Cytokinins Associated With Metamorphic Vegetative Growth in Elaeocarpus hookerianus

Abstract

Elaeocarpus hookerianus, a species endemic to New Zealand, exhibits metamorphic vegetative growth. The juvenile characteristically has small, thin leaves and an entangled branch habit, whereas the adult is arborescent with larger leaves. A transitional stage with branch pattern and leaf morphology intermediate between the juvenile and adult forms is also discernible. The three developmental stages exhibited by this species provide an appropriate system for examining possible correlations between growth habit and cytokinin content. Except for an unknown non-hydroxylated cytokinin, the cytokinins detected in E. hookerianus were similar to those measured by others in various plants. A trend of decreasing concentration of active cytokinin and of increasing concentration of storage cytokinin as a percentage of total cytokinin was measured between juvenile, transitional and adult forest-grown leaves. This trend was confirmed by measuring cytokinins from leaves of juvenile and adult plants propagated and grown in a glasshouse. While cytokinin concentration changes were correlated with modifications in branching pattern and leaf morphology, further work is needed to establish if these are causally linked.