© 1996 Heron Publishing—Victoria, Canada
Requirements for in vitro rooting of Quercus robur and Q. rubra shoots derived from mature trees
M. C. Sanchez, M. C. San-Jose, A. Ballester and A. M. Vieitez
Instituto de Investigaciones Agrobiológicas de Galicia (CSIC) Apartado 122, 15080 Santiago de Compostela, Spain / Received February 2, 1996
Summary
Stabilized shoot cultures initiated from crown material of six adult Quercus robur L. trees and from basal epicormic shoots of a Quercus rubra L. tree showed good in vitro rooting capacity. An initial five-day dark period generally improved the rooting response but
was detrimental to plantlet quality. There were clonal differences in rooting capacity. The concentration and exposure time
of the indolebutyric acid (IBA) treatment were critical for root induction. In both species, best rooting efficiency was achieved
by culture in medium containing 25 mg l–1 IBA for 24 h and subsequent transfer to an auxin-free medium containing 1% activated charcoal. For all clones tested, the
charcoal benefited both shoot quality and root system development, the latter being enhanced by the formation of many lateral
roots. Total root system area and length, measured with a digital image analyzer, were significantly greater in medium containing
charcoal than in medium lacking charcoal. Because darkening the basal part of the shoots with aluminum foil during the rooting
phase only caused a small increase in rooting, we conclude that the large effect of charcoal on rooting was the result of
adsorption of inhibitory compounds from the medium or the explant or both, rather than of basal darkening. Other factors affecting
the rooting response of Q. robur were: (a) the position on the tree of the material from which cultures were initiated (the topophysical effect); and (b)
shoot quality. Recycling the same horizontally placed explant on multiplication medium allowed three successive crops of shoots
to be obtained, and rootability was typically maintained from crop to crop.
Keywords:
charcoal, image analysis, micropropagation, pedunculate oak, red oak.
