Micropropagation and Phase Specificity in Mature, Elite Douglas fir

Abstract

Abstract Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] plantlets, micropropagated from axillary buds of nodal segments from invigorated stems and adventitious buds from young needles of two 60-year-old trees, have been established in soil. Stem tips with half-pruned-back needles from the lower crown, when placed on DCR medium, sprouted buds in 90% of explants. Shoots from bud sprouts were plagiotropic when collected from explants of shoots with a horizontal and downward growth habit. By contrast, upright growth of micropropagated shoots was observed in all explants from branches with an upright habit. After four subcultures (3- to 4-week intervals on 0.5 mg·liter−1 BA in DCR), sprouted shoots of nodal segments from all expiant sources produced four to six multiple buds. With excised needles of sprouted buds, numerous (> 10) adventitious buds formed after 11 to 12 weeks on needle surfaces after the fifth subculture on DCR with 0.5 mg·liter BA. All adventitious and axillary buds elongated on 0.5 DCR lacking plant growth regulators. Rooting of the elongated shoots was induced in 20% of the explants with 0.2 mg·liter−1 each of NAA and IBA. In all instances, buds programmed for the development of female reproductive cones continued their phase-specific development even under conditions conducive to rejuvenation of vegetative tissues. Chemical names used: N-(phenylmethy)-1H-purin-6-amine (BA); 1-naphthaleneacetic acid (NAA); 1H-indole-3-butyric acid (IBA).