Soil moisture and its vertical transport were studied by use of observation data of soil water budget carried out at a grass field throughout one year.
(1) Bowen's ratio increases gradually with decreasing soil moisture near the surface when fine weather lasted for several days, but its seasonal increase towards winter is much more remarkable, independent of soil moisture. It is also shown, from the observed variation in soil moisture and ground water level, that soil moisture is discharged by evaporation only from the surface layer of soil in winter and through the deeper layers in summer. These results show that the activity of vegetation plays an essential role in evapotranspiration and soil moisture transfer.
(2) A theory with a simple model was developed from the viewpoint that the vertical transfer of moisture takes place in the vapor phase within the unsaturated layers of soil. The effect of soil moisture on the rate of evapotranspiration was discussed. A fundamental equation of vapor diffusion in soil layers was deduced, and the values of diffusivity and other constants were estimated. The effect of transpirating vegetation was considered as the moisture sink. Following results are obtained: the moisture change does not reach in winter the level of about 15cm depth within a dry spell for several days. The moisture in summer, on the whole, remains lower than that in winter down to about 20cm depth. The rate of evapotranspiration decreases gradually with decrease in surface soil moisture. Satisfactory agreement was obtained between observed and theoretical values. The observed facts may be explained by assuming that the moisture transfer in the soil layer near the surface takes place in the vapor phase.

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温室の暖房設計ならびに経営的研究に必要な暖房デグリーアワーを求めるために, 温室内の気温の夜間低下の式と外気温の夜間低下との式を利用した。これらの関係式から導いた暖房デグリーアワーの式に最低気温の平均データを代入してデグリーアワーを計算した。それらの資料から経験的につぎの関係のなりたつことがわかつた。
D_h=5.9(T_c-T_min)^1.22,
ここでD_h, 暖房デグリーアワー; T_c, T_min, 温室の暖房設定気温, 外部の最低気温(℃)。この関係式はT_cが変化しても成立した。
T_cを5°, 10°, 15℃と3段階にかえた時の冬期間についての積算デグリーアワーの地理的変化が第4図に示されている。T_c=5℃では, デグリーアワーの絶対値は小さいが日本の北と南との比は著しく大きいことがわかつた。T_cの値が増加するにつれて絶対値は増大し, 南・北の比は次第に減少した。T_c=15℃では絶対値は10k℃hr～50k°hrの間に変化し, 比は大体5.0に減少した。デグリーアワーの値と燃料の発熱量と燃料効率の値を利用して必要燃料量を求め, 計算図 (第5図) を作成した。この図を利用すると, 温室の放熱係数 (H_T) と放熱比 (R′) とから容易に必要燃料量を求めることができる。
温室の放熱係数は外部の風速, 有効放射, 換気率, 温室の材質, 凝結熱伝達の有無によつて大きく変化する。それゆえ, 放熱係数H_Tの正確な値は余り知られていない。また, 以上の計算では暖房デグリーアワーの平均値を求めたが, 温室暖房の実際においては, 年による暖房デグリーアワーの変化を考慮しなければならない。この2つの問題に関する研究を早急になすことが必要である。

