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)

Elevated ground-level ozone acts as a phytotoxic pollutant that enters leaves and causes oxidative stress, reducing photosynthesis and plant growth. When photosynthesis is suppressed, crops yield less and trees show foliar injury, while sensitive plant species exhibit slower growth and lower productivity. This combination—lower yields and visible leaf damage along with reduced growth—best matches the ecosystem effects of ozone exposure. The other ideas don’t fit: ozone isn’t about soil becoming more compact, it doesn’t typically increase water retention in leaves (it tends to stress stomata and can raise water loss), and ecosystems do experience effects, so saying there’s no impact isn’t accurate.