Differences in Architecture and Shoot Growth during Stagnant and Extension Growth Phases of Acanthopanax sciadophylloides(Araliaceae)

The shoot growth of a deciduous tree, Acanthopanax sciadophylloidesFranch. et Savat. shows inter-annual intermittent repetitionof two distinctive phases, a stagnant growth phase (S-phase)and vigorous extension-growth (E-phase). To help understandthe differentiation mechanism, shoot development was studiedover time in both shoot phases. S-phase and E-phase shoots weredistinguished from each other by morphological traits: S-phaseshoots are characterized by higher allocation to leaves anda shorter period of stem growth, while E-phase shoots show continuousstem extension over the growing season. Specific leaf area didnot differ between the two phases. This shoot differentiationwas similar to the morphological differentiation of shoots betweenlong vs. short shoots found in some temperate trees. Leavesof both phases were well-dispersed through adjustment of petiolelength and leaf-blade size to reduce mutual shading within ashoot. Stem-wood density of current-year shoots was lower inE-phase compared with S-phase shoots. Leaves produced earlyin the season affected the growth phase of the following year.These results suggest that annual shoot differentiation of A.sciadophylloides was determined during the previous season andreflects leaf productivity in a given habitat during that growingseason. Copyright 2001 Annals of Botany Company Acanthopanax sciadophylloides, Araliaceae, biomass allocation, intermittent shoot growth, leaf display, shoot architecture, shoot differentiation