DEVELOPMENT AND GROWTH OF PLANTLETS OF PINUS-CONTORTA REGENERATED FROM ADVENTITIOUS BUDS

Before micropropagation techniques can be applied to a particular spec ies, it is crucial to optimize the method and to determine how the mic ropropagated plants grow in the field. Adventitious shoots developed o n embryos of Pinus contorta Dougl. ex Loud. after a 2 h pulse treatmen t with 250 mu M N6-benzyladenine. The time to first subculture after t he pulse treatment influenced the yield of adventitious shoots. On ave rage, 68% of the adventitious shoots had developed roots 12 weeks afte r treatment with 1.25 mM indole-3-butyric acid for 6 h. The auxin trea tment stimulated early rooting (i.e. within 6 weeks) but had no effect on late rooting (i.e. after 6 weeks). The size of the plantlets was o f importance for their survival when potted. All plantlets with a dist inct stem elongated during the first growth period while some without did not. The relative height growth rate of plantlets was similar to t hat of seedlings. In the field the increase of height was similar for plantlets and seedlings. Plagiotropy was higher for the plantlets than for the seedlings (35 and 10% respectively). We concluded that most p lantlets of P. contorta elongate normally and have a similar gross mor phology to seedlings.