Asexual propagation of Juniperus procera from Ethiopia:: a contribution to the conservation of African pencil cedar

The rooting responses of branch cuttings of Juniperus procera Hochst. ex Endl., obtained from young (Class I) and mature (Class II) source plants to four plant growth regulators (PGRs), namely, indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), naphthaleneacetic acid (NAA), and 2,4-dichlorophenoxyacetic acid (2,4-D) applied at various concentrations (10(-3)-10(-9) M) were examined in sand culture. Assessments on rooting, as well as an root number and root length, of the cuttings were conducted 16 and 32 weeks after treatment. Histological origin of root primordia was examined microscopically. Establishment and performance of stecklings were assessed on sample rooted cuttings. Only 2% of the cuttings obtained from young (Class I) source plants rooted 16 weeks after treatment; and 24% of these cuttings rooted 32 weeks after treatment. Of the cuttings collected from mature (Class II) source plants, only a single cutting could root 32 weeks after treatment. The maximum attainable rooting percentage was 60, and was obtained from cuttings of Class I stock plants when these were treated with IAA at 10(-7) M. Cuttings treated with 10(-6) M IAA and the control resulted in a relatively higher root number (17+/-4.1 and 17+/-1.7). Those that were treated with 10(-3) M NAA yielded relatively longer roots (372.3+/-51.5 mm). Mean root number and length of the control were significantly greater than most of the PGR treatments (p<0.05). In this species, cells of callus tissue, cambium, cortex, as well as xylem cells, could give rise to root primordia. Stecklings with well developed root systems were easily established and grew well indicating the suitability of the species for propagating through vegetative means. (C) 1998 Elsevier Science B.V. All rights reserved.