Long-term ozone exposure of potato: free radical content and leaf injury analysed by Q-band ESR spectroscopy and image analysis.

This paper presents Q-band electron spin resonance (ESR) studies on free radicals (FR) generated in potato leaves exposed to different O3 levels in open-top chambers (OTC), together with a quantitative study of the relationship between FR signal intensity and area of potato leaf damage. The advantages of Q-band when compared to X-band ESR spectroscopy are analysed, the main advantage being an absence of overlapping between Mn(II) and FR signals, allowing a quantitative study of FR signal intensity. This study also reports on a graphical method developed to quantitatively measure the damaged area on leaves caused by ozone exposure. Results indicate a direct relationship between FR signal intensity (measured as area under the signal) and percentage of O3 damage and clearly demonstrate a close relationship between visible ozone-induced symptoms and permanent FR concentration in potato leaves.