• Journal of Korean Society of Forest Science
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• v.84 no.4
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• pp.489-494
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• 1995

Seedlings and grafts of Betula pendula and Betula platyphylla var. japonica were grown under partially controlled environments in a greenhouse and in a plastic-greenhouse installed inside a laboratory. Plant growth conditions such as photoperiod, temperature, nutrient supply were partially controlled to enhance the vegetative and reproductive growth of the birch seedlings and grafts. By the treatments twenty and seventy one percents of the seedlings, respectively, for the Betula pendula and Betula platyphylla var. japonica developed visible floral organs between 250 to 508 days after seeding. By the same treatments eighty and fifty three percents of the grafts, respectively, for Betula pendula and Betula platyphylla var. japonica developed visible male catkins between 51 to 497 days and female catkins between 365 to 396 days after grafting. Breeding cycle of birch species can be reduced to a great extent by the induction of precocious flowering at early stages of seedling and graft development.

• Journal of Korean Society of Forest Science
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• v.84 no.4
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• pp.495-501
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• 1995

Betula pendula and B. platyphylla var. japonica seedlings and/or grafts growing inside and outside of a plastic-greenhouse were treated with growth regulators to induce flowering at early stages of seedling and graft developments. The seedlings began to develop female catkins visibly in eight to nine months after seeding and in five months after the first treatment of growth regulators. Thirty three percents of the seedlings grown under controlled environment in the plastic-greenhouse with sufficient nutrient supply developed female catkins both in control plants and in the plants treated with IAA, $GA_3$ and kinetin, while none on the control plants grown in the field showed any sign of the development of floral organs. Sixty seven percents of the seedlings treated with ABA and SADH grown in the Plastic-greenhouse developed female catkins. All the seedlings treated with 6.24 mM of SADH developed female catkins. SADH treatment to 2-5 year old seedlings and grafts of birch had a tendency of positive effect on inducing and increasing the flowering of the two birch species.