Growth of Ryegrass (Lolium perenneL.) Exposed to SO2

Abstract

The effects of exposure to SO₂ (50 and 400 μg m⁻³ SO₂) on the growth, photosynthesis, and respiration of perennial ryegrass (Lolium perenne L.) cv. S23 were examined in two successive growth periods of 29 and 22 d. At the higher concentration of SO₂, there was some visible injury of the leaves and specific leaf area was reduced, but yield, net photosynthesis, and dark respiration of the plants were not significantly affected by exposure. The treatment was also without effect on the transpiration coefficient of the plants and their number of tillers. The plants exposed to the lower concentration of SO₂ showed no signs of injury and did not differ in any of the measured characteristics from plants grown in SO₂-free air. Content of S in the shoots increased linearly with the concentration of SO₂, the additional S being found in the sulphate fraction whilst organic S was unchanged. The results are discussed in relation to earlier findings that yield of ryegrass exposed to SO₂ may be reduced without visible signs of injury.