Some Biochemical Compounds Associated with Rooting of Carya illinoensis Stem Cuttings1

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Abstract
Hardwood and softwood pecan cuttings were exposed to various preconditioning treatments prior to propagation. Some softwood cuttings girdled and those girdled and etiolated, rooted and/or retained their leaves. These were the only softwood cuttings that retained their leaves throughout the rooting period. Cuttings from other treatments displayed no rooting activity. Three to 4 areas of endogenous rooting-cofactor activity corresponding to specific Rf values were located in basal extracts of all cuttings by paper chromotography and the mung bean rooting bioassay. Two consistent areas of root inhibitory activity corresponding to specific Rf values were evident in cuttings from all preconditioning treatments, except one. Cool temperature storage of hardwood cuttings removed the root-inhibitory activity in one of these areas. A compound similar to juglone was extracted from leaves and stems of the pecan stock plants. This compound was associated with one of the areas of root-inhibitory activity. “Units of promotion,” values based upon the relative amounts of endogenous root promoting cofactors and rooting inhibitors present, were reliable indicators of rooting potential. Factors other than rooting-cofactor compounds appear to limit the rooting of pecan cuttings. The presence of root inhibitory substances appears to play a significant role in the rooting complex of pecan stem cuttings.

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