Effects of Auxins and other Factors on the Rooting of Pinus contorta Dougl. Cuttings

The effects are investigated of applications of NAA and IBA upon root number, root type and time to form first roots in cuttings of Pinus contorta Dougl. Cuttings treated with NAA generally formed thick, fleshy, unbranched roots, while those receiving IBA produced a thin, finely-divided root system. Both types of roots developed when the two hormones were applied together. The time taken for first roots to form, and the final number of rooted cuttings were also greatly increased when hormones were applied in the range 1–10 μg per cutting. Boric acid applied in combination with hormone treatments increased rooting, but boron alone was ineffective. There were marked differences between clones in their rooting responses to both hormone and boron treatments.