Stem-cutting anatomy and biochemical responses associated with competence for adventitious root differentiation in Acca sellowiana (Myrtaceae)

Abstract

Successful development of adventitious roots (AR) in cuttings imposes an important limitation to the propagation of woody plants and in some species, the ability to form AR is strongly affected by genotype. However, we lack an understanding of the differences among genotypes underlying such different responses in various species. We examined the anatomical and biochemical effects of exogenous indol-3-butyric acid and type of cutting in rooting experiments of two Acca sellowiana genotypes with contrasting rooting ability. New meristems developed outside the cambial ring, without callus formation by day fourteen and new adventitious roots grew through the cortex emerging by day 28. Both anatomically in vivo and biochemically in vitro, cuttings from the different genotypes behaved differently. We found anatomical differences between the genotypes that might explain the differences in rooting ability. An earlier development of a periderm was present in the difficult-to-root genotype. This secondary dermal tissue could be used as a reliable phase-change marker to distinguish juvenile from mature plant parts which have lost rooting capacity.