controller was constructed to control the electric current to the thermomodule by the action of a power relay which was activated by a signal from the dew point transducer (Fig. 3) .
This system performed the control of dew point within ± about 0.5°C at the dew point range of 20-14°C (Fig. 8) .

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Humidity distribution in a plant population is complicated with many environmental factors and physiological functions even in controlled environment. The present paper deals with analyses of humidity distributions in the cucumber plant population under different air currents with reference to plant growth. The humidity in the plant population was increased by irradiation and evaporation from soil, and the humidity distribution was remarkably influenced by air current. Increased air velocities higher than 0.9 m sec^-1in lateral air current made the humidity in the plant population close to that of controlled air. However, these velocities were estimated to exceed the optimum velocity for plant growth. When the air velocity was reduced to 0.2 m sec^-1, the horizontal gradients of humidity were smaller in downward air current as compared with those in upward and lateral air currents. Therefore, it is certain that each of the plants in the population can be exposed to almost the same humidity in downward air current. On the other hand, the plant growth was more uniform in downward air current than in upward and lateral air currents. From these facts, it could be estimated that the downward air current is preferable for minimizing the horizontal differences in humidity in the plant population, in order to make plant growth more uniform for exact analyses of plant responses to environmental factors.

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One-week-old seedlings of sunflower (Helianthus annuusL. cv. Russian Mammoth) which were sown in artificially-lighted growth cabinets were subsequently exposed to 0.05 or 0.1 ppm SO₂for 5 weeks. The plants were harvested at intervals of 7 days, and relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), leaf weight ratio (LWR) and specific leaf area (SLA) were obtained. No remarkable changes were caused by SO₂exposure in the dry weight of stem, root and whole plant. However, the leaf area and the leaf dry weight of plants exposed to 0.05 and 0.1 ppm SO₂were markedly increased from harvesting on the 3rd week (2 weeks' exposure) . Exposure to 0.1 ppm SO₂resulted in 20-25% reduction of NAR during the later stage (4 to 6 weeks), whereas RGR was slightly decreased. Exposure to 0.05 and 0.1 ppm SO₂ caused the increase in LAR and LWR but not SLA. Same treatments also brought about the acceleration of leaf senescence and the depression of flower bud development and stem elongation.

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Soils from several forests were sampled, and incubated at 25°C until the direct effects of disturbance by soil sampling were extinguished. The rates of CO₂evolution of these soils varied considerably among the soils from different forests. The rates were not correlated with pH of soil, water content, number of heterotrophic bacteria or the amount of total organic carbon, but highly correlated with the amount of dissolved organic carbon in soil solution obtained by a centrifugation at 13, 000×g for 40 min at 4°C.
Even in the soil from the same forest, the rate of CO₂evolution Y (mg C/kg dry soil/hr) increased rapidly then decreased gradually, when the soil was air-dried and wetted. Whereas, the amount of dissolved organic carbonX (mg C/ kg dry soil) also changed in the same manner, and the relation betweenXandYwas expressed by a simple equation ofY=aXexcept of soils immediately after wetting. The gradient (a) at 25°C differed considerably among the soils from different forests as in 0.355 of Kanto loam soil at Fuchu, 0.077 of volcanic soil at Shikaoi, 0.072 of alluvial soil at Obihiro, 0.131 of volcanic soil at Kagoshima and 0.125 of lime soil at Nago. The reason for the differences of the gradient (a) among the soils from different forests left to be studied.
Furthermore, some mutual relations of the rate of CO₂evolution were also discussed, the amount of dissolved organic carbon and the amount of hetero-trophic microbes in soil.

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The relationship between distribution of leaf temperature and stomatal aperture was examined by measuring leaf temperature and the central pore of stomata. Distribution of leaf temperature within a leaf was illustrated by the digital image processing system through the input of thermal camera. Stomatal aperture was quantitatively determined by the same digital image processing system under the output of SEM (scanning electron microscope) . When the light is switched on after the 5 hr dark incubation of the leaf, leaf temperature oscillates transiently and then becomes stationary value. In the process, let the stationary value before light be Dark, the maximum value of leaf temperature be A, the maximum value of its differential be B, the minimum value of leaf temperature be C, and the stationary value after light be D, so at Dark, A and D, some interesting relationships were observed between the distribution of leaf temperature and stomatal aperture. Now let the correlation coefficient between leaf temperature and stomatal aperture be γ_Dark, γ_A, and γ_D respectively, finally we had γ_Dark=-0.91, γ_A=-0.80 and γ_D=-0.89 with respect to sunflower and γ_Dark=-0.99, γ_A=-0.95 and γ_D=-0.99 with respect to orange. However, at B and C, there was no tendency in the correlation coefficients. For leaf temperature might be determined by several transient phenomena. We concluded that the image processing procedure in this study was one of the most effective methods for investigating physical and physiological phenomena in plant growth.

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