Intermittent shoot growth in saplings of Acanthopanax sciadophylloides (Araliaceae)

Abstract

Annual shoot growth on a monopodial orthotropic stem of saplings of Acanthopanax sciadophylloides in a deciduous mixed forest in northern Japan was classified into two distinct phases: stagnant (S-phase) and extension phase (E-phase). Both S- and E-phases were observed in an intermittent manner on the same stem. S-phase growth was repeated more on stems in closed canopies than in canopy gaps. S- and E-phase shoots differed in morphological and phenological performance. S-phase shoots flushed and stopped elongation by mid-spring, while E-phase shoots continued elongating until mid-summer with expansion of new leaves. S-phase shoots also allocated less biomass to stems than E-phase shoots. These results suggest that the intermittent sequence of the two growth phases corresponds to time-differentiation of adaptive performance in this species. Saplings of A. sciadophylloides are distributed over a wide range of environments as a result of this temporal adjustment.