THE INTERACTIVE EFFECT OF IRRADIANCE AND SOURCE OF NITROGEN ON GROWTHAND ROOT RESPIRATION OF CALAMAGROSTIS-EPIGEJOS

Growth and respiratory processes of Calamagrostis epigejos (L.) Roth w ere studied as part of a comprehensive ecological project aimed at exp laining the acclimation potential of some perennial grasses upon chang es in climatic and edaphic factors after logging activity in forests. We investigated the relative growth rate (RGR), the respiration rate a nd the contribution of the different respiratory pathways in roots of Calamagrostis epigejos grown at two levels of irradiance and with nitr ate or ammonium as N-source. The respiration rate as well as the RGR d ecreased significantly but the leaf area ratio (LAR) increased upon tr ansfer to shade. The LAR increase was caused by both a greater specifi c leaf area (SLA) and a greater leaf weight ratio (LWR). The relative contribution of the alternative (AP) and the cytochrome pathways to to tal respiration rate was the same in both radiation regimes. The ammon ium form of N-nutrition had a significant stimulative effect on AP act ivity in shaded plants. The AP capacity was significantly higher in am monium-fed plants grown at both irradiance levels. A possible role of the AP in plants with low energy input and with ammonium ions as N-sou rce is discussed.