How can ozone and acid deposition cause foliar injury in forest ecosystems even when soil pH remains buffered?

• A. Ozone damages leaf tissue and impairs photosynthesis; acid deposition damages leaf surfaces; both can reduce forest productivity independent of soil buffering.
• B. They only affect roots, not leaves.
• C. They enhance photosynthesis.
• D. They only matter if soil pH drops to below 4.

Answer: (A)

Atmospheric pollutants can injure leaves directly, without any change in soil chemistry. Ozone is highly reactive inside the leaf fluid once it enters through stomata, creating reactive oxygen species that damage cell membranes and chloroplasts. That damage lowers photosynthesis and overall leaf function, leading to reduced growth and productivity. Acid deposition on the leaf surface can irritate or burn the cuticle and epidermal tissues, disrupt gas exchange, and cause tissue injury on the leaf itself. Because these effects happen at the foliage level, they can occur even when soil pH is buffered and root health remains unaffected. So, ozone’s direct leaf tissue damage and acid deposition’s direct leaf surface injury can reduce forest productivity independently of soil conditions.