The effects of ozone episodes on autumn leaf fall in apple

SUMMARY Mature apple (Malus domestica Borkh.) trees were exposed to episodes of 100 and 150 nl I1 ozone in 1990 and 1991 respectively, in open-top chambers at the University of Nottingham, Sutton Bonington Campus, UK. The episodes were for 8 h daily and for not more than 3 d in succession, with a seasonal total of 37 d in each year. Leaf fall was monitored by counting leaves on marked shoots at frequent intervals. A significant interaction between ozone exposure and leaf age was observed: exposure to ozone accelerated autumn leaf fall in old leaves. The relationships between experimental conditions, leaf age and plant material are discussed, and the implications for UK flora are considered.