EFFECT OF NITROGEN STRESS ON GROWTH, SOLUBLE METABOLITES, AND GLUTAMINE SYNTHETASE ACTIVITY OF JACK PINE CALLUS CULTURES

Abstract

Jack pine (Pinus banksiana Lamb.) callus cultures were grown in half-strength unmodified Litvay medium (control) and in media containing either no-nitrogen or nitrate. Almost no growth occurred in absence of nitrogen and in medium containing only nitrate. Glutamine synthetase (GS) activity was drastically reduced in comparison to callus grown in control medium. The pool of amino acids decreased by 66% in medium containing nitrate, and further by 50% in absence of nitrogen. Meanwhile total and reducing sugars sharply increased, and were 14 times higher in N-NO₃ ⁻ and 22 times higher in nitrogen-free medium. Thirteen amino acids were identified in the control. Changes in the abundance and the relative content of amino acids confirmed that glutamine is the preferred nitrogen transport compound in Pinus. Jack pine cultures seemed to have a low capacity for nitrate uptake and assimilation as shown by the low GS activity and the decrease of glutamine content in nitrate-fed calli.

ACKNOWLEDGMENTS

We thank M.J. Houle for her excellent technical assistance in biochemical analysis. This research was funded by a FODAR grant (Réseau des Universités du Québec) to S.L. and M.F.T., a grant (Coopération Québec/Provinces canadiennes) from Ministére de l'Enseignement supérieur et de la Science du Québec to M.F.T. and a grant from MCUO, Ontario-Québec Exchange program to C.C. G.C.R. received a fellowship from Ministére de l'Enseignement supérieur et de la Science du Québec.