THE EFFECTS OF OZONE EPISODES ON AUTUMN LEAF FALL IN APPLE

Mature apple (Malus domestica Borkh.) trees were exposed to episodes o f 100 and 150 nl l-1 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 successi on, with a seasonal total of 37 d in each year. Leaf fall was monitore d by counting leaves on marked shoots at frequent intervals. A signifi cant interaction between ozone exposure and leaf age was observed: exp osure to ozone accelerated autumn leaf fall in old leaves. The relatio nships between experimental conditions, leaf age and plant material ar e discussed, and the implications for UK flora are considered.