Influence of Stock Plant Carbohydrate and Nitrogen Content on Rooting Stem Cuttings of Hedged Loblolly Pine

Abstract

Containerized, 2.5-year-old, hedged stock plants of four, full-sib families of loblolly pine (Pinus taeda L.) were fertilized daily with a complete nutrient solution containing 10, 25, 40, 55, or 70 ppm N, which resulted in a range of stock plant soluble carbohydrate (SCHO) and tissue N levels. SCHOs included myo-inositol, glucose, fructose, sucrose, and raffinose. Nitrogen concentrations and SCHO: N ratios ranged from 1.23% to 2.24% and 16:1 to 29:1, respectively. Softwood cuttings were taken in May and July 1995 and placed under intermittent mist. May cuttings rooted at significantly greater percentages than July cuttings (60% vs. 34%). Averaged over all N treatments, the best rooting family (56%) contained the highest tissue concentration of SCHOs (465 mg·g–1 dry weight) and had the highest SCHO: N ratio (26:1), whereas, the poorest rooting family (39%), exhibited the lowest level of SCHOs (357 mg·g–1 dry weight) and the lowest SCHO: N ratio (21:1). Rooting exhibited a quadratic response in regards to N fertilization levels and tissue SCHO concentrations. For both rooting trials, maximum rooting (83%) was noted for May cuttings taken from stock plants of one family fertilized with 40 ppm N, which corresponded to a tissue N concentration of 1.95% and a SCHO: N ratio of 22:1.