Growth and Leaf Gas Exchange in Three Birch Species Exposed to Elevated Ozone and CO2 in Summer
Growth and Leaf Gas Exchange in Three Birch Species Exposed to Elevated Ozone and CO2 in Summer
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DOI：
10.1007/s11270-012-1253-y
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发表时间：
2012-07
期刊：
影响因子：
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通讯作者：
Y. Hoshika;Makoto Watanabe;Naoki Inada;T. Koike
中科院分区：
文献类型：
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作者：
Y. Hoshika;Makoto Watanabe;Naoki Inada;T. Koike
我们研究了夏季臭氧和二氧化碳浓度升高对日本三种代表性桦树品种（山桦、帝王桦和白桦）生长和光合性状的影响。三种桦树种的幼苗在 16 个开顶室中生长，从 7 月到 10 月，它们暴露于两种水平的臭氧（每天 7 小时 6 和 60 nmol mol−1）以及两种水平的 CO2（白天 370–380 和 600 μmol mol−1）。在帝王桦或白桦中没有发现臭氧的不利影响，但在夏季，臭氧浓度升高会降低山桦的枝条生物量和净光合作用，并加速叶子脱落。升高的CO2促进了根部发育，从而降低了山桦和白桦的地上部干质量（茎+枝）与根干质量的比率（S/Rratio）。相比之下，由于光合作用的下调，帝王桦的干质量在环境二氧化碳和升高的二氧化碳之间没有差异。对二氧化碳和臭氧的综合影响的研究表明，二氧化碳浓度升高并没有改善夏末臭氧对山桦的影响。在考虑CO2对臭氧破坏的改善作用时，需要考虑物种和季节。
We examined the effects of ozone and elevated CO2concentration in summer on the growth and photosynthetic traits of three representative birch species in Japan (mountain birch, Monarch birch, and white birch). Seedlings of the three birch species were grown in 16 open-top chambers and were exposed to two levels of ozone (6 and 60 nmol mol−1for 7 h per day) in combination with two levels of CO2(370–380 and 600 μmol mol−1for daytime) from July to October. No adverse effects of ozone were found in the Monarch birch or the white birch, but elevated ozone in summer reduced branch biomass and net photosynthesis, and accelerated leaf abscission, in the mountain birch. Elevated CO2promoted root development and thereby reduced the ratio of shoot dry mass (stem + branch) to root dry mass (S/Rratio) in the mountain birch and white birch. In contrast, there was no difference in dry mass between ambient and elevated CO2for the Monarch birch, due to downregulation of photosynthesis. Studies of the combined effect of CO2and ozone revealed that elevated CO2did not ameliorate the effect of ozone on mountain birch in late summer. In considering the ameliorating effect of CO2on ozone damage, it is necessary to take account of the species and the season.