日中は光合成, 夜間は呼吸を測定することによって, 自然光下のキュウリ植物にとって最適な環境条件の組合せを求めるため, おもに気温に関して, 電算機による連続制御実験を3回行った。
電算機により選定された気温と日射量とには十分相関があり, また午前と午後の積算光合成量の比はほぼ1である。
液肥の電気伝導度の変化に呼応して, 呼吸が変化し, 生長速度の低下と光合成および呼吸量の減少にかなりの相関がみられる。
山登り法における日射量と炭酸ガス濃度の項に双曲線関数関係を導入したが, その制御作動は満足できるものであった。

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Because diffuse radiation flux exceeds usually about 30 per cent of the total downward short-wave radiation in vinylhouses on clear days, it is one of the most important factors influencing leaf photosynthesis and transpiration of crops raised in vinylhouses. Although many studies have been made on the penetration of direct solar radiation into vinyl- and glass- houses in recent years, relatively little work has been made on problems of diffuse radiation flux, particularly on the derivative (or complementary) diffuse radiation flux due to scattering of direct solar radiation by vinyl films (or glass) and the floor surface, and on the angular distribution of diffuse radiation. In this paper, experimental data obtained in vinylhouses with and without crop plants (see Fig. 1) were analyzed to make clear characteristics of diffuse radiation environment in vinylhouses. The results obtained can be summarized as follows.
Experimental data reveal clearly that the downward diffuse radiation flux is higher inside than outside vinylhouses, implying that some derivative diffuse radiation flux is reaching the floor surface (see Fig. 2 A and B). The effective scattering coefficient (ω_ef) characterizing the generation of downward derivative diffuse radiation flux in vinylhouses can be evaluated by Eq. (8). The magnitude of ω_ef increases curvilinearly with the increment of solar height as shown in Fig. 3 B and can be expressed as follows:
ω_ef=ω_ef.maxsin h_o,
where ω_ef.max denotes the maximum of ω_ef to be observed when sun is at the zenith. The above relation indicates evidently that the scattering function of vinylfilms differs from the diffuse scattering and is prolonged strongly forward (in the direction of the incident light). The existence of micro water droplets on the vinylfilms influences significantly the magnitude of ω_ef. The daily mean of ω_ef for a vinylhouse with micro water droplets is about three times as large as it (‹ω_ef›_day=0.045) for a vinylhouse without micro water droplets. On clear days, the contribution of penetrated sky diffuse radiation to the total downward diffuse radiation flux in a vinylhouse decreases progressively with increasing solar height, with the consequent increment in the role of the derivative diffuse radiation flux (see Fig. 2 D).

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In order to study the irregularity of the angular distribution of downward diffuse radiation inside and outside vinylhouses, hoods with different opening angles are mounted on a pyranometer of Eppley type screened from the sun (see Fig. 1). On a clear day (April 1, 1975), the curves showing the contribution of each sky band to the diffuse radiation flux on the horizontal surface inside and outside a single-ridge vinylhouse without crop plants shift clearly from a type with the predominant contribution of lower sky bands to a type with more contribution of upper sky bands with increasing solar height. In a seven-ridges vinylhouse in which cucumber plants are raised in rows, the curves showing the contribution of each sky band are characterized by the curve with peak at the middle sky band between 30° and 60° of the zenith angle, independently of the distribution curve outside the vinylhouse (see Fig. 2). On a cloudy day, the curves characterizing the contribution of each sky band are found to be similar roughly to that for uniform overcast sky (UOC). The diffuse radiation distribution index (X_d) is defined by Eq. (3) to describe quantitatively the diffuse radiation flux received on the horizontal surface from each sky band and presented as a function of solar height in Fig. 3. If it is assumed that the diffuse radiation field is uniform with respect to the azimuth angle, the angular distribution of diffuse radiation beam is approximately obtained by processing the data presented in Fig. 4 by Eq. (5). As shown in Fig. 5, on a clear day, the angular distribution of diffuse radiation beam in a seven-ridges house show a peculiar type due to the existence of cucumber plants and the seven-ridges structure of house.
The numerical integration of Kondrat'ev's equation (Eq. 7), using the data of angular distribution of diffuse radiation presented in Fig. 4, gives the diffuse radiation flux on sloped leaves as a function of X_d. Fig. 6 A shows that the diffuse radiation flux on sloped leaves as the ratio to that on a horizontal leaf for the same diffuse radiation field is higher than that for UOC condition throughout the whole range of slope of leaves. On the other hand, in cases that the values of X_d are positive, the diffuse radiation flux on sloped leaves is lower than that of leaves with the same slope under UOC-conditions. The deviation of curves from that for UOC-condition is well expressed by Eq. (9) with acceptable error. The values of constants A and B characterizing the magnitude of the deviation of curves depend largely on X_d as shown in Fig. 7 and can be expressed by Eq. (10). The total amount (↓q_T(X_d, β)) of downward diffuse radiation flux impinging on both surfaces of sloped leaves is independent of the slope and equals to the diffuse radiation flux on a horizontal leaf, when the diffuse radiation field is uniform. If the diffuse radiation field differs from the uniform one as observed in vinylhouses, however, ↓q_T(X_d, β) changes largely with the slope of leaves. When Xd is negative, ↓q_T(X_d, β) increases with the slope and reaches the maximum at β=90°, whereas ↓q_T(X_d, β) decreases monotonically with the slope of leaves when X_d is positive. The change of total amount of diffuse radiation flux on leaves with the slope and the structure of diffuse radiation field can be evaluated by Eq. (12).

