Abstract
Seasonal changes of the number of immature tracheid layer and starch grain content in Pinus densiflora were observed periodically from late February, 1966 until middle January, 1967. Sample pieces were taken from the stem of 50-year-old trees and 2-year-old seedlings every 10 days, and cross sections of each sample piece were observed under ordinary and poralized light microscope.
The number of immature tracheid layer of adult trees attained to a maximum in April May, but those of seedlings did not seem to vary outstandingly throughout the year.
There were two maxima and two minima in the starch content of secondary phloem of adult trees, first maximum occurring in April and May, second maximum in December, first minimum in September and second minimum in January. In the seedlings, on the other hand, there was a maximum in April, May and June, and a minimum in January as a general tendency, while some differences were found in the length of maximum period between current shoot and 2-year-old stem, and also in the pattern of annual fluctuations between cortex (plus phloem) and pith.
On the basis of these results, some correlations between seasonal changes of cambial activity and starch content were discussed.
