Experiments investigated the influence of drought conditioning stock plants and an auxin-based plant growth regulator (PGR) on adventitious root formation of terminal stem cuttings taken from containerized firebush and Fraser's photinia stock plants. Drought conditioning (DC) treatments were initiated in a glass greenhouse and included: irrigation every day (no DC), irrigation every other day (medium DC), and irrigation every fourth day (high DC). Plants were subjected to DC for 16 consecutive days. Following DC treatments, all plants were irrigated and left overnight. Terminal stem cuttings were taken the following day and an 0.3% auxin talc formulation was used as the PGR. Plant growth regulator/DC treatments included: no DC ± PGR, medium DC ± PGR, and high DC ± PGR. Cuttings were placed under intermittent mist and heating pads maintained media temperature. After 21 and 78 days cuttings were evaluated for rooting percentage, number of roots, and length of the longest root. For firebush, rooting percentage was near 100% for all treatments. Number of roots and length of longest root for firebush cuttings was greatest for cuttings treated with PGR. For Fraser's photinia cuttings, rooting percentage was highest for cuttings treated with high DC + no PGR treatments. Cuttings treated with medium DC or high DC ± PGR treatment produced the greatest number of roots, while mean root length was longest for cuttings treated with medium DC + PGR and high DC + no PGR.
Manuscript No. T-4-552 of the College of Agricultural Sciences and Natural Resources. Support for this project was provided in part by a grant from the State of Texas Higher Education Coordinating Board.
2Graduate Teaching Assistant and Assistant Professor, respectively.