Seasonal and SO2-induced changes in epicuticular wax of ryegrass

Epicuticular wax was extracted from SO₂-sensitive (S23) and SO₂-resistant (BR) genotypes of ryegrass (Lolium perenne) exposed continuously for 4 weeks to 0, 0.05 or 0.15 ppm SO₂ under winter or summer conditions. The differences found between genotypes in the composition of the acid and alkane fractions of the extracted wax were further modified by season and exposure to SO₂. Estimates of relative amounts of epicuticular wax showed that both genotypes produced more wax in the winter experiment, with BR producing more wax than S23. Exposure to 0.05 ppm in the winter experiment had little effect on the amount of wax produced by either genotype while exposure to 0.15 ppm SO₂ greatly reduced wax production in BR but increased wax production in S23. These changes in wax production could have been due to a general effect of SO₂ on metabolism regulating the flow of carbon into the pathways synthesizing wax components rather than to specific inhibition or enhancement at particular steps in these pathways. Exposure to SO₂ in the summer experiment had little effect on the amount of wax produced by both genotypes but did have an effect on wax composition.