Influence du type de nutrition azotée sur le déclenchement de la chlorose du sapin de Nordmann (Abies nordmanniana, Spach, 1842)

Abstract

(Fig. 4). Le (Fig. 3); -a Ca increase in the needles (Fig. 3) and particularly in the roots (Fig. 4) (Fig. 3) and also by the root analyses (Fig. 4).The Nordmann fir behaves as a &dquo;nitratophobic&dquo; species that has difficulty in reducing the absorbed nitrate nitrogen. At the needle level, chlorosis is characterized by a decrease in the HCF extractable Fe and Mg contents if the plant control cultivated in ammoniacal conditions is considered as reference.Moreover, the common feature of the two kinds of chtorosis is the accumulation of a large quantity of calcium at the root level. This is due to the formation of calcium carbonate coatings (Figs. 5 and 6) resulting from CaCO 3 precipitation from the bicarbonate-rich solutions as shown by the carbon isotope analyses.

The role of ectomycorrhizal fungi in calcareous soil tolerance by "symbiocalcicole" woody plants

“…Reduction of the calcium concentration in the leaves was noticed with Eucalyptus dumosa (Lapeyrie and Chilvers, 1985) and Pinus nigra nigricans (Le Tacon, 1978 (Piou, 1979) (Gay, 1987) or on the plant gene expression (Hilbert and Martin, 1988), the role of mycorrhizal fungi in calcareous soil could also be considered through their action at the soil-plant interface. It is clearly established that some fluxes of ions are dependent on the presence of the symbiotic fungus (Rygiewicz and Bledsoe, 1984 (Khalil et al, 1989). Perturbation of nitrogen metabolism observed on calcareous soil in the absence of mycorrhizas (Le Tacon, 1978) appears to be overcome through the symbiosis.…”