Article Growth and Photosynthetic Responses of Seedlings of Japanese White Birch, a Fast-Growing Pioneer Species, to Free-Air Elevated O3 and CO2 Mitsutoshi Kitao 1,* , Evgenios Agathokleous 2 , Kenichi Yazaki 1 , Masabumi Komatsu 3 , Satoshi Kitaoka 4 and Hiroyuki Tobita 5 1 Hokkaido Research Center, Forestry and Forest Products Research Institute, Sapporo 062-8516, Japan;
[email protected] 2 Key Laboratory of Agrometeorology of Jiangsu Province, School of Applied Meteorology, Nanjing University of Information Science & Technology (NUIST), Nanjing 210044, China;
[email protected] 3 Department of Mushroom Science and Forest Microbiology, Forestry and Forest Products Research Institute, Tsukuba 305-8687, Japan;
[email protected] 4 Research Faculty of Agriculture, Hokkaido University, Sapporo 062-0809, Japan;
[email protected] 5 Department of Plant Ecology, Forestry and Forest Products Research Institute, Tsukuba 305-8687, Japan;
[email protected] * Correspondence:
[email protected] Abstract: Plant growth is not solely determined by the net photosynthetic rate (A), but also influ- enced by the amount of leaves as a photosynthetic apparatus. To evaluate growth responses to CO2 −1 −1 and O3, we investigated the effects of elevated CO2 (550–560 µmol mol ) and O3 (52 nmol mol ; 1.7 × ambient O3) on photosynthesis and biomass allocation in seedlings of Japanese white birch (Betula platyphylla var. japonica) grown in a free-air CO2 and O3 exposure system without any lim- Citation: Kitao, M.; Agathokleous, E.; itation of root growth. Total biomass was enhanced by elevated CO2 but decreased by elevated Yazaki, K.; Komatsu, M.; Kitaoka, S.; O3.