In vitro formation of axillary buds by immature shoots of Ponderosa pine

Abstract

Axillary buds were induced from immature shoot explants taken from terminal buds of branches from 29- and 34-year old ponderosa pines (Pinus ponderosa Dougl ex Laws). The effect of collection time, position on the donor tree from which the explants were taken, and plant growth regulators on axillary bud formation was investigated. Explants from branches taken in late October formed axillary buds, whereas explants from branches collected in February 1988 produced a large amount of callus. The ability to form axillary buds was significantly greater for explants from the upper crown than from the lower portion of the tree. Explant elongation occurred and basal needle primordia swelled on Murashige & Skoog media (MS) containing 2.2 μM 6-benzyladenine (BA) and 5.4 μM naphthalenacetic acid. When transferred to a MS medium containing 4.4 μM BA, 59% of explants formed axillary buds.