Quiescent 6-year-old lodgepole pine (Pinus contorta Dougl. var. latifolia) were transferred in midwinter from outdoors to warm, long-day greenhouse conditions. Vascular cambia from these trees were harvested on the day of transfer and weekly thereafter until xylem development became apparent. The stage of cambial reactivation in each tree was assessed by microscopy. Cambial extracts were then analyzed quantitatively by high-performance liquid chromatography (HPLC) at four ultraviolet wavelengths. A major HPLC peak, at 254 nm, was associated with radial expansion of cambial derivatives and increased markedly with secondary-wall formation and lignification in differentiating tracheids. The presence of this peak suggests a facile means for assessing commitment to tracheid differentiation in lodgepole pine.
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