© 1995 Heron Publishing—Victoria, Canada
Genetic variation in rooting ability of loblolly pine cuttings: effects of auxin and family on rooting by hypocotyl cuttings
Michael S. Greenwood (1) and Robert J. Weir (2)
1. University of Maine, 5755 Nutting Hall, Orono, ME 04469-5755, USA / 2. North Carolina State University, Box 8002, Raleigh, NC 27695-8002, USA / Received January 6, 1994
Summary
After about 20 days, hypocotyl cuttings from 20-day-old loblolly pine (Pinus taeda L.) seedlings rooted easily in the presence of the auxin indole-3-butyric acid (IBA), with roots forming directly from xylem
parenchyma. In contrast, woody cuttings from 1–2-year-old hedged seedlings formed roots indirectly from callus tissue in 60–90
days, but IBA had little effect on rooting. Variation in rooting among hypocotyls from both half- and full-sib families was
highly significant in response to IBA, and rooting did not occur within 20 days unless IBA was applied. Hypocotyls from poor
rooting families tended to produce fewer roots per cutting than hypocotyls from good rooting families. Rooting by woody cuttings
and hypocotyl cuttings from the same nine full-sib families was weakly correlated, raising the possibility that at least some
common genetically controlled processes were affecting rooting by both types of cutting. The phytotropin N-1-naphthylphthalamic acid (NPA), supplied at 1 µM with 10 µM IBA, significantly inhibited rooting by hypocotyl cuttings from
both good and poor rooting families, but there was no significant family × treatment interaction. Family variation in rooting
ability may be a function of the frequency of occurrence of auxin-responsive cells in the hypocotyls.
Keywords:
indole-3-butyric acid, N-1-naphthylphthalamic acid, Pinus taeda, Pinus elliottii, phytotropin, slash pine.
