Long-Term Effects of Gibberellin on the Growth of Loblolly Pine Seedlings

A study of the long-term effects of gibberellin on the growth of potted loblolly pine seedlings was carried out from June 1958 to Oct. 1959. Seedlings growing under long-day photoperiod were treated monthly for 9 months with gibberellin, in aqueous solution and in hydrous lanolin paste. Concentrations of 10, 100 and 1000 ppm of gibberellin were used in spray applications while 50 mg of pure lanolin (control), 25, 50 and 75 mg of lanolin containing 1% GA were used in hydrous paste application. Although spray applications of gibberellln produced significant increases in height growth (observed for 17 months), when treatment was discontinued the difference between treated and control seedlings decreased. The most consistent effect of gibberellin on loblolly pine seedlings seems to be reduction of root-shoot ratio.