RESPONSES TO SO2 POLLUTION IN 41 BRITISH HERBACEOUS SPECIES

1. Seedlings of 41 British herbaceous species of contrasting functiona l type were screened for sensitivity to SO2 pollution in a large-scale 'Solardome' exposure facility. Sand was used as a growing medium and there was an ample supply of water and mineral nutrients. Plants were exposed continuously for 83 days to 100 nll(-1) SO2 (v/v in air), with a series of higher peaks of SO2 concentration, the frequency and dura tion of which increased with time. 2. Exposure to SO2 caused significa nt (P<0.05) reductions in the dry mass of whole plants, roots and shoo ts in the cases of 18, 19 and 12 of the species, respectively. General ly, the adverse effect on root growth was greater than the adverse eff ect on shoot growth. Total leaf area was reduced in seven species in r esponse to SO2. 3. Significant correlations were found between per cen t response to SO2 exposure and C-S-R functional type. These were expli citly related to relative growth rate in the seedling phase, a predict or of stress-tolerance. Slow-growing, perennial species (stress tolera tors), were less susceptible under exposure to SO2 than were faster-gr owing, perennial species (competitors) or faster-growing, annual speci es (ruderals). 4. The general pattern of species responses to SO2 was similar to that previously reported for O-3 fumigation but it contrast s markedly with that found among a similar range of species growing un der elevated CO2.