Polyamines and glutathione metabolism in N fertilized Scots pine seedlingsduring cold hardening

Scots pine (Pinus sylvestris L.) seedlings in an experimental field in nort hern Finland (65 degrees N) were subjected to two doses (0.5 or 1.0 g per s eedling) of ammonium nitrate (NH4NO3 x Ca(OH)(2)) fertilizer on two differe nt dates (June 6 or July 6, 1936). The effect of an increased supply of nit rogen (N) on certain compounds related to N metabolism and cold hardening w ere investigated. Samples for the analysis of free polyamines (PAs), glutat hione, glutathione reductase (GR; EC 1.6.4.2) and gamma-glutamyltranspeptid ase (gamma-GT; EC 2.3.2.2) were harvested on three occasions during cold ha rdening in autumn 1936 (on Aug. 5(th), Aug. 19(th) and Sept. 30(th)). The l evels of PAs generally increased as a function of dose and delay in fertili zation, while responses of glutathione concentration, proportion of reduced glutathione (GSH %), GR and gamma-GT activities varied. PA levels generall y decreased during hardening while responses of the compounds of glutathion e metabolism varied. Glutathione concentration in fertilized plants tended to decrease during hardening, while that in non-fertilized ones showed no c lear response. The GR activity increased considerably and the gamma-GT acti vity showed no significant response during hardening.