Although a great number of attempts have been made to evaluate the canopy photosynthesis, almost all of them have mainly been devoted to calculations of photosynthesis of horizontally uniform canopies such as well grown rice, maize, wheat and soybean field. Hence it seems that less information is obtained on light environment and photosynthesis of a hedgerow type canopy usually adopted for the cultivation of horticultural crops. This paper presents an approach to the light environment within hedgerow type canopies, particularly the penetration of direct sunlight into them. A silhouette method was used to obtain phytometrical data of cucumber canopies (var. Ougon) raised in a vinylhouse. The phytometrical measurements were repeated at an interval of one week during the period from April 25 to May 16 in 1973.
In the calculation of penetration of direct solar radiation into the hedgerow type canopy, the cross section of the cucumber row was divided into two parts: the first part is irradiated by direct sunlight penetrated through the top surface of the canopy and the second by sunlight penetrated through the side surface of the canopy. Geometrical characteristics for the first part can be obtained by the ordinary method (Eqs. 2-4, c.f., UCHIJIMA et al., 1968).
In order to assess the geometrical characteristics (effective leaf area projection function G_L^←, extinction coefficient of direct sunlight k_d^←) of the second part of the canopy, the rectangular system (x, y, z) set in parallel with the cross section of row is transformed to a new system x′=z, y′=y, z′=x by rotating only the z-axis at 90°. Extinction coefficient of direct sunlight in the second part k_d^← is given as a function of the angle of incidence of solar rays on the side surface of the crop rows, which is defined by both the sun and row directions. Numerical experiments are made to determine the dependence of the extinction coefficient k_d^← on the directions of the sun and row. Results obtained are summarized as follows:
(1) A following simple relation was obtained between the leaf area of cucumber crop A and the product of leaf length l (from joint of leaf-stalk to leaf-tip) and leaf width w, and used to determine non-destructively the canopy structure of cucumber crop:
A=0.937(l⋅w)-9. (cm²)
(2) Inclination angle of cucumber leaves increases with the depth of the crop layer, viz., with leaf age, and the foliage inclination angle of leaves (β_L) also increases with the progress of plant stages (early stage-14°, middle stage-21-24°). It seems that the azimuthal distribution of leaf area shows predominance in a direction perpendicular to the row direction (E45°S-W45°N)(Fig. 3).
(3) The effective leaf area projection function for the whole stand G_L^↓ calculated from Eq. (2) increases with increasing sun altitude h_o, and its dependence on h_o agrees fairly well with the theoretical result for a horizontal-leaved cancopy (ROSS, 1970). The value of G_L^↓ changes a little with depth of the crop layer (Fig. 4).
(4) Extinction coefficient k_d^↓ of direct solar radiation in the first part of the cucumber canopy is shown as a function of sun altitude (Fig. 8). Diurnal changes of extinction coefficient k_d^← calculated from the following equations for the four rows with different direction (N-S, E-W, E45°S-W45°N, E45°N-W45°S) show different features with the time of a year (Fig. 6, 7).
k_d(b_n, i)^←=soc i G_L(b_n, θ_o)^←

View full abstract

Physical environment in stone rooms of old tombs is considered to have a great influence on the deterioration of their mural paintings, carvings and stone walls themselves. In order to obtain environmental data in this kind of room we measured temperature and humidity inside the stone room of the Ohtsuka old tomb located at the Keisen town near Fukuoka city.
Based on this observation we investigated the environmental conditions from the view point of the conservation of treasures.
The results obtained are:
(1) There is hardly any change of daily temperature and humidity in this stone room.
(2) The yearly change of temperature in the stone room is almost equal to that of soil temperature at about 3.00 meters deep.
(3) The humidity in the stone room was kept close to 100%.
(4) After persons entered this stone room, both temperature and humidity changed suddenly. The sudden change of these two factors is considered to be unfavorable to the preservation of treasures.

View full abstract

Light is the primary ecological factor limiting growth and yield of crops cultivated in glass or vinyl houses. A simple relation proposed in a previous paper (Iwakiri and Inayama, 1974) was applied to determine the penetration of direct sunlight into cucumber canopy rows with four different azimuth angles such as φ_r=0°(N-S), φ_r=90°(E-W), φ_r=45°(E45°N-W45°S), and °_r=135°(E45°S-W45°N). It is assumed in the calculations that the length of each cucumber row is infinite so that the end effect can be neglected. Phytometrical data obtained on May 16 (at five weeks after transplanting) were used to calculate the extinction coefficients (k_d^↓ and k_d^→) as influenced by both sun and row directions. As in the previous paper, the cross section of each cucumber row was first divided into twenty five sub-blocks of 20cm wide and 30cm deep. The twenty five blocks were divided into the two parts in which leaves are irradiated by direct sunlight incident on the top surface and on the lateral face, respectively. The following relations were used to calculate the attenuation of percent sunlit leaf area with the optical depth along light path:
d_n=exp{-Σⁿ_n=1k_d^↓, _nΔF_n^↓},
d_m=exp{-Σ^m_m=1k_{d, m}^←ΔF_m^←},
where d_n and d_m denote percent sunlit leaf areas at the boundary of blocks n and m (integers n and m being the orders of block counted from top and lateral surfaces of cucumber row, respectively); k_{d, n}^↓ and ΔF^↓_n extinction coefficient and partial leaf area index in the block irradiated by sunlight incident on top surface, respectively, and k_{d, m}^← and ΔF^←_m extinction coefficient and partial leaf area index of the block irradiated by sunlight incident on lateral surface of row. The mean sunlit leaf area in blocks n and m were determined by
d_n={d_n+d_n-1}/2,
d_m={d_m+d_m-1}/2,
where d_n and d_m are respective percent sunlit leaf areas in blocks n and m.
The results so obtained can be described as follows:
1. The light environment in an isolated cucumber row was firstly studied in relation to the direction of sun and row. The percent sunlit leaf area of a cucumber row as defined by F_l/F_t, where F_t and F_l are leaf area index and sunlit leaf area index, respectively, showed a characteristic diurnal change (Figs. 8 and 9).
The percent sunlit leaf area of an N-S oriented row decreased with sun altitude in all seasons. This is mainly due to that the direct sunlight incident on a side surface that plays a very significant role in the light environment when sunrays are perpendicular to the side surface of an N-S oriented row. The role of direct sunlight incident on a side surface becomes less with an incident angle.

View full abstract