A semi-empirical model was proposed for the simulation of leaf temperature (T_l), and rates of net photosynthesis (P_n) and transpiration (E) of a single rice leaf in steady-states. The model consisted of two main sub-models: one is for solving the energy balance equations to give E and T_l and another for P_n. In both models the energy and mass transfer processes were expressed in terms of the diffusion resistances, namely, the boundary layer (r_a), the stomatal (r_s) and the overall mesophyll or residual (r_M) resistances. Both the sub-models were thus connected by the resistances and T_l. The diffusion resistances in dependence of wind speed (U), shortwave radiation flux intensity (I_s), the leaf temperature (T_l) and ambient humidity were formulated by means of physical and/or empirical equations. By incorporating experimentally specified parameters into the simultaneous equations thus derived, simulations were made to obtain P_n, E and T_l for various environmental conditions.
The following results were obtained from the simulations. First, with the increase in the radiation intensity (I_s) up to about 0.5cal cm^-2min^-1, E increased very sharply due to the opening of the stomata, resulting in T_l decrease or only a slight increase, and above this I_s level E and T_l both escaped from the stomatal regulations and increased proportionally to I_s. The leaf air temperature difference (T_l-T_a) was larger the lower the T_a. Second, three types of curves were derived in photosynthesis (P_n)-radiation (I_s) relation, depending on the environmental conditions; a non-saturation type curve at lower T_a, a saturation type curve at near optimal T_a and an optimal type curve at supra-optimal T_a with low humidity. The difference in P_n-I_s curve was attributable to I_s effect on T_l which in turn reflected on r_s and r_M. Third, as a result of the response of r_s to the leaf air vapour pressure difference, P_n and E at lower humidity were suppressed considerably, resulting in T_l increase. Fourth, with increasing wind speed (U), P_n and E at optimal or above optimal T_a increased, whereas those at sub-optimal T_a decreased. These contradicting effects of U on P_n and E appeared through its effects on r_a and T_l.
The simulation results were compared with measured data on rice leaves by a leaf chamber method and also with data by other workers. Except for T_l at higher I_s and T_a, the model well explained the observed responses in P_n, E and T_l to the environments.

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The volumetric water balance of hypothetical root zone in a plastic house contains the runoff rate through the soil under the plastic wall (horizontal water flow) and the rate of capillary rise through the bottom of the root zone (vertical water flow). To improve the water management of the root zone, the development of an estimating method of both water flows is necessary.
In this paper, the characteristics of both water flows and their contribution to the water balance are described through the experimental studies which were done by using the soil containers buried near the plastic wall to measure each water flow. The results obtained are as follows:
1) The total water flow into the root zone of the east bed during the period of 104 days of tomato cultivation, which corresponds to the stage from flowering of third cluster to harvest of sixth cluster, was 119.6mm of water. This amounts to about 40% of that of irrigation water or to about 30% of the evapotranspiration during the same period.
2) Since the ratio of the vertical water flow to the horizontal one was 1.63, suggesting that most of the water flow was through the deeper soil layer than the root zone.
3) The vertical water flow was closely related to the difference in the soil moisture suction between the root zone and the 40cm depth under the ground surface outside the house or 80cm depth under the ground surface inside the house. The relation between these differences in suction when expressed as the mean value for 15-days period resulted in a straight line.
4) On the other hand, the horizontal water flow could not be related to any difference in the soil moisture suction. However, it was shown that the horizontal water flow was connected with the evapotranspiration rate during the same period.
5) A multiple regression equation (Eq. 6) for the estimation of total water flow into the root zone was presented, which was composed of the difference in the soil moisture suctions and the evapotranspiration rate.

