生殖器官の生産量からみたシイ林の有性生殖

Saito, Hideki, Nakai, Kunihiko, Amino, Hisakazu, Iwatsuki, Teppei, Hasegawa, Hirokazu, Takeoka, Masaji

In a mature stand of Shii chinkapin (Castanopsis cuspidata SCHOTTKY) at Matsuotaisya shrine, Arashiyama, Kyoto, annual production rates of reproductive organs were studied using 20 litter traps (each 50cm×50cm in mouth area) in 1986-1989,and those of pollen were estimated by multiplying the number of fallen male catkins per ha per year by the mean amount of pollen per catkin before anthesis. The main results were as follows. The pollen production rate of 218-359kg d. w. (ha)^<-1> (yr)^<-1> was one of the highest among other species, and that of 64.2-103×(10)^<12>(ha)^<-1> (yr)^<-1> was by far the largest number; moreover, these showed small year-to-year fluctuations. Such a huge number of pollen grains, however, was balanced by the number of ovules in a stand (numerical ratio of pollen grains to ovules : 4.1-8.3×(10)^5). The light pollen grains (1.94-4.30×(10)^<-6>mg d. w.) save the assimilation products invested in pollen formation. Dry matter of reproductive organs by the year of anthesis was within the range 1609-1803kg d. w. (ha)^<-1>, and those of male and female parts were inversely proportional to each other. Annual production rates were within the range 1237-2204kg d. w. (ha)^<-1> (yr)^<-1>, equivalent to values in years of average to poor seed crop. There was no relationship between the annual production rates (by weight) of male and female parts, because fruit maturation requires two growing seasons. In three years among four, the 0-and 1-yr-old parts showed equal dry weight allocation. Seedmaturing ratios or numerical ratios of mature nuts to total female flowers were small (5.5%-10.6%), being approximately equal to those of other species. The year-to-year trend in nut production (by number) parallelled those of seed-maturing ratio and the number of female flowers. Mean nut weight vs. assimilation products necessary for producing a single nut, calculated by dividing the drymatter production rate of overall parts by the number of nuts, was 1 : 3 in a year with an average seed crop, and 1 : 6 in a year with a poor crop. This seed production effort was similar to those of five other barachorous species.

生殖器官の生産量からみたシイ林の有性生殖

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