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

Zygotic embryos of Pinus contorta Dougl. ex Loud. developed adventitio us buds after a pulse treatment with 250 muM benzyladenine for 2 h. Th e number of embryos forming adventitious buds, as well as the number o f adventitious buds per embryo, depended on the length of time after p ulse treatment before the embryos were transferred to fresh medium. Ad ventitious 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 t issue 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 correlatio n between the initial weight of the plantlets and their relative growt h rate per day. Thus, plantlets classed in the group with highest init ial fresh weight had a relative growth rate of 7.3%. Differences in gr owth rate between plantlets and seedlings are discussed.