Biochemical changes in needles of Pinus radiata D. Don trees in relationship to long-term ozone exposure indices

Ambient concentrations of ozone in Europe are high enough to cause negative effects on vegetation. Therefore, many efforts have been made to determine exposure indices and critical levels for protection of vegetation. In this context, the choice of a suitable attribute to determine the pollutant eff ect is of paramount importance. Until now, much of the work has been done w ith attributes such as biomass or growth. In the present work correlation f actors have been established between biochemical parameters (peroxidase act ivity, ascorbate and sulfhydryl contents) of Pinus radiata trees and exposu re indices of ozone. Our results show that peroxidase cannot be used as an indicator of effects of long-term exposure to ozone but still remains as an excellent indicator of short-term ozone fluctuations in the field. Ascorba te may act as an intermediate indicator responding to both short fluctuatio ns and long-term exposures to ozone. Finally, sulfhydryl may be used as a l ong-term indicator in relation to the AOT (average over threshold) exposure index. Our results also point to the fact that Pinus radiata may be affect ed by ozone at AOT values lower than 10 ppm.h as already observed with othe r tree species. (C) 2001 Elsevier Science Ltd. All rights reserved.