Involvement of secondary metabolism in the response of two differently sensitive poplar clones to a long-term exposure to ozone

At the end of the 15-days O3 exposure (60 nl l-1, 5 h day-1), the O3-sensitive poplar clone (Eridano) displayed a significant H2O2 accumulation and a less pronounced increase in NO levels as compared to the tolerant clone I-214. In both clones, the activity of some of the main enzymes involved in the phenylpropanoid metabolism was significantly enhanced by O3 exposure. Results lead to hypothesise a preferential involvement of NO, rather than H2O2, in inducing such a response.