Effects of Nitrogen Supply on the Sensitivity to O₃ of Growth and Photosynthesis of Japanese Beech (Fagus crenata) Seedlings
2007
Yamaguchi, Masahiro | Watanabe, Makoto | Matsuo, Naoki | Naba, Junichi | Funada, Ryo | Fukami, Motohiro | Matsumura, Hideyuki | Kohno, Yoshihisa | Izuta, Takeshi
To obtain basic information for evaluating critical levels of O₃ under different nitrogen loads for protecting Japanese beech forests, two-year-old seedlings of Fagus crenata Blume were grown in potted andisol supplied with N as NH₄NO₃ solution at 0, 20 or 50 kg ha-¹ year-¹ and exposed to charcoal-filtered air or O₃ at 1.0, 1.5 and 2.0 times the ambient concentration from 16 April to 22 September 2004. The O₃ induced significant reductions in the whole-plant dry mass, net photosynthetic rate at 380 μmol mol-¹ CO₂ (A ₃₈₀), carboxylation efficiency (CE) and concentrations of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and total soluble protein (TSP) in the leaves. The concentrations of Rubisco and TSP were negatively correlated with the concentration of leaf acidic amino acid, suggesting that O₃ enhanced the degradation of protein such as Rubisco. The N supply to the soil did not significantly change the whole-plant dry mass and A ₃₈₀, whereas it significantly increased the CE and concentrations of Rubisco and total amino acid. No significant interactive effects of O₃ and N supply to the soil were detected on the growth, photosynthetic parameters and concentrations of protein and amino acid in the leaves. In conclusion, N supply to the soil at <=50 kg ha-¹ year-¹ does not significantly change the sensitivity to O₃ of growth and net photosynthesis of Fagus crenata seedlings.
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