THE EFFECTS OF SO2 FUMIGATION ON THE NITROGEN-METABOLISM OF ASEPTICALLY GROWN SPRUCE SEEDLINGS

Aseptically grown spruce seedlings were cultivated in a hydroponic sys tem, where the roots were separated from the shoots by a gastight, sil icone material. The plants were fumigated with four SO2 concentrations (93, 190, 270 and 530 mu g m(-3)) for nine weeks. Up to 270 mu g m(-3 ) of S0(2), an inhibition of nitrogen metabolism (enzyme activities of nitrate reductase (NR) and glutamine sythetase (GS) and nitrate conte nt) in the shoot was compensated by a stimulation in the root, while n itrogen uptake was unaffected. Only the treatment with 530 mu g m(-3) of SO2 decreased enzyme activities, nitrate content in both roots and shoots as well as nitrate uptake, and inhibited the growth of plants. Increases in the content of thiols and superoxidismutase activity are discussed in terms of SO2 detoxtfication.