Effects of SO2 on photosynthesis and peroxidase activity in Scots pine needles

Short-term exposure to high concentrations of SO₂ caused a temporary decrease in the photosynthetic rate, while both short-term and long-term exposure to low concentrations of SO₂ increased photo-synthesis after the exposure. Low SO₂ concentrations did not cause any change in peroxidase activity. Thus peroxidase activity does not seem a suitable method in monitoring latent injury caused by low SO₂ concentrations.