Scientia Horticulturae, 10 (1979) 395--399 395 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands EFFECT OF ACID OR BASE PRETREATMENT ON AUXIN RESPONSE OF DAMASK ROSE CUTTINGS M. KHOSH-KHUI and E. TAFAZOLI Department of Horticulture, College of Agriculture, Shiraz University, Shiraz (1ran) (First received 24 July 1978; in revised form 18 December 1978) ABSTRACT Khosh-Khui, M. and Tafazoli, E., 1979. Effect of acid or base pretreatment on auxin re- sponse of Damask rose cuttings. Scientia Hortic., 10: 395--399. Hardwood stem cuttings of Damask rose (Rosa damascena Mill.) were dipped in H2SO 4 or NaOH prior to application of 0, 1000, 2000 or 3000 mg 1 "1 indolebutyric acid (IBA) or naphthaleneacetic acid (NAA). Acid pretreatment significantly increased root number, root length and root dry weight per cutting, but did not affect rooting-percentage. Rooting was significantly enhanced by auxin pretreatment, and NAA was superior in increasing root length and root fresh weight; 2000 mg 1 "1 of auxin was the most suitable concentration for promotion of rooting under the conditions of the study. INTRODUCTION Damask rose (Rosa damascena Mill.) is grown in many parts of Iran for ex- tracting rose water and oil. Traditionally, the propagation of this plant is ac- complished with either hardwood stem cuttings or suckers from old plants. Although the first practice is preferred for its convenience, most growers use the second method since many cuttings fail to produce roots. Auxins have been variable in their effectiveness in promoting adventitious root formation in other species of Rosa. Papandreou (1972) used different con- centrations of IAA or NAA on cuttings of R. indica major soon after cutting or after 3 weeks at 5 ° C. Rooting was increased with 500 mg 1 "1 IAA or 2000 mg 1 "1 NAA in cuttings which did not receive cold treatment. Bhujbal and Kale (1973) treated R. multiflora, R. bourboniana and R. moschata cuttings with various concentrations of IAA, IBA or IAA+IBA and R. multiflora produced the greatest rooting-percentage (90%), and number and length of roots with 1000 mg 1 "I IAA+IBA. R. b6urboniana performed relatively poorly throughout, doing best in IBA 1000 mg l "1. All treatments improved the rooting and growth of R. moschata cuttings, especially IBA at 1500 mg 1-1 and IAA+IBA at 500 mg 1 "1 of each. Azimi and Bisgrove (1975) reported that R. multiflora cuttings showed the highest root-dry-weight/cutting with 750 mg 1 "1 IBA, whereas cuttings of R.