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Volume 46, Issue 2
Displaying 1-7 of 7 articles from this issue
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Masuyuki TAKAICHI, Tsutomu YONETANI1990 Volume 46 Issue 2 Pages 71-77
Published: September 10, 1990
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSRelationship between temperature distribution and freezing of a young tea plant (Camellia sinensis L., cultivar ‘Yabukita’, two years old) was investigated in a field condition. Freezing of the plant was detected by temperature rize with fine thermocouples (0.1mm in diameter) inserted in the stems and attached to the leaves.
The lowest nighttime temperature of the plant (plant hight: 65cm) was observed on leaves at about 35cm above ground. The leaf temperature was 3-4°C lower than the air temperature at 1.5m hight (Ta150) when wind speed U150 and net radiation Rn were below 0.5m/s and -60W/m2, respectively. Freezing of plant body was found to spread to all shoots through trunk in a relatively short period of from several to a dozen minutes. A boundary of frozen and unfrozen part was at the lowest part of trunk in a straw mulch layer.
Relatively wet conditions when dew-point temperatures around leaves at about 35cm height were above -2°C, freezings did not occur until leaf temperatures fell below about -2°C in spite of adequate dew formation. Conditions when dew-points were -2 to -4°C, freezing temperatures of the leaves were changed with and nearly equall to the dew-points. More dry conditions when dew-points were below -4°C, freezings occurred at almost constant temperatures of -4°C, and they seemed not to be related to the dew-points. In these conditions, freezings might occur first in stem tissues without dew formation on leaves.View full abstractDownload PDF (420K) -
1990 Volume 46 Issue 2 Pages 78
Published: September 10, 1990
Released on J-STAGE: February 25, 2010
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Taichi MAKI, Yoshitaka KUROSE1990 Volume 46 Issue 2 Pages 79-86
Published: September 10, 1990
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe local meteorological observation was carried out at Takase Basin and the south west slope of Osa Mountain, Kagawa Prefecture on clear-fine day in winter, Jan. 19-21, 1988.
The cold air lake was observed at the bottom of Takase Basin and the thermal belt observed at the slopes of 100-500m of Osa Mountain and 100-200m of Asahi Mountain. The vertical differences of both air and surface temperatures for the typical inversion layer were 6-7°C and about 10°C, respectively, and the thickness of the inversion layer was 80-100m at the basin bottom. In the case of small cold air current, the cooling seemed to be larger, because the air current was easy to stand on the gentle slope. The pan-type distribution of isotherm was recognized at the basin.
The change of wind direction and the frequency of weak wind of 1m/s were higher at the basin bottom. The cold air current of 1 to 3m/s was observed at the slope and its wind speed was relatively heigher at the lower region of the slope. The cold air current seemed to blow from the elevation of about 400m. The stronger the wind speed of the air current was, the higher the air temperature was at the foot of the mountain, however, the air temperature seemed to be constant in the case of wind speed over 3m/s.
The relative humidity and the appearance frequencies of dew and frost were higher at the basin bottom, but lower at the slope and the foot of the mountain in the case of cold air current. The air was dry and its temperature was high at the observation base of 160m in the blowing period of cold air current. The amounts of dew and frost were few, and the latent heat flux by evapotranspiration was occasionally released from the soil surface even at night. As the cold air current blowing from the thermal belt is the warmer wind at the slope and supplies the sensible heat to the crop at the foot of the mountain, its utility is high as meteorological resources along with the thermal belt.View full abstractDownload PDF (540K) -
Haruo SUZUKI, Shinichi TANAKA1990 Volume 46 Issue 2 Pages 87-92
Published: September 10, 1990
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSAlthough the actual effects of light fluctuations within plant canopies have not still been clarified, some applied examples of fluctuating light to cultivation exist due to the conversion control of continuously irradiated artificial light to intermittently irradiated fluctuating light. In this study, indoor experiments were conducted for the purpose of obtaining the characteristics of fluctuating light within some plant canopies.
(1) As a result of the wind tunnel experiment relating to light fluctuations, the frequency bringing the spectral density of the fluctuating light within each plant canopy (height: about 20cm) to a definite level or more was in the order of paddy (28Hz)>corn (22Hz)>burdock (17Hz)>carrot (13Hz)/broad bean (11Hz)/soybean (10Hz) in the case of wind velocity of 1.7ms-1. With respect to six plant canopies, differences were small in the peak frequency between a weak wind (1.7ms-1) and strong wind (2.5ms-1), and the peak frequencies of both cases were within a range of 1.5-3.5Hz. The peak value of power spectra became large in proportion to the increase in wind velocity and this relation was also confirmed within the observed frequency range (Fig. 4).
(2) The observed frequency range of fluctuation of light was proportional to the wind velocity at different plant heights of broad bean and corn. All were formed as regression equation. In corn regression lines were arranged according to plant height, whereas in broad bean those were not arranged.View full abstractDownload PDF (338K) -
Nobutaka MONJI, Ken HAMOTANI, Yukio OMOTO1990 Volume 46 Issue 2 Pages 93-96
Published: September 10, 1990
Released on J-STAGE: February 25, 2010
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Michiko TAKAGAKI1990 Volume 46 Issue 2 Pages 97-101
Published: September 10, 1990
Released on J-STAGE: February 25, 2010
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Akira MIYATA1990 Volume 46 Issue 2 Pages 103-106
Published: September 10, 1990
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSDownload PDF (556K)
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