Visual assessment of foliar injury induced by ozone on indicator tobacco plants: A data quality evaluation

A group of 50 inexperienced scorers were asked to estimate - using standard reference photos - foliar injury induced by the gas pollutant ozone on the supersensitive indicator plant tobacco (Nicotiana tabacum L.) cv. Bel-W3. The average accuracy level was 56.1% (95.9% when the classes nearest to the reality were also considered correct) and the average repeatability was 65 .4%. The extreme classes were easily scored. Central classes proved to be m ore difficult to be evaluated: this may depend on the fact that two leaves may have similar actual total injured area, but substantially different num bers and spatial distribution of the lesions. In some cases we observed a p revalence of overestimation errors in the high classes and underestimation in the low classes: this is in contradiction with the Weber-Fechner law. It is noteworthy the very short time required by operators to score, regardle ss of the results.