Anatomical and Biochemical Events duringin vitroRooting of Microcuttings from Juvenile and Mature Phases of Chestnut

A comparative study of thein vitrorooting process of chestnut(Castanea sativa)shoots of the same genotype exhibiting juvenile(easy-to-root) and mature (difficult-to-root) characteristicsis described. The two culture lines originated from shoots collectedfrom the base (juvenile) and crown (mature) of an 80-year-oldtree. Anatomically, juvenile and mature shoots had a similarstem structure at the time of excision, the main differencebeing that secondary phloem and xylem were more developed inmature than in juvenile shoots. A substantial reactivation ofcell division was observed in both shoot lines 48 h after theroot inductive treatment with indole-3-butyric acid. Meristemoidsand root primordia developed only in juvenile shoots, beginning3 d after the inductive treatment, and the first adventitiousroots emerged 10 d after treatment. However, in mature shootspericlinal divisions of cambial cells occurred, especially onthe phloem side, maintaining the normal orientation of the cambialderivatives. No meristemoids formed in this proliferating tissue.During the time course of the rooting process, more endogenousindole-3-acetic acid (IAA) was detected in mature than in juvenileshoots, indicating that the level of IAA is not the limitingfactor accounting for the lack of rooting capacity in matureshoots. The levels of polyamines (putrescine, spermine and spermidine)were also higher in mature than in juvenile shoots.Copyright1999 Annals of Botany Company Adventitious rooting, anatomy, auxins,Castanea sativaMill., chestnut, juvenile phase, mature phase, polyamines, tissue culture.