MORPHOGENETIC RESPONSE OF VEGETATIVE BUD EXPLANTS OF ADOLESCENT AND MATURE PICEA GLAUCA (MOENCH) VOSS IN VITRO*

SUMMARY The formation of adventitious shoot primordia on cultured explants from vegetative buds of Picea glauca (Moench) Voss varied with the source tree. The best response, i.e. the highest number of responsive explants (10/25) and of shoot primordia per responsive explant (average 8.1), was found with buds excised from a tree in a natural stand (15 to 18 years old). However, explants from only one other tree of eight natural stand trees responded with shoot primordium formation. By comparison, explants from four out of five orchard trees (scions 25 to 28 years old) produced shoot primordia in vitro. Of the material compared, the explants which were most likely to show shoot primordium formation were from the terminal bud and the nearest lateral buds of a main lateral branch. Explants from similar buds on subdominant branches of highest hierarchy are also included in this category. Finally, the original size did not significantly influence the number of shoot primordia produced on responsive explants 12 weeks after explantation.