The study looked at how olive trees respond to drought by analyzing the phenolic compounds in their roots. They found that water-stressed olive trees had higher levels of total phenols compared to well-watered trees. Verbascoside was the main compound in well-watered trees, while oleuropein was dominant in water-stressed trees. The ratio of oleuropein to verbascoside varied between the two conditions, suggesting it could be a marker for drought resistance in olive trees. Additionally, certain flavonoid glucosides showed significant changes under water stress.