For investigation of the relationship between plant growth and environmental factors in a plant factory, an experimental plant factory has been built and some experiments have been carried out. Leaf lettuce was grown in a hydroponic system under artificial light condition. Arial environment such as air temperature, humidity and CO₂ concentration were controlled. Root environment such as EC and pH were monitored and controlled by a microcomputer.
In the first experiment, EC level was maintained at a constant set-point and the difference between the set-point and the actual value was summed up when the latter value was corrected. Transpiration was also calculated from the water depression in the tank. Then it was summed up through the growing period.
Following results were obtained:
(1) The EC decrement showed high correlation with the transpiration, regardless of light intensity and (2) the transpiration rate per EC decrement decreased as the EC of nutrient solution became higher.
In the second experiment, the effects of light intensity, lighting cycle and EC of nutrient solution on tipburn injury were examined.
Following results were obtained: (3) The tipburn occurrence became later under the conditions that the EC was low and the duration of a lighting cycle was short and (4) the tipburn occurrence became later under the conditions that the light intensity was low and the duration of a lighting cycle was short.
Effect of the duration of a lighting cycle on the tipburn occurrence showed larger as the light intensity increased. From the results of Tibbitts et al (1985), it is, therefore, considered that the pressure of laticifer or the Ca concentration in the wall of laticifer increases with the increase of the duration of lighting cycle and this could cause the tipburn.

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堆肥発酵熱を利用した土壌加温システムの最適設計・制御の方法を, プロセス設計の概念に基づいて検討した。混合素材の熱的物性値, 土壌加温に必要な熱量, 温室内微気象条件などが前提条件として与えられ, 熱抽出管の規格が決められているとき, 最適化によって決定すべき決定変数は, 熱抽出管の配管間隔と熱抽出管内の通水量の二つで, 操作の安定性, 熱効率の向上, 熱源装置の設備費軽減の観点からそれらの最適値が求められた。更に, 本システムを小規模施設へ適用することを前提に, 土壌加温トータルシステムのフローシートの一例を示し, 操作要領を記述した。ここで得られた決定変数の数値, 操作要領, フローシートは機器設備の詳細設計を行う際の基礎となるだろう。

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著者らの乾砂層の非等温定常モデルによれば, 乾砂層内の水蒸気上昇フラックス, すなわち乾燥砂面からの蒸発速度は, 勾配が極めて急でない限り, 層内の地温勾配の影響をほとんど受けない。
この点を確かめるために簡単な室内実験を行った。砂丘地表層内の地温勾配は, 夏の晴天日には5Kcm^-1を超えることもあるが, 本実験で得られた最大値は約3Kcm^-1であった。しかし, 少なくとも本実験条件の下では, 上記モデルの予測を確かめることができた。
砂の乾燥は恒率乾燥と減率乾燥の2段階に分けることができ, これらは乾砂層形成前後にほぼ対応する。砂丘地では, 降雨・かんがい直後を除けば, 減率乾燥が支配的であるから, 地表面の温度と含水量および乾砂層厚から蒸発速度を推定することができる本法は, 砂丘地の水収支を明らかにする上で有用と考えられる。

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植物の凍結温度に及ぼす結露の影響を調査するために, ダイズ葉面に人為的に水を付着させ模擬的結露状態を与え, 放射冷却条件下で凍結させた。その結果, 次の知見が得られた。
1) 葉面の露は葉の凍結温度を有意に高くし, その存在は霜害時には有害になる。
2) 葉面の水滴量が多くなると, 葉の凍結温度は上昇した。
3) 水滴量が少ない場合には, 葉が先に自発凍結することがあった。
4) 過冷却度が小さい場合, 葉面上の露の凍結がただちに葉の凍結に結びつくとは限らず, 両者の凍結に時間差を生ずることがある。
5) 過冷却が進むと, 水滴が凍結した際の植氷作用を受け, 同時に葉が凍りやすくなった。

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The use of nonwoven fabrics or cheesecloth for covering crops has become a common practice to promote crop growth or to protect crops from extreme weather or pests. The term, “row cover”, is used in the present study to refer to this type of covering. There are several different ways of employing a “row cover”, e. g. direct covering without any supporting materials (contact type), and the use of simple frame structures for suspension of the cover (floating type). There are many kinds of row covers, each differing in material and/or in porosity. These differences in covering method or row cover type can affect the microclimate under the row cover. In the present study, the longwave length radiation properties of several row covers were determined and their effects on nocturnal radiation and leaf temperature under the row cover were examined.
Longwave length radiation properties, i.e., transmissivity, emissivity and reflectivity of the five different commercial row covers (A, B, C, D and E) were measured by the method proposed by Okada (1983). The porosity of the row covers was photographically determined. The results are shown in table 1. The relationship between transmissivity and porosity of the row cover is plotted in Fig. 1. The transmissivity depended linearly on the porosity except for row cover C. Row cover C is made from a highly transmissive material polypropylene, while the rest of the row covers are made from materials with low transmissivity, e.g. polyester (A and B) or polyvinylalcohol (D and E).
To express the reduction ratio of nocturnal net radiation flux under the row cover to the outside, a protection index PI, as given by Eq. 1, was used. The PI of each film was measured in field experiments. The PI was clearly related to the transmissivity (Fig. 2) as shown in the empirical Eq. 6 developed from the data.
Based on the heat balance of a leaf surface, Eq. 5 was derived to estimate the temperature difference between a leaf and the ambient air. The differences calculated from this equation showed good agreement with those observed on the model leaf during night period.
By using Eq. 5, the relationship to describe the temperature difference between a leaf and the surrounding air within a space covered by a row cover and the PI was predicted (Fig. 4). The point of PI=0 corresponds to an uncovered condition in Fig. 4. From this figure, the leaf temperature under the row cover can be compared to an uncovered one. Assuming a floating type of row cover with open sides where the air temperature and wind speed are the same as the outside, the difference in the leaf temperature between covered and uncovered condition is about 2°C at a wind speed of 10cm/s and PI=0.5. The leaf temperature under a row cover could drop below the outside air temperature for a contact type covering, where the wind speed typically is only one tenth of the outside wind speed. These tendencies agreed well with measured data given in previous reports.

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In the previous paper (Quan and Takakura, in press) a method of estimating the seasonal cooling or heating load of a greenhouse by simulation model was discussed. The method was shown to be able to predict the loads with accuracy but had the problems of long calculation time and a lot of input data. It is desired to develop a more simple calculation system as a supplement of computer calculation. A statistical analysis approach based upon the simulation results of the previous paper was discussed in this paper. Seasonal cooling load could be calculated by integrating the daily loads. Hence, the simulated values of daily loads were used as basic unit here, which were divided into daytime and nighttime loads and sub-divided into cooling loads and heating loads. Some results are shown below.
1) The nighttime cooling or heating load could be estimated by using the nighttime degree hour (eq. (2) and (3) for heating loads and eq. (4) and (5) for cooling loads, where, _nDH is nighttime heating or cooling degree hour).
2) The daytime cooling load or heating load could be estimated by using the daytime degree hour and the solar radiation transmitted into greenhouse (Table 1) or by using only the latter one (eq. (7)).
3) The equations for calculating the cooling or heating degree hour (eq. (10)-(14) and the diagrams for reading the values (Fig. 3, Fig. 4) were obtained.
4) The heat transmission coefficients in both cooling and heating time were analyzed (Fig. 5).
5) The coefficient of heat transfer by infiltration in greenhouse cooling was described with the presence of both sensible and latent heat transfer (eq. (15)). Larger part of latent heat transfer was seen in cooling time than in heating time.

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