Abstract
Potted, two-year-old Pinus densiflora seedlings grown under outdoor condition were carried into the greenhouse, which had an adjusted minimal temperature of 18°C, on February 20th, March 2nd, 12th, and 22nd before budding. They were again returned to the outdoors on May 21st. Afterwards, we determined the percentages of lammas shoot formation, the lengths of winter buds at the end of December, and the numbers of male and female flowers in the next spring. As heating treatments in the greenhouse initiated earlier, the percentages of lammas shoots and the lengths of terminal buds became greater. The number of the male flowers in the heated seedlings became more abundant than that of outdoor seedlings, while the number of the female flowers became fewer. The elongation of the terminal buds as the result of the lammas shoot formation seemed to be related to the differentiation of the male flowers. However, the number of the male flowers was infrequent in excessively-elongated buds. Moreover, few seedlings had both male and female flowers in any treatment.
