Effects of NH⁺₄‐N and NO⁺₃‐N on growth and metabolism of Sphagnum magellanicum

Photosynthetic CO 2 ‐fixation, chlorophyll content, growth rate and nitrate reductase activity were used to examine the influence of NH + 4 ‐N and NO − 3 ‐N on Sphagnum magellanicum cultivated under defined conditions in phytotrons. NO − 3 ‐concentrations up to 322 μ M were found to be favourable. Increased NH + 4 concentrations, however, resulted in growth inhibition and decreased chlorophyll content at concentrations ≧ 255 μ M ; e.g. 600 μ M NH + 4 caused a 20% reduction of nitrate reductase activity and net photosynthesis. For raised bog Sphagna an improved standard nutrient solution is proposed with the following ion concentrations (μ M ): 55 Na + ; 17 K + ; 95 NH + 4 ; 22 Ca 2+ ; 22 Mg 2+ ; 2 Fe 3+ ; 20 Cl − ; 100 NO − 3 ; 57 SO 2‐ 4 ; 7.4 H 2 PO − 4 ; trace elements: A‐Z solution (Hoagland) 50 μl 1000 ml −1 ; pH 5.8.