Reproduction

Abstract

Initiation of the first reproductive organs (also termed strobili or flowers) is commonly considered the end of the juvenile phase and the onset of reproductive maturity in forest trees (Wareing 1959; Giertych 1976c; Poethig 1990). The evidence to date suggests that this phase change is correlated with some minimum number of growth cycles and/or minimum tree height or size (see Chalupka and Cecich 1997). Consequently, Dormling et al. (1968) proposed two ways of shortening the juvenile phase in Picea abies under controlled conditions: (1) if the deciding factor is the number of completed growth cycles, it would be possible to accelerate a phase change by shortening the individual growth cycles; (2) if the deciding factor is determined by tree size, then an accelerated change in phase could be achieved by artificial stimulation of growth in phytotron conditions.