INDUCTION, ROOTING, AND GROWTH CAPACITY OF ADVENTITIOUS SHOOTS OF PINUS-CONTORTA

Zygotic embryos of Pinus contorta Dougl. ex Loud. developed adventitious buds after a pulse treatment with 250 muM benzyladenine for 2 h. The number of embryos forming adventitious buds, as well as the number of adventitious buds per embryo, depended on the length of time after pulse treatment before the embryos were transferred to fresh medium. Adventitious shoots pulse-treated with 1.23 mM indole-3-butyric acid for 6 h started to develop roots within 3 weeks and after 3 months 75% of the shoots had developed roots. Roots usually emerged from vascular tissue that was connected to the vascular cylinder in the stem. However, roots could also be initiated directly from the vascular cylinder in the stem. The average relative growth rate per day for plantlets was 5.9% compared with 9.3% for seedlings. However, there was a correlation between the initial weight of the plantlets and their relative growth rate per day. Thus, plantlets classed in the group with highest initial fresh weight had a relative growth rate of 7.3%. Differences in growth rate between plantlets and seedlings are discussed.