The effect of ozone and season on the pool sizes of cyclitols in Scots pine (Pinus sylvestris)

Summary The effect of 100 and 200 g · m^-3 (50 and 100 ppb) ozone and ambient air on 4-year-old grafts of a Scots pine clone was tested in closedtop fumigation chambers. Ozone decreased the myo-inositol and inccreased the pinitol levels in the 1-year-old needles, whereas the effect in the current-year needles was less distinct. In neither case did ambient air lead to any detectable effects on these parameters compared with controls. However, there was a pronounced chamber effect in the levels of myo-inositol and pinitol compared with trees standing in the open field, where inositol was higher and pinitol lower. There is some evidence, based on visible symptoms as well as biochemical changes, that season is an important modifier of the effect of ozone on Scots pine.