Averge coefficients of water-vapor transfer by forced convection from a single and both wet surfaces of leafshaped flat plates inclined to an air-flow were experimentally obtained. These results may be valid for analyses of the mass transfer from leaves inclined to the wind-direction or fluttering leaves within a plant canopy.
Leaf-models of thin elliptic plates with diameters of 5cm and 10cm were placed in the test section of an Eiffel-type wind-tunnel so as to set the short diameter in the direction of air-stream. The amount of evaporation from the wet surface of a plate was measured by weighing-method, in the ranges of wind velocities between 0.5 and 7m/s and the angles of the plate to air-flow between 0° and 90°, under the conditions of constant air-temperature and relative humidity.
Since the plates were not heated, the temperature of the surface, except for the vicinities of the leading and trailing edges of the plate was nearly uniform so that the variation of the water-vapor concentration over the surface can be neglected.
Average vapor-transfer coefficients (D_f, cm/s) were calculated by the following equations: for the plate with a single side wetted, D_f=w/ΔC-D_n, for the plate with both sides wetted, D_f=2ΔC-D_n, where, w is mean rate of evaporation in g/cm²s, and ΔC is the difference in vapor concentration between the surface and the air outside the boundary-layer over the plate in g/cm³. D_n is the transfer coffeicient due to the effect of free convection and calculated after Grashof number and so on.
The results obtained are as follows:
1) The average forced-convection transfer-coefficients of the plate parallel to the air-flow, for a single side and both sides wetted, were proportional to the 0.5-th power of wind velocity and the values agreed well with the theoretical ones for laminar boundary-layer over the plate.
2) For average transfer coefficients of the single wetted surface facing windward, it was confirmed that the 0.5-th power law for the wind velocity was applied in the whole range of the inclination-angles, and the proportional constant increased gradually with increasing angle of incidence. The value of the proportional constant of the transfer-coefficient for a plate perpendicular to the flow was about 1.2 times as large as that for a parallel plate.
3) For a single surface facing leeward, except for the angles between 10° and 20°, the average transfer-coefficients were apparently proportional to the 0.5-th power of wind velocity. An increasing incidence-angle over 30° diminished the proportional constant to about 80% of that for the parallel plate.
In the range of the incidence angles from 10° to 20°, the average transfer-coefficient was approximately proportional to the power between 0.6 and 0.7 of wind velocity.
4) The character of the average transfer-coefficient of the plate with both sides wetted showed the averaged character of those for respective single sides wetted.
Except for the angles between 10° and 20°, an apparent exponent of the wind velocity for the average transfer-coefficient was 0.5, and the change in prorortional constant did not appeared for the change in the inclination-angles.
In the range of the angles between 10° and 20°, the average transfer-coefficients were correlated with wind velocity by the exponent of about 0.6.

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It is a well-known fact that the ground temperature is stable all the year round. Paying attention to this fact, a new type greenhouse was devised for the purpose of making use of the difference between the temperature inside of the greenhouse and that in the ground. This newly devised greenhouse is called by the author “an earth-air heat exchange greenhouse”.
Fig. 1 shows the structure of an experimental “earth-air heat exchange greenhouse”. Many earthen pipes are laid in the ground at the depth of 64cm, 100cm and 136cm in 10 rows at 36-cm intervals, so that they may serve as the earth-air heat exchangers. With the help of a motor-fan installed on the wall, the air is circulated throughout the inside of the greenhouse and the pipes. The greenhouse room is heated in the night-time, while cooled in the day-time by the circulated air which was heated or cooled by passing through the heat exchange pipes. Since the ground has by a the grater heat capacity than air, excessive heat conveyed by the air can easily be accumulated in the ground in the day-time. In other words, in case of this greenhouse, its heat balance phase is by far expanded, as compared with that in the case of a conventional geenhouse. Therefore, extra-high temperature in a greenhouse is saved as a result of accumulating the excessive heat in the ground during the daytime, and the accumulated heat is available in the night-time.
An example of changes in temperatures in winter season is shown in Fig. 2. The temperature under the ground being maintained at about 10°C, the air temperature inside of the greenhouse is kept at about 7°C, even if the outside air temperatue drops to -5°C in the night-time.
This closed thermo-control system is especially effective in case of CO₂ and other gas control culture in the greenhouse.

