Effect of nitrogen concentration and cotyledons on nitrogen preference in seedlings of Cedrus atlantica Manetti

The organic matter constitutes the most important source of nitrate and ammonium in coniferous forest soil, which are the two major nitrogen forms used by plants. The preference and/or adaptation of one N-form over another by seedlings genotypes is a determinant factor in the success of reforestation programs, not only for cedar species but any other forest essence. In a controlled growth chamber, the seedlings of two provenances of Cedrus atlantica M. (Gouraud and Moudmame) are grown on natural soil or on organic matter fertilized with different N-form and concentration. Our results show a high nitrogen requirement and a different preference towards nitrogen forms which is mainly manifested at secondary roots. On the other hand, variations in the cotyledons affect the growth and the response of the seedlings to the nitrogen form and thus reveal different forms of adaptation to nitrogen nutrition which are linked to the cotyledons and to the age of seedlings. The growth response of C. atlantica to nitrogen form and concentration is discussed in light of the effect of the provenance and cotyledons. Taken together, these results suggest that knowledge of the nitrogen requirements of the different genotypes of C. atlantica at the juvenile stage could be a good tool for successful reforestation of this forest species.