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Evaporation from wet surface of an elongated plate was measured in laminar air flow, in order to clarify the convection coefficient of water-vapor transfer across the boundary layer on a leaf-blade of rice plant. The plate was shaped like a rice leaf of 30cm length in the direction of air flow and the maximum width 1cm, and a rectangular plate of the same dimensions was also used.
The forced-convection transfer coefficient on a leaf shaped plate is about 1.05 times as large as that on a rectangular plate. This is smaller than the ratio between the coefficient for an elliptic plate and that for a rectangular one, which is attributable to the shape of a rice leaf-blade.
When the plate is not heated, the distribution of water-vapor density over the surface along the flow direction is so slight that the effect of the distribution on the transfer can be neglected. On the other hand, when the plate is uniformly heated, the difference in water-vapor density between the surface and the ambient air varies to be proportional to the 0.1 to 0.3 power of the distance from the leading edge of the plate. The vapor density distribution leads to an increase in forced-convection transfer coefficient for a heated plate by a factor of about 1.1 over that for a non-heated one.
The average coefficient of convection transfer may be represented by the sum of the coefficient for forced convection and the buoyancy term, which is given approximately by the free-convection transfer coefficient for a flat plate in the laminar range.
The average coefficient of forced-convection transfer from each side surface of an elongated rectangular plate is proportional to the 0.5 power of the wind speed for every angle of the attack of air flow when wind is not too strong. Above a certain wind speed, the coefficient is proportional to the 0.8 power of the speed. For a plate in parallel with the air flow, the critical wind speed at which the transition occurs is about 8m/s. For a plate inclined to the flow, the transition on the surface facing winward occurs at a relatively high wind speed, and that on the surface facing leeward at a relatively low wind speed.
For the wake side surface of a plate with an attack angle of about 5°, the forced-convection coefficient may be expressed as varying in a 0.55 power of wind speed. However, it seems to be practical to take that the coefficient is proportional to the 0.5 power of the wind speed.
In the laminar range, the average forced-convection transfer coefficient for an elongated rectangular plate is considerably larger than that estimated from the laminar boundary layer theory for an isothermal infinite strip of plane surface with the same dimensions parallel to the flowing fluid.
Moreover, the transfer coefficient on each side surface of an inclined flat plate is larger than that of a plate in parallel with the air flow. The ratio of the former coefficient to the latter increases with the increasing attack angle of the flow on the plate.
The mean value of the transfer coefficient of both side surfaces of a flat plate is approximately equal to the geometric average of those of each side surface with the same attack angle.
In the laminar flow, the average forced-convection transfer coefficient for a bent rice-leaf of 30cm length and 1cm in the maximum width may be about 5 to 6 times as large as the value obtained from the boundary layer theory for the isothermal surface of a flat-rectangular plate of the same dimensions in parallel with the air flow, mainly because of three factors such as the correction due to the dimension, the effects of non-homogeneous temperature distribution over the leaf surface, and the leaf inclination effect.

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