Root Regeneration of Liriodendron tulipifera in Response to Auxin, Stem Pruning, and Environmental Conditions

Abstract

Root regeneration of tulip tree ( Liriodendron tulipifera L.) was greater when seedlings were transplanted in the spring than in the fall. Indolebutyric acid–potassium salt (IBA) applied to the roots increased root regeneration with the greatest response at 1000 to 3000 mg liter −1 in the spring and 3000 mg liter −1 in the fall. Root regeneration and shoot growth increased as time of chilling at 2°C prior to transplanting increased from 0 to 1680 hours; 1008 hours satisfied the chilling requirement. Photoperiod did not directly influence root regeneration during either season. Root regeneration and shoot growth of shoot-pruned plants interacted with season, IBA treatment, and level of stem pruning. Decreasing sunlight intensity by 20%, 47%, or 74% reduced root regeneration and shoot growth. IBA improved root initiation over untreated plants at all light intensities tested, but subsequent growth of these roots decreased with decreased light.