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To make clear the relationships between wind profile parameters and aerodynamic properties of the plant canopy, an analysis of wind profiles above canopy was carried out.
The results are summarized as follows:
(1) The equations of wind profile parameters ζ₀(=z_o/H) and δ(=d/H) were obtained in terms of u_H/u_* and C_D as follows:
ζ₀=(β₀/ku_H/u_*)^1/(1-m)exp[-k/(1-m)-u_H/u_*]=(β₀/k√C_D)^1/(1-m)exp[-k/(1-m)√C_D],
and
δ=1-(β₀/ku_H/u_*)^1/(1-m)exp[-km/(1-m)u_H/u_*]=1-(β0/k√C_D)^1/(1-m)exp[-km/(1-m)√C_D],
where z_o is roughness length, d zero-plane displacement, H height of canopy top, u_H wind velocity at the height of H, u_* friction velocity, C_D total drag coefficient of the canopy, ζ₀ the relative roughness length, and δ the relative zero-plane displacement. β0 and m are empirical constants.
(2) The empirical constants (β₀ and m) may be determined by the equation,
λ₀=β₀ζ^m₀=-k²(1-δ)/ln(1-δ/ζ₀) The values of β₀ and m estimated for several canopies are shown in Table 1. The main cause of differences in β₀ and m may be ascribed to the changing of aerodynamic structure of canopies.
(3) The relation among z_o, d and H was derived as:
lnH-d/z₀=k²/β₀H(H-d)/(z₀/H)^m.
The above relation seems to be applied for various types of plant canopies.
(4) The dependences of ζ₀(=z_o/H) and δ(=d/H) for Japanese larch canopies (Allen, 1968), maize crop (Maki, 1975a, 1976), and pasture grass (Kotoda, 1979) upon the total drag coefficient C_D were fairly well approximated by Eq. (14) and Eq. (15), respectively.

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Traditional planting date of rice seedlings on flooded paddy fields is around 10th of May in Pacific Ocean costal district (Miyagi prefecture) of south Tohoku in Japan, and it has been believed that the transplanting before this date is difficult because air temperature is not yet high enough for rice growth, or even harmful. In this district, however, one of the peak periods of solar radiation intensity appears in the spring. This work was made with the aim to increase the rice yield by advancing the planting date so as to utilize the rich radiation energy in the spring of this district.
The temperature conditions in this district were re-examined in 1977 and 1978 for the last decade of April. Several observation spots were spaced over this district (see Fig. 1), and air and water temperatures were measured. Since the numbers of the spots for the water temperature were limited, the spatial distribution of the water temperature was estimated from those of the air by using empirical equations given in Table 1. The averages of the daily maximum, the daily minimum and the daily mean air temperatures over the last decade of April in this district were found to distribute in the ranges of 14-17°C, 2-6°C and 8-12°C, respectively (Figs. 2 and 3), and these temperature conditions were considered not to be sufficient for the rice growth, or even harmful. As is shown in Figs. 2 and 3, however, the averages of the daily maximum, the daily minimum and the daily mean water temperatures over the same period were in the ranges of 24-28°C, 3-9°C and 11-15°C, respectively and considerably higher than those of the air. Since the shoot apical region of rice is in water at the early growth stage of the plant, the rice at this stage is more strongly affected by water temperature than by air temperature. From these facts we concluded that in most part of this district the water temperature at the last decade of April is high enough to permit the rice growth and developments without suffering severe cold damages.
The effects of early transplantings on the growth and yield of rice were, then, examined by the field experiments made in 1977 and 1978. The rice cultivar used for the experiments was ‘Sasanishiki’ and 10 experimental fields were distributed over this district (Fig. 1). In each field the rice seedlings (raised in a nursery green house) were transplanted on different dates, which were 0-18 days before the traditional planting date. With advancing the planting date, the plant dry weight and the grain yield, both, linearly increased in both years (Figs. 5 and 6). When the plants were transplanted before the end of April, the yield in both years was above 600kg/10a which was significantly higher than the traditional yield level of this district. The advantage in the yield of the early transplantings was considered to be realized mainly through inceased total sunshine duration that the plants received during the growth, because the sunshine duration increased with advancing the transplanting date and because the yield was approximately linearly proportional to the sunshine duration (Fig. 5). The cumulative water and air temperatures at the grain-filling stage (40 days after the heading) also increased 3 to 7% by the early transplanting of 20th of April.

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The convective heat transfer coefficient at the greenhouse inside surface has been one of the unknown variables for heating designs and its relevant problems are discussed in the present paper in relation to the form of heating pipe placement.
Several forms of pipe placement were examined using a small greenhouse model and each produced a considerably different pattern of the inside air temperature distribution. Largely due to these different temperature patterns, the heat transfer coefficient which determines the convective heat flux from a growing area to the inside cover surface varied with each form of pipe placement. Both low pipe placement and piled side pipe placement revealed a uniform temperature profile in the growing area, but the coefficient was smaller in the low pipes. This was due to the fact that the temperature near the cover surface was higher in the piled side pipes. Full overhead pipe placement resulted in pronounced thermal stratification, air temperature above the pipes being much higher than that in the growing area. This caused exceptionally large values of the coefficient. Both the thermal stratification and the large coefficient were reduced to a certain degree when the combination of overhead and low, side pipes was applied.

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