PHOTOSYNTHETIC RESPONSE TO OZONE OF 2 POPLAR CLONES SHOWING DIFFERENTSENSITIVITY

The mature leaves of two clones of poplar were fumigated with 150 ppb of ozone for 5 h. In both clones a strong reduction in photosynthetic activity was observed, but the kind of the response appeared to be dif ferent. The resistant clone showed an effect at both stomatal and meso phyllic levels and this appeared to be a consequence of regulatory mec hanisms more than effects of O-2 injury. A rapid recovery of photosynt hetic ability was observed when the ozone was removed. The sensitive c lone appeared not to be able to undergo this regulatory sequence, so t he effects of ozone were stronger and not reversible. (C) 1998 Elsevie r Science Ltd.