Modification of ozone effects on photosynthetic capacity of winter wheat (Triticum aestivum L. CV. perlo) at different levels of water availability

Abstract

Attached leaves were used for the determination of the photochemical capacity by means of a portable fluorimeter. Repeated fluorescence measurements showed the negative effects of ozone on photochemical capacity and these negative effects increased with increasing ozone doses. But impairments of photochemical capacity were smallest if severe water stress co-occurred with ozone exposures. The upper leaf sides experienced more reduction of photochemical capacity in well-watered plants than the lower leaf sides, possibly by the additional effect of light stress on the upper leaf sides. In diurnal studies, a decline of Fv/Fm was observed at noontime and a recovery at evening in both control and ozone-fumigated leaves at two extreme water capacities (w.c.) (75% and 35% of w.c.). The extent of depression and recovery of Fv/Fm was not significantly varying. The oscillations of Fv/Fm could be due to short-term disturbances in the photosynthetic capacity, due to oxidative stress.