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水稲が倒伏すると, 茎葉部は部分的に遮光されて受光条件の悪い状態におかれ光合成が著しく抑制され, 特に下敷きの葉は倒伏後の経過日数が長くなるに従い次第に黄化するため, 葉の光合成機能が低下するものと考えられる。
したがつて, 倒伏にもとづく光合成能の減退は倒伏被害を発生させる重要な因子と解されるので, これらの問題を解明するための一助として, 遮光による光合成量の減少, および倒伏後の経過日数と光合成との関係, につき正常稲の場合と比較検討するため本研究を行なつた。
すなわち, 光合成におよぼす遮光の影響を調べるため, ポットに土耕裁培した水稲コシヒカリを, 出穂2週間後に挫折倒伏処理し, さらに1週間放置した後, 種々の遮光条件下で¹⁴CO₂同化処理を行なつた。なお正常・倒伏両稲の葉の光透過率についても比較を試みた。一方倒伏後の経過日数と光合成との関係を調べるため, 出穂1, 2週間後に同一品種水稲をそれぞれ挫折倒伏させて放置し, 出穂後3週間を経過した時期に, 同一光条件下で¹⁴CO₂同化処理を行なつた。
稲葉の光透過率は, 倒伏稲>正常稲であり, この差異は倒伏稲では葉が黄化し葉緑素含量が低下したことによるものと考えられる。
光合成におよぼす遮光の影響を正常・倒伏両稲について比較すると, 炭酸同化量は, 同一光条件下では, 正常稲>倒伏稲であり, 受光量の減少に伴い両稲とも同化量は減少するが, その減少傾向は両稲とも異ることを認めた。
なお, 倒伏後の経過日数と光合成との関係をみると, 経過日数すなわち倒伏前歴が長くなるほど炭酸同化量は正常稲の場合に比し著しく低下することが認められた。
以上のことから, 水稲の倒伏にもとづく光合成の減退は, 主として倒伏に伴つて生ずる遮光および葉緑素含量の低下に起因するものと解される。

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When parallel light comes into foliage, a part of it is scattered by reflection and transmission of leaves. A foliage exposed to parallel light is divided into two parts: 1) sunlit part receiving both parallel and scattered light and 2) shaded part receiving only scattered light. Leaves of foliage were assumed to be inclined at a fixed angle (α) against the horizontal, and distributed at random as to leaf position and angle of leaf orientation (β).
The gross photosynthesis of a foliage (P_t) exposed only to parallel light with a constant angle of incidence (θ) was calculated by the author's method^{4, 5)}, for a horizontal-leaf (α=0°), an oblique-leaf (α=45°) and a vertical-leaf (α=90°) foliage (LAI=5 and 10). On the other hand, the gross photosynthesis of a foliage under isotropic light conditions (P) was calculated by using the equation given by MONSI and SAEKI⁶⁾, and the results were compared with P_t.
1) Mean gross photosynthesis p_d of sunlit part at F (cumulative leaf area index)=0.
When (π/2-θ)≥α, exposure of leaves to a parallel light in sunlit part is limited to adaxial leaf surface for any β value. When (π/2-θ)<α, the sunlit part is exposed adaxially in the range of β≤π/2+sin^-1 (cotα·cotθ), and abaxially in the range of β>π/2+sin^-1 (cotα cotθ). p_d was calculated as the average for β ranging from 0 to π.
θ-p_d relation was considered for fixed values of I_D (intensity of incident parallel light on a plane perpendicular to the rays).……The increment of θ decreases p_d when (π/2-θ)≥α, and increases p_d when (π/2-θ)<α. Furthermore, the θ-p_d relation was discussed also for the light condition where the value of I (horizontal intensity of incident parallel light) is kept at a fixed by varying the θ value according to the change of I_D as shown by I=I_D cosθ.
2) Relationships between θ and P_t under constant I_D.
When α=0°, the increment of θ diminishes the intensity of light received by leaves both in sunlit and shaded parts, and hence reduces P_t. When α=90°, however, P_t has its maximum at a certain value of θ which becomes somewhat small with increasing I_D and LAI. This variation of θ giving the maximum P_t depends theoretically upon the ratio in area between the sunlit and the shaded part and upon the photo-synthetic rate in each part. The decreasing tendency of P_t at α=45°with increment of θ is similar to that at α=0°in the θ range of 0°to about 30°, and similar to that at α=90°in the θ range of about 60°to 90°.
3) I(=I_Dcosθ)-P_t curves under constant I_D or under constant θ.
When α=0°, P_t is fixed for a constant value of I, even if I is given by any combination of I_D and θ. When α=45°and 90°, I-P_t curves under a constant value of I_D are different from those under a constant value of θ.
From these curves, θ-P_t relation was deduced for the light condition of fixed I values which are decided by changing the θ value according to the variation of I_D.

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