VEGETATIVE PROPAGATION OF CORDIA-ALLIODORA (RUIZ AND PAVON) OKEN - THE EFFECTS OF IBA CONCENTRATION, PROPAGATION MEDIUM AND CUTTING ORIGIN

The effects of different concentrations of IBA, rooting media and cutt ing origins on the rooting of leafy stem cuttings of Cordia alliodora (Ruiz & Pavon) Oken were investigated in three experiments using non-m ist propagators. During the rooting period, changes in dry mass, photo synthetic rate, stomatal conductance and relative water content (RWC) of the cuttings were assessed. In Experiment 1, cuttings treated with 1.6% IBA achieved 70% rooting after 9 weeks. Bud growth in cuttings wa s inhibited by increasing concentrations of IBA, which were associated with higher final rooting percentages. No significant treatment diffe rences in RWC or dry mass were found between IBA concentrations, altho ugh the dry mass of cuttings in all treatments tended to increase duri ng the rooting period. In Experiment 2, higher rooting percentages wer e recorded in gravel (89%) and sand (88%) than in sawdust (76%). Altho ugh the water content of sawdust was relatively high, cuttings in this treatment displayed significantly lower stomatal conductances (g(s)), which may be attributed to death of stem tissue resulting from anoxia . In Experiment 3, highly significant differences (P < 0.01) were reco rded between node positions with respect to rooting percentage, values ranging from 21.3% for Node 2 to 46.3% for Node 5 (basal). Cuttings a ctively photosynthesized during the rooting period, with photosyntheti c rates (P-n) of 0.68-6.70 mu mol CO2, m(-2) s(-1) recorded. However, no clear relationship between P-n and rooting ability was apparent. Co ntrary to previous studies with this species, it was concuded that C. alliodora cuttings may be rooted relatively easily using the propagati on system described. However, the close relationships recorded between P-n, irradiance and leaf-air vapour pressure deficit (VPD) suggest th at propagator microclimate should be carefully managed if optimal root ing percentages are to be achieved.