ROOTING POTENTIAL IN PLUM HARDWOOD CUTTINGS .2. RELATIONSHIPS BETWEEN SHOOT VARIABLES AND ROOTING IN CUTTINGS FROM DIFFERENT SOURCES

There was a positive correlation between shoot length and the proximal diameter of the prepared cutting in stockplant sources of Prunus insitititia 'Pixy' that had different rooting potential. The precise relationship depended on source, with shoots from a severely pruned micropropagated source, and those developing from the trunks of various stockplants, usually being thinner for any given length than normal distal cuttings from pruned and non-pruned conventional source stockplants. To a large extent rooting percentage, root numbers and root length increased between sources as the overall ratio of proximal stem diameter to shoot length decreased. Cuttings from the relatively thick, short shoots of the unpruned source were among the poorest rooting, while those from the relatively thin, long shoots from the trunk, and from the micropropagated source, rooted best. This between-source effect reflected the fact that within the less ready rooting sources there was also a negative correlation between the proximal diameter of the cutting and its rooting ability. This relationship was lost progressively as the rooting potential of sources increased, thus giving no opportunity for a trend to occur in the trunk-derived cuttings from the micropropagated source where virtually all cuttings rooted.