Differentiation of the dynamic variables affecting rooting ability in juvenile and mature cuttings of cherry ( Prunus avium )

SummaryThe rooting potential of four types or origins of Prunus avium cuttings from the same mature trees (over 20 years-old) was compared using a mist propagation bed during early Summer (June). The cuttings originated from juvenile sucker shoots of the current and previous year, and mature crown shoots (current year’s lateral ‘long-shoots’ and multi-year terminal ‘short shoots’). The morphological differences in inter-node length, stem diameter and leaf area between the four cutting types were highly significant (P = 0.05), leading to large differences in cutting volume and, so it is argued, to assimilate reserves. Juvenile cuttings rooted well (65% and 77% rooting for hardwood and softwood shoots, respectively), while mature cuttings rooted poorly (4% and 7% for mature hardwood and softwood cuttings, respectively). Leaf abscission was significantly more frequent in mature hardwood cuttings (16 – 78%) than in the other cutting types (1.6 – 9%) at the end of the propagation period. Leaf loss resulted from two processes: abscission and leaf rotting. Physiologically (i.e., in carbon assimilation, leaf transpiration and stomatal conductance), the four cutting types were not significantly different early in the post-severance period (day-4); but, by day-22, stomatal conductance was lowest in mature hardwood cuttings that still had leaves. At this time, the most physiologically-active unrooted cuttings were from juvenile hardwood and mature softwood shoots. The extent of physiological and morphological variability between cutting types and their probable impact on processes affecting rooting ability is complex and highly interactive. Consequently, it is not possible to explain the causes of the variation in rooting ability between juvenile and mature cuttings, although this study suggests that the constraints to rooting are likely to reflect physiological differences between the different cutting types. It is concluded that, to resolve the debate about factors that affect the rooting ability of juvenile and mature cuttings (i.e., ontogenetic vs. physiological ageing), there is a need to achieve morphological and physiological comparability in the tissues.