© 2001 Heron Publishing—Victoria, Canada
Root system architecture and receptivity to mycorrhizal infection in seedlings of Cedrus atlantica as affected by nitrogen source and concentration
Hassan Boukcim (1), Loïc Pages (2), Claude Plassard (1) and Daniel Mousain (1)
1. Unité de Science du Sol et des Symbiotes des Racines, Institut National de la Recherche Agronomique, 2 place Viala, 34060
Montpellier Cedex 1, France / 2. Unité de Recherche d'Ecophysiologie et Horticulture, INRA, Domaine Saint-Paul, Site Agroparc, 84914 Avignon Cedex 9, France / Received November 6, 1999
Summary
Effects of nitrogen (N) source and concentration on root system architecture and receptivity to mycorrhizal infection were
studied in seedlings of Atlas cedar (Cedrus atlantica Manetti) grown in root observation boxes in a controlled-environment chamber. Nitrogen was supplied in a solution containing
either NO3– or NH4+ at a concentration of either 0.25 or 5.0 mM. Root extension was recorded twice weekly by tracing the roots growing in contact
with the transparent face of the root observation box. Among treatments, lateral root production and branching density were
greatest with 5.0 mM NO3–. Inoculation with mycelium of Tricholoma cedrorum Malençon was carried out 3 months after the start of the N treatments. The highest percentage of mycorrhizal roots, and the
greatest amounts of living mycelium (estimated by the ergosterol assay) were observed in the NO3– treatments. Differences in root branching density among the N treatments were insufficient to explain the observed differences
among treatments in the extent of mycorrhizal infection of seedlings.
Keywords:
ammonium, Atlas cedar, mycorrhiza, nitrate, root system, Tricholoma cedrorum.
