The effects of low concentrations of sulphur dioxide on the growth of four broadleaved tree species.
Seedlings of Betula pendula, B. pubescens, Quercus robur and Acer pseudoplatanus were exposed to 150-170 mu g/m3 SO2 in fumigation chambers for periods of 14-71 weeks in 3 experiments. There was no significant effect on stem or root dry wt. in any of the species. Leaf area ratio and specific leaf area of B. pubescens were significantly reduced, but there was no effect on leaf growth in B. pendula or Q. robur. Leaf area and leaf wt. of A. pseudoplatanus were reduced only in one experiment. SO2 stimulated ht. growth in A. pseudoplatanus and Q. robur but only in the second year of exposure. Senescence of Q. robur leaves was advanced by 9-12 days. The sulphur content of leaves was increased in all species. It was concluded that the broadleaved spp. studied are more tolerant of prolonged exposure to SO2 than Pinus sylvestris [see FA 39, 2423].