Junichi Naba

Tokyo University of Agriculture and Technology, Edo, Tōkyō, Japan

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Publications (2)1.93 Total impact

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    ABSTRACT: We examined the growth and photosynthetic responses of Japanese forest tree species to sulfur dioxide (SO2) under different nitrogen (N) loads to soil. We grew Quercus serrata, Fagus crenata, Castanopsis sieboldii, Larix kaempferi, Pinus densiflora, and Cryptomeria japonica seedlings in Andisol supplemented with N as NH4NO3 solution at 0, 20, and 50 kg ha−1 year−1. Seedlings were exposed daily to charcoal-filtered air or SO2 at 10, 20, and 40 nl l−1 for two growing seasons. Except for C. japonica seedlings, exposure to SO2 at a relatively low concentration stimulated whole-plant growth, especially under a relatively high N load. The effects of N load on the negative impact of SO2 on whole-plant growth were synergistic in Q. serrata, F. crenata, C. sieboldii, and P. densiflora, counteractive in L. kaempferi, and additive in C. japonica. In Q. serrata, F. crenata, C. sieboldii, and P. densiflora seedlings, the different responses of whole-plant growth to SO2 among the N treatments were because of the effect of N load on the response of the net photosynthetic rate to SO2. L. kaempferi seedlings showed N load-induced tolerance of whole-plant growth to SO2. This was explained by the effect of N load on the responses of photosynthesis and development of assimilative organs to SO2. The different growth responses to SO2 among the N treatments were explained by the effects of N load on the SO2 uptake rate (evaluated by stomatal diffusive conductance) or the accumulated SO2 uptake (evaluated by foliar S concentration).
    Trees 10/2012; 26(6):1859-1874. · 1.93 Impact Factor
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    ABSTRACT: 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 50kg 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 380μmol 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 ≤50kg ha−1 year−1 does not significantly change the sensitivity to O3 of growth and net photosynthesis of Fagus crenata seedlings.
    Water Air and Soil Pollution Focus 01/2007; 7(1):131-136.