INDUCTIVE EFFECTS OF ACC AND NAA ON XYLOGENESIS IN RED PINE

摘要

Investigating both one- and two-year-old branch cuttings of red pine (Pinus resinosa), it was found that a combination of exogenous auxin (1-naphthalene acetic acid, NAA) and the ethylene precursor 1-aminocyclopane 1-carboxylic acid (ACC) induced cambial derivatives to differentiate into primary xylem tracheids at the trace-cambium junction, simulating the 'tracheid-differentiation factor' inductive anatomical effect of an intact fascicle of pine needles. Tracheary elements (TEs) having annular, spiral, scalariform, or reticulate secondary-wall ribs were induced after injecting NAA + ACC in water into the prophyll-sheath cavity, also after NAA had been injected into the cavity and ACC provided through cutting bases. Auxin alone promoted cambial celldivision and primary-wall radial expansion, and the treatment rarely also yielded new secondary xylem bordered-pitted TEs. ACC alone induced anomalous wall bars (AWBs) at 88%, and primary TEs in 26%, of junctions. High NAA: ACC ratios yielded high ratios of secondary to primary TEs.