Needle and root responses of small Pinus sylvestris seedlings exposed to sulphur dioxide and simulated acid rain

Abstract

Six‐week‐old Pinus sylvestris seedlings were exposed separately and simultaneously to sulphur dioxide and simulated sulphuric acid irrigation applied through the growth medium. At the end of experiments the growth of seedlings and the sulphur content of the needles were measured and the structural changes in the primary needles and growing long root tips at the light and electron microscope level were observed. Seedlings exposed to sulphur dioxide showed an increase in needle sulphur content without visible alterations or changes in the growth of seedlings. In needle mesophyll cell chloroplasts thylakoid swelling and decrease in size of starch grains were observed. Combined sulphur dioxide and simulated sulphuric acid irrigation caused greater ultrastructural alterations in needles than sulphur dioxide alone. Acid irrigation alone did not have any effect on the needles, but it caused injuries in the root cortical cell ultrastructure, whereas sulphur dioxide alone did not cause any observable structural effects on the roots.