POLLEN PRODUCTION IN 60-YEAR-OLD PLANTATIONS OF CHAMAECYPARIS OBTUSA

Abstract

The annual production rate of pollen grains was studied in 55-and 60-year-old plantations of Japanese cypress, Chamaecyparis obtusa SIEB. et ZUCC. in Mt. Hiei, Kyoto, for three years, 1978 to 1980. The production rates of male flowers after pollen release caught by litter traps were 11.35 kg ha^<-1>y^<-1> to 163.3 kg ha^<-1>y^<-1>, Mean dry weight of pollen grains produced per male flower (1.12mg) was obtained as the difference between mean dry weight of male flowers just before pollen release (1.99mg) and that after pollen release (0.870mg). The production rates of pollen grains in dry weight ranged from 14.59 kg ha^<-1>y^<-1> to 209.9 kg ha^<-1>y^<-1>, based on the ratio of dry weight of pollen grains per male flower to that of male flower after pollen release. One pollen sac of C. obtusa contained 2,495 to 4,675 pollen grains on an average, according to the position of cone scales on a floral axis and the number of pollen sacs per cone scale. Accordingly the mean number of pollen grains per male flower amounted to 198,200. The maximum value of production rates of pollen grains in number reached 3.72×10^<13> No. ha^<-1>y^<-1> for 1978,based on the ratio of number to dry weight of pollen grains per male flower.