Name two ecosystem effects of elevated ground-level ozone.

• A. Increased soil compaction.
• B. Reduced crop yields and foliar injury to trees; suppressed growth and productivity in sensitive plant species.
• C. Enhanced water retention in leaves.
• D. No effect on ecosystems.

Answer: (B)

Ground-level ozone acts as a phytotoxic pollutant that causes oxidative stress in plants. When ozone enters through the stomata, it generates reactive oxygen species that damage cell components and the photosynthetic machinery. This leads to lower photosynthesis, reduced carbohydrate production, and slower growth. At the same time, ozone can produce foliar injuries that are visible on leaves, such as bronzing or stippling, especially in sensitive species like many trees. Over time, chronic exposure suppresses growth and productivity, altering forest composition and reducing crop yields. So the ecosystem effects you’d expect from elevated ozone include both reduced crop yields and foliar injury to trees, along with suppressed growth in sensitive plants. The other options don’t fit because ozone doesn’t cause soil compaction or enhanced water retention, and ecosystems do experience effects from ozone, not zero impact.