Influence of Ambient Ozone Pollution on Olive Leaf Gas Exchange Irrigated with Saline Water

Abstract

Saline water is often available for irrigation and ambient ozone pollution is significant in the Mediterranean region. These two factors may negatively affect cultivated plant productivity. We studied the effects of a combination of these stress factors on leaf gas exchange of young olive trees, a major crop in the above region. Two-years-old 'Konservolea' and 'Kalamata' olive plants grafted on seedling rootstock were grown in sand: perlite mixture irrigated with half strength Hoagland's solution containing or not 100 mM NaCl. In open top chambers, the plants received outside air with ambient ozone or charcoal-filtered air from April to September. Leaf gas exchange parameters and chlorophyll fluorescence were measured periodically. High ozone concentrations from May to September able to damage plants (daylight mean ozone concentration >60 nL L(-1)) did not affect the olive leaf functions studied, showing that young olive trees are relatively resistant to ozone levels found around the Mediterranean region. Irrigation with 100 mM NaCl solution decreased stomatal conductance by around 45%, photosynthetic rate by more than 35% and Fv/Fm values below 0.75. Both studied olive cultivars showed similar behavior to salinity stress possibly due to the seedling rootstock on which both cultivars were grafted. The combination of salinity and ambient ozone stress did not result in any further effects to leaf gas exchange besides the ones from the salinity stress alone. (C) 2011 Friends Science Publishers