Olive Oil for Dressing Plant Leaves so as to Avoid O3 Injury

The persistence of high ground-level ozone (O-3) concentration in most regions of the northern hemisphere has severe implications to crop production, wild plant conservation, and forest sustainability. Therefore, methods for plant protection against O-3 and O-3 biomonitoring are of high relevance; however, there is not a method that can be applied in cultivations, which are intended for human consumption. After spraying bean (Phaseolus vulgaris L. cv. Pinto) seedlings with ethylene diurea, olive oil, or myclobutanil and exposing them to O-3-enriched air (90 nmol mol(-1)) for a week (8 h day(-1)), we found that commercial olive oil can be effectively used as a protectant of plants against O-3. This protection is attributed to avoidance of O-3 uptake into the mesophyll, via decreased stomatal conductance. Olive oil can be applied even in organic cultivations, either for biomonitoring purposes or for short-term protection of plants during O-3 episodes. Further studies are needed in order to investigate potential direct reaction of O-3 with olive oil. Yet, attention should be paid when myclobutanil is applied to plants which are used for O-3 biomonitoring purposes due to potential confounding effects by increasing O-3-caused visible injury to plant leaves.