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The experiments were carried out to clarify the relation between the photosynthetic rate of higher plants and light quality. Five species were employed. They hat been grown with gravel culture in greenhouse from February to April. Photosynthetic rate of single leaf was measured with an assimilation chamber under light of red, orange, yellow, green and blue of colored fluorescent lamps. The results were as follows.
(1) Photosynthetic rates of cabbage and swisschard showed maximum under the red light and minimum under the blue light. Photosynthetic rate decreased with the shorter wave length of light.
(2) In a case of lettuce, the red light showed the principal maximum and the blue light showed the second maximum. The green light had the least efficiency.
(3) Kidney bean and cucumber showed the principal maximum in the red light, but a difference of photosynthetic rate between the green light and blue light was not recognized.
The results of the first are in close agreement to Gabrielsen's experiment. The secend pattern is similar to Hoover's one. The third are an intermediate type between Gabrielsen's and Hoover's.
The discrepancy of photosynthetic activity in blue and green regions may be explained by means of the absorbing coefficient spectrum within the leaf.
The transmittive spectra of surface layers below the cuticle of cabbage and lettuce leaves (about 30μ thickness) were measured. Most of blue light is absorbed by the first 60μ-90μ surface layer. Green light is absorbed all over within the leaf. If we consider from a viewpoint of the light distribution, the former is not efficient to photosynthesis. The latter has the more efficiency. This means that a change in the absorbing coefficient K_λ gives variety to photosynthetic activity and that the greater absorbing coefficient K_λ has the less photosynthetic activity in thick leaf and much photosynthetic rate in thin leaf.
It is inferred that photosynthetic activity is decided by how the light is converged within leaf. Such results can be explained well by the application of Monsi-Saeki theory in plant canopy.

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Water vapor transfer from a model leaf set in a wind tunnel and that from citrus leaves formulating a canopy in the field were measured by using the leaf-like surface evaporimeter method due to HASESA and TAKECHI (1973), in order to make clear the wind dependence of forced convection water-vapor transfer coefficients over leaves within plant canopies. Local evaporation rates (w) at the point of 2cm from the leading edge of a leaf-like surface evaporimeter were determined respectively in the model and citrus canopies.
The following relation was used to separate the effect of buoyancy term from the measured evaporation rates and to determine the local transfer coefficient due to forced convection(D_f)
D_{f, EXP}=w/ΔC-D_{n, CALC}
were, ΔC is the departure of water-vapor concentration at the wet surface of the model leaf from that in the general air flow and D_{n, CALC} the water vapor transfer coefficient due to free convection. Because the leaf-like surface evaporimeter is flat, smooth and rigid, it is possible to assum that the influence of three factors such as leaf-fluttering, surface roughness and leaf curvature upon the transfer coefficient can be disregarded. The comparison between measured water-vapor transfer coefficients and standard coefficients (D_{f, STD}) calculated from theoretical relations for a flat plate (in longitudinal flow) similar to the evporimeter in the size and surface temperature distribution enabled us to make clear the influence of canopy air-flow on the transfer coefficient over leaves.
The results obtained for the surface evporimeter in longitudinal air flow are as follows:
1. The water vapor transfer coefficient due to forced convection over the model leaf set in the front of model canopy agreed satisfactorily with those calculaled from the laminar boundary layer theory, because the air flowing on the model leaf was free from the air disturbance by the model canopy.
2. Although the wind dependence of transfer coefficients over the model leaf set within and behind the model canopy was expressed by the 1/2 power law, the absolute values were to some extent larger than theoretical values. The difference between measured and calculated transfer coefficients was gradually large with the increment of leaf area density of the model canopy. When the leaf area density was retained constant throughout experiments, the values of transfer coefficient were independent of the tion of the model leaf within the model canopy along the direction of air-flow.
3. Under the conditions that the model leaves were oriented so as to shelter behind windward leaves, values of exponent of the wind-transfer coefficient ranged betweeh 0.6 and 0.7. In this case, the fetch-dependence of the watervapor concentration over the surface of the model leaf was quite similar to that over a flat plate on which turbulent boundary-layer was built up.
4. When the model leaves were set at different distances behind the model canopy, the influence of air-flow disturbance due to the canopy upon the water vapor transfer coefficient diminished gradually with increasing the distance from the canopy.
In order to study the effect of the angle of attack of air flow on the water vapor trasfer, experiments with the model leaves inclined against the horizontal plane at different angles were carried out in the model canopy. As can be seen in Fig. 4, in the range of inclination angle between 10° and 20° the values of transfer coefficient were somewhat larger in comparison with those over a flat plate in longitudinal air flow. However, the effect of inclination angle on the transfer coefficient over the model plate decreased rapidly with departure from that inclination range and the values of transfer coefficient became nearly equal to or slightly smaller than the standard transfer coefficient.

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