Abstract
To clarify the effects of ambient ozone concentrations on the physiological functions and the growth of beech (Fagus crenata) seedlings, an open-top chamber study was carried out for three growing seasons of 2002-2004 in the Tanzawa Mountains. Two-year-old beech seedlings were exposed to non-filtered air (NF) or charcoal-filtered air (CF) in open-top chambers. The mean concentrations of ozone in the NF and CF treatments were 0.046 and 0.011 ppm, respectively. Chlorophyll content (SPAD value), dark adapted photosystem II quantum yield (Fv/ Fm), growth parameters (height, stem diameter, total dry weight), defoliation and the number of buds were measured. Ozone significantly reduced SPAD value in autumn 2003 and during the growing season of 2004. The Fv/ Fm significantly reduced at the end of the growing season of 2004. Height and stem diameter significantly reduced in 2004, and the total dry weight reduced by 61.3% in the NF treatment compared to that in the CF treatment at the end of the experiment. Early defoliation was observed in the NF treatment. The reduction in the number of buds in the winter of 2004 suggested that the growth of beech seedlings will be reduced greatly in the next year. These results obtained in the present study shows the negative effects of ozone on beech under field conditions in the Tanzawa Mountains.
