GROWTH AND PIGMENT PRODUCTION IN 2 SUB-ARCTIC GRASS SPECIES UNDER 4 DIFFERENT UV-B IRRADIATION LEVELS

The aim of the experiment was to test the sensitivity of grasses from a subarctic region to a range of different ultraviolet-B (UV-B, 280-32 0 nm) levels. Seedlings of Calamagrostis lapponica and tillers of Cala magrostis purpurea were grown for 50 days in a greenhouse at 4 differe nt levels of UV-BB, radiation (no UV-B, ambient W-B,UV-B corresponding to 15 and 25% ozone depletion, respectively, at 68 degrees N, norther n Sweden on July 27th). In C. purpurea total plant dry weight was sign ificantly reduced at the 15% level compared to all other treatments, w hilst tiller number was reduced when compared to the non UV-B treatmen t only. Reduced growth at the 15% level was accompanied by significant increases in shoot to root ratio (S:R), leaf area ratio (LAR) and lea f weight ratio (LWR), which were due to changes in both specific leaf area (SLA) and root growth. Similarly, in C. lapponica there were redu ctions in total dry weight at the 15% level, although differences in p artitioning were only observed in LWR which was significantly greater than in the non UV-B treatment. There was a difference in tiller numbe r in C. lapponica between all treatments. A reduced number of tillers was observed with increasing W-B exposure from zero UV-B to the 15% le vel, whilst tiller number was significantly higher at the 25% level th an in all other treatments. In C. lapponica, differences were apparent in the amount of UV absorbing pigments. Plants exposed to ambient UV- B and the 15% level had significantly more UV-B absorbing compounds th an those in the 25% and non UV-B treatments. All these results suggest that the 15% ozone depletion level was the most harmful to plant grow th and few damaging effects were observed at the higher 25% ozone depl etion level.