1981 Volume 49 Issue 4 Pages 523-533
Seasonal changes in the mean values of solar radiation, air temperature and fruit temperature for a ten day period were measured at different locations on satsuma mandarin trees (Citrus unshiu Marc. var Sugiyama) of the open center and hedgerow formes during the period from late-July to mid-December in 1976 and 1977. And the correlation between cumulative solar radiation, cumulative air temperature and cumulative fruit temperature were investigated. The results are given as follows.
1. Each location on the open center form tree was grouped into four, according to the seasonal changes of mean flux of solar radiation, expressed as the mean of each ten day period. The south side and top of the west side were continuously exposed to the highest amount of solar radiation. The tops of the east side and north side were next, and were followed by the skirt of the east and west sides. The skirt of the north side and interior received the lowest amount of solar radia tion. This suggested that the south side and the tops of the east, west and north side were more strongly exposed to direct solar radiation than the skirt of the north side and interior.
Each location on the hedgerow form tree was grouped into three. The tops of the east and west side belonged to the highest group. The skirt of the east side and all of the west side were in the intermediate group, and the interior was in the lowest group.
The mean air temerature for ten days of a month was almost the same in all locations of both form trees. And for the open center form tree, the cumulative air temperature in the interior and top of the west side were higher than those for all of the north side and the skirt of the west side.
The mean fruit temperature for ten days of a month was generally higher at the top locations than at the skirt locations in the canopies of both form trees.
The cumulative fruit temperature was high at the tops of south and east side, and was low at the skirt of north side.
2. In both form trees, the regression coefficient of the cumulative solar radiation to the cumulative fruit temperature was low at the location with high solar radiation flux. A high positive correlation coefficient was also found between cumulative solar radiation and cumulative fruit temperature. The regression coefficient of cumulative solar radiation to cumulative fruit temperature was higher in the open center form tree than in the hedgerow form tree. This suggested that the fruit temperature was more strongly influenced by solar radiation in locations with thick leaf layers than in other locations.
3. The regression coefficient of the cumulative air temperature to the cumulative fruit temperature tended to be higher at locations exposed to direct solar radiation. At such locations, the cumulative fruit temprature was influenced much more by the cumulative air temperature. On the other hand, the regression coefficient was lower in the interior. This suggested that the fruit temperature in the interior was influenced more strongly by solar radiation than by air temperature.
