C-allocation of flowering and deblossomed strawberry in response to elevated ozone.

•  A direct assessment of carbon distribution was made in fruiting and deblossomed strawberry (Fragaria × ananassa) in order to investigate the mechanisms of ozone (O ) action on fruit yield. •  Fruiting and deblossomed strawberry plants were treated with 92 ppb ozone or filtered air in open-top chambers for 69 d. Either leaf 1 or leaf 3 (from the most recent fully expanded) were exposed to a 30-min CO pulse. The sink strength and relative specific uptake of sink tissues were determined after 24 h and 48 h. •  Ozone did not affect the sink strength of fruits, but there was a trend to decreasing relative specific uptake of fruits when leaf 1, but not when leaf 3, was labelled. Ozone increased the sink strength of leaf blades younger than the source leaf when leaf 3 was labelled. Leaf 3, but not leaf 1, distributed assimilates mostly to the fruit. Ozone increased the sink strength of petioles in deblossomed plants. •  There were important differences between source leaves of different age, both in overall carbon allocation to different sinks and the effects of ozone, which influenced the relative importance for fruit yield of effects of ozone on photosynthesis and on carbon allocation.