Nitrogen metabolism inErica and soybean,two species differing by their sensitivity to inorganic N source

Growth of soybean was not altered, whatever the inorganic N-source (NO₃, NH₄ or a NO₃/NH₄ mixture); conversely, growth of Erica x darleyensis plants in vitro decreased more in. NH₄ medium than in a NO₃ medium, compared to a NO₃/NH₄ medium. The GS/GOGAT pathway (in NH₄ medium), the nitrate and nitrite reductase activities (in NO₃ medium), as the contents in free nitrogenous forms and total nitrogen (in NO₃ and NH₄ media) were not more altered in Erica than in soybean, compared to a NO₃/NH₄ medium. PEPCase activity was the highest in soybean irrespective of the N-treatments; the involvement of PEPCase in N-metabolism could be explained by its function in ionic and osmotic balances rather than its function in supplying carboxylates as acceptors for NH₄-assimilation.