The effects of a shelter-hedge on sensible heat transfer from the surface of a hotbed were measured about a prototype of hotbeds in field and a model in a wind tunnel. The similarity problem between field measurement and model test was examined by using the data of heat transfer from the outer surface of hotbeds. And some model experiments were carried out to make clear the proper usage of shelter-hedge for the hotbed.
The results obtained are summarized as follows:
(1) Eq. (3) and Eq. (4) were used as a similarity law to compare the results obtained in model tests with those from field measurements. And the results of model test were in well accordance with those from field measurements (Fig. 4).
(2) When the wind direction was perpendicular to a shelter-hedge, the effect of the shelter-hedge on reduction of heat transfer from a hotbed was distinguished. But in the case of the angle of the wind direction to a shelter-hedge was 45deg., the effect decreased extremely (Fig. 4).
(3) The difference between the surface temperature of the hotbed and the air temperature slightly influenced the coefficient of sensible heat transfer under the calm condition. But the influence became negligible under the windy condition (Fig. 5).
(4) The effects of closeness of the shelter-hedges on sensible heat transfer from the outer surface of the hotbed were examined by using the shelter-hedges with closeness of 30, 65 and 80%. The results indicated that the shelter-hedge with closeness of 30% was not useful to diminish the heat transfer. But the shelter-hedges with closeness of 65 and 80% were useful to diminish the heat transfer from the upper surfaces of hotbeds.
(5) When the purpose of the shelter-hedge was to reduce heat transfer from hotbeds, the optimum distance between the shelter-hedge and the hotbed was about four times of the height of the shelter-hedge.

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The photosynthetic function of a crop, which characterizes a response of leaves in the fixation of carbon dioxide to radiation intensity, temperature, humidity and so on, is a most important factor influencing the magnitude of canopy photosynthesis. The measurements of photosynthetic fixation of carbon dioxide were carried out using an enclosure method with cucumber crops (var. Ougon) raised in pots. The pots with cucumber crops were placed in a vinyl house without heating from transplanting (April 10, 1973) to the days before the measurements. The ages of the leaves used to measure CO₂-fixation were in the range between 4 and 45 days after unfolding. The data so obtained were processed to clarify the photosynthesis of cucumber leaves dependent on radiation, temperatures (leaf and air), and leaf age and the results can be summarized as follows:
(1) The shape of light-photosynthesis curve of a leaf is affected by the number of days after its unfolding. Namely, the light-photosynthesis curve changes clearly with leaf age from a less plateau type response with high photosynthesis for younger and vigorous leaves to a plateau type response with low photosynthesis for older and frail ones. The photosynthetic rate of a leaf at the light saturation (P_m) reaches a maximum at a certain leaf age and decreases afterwards. The dependence of P_m on leaf age (d) is approximately expressed as follows:
Pm=23.8+1.248d-0.0361d²
Since newly unfolded leaves and old leaves are in the top and bottom layers of the canopy, respectively, the profile of P_m can be characterized by a curve with its maximum between 0.5H and H, where H is a height of the canopy.
(2) The values of the parameter (b) characterizing the shape of light-photosynthesis curve were found to be approximately 110mgCO₂ dm^-2 hr^-1/(ly min^-1) independent of the leaf age. The photosynthetic function of leaves in a layer in the canopy can be, therefore, determined very easily in terms of P_m and b.
Photosynthetic fixation in the leaf was measured under a constant level of radiation (I≅0.65ly min^-1) and various temperature conditions, in order to obtain information of the response of photosynthesis to temperature. Fig. 3 presents changes in relative photosynthetic activity (R_T) of the leaves with leaf and air temperatures in the measuring chamber (T₁ and T_a). They are approximated by a quadratic function of leaf temperature as follows:
R_T=0.05T₁-0.00076T²₁.
The above relation indicates that the rate of photosynthetic fixation of CO₂ by the cucumber leaves reaches a maximum in a range of leaf temperature from 30 to 35°C. However, the optimum air temperature for photosynthesis shifted toward the lower temperature side by a magnitude of about 5°C, because the leaf temperature exceeded the air temperature by about 5°C.
(3) Specific leaf area (SLA) is a determinant of the size of photosynthetic apparatus and plays a very important role in the simulation of the crop growth. The values of SLA ranged between 250 for cucumber crops raised in pots and 400cm²g^-1 for those raised in usual soil bed. As can be seen in Fig. 5, it is reasonable to assume that a mean values of SLA for cucumber crop is approximately 300cm²g^-1 independent of days after unfolding, although there is a considerable scatter of data.

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The effective utilization of solar energy has been urgently required in the fields of agriculture and industry from the view point of energy saving. In order to fulfill this purpose, it would be essential to develop economical and highly reliable pyranometer to measure intensity of solar energy.
Pyranometer of this type using N on P type silicon solar cell used for artificial satellites has been developed.
As a result of three year running test with a thermopile type pyranometer, it was found that this new type has the output of smaller zero drift, quicker response and better stability. In addition to these, error caused by temperature dependence peculiar to semiconductors has been minimized by adopting temperature compensator.
Japan Meteorological Agency has examined this type for one year and admitted the accuracy of within±2.5% error.

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The rate of transpiration from plant leaves and leaf temperature in the case of changing transpiration with a meteorological factor have been calculated from the equation of stationary energy-balance for a single leaf. The results obtained are represented in the forms of the relations between the transpiration rate and the difference of leaf and air temperatures, under some climatological conditions. Further, some observations are compared with the calculated results.
i) Variation with solar radiation.
When assuming that the stomatal aperture in terms of the coefficient of internal vapor transfer increases with solar radiation and the other meteorological factors are fixed, an increase in solar radiation under the conditions of lower air-temperature, higher humidity and smaller internal-transfer-coefficient increases both transpiration rate and leaf temperature. Under the opposite conditions, the increase in solar radiation increases the transpiration rate and decreases the leaf temperature, until the increase of the radiation increases both transpiration rate and leaf temperature when the radiation is above a certain amount.
When the internal-transfer-coefficient remains constant as solar radiation varies, the transpiration rate and leaf temperature show a nearly proportional relationship, i.e. the transpiration rate increases and the leaf temperature rises with increasing solar radiation.
ii) Variation with air temperature.
In both cases when the internal-transfer-coefficient increases with air temperature and when it remains constant as air temperature varies, an elevation of air temperature produces an increase in transpiration rate and a decrease in temperature difference between leaf and air; the leaf temperature rises with air temperature.
iii) Variation with relative humidity.
In all cases when the internal-transfer-coefficient decreases or increases with decreasing humidity and when the coefficient remains constant, the transpiration rate increases as humidity varies and the leaf temperature is decreased. The relationships between them are almost linear.
iv) Variation with wind speed.
Simulation was done on the assumption that the internal-transfer-coefficient remains constant as wind speed varies.
When the transpiration is suppressed under the conditions of lower air temperature, higher humidity and smaller internal-transfer-coefficient and the leaf-air temperature difference becomes larger under the conditions of higher solar radiation, an increase in wind speed diminishes both transpiration rate and leaf temperature.
Under the opposite conditions, the increase in wind speed increases both transpiration rate and leaf temperature.
Under the medial conditions of air temperature, relative humidity, internal-transfer-coefficient and solar radiation, the tendency for the transpiration rate to increase with wind speed is general and then the leaf temperature falls.
v) Observations.
The relations between transpiration rate and leaf temperature obtained from some experiments using citrus, sweet potato and paddy rice plant in controlled environments were in good agreement with the simulation of the leaf-heat-balance.

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[in Japanese]

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