Polyamines and glutathione metabolism in N fertilized Scots pine seedlings during cold hardening

Scots pine (Pinus sylvestris L.) seedlings in an experimental field in northern Finland (65 degrees N) were subjected to two doses (0.5 or 1.0 g per seedling) of ammonium nitrate (NH4NO3 x Ca(OH)(2)) fertilizer on two different dates (June 6 or July 6, 1936). The effect of an increased supply of nitrogen (N) on certain compounds related to N metabolism and cold hardening were investigated. Samples for the analysis of free polyamines (PAs), glutathione, glutathione reductase (GR; EC 1.6.4.2) and gamma-glutamyltranspeptidase (gamma-GT; EC 2.3.2.2) were harvested on three occasions during cold hardening in autumn 1936 (on Aug. 5(th), Aug. 19(th) and Sept. 30(th)). The levels of PAs generally increased as a function of dose and delay in fertilization, while responses of glutathione concentration, proportion of reduced glutathione (GSH %), GR and gamma-GT activities varied. PA levels generally decreased during hardening while responses of the compounds of glutathione metabolism varied. Glutathione concentration in fertilized plants tended to decrease during hardening, while that in non-fertilized ones showed no clear response. The GR activity increased considerably and the gamma-GT activity showed no significant response during hardening.