Lifting Date Influences the Ability of Auxins to Promote Root Regeneration of Colorado Spruce

Abstract

Abstract The inability of older conifer seedlings to regenerate new roots after bare-root transplanting can lead to plant death. Lifting date and auxin treatments were evaluated for their effects on root regeneration of Colorado spruce (Picea pungens Engelm.). Roots of five-year-old plants were treated monthly during fall and spring with 1000, 5000, or 10,000 mg/L of indole-3-butyric acid (IBA), 5000 mg/L of phenyl indole-3-thiolobutyrate (P-ITB), or 100% ethanol (control). After treatment, plants were grown in a greenhouse for 30 days before total number, length and dry weight of new roots were determined. Spruces treated with 1000 and 5000 mg/L of IBA in November had the greatest new root weight (1.4 g) and number (5000), respectively, per plant compared to 0.1 g and 200 roots per plant for controls. Plants dug in May produced the least number, weight and length of new roots for all treatments. Plants treated with P-ITB produced consistently greater numbers of new roots over the first three lifting dates than did controls. Absolute ethanol appeared to inhibit root regeneration. Data indicate that lifting date affected the ability of auxin to stimulate root regeneration on bare-root Colorado spruce.