Journal Article Difference in photosynthetic responses to free air ozone fumigation between upper and lower canopy leaves of Japanese oak (Quercus mongolica var. crispula) saplings

Watanabe, Makoto  ,  Hoshika, Yasutomo  ,  Inada, Naoki  ,  Koike, Takayoshi

71 ( 3 )  , pp.227 - 231 , 2015-09 , The Society of Agricultural Meteorology of Japan(日本農業気象学会)
To clarify the difference of ozone (O-3) sensitivity of photosynthesis in leaves located different canopy positions, we investigated photosynthetic responses of Japanese oak saplings to free air O-3 exposure, and compared the results with Siebold's beech saplings reported previously. The O-3 at 60 nmol mol(-1) during daytime was fumigated for two growing seasons, from 6 August to 11 November 2011 and from 17 May to 10 November 2012. In June, August and October of 2012, we determined photosynthetic activity of upper and lower canopy leaves. The exposure to O-3 increased the ratio of intercellular CO2 concentration to ambient CO2 concentration in October, indicating stomatal sluggishness. We observed an O-3-induced, significant decrease in light-saturated net photosynthetic rate (A(sat)) with no significant interaction between O-3 effect and canopy position for A(sat). Therefore, we conclude that the O-3 sensitivity of photosynthesis in upper and lower canopy leaves was similar in Japanese oak, while our previous study reported that the upper canopy leaves of Siebold's beech have a higher O-3 sensitivity than lower canopy leaves.

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