TOWARDS UNRAVELING THE COMPLEX INTERACTIONS BETWEEN MICROCLIMATE, OZONE DOSE, AND OZONE INJURY IN CLOVER

This paper describes the results of a sales of experiments designed to identify the relative importance of various factors which modify the responses of a sensitive species to ozone. The experiments were conduc ted in a closed chamber exposure system, enabling clover plants (Trifo lium subterraneum L. cv Geraldton) to be exposed to ozone doses rangin g from 0 to 1800 ppbh, accumulated over 40 ppb (AOT40) for 7 h d(-1), over 1 to 3 days. Microclimatic conditions during exposure ranged from 80 to 460 mu mol m(-2) s(-1) photosynthetically active radiation (PAR ), 26 to 61 percent relative humidity (%RH) and 16 to 36 degrees C tem perature. No clear dose response relationships was established for 1, 2 or 3 day exposures due to the influence of micro climatic and other factors during exposure. Artificial Neural Networks were used as a too l to identify patterns within the dose response data set and to clarif y the effects of various microclimatic and dose topography responses, during multiple day exposures. Analysis of the trained neural network revealed that AOT40 on individual exposure days was the most important influences PAK on the first and third days of exposure, the mean rela tive humidity and the mean temperature for all days also had strong in fluences. Leaf age also had an influence but this was weaker. This pap er describes thee results in relation to the influences acting upon th e plant and how these affect ozone uptake and resulting ozone injury.