The hydroxyl radical (·OH) is generated in polluted dew on the needle surfaces of Japanese red pine (Pinus densiflora Sieb. et Zucc.). This free radical, which is a potent oxidant, is assumed to be a cause of ecophysiological disorders of declining trees on the urban-facing side of Mt. Gokurakuji, western Japan. Mists of ·OH-generating N(III) (HNO2 and NO2-) and HOOH+Fe+oxalate solutions (50 and 100 μM, pH 5.1-5.4) simulating the dew water were applied to the foliage of pine seedlings grown in open-top chambers in the early morning. Needles treated with 100 μM N(III) tended to have a greater maximum CO2 assimilation rate (Amax), a greater stomatal conductance (gs) and a greater needle nitrogen content (Nneedle), suggesting that N(III) mist acts as a fertilizer rather than as a phytotoxin. On the other hand, needles treated with 100 μM HOOH+Fe+oxalate solution showed the smallest Amax, gs, and Nneedle, suggesting that the combination of HOOH+Fe+oxalate caused a decrease in needle productivity. The effects of HOOH+Fe+oxalate mist on pine needles were very similar to the symptoms of declining trees at Mt. Gokurakuji.
All Science Journal Classification (ASJC) codes
- Health, Toxicology and Mutagenesis