The gibberellin synthesis inhibitors, ancymidol and flurprimidol, promote in vitro rooting of white pine microshoots.

Ancymidol and flurprimidol were tested for their ability to induce in vitro rooting on axillary proliferated shoots of white pine (Pinus strobus L.). Shoots were treated for 30 days (pulse) with growth regulators, then subcultured to 0.5X medium for conifer morphogenesis without growth regulators. A pulse treatment containing 5 μM ancymidol and 0.54 μM naphthaleneacetic acid resulted in 43% rooted shoots, whereas a pulse treatment with 0.54 μM naphthaleneacetic acid alone resulted in 7% root formation. Flurprimidol also stimulated rooting of white pine shoots, but was less effective than ancymidol. No detrimental effects on shoot growth were observed with the gibberellin synthesis inhibitors at the 5 μM concentration used. Some rooted shoots were successfully acclimatized to the greenhouse.