Physiological responses of field-grown strawberry ( Fragaria × Ananassa duch.) exposed to acidic fog and ambient ozone

Abstract

Physiological responses of field-grown strawberry ( Fragaria × ananassa Duch. Chandler) were monitored to examine the mechanistic basis of acidic fog and ambient ozone (O 3) impacts on growth and yield. Strawberry plants were exposed to simulated fog (pH 7.24, 2.69, or 1.68) twice weekly for 11 weeks, singly or in combination with ambient levels of O 3 in open-top field chambers. Applications of highly acidic fog (pH 1.68) caused significant reductions in growth, but leaf gas exchange process rates on a leaf area basis were not significantly affected despite the development of interveinal necrosis. However, calculated rates of whole-plant photosynthesis were associated with the observed negative impacts of pH 1.68 fog on vegetative growth. In contrast, plants grown in ambient O 3 (whole-study 12 hr average of 66 ppb) exhibited no significant alterations in growth, but yields were higher than in plants exposed to charcoal-filtered air. Exposure to ambient O 3 induced depressions in leaf gas exchange on a unit areas basis (i.e. net photosynthesis, stomatal conductance of water vapor, and transpiration), but calculated whole-plant photosynthesis was similar in charcoal-filtered air and O 3-exposed plants due to differences in leaf area per plant (i.e. 14% higher in O 3-exposed plants). It is concluded that acidic fog-induced alterations in strawberry growth were predicated upon the development of extensive foliar injury leading to the inhibition of whole-plant photosynthesis. However, in O 3-exposed plants, whole-plant photosynthetic rates were conserved, suggesting that impacts on assimilate partitioning may play a more prominent role.