title: High CO2 concentration increases relative leaf carbon gain under dynamic light in Dipterocarpus sublamellatus seedlings in a tropical rain forest, Malaysia.
abstract: Understory plants in tropical forests often experience a low-light environment combined with high CO2 concentration. We hypothesized that the high CO2 concentration may compensate for leaf carbon loss caused by the low light, through increasing light-use efficiency of both steady-state and dynamic photosynthetic properties. To test the hypothesis, we examined CO2 gas exchange in response to an artificial lightfleck in Dipterocarpus sublamellatus Foxw. seedlings under contrasting CO2 conditions: 350 and 700 μmol CO2 mol(-1) air in a tropical rain forest, Pasoh, Malaysia. Total photosynthetic carbon gain from the lightfleck was about double when subjected to the high CO2 when compared with the low CO2 concentration. The increase of light-use efficiency in dynamic photosynthesis contributed 7% of the increased carbon gain, most of which was due to reduction of photosynthetic induction to light increase under the high CO2. The light compensation point of photosynthesis decreased by 58% and the apparent quantum yield increased by 26% at the high CO2 compared with those at the low CO2. The study suggests that high CO2 increases photosynthetic light-use efficiency under both steady-state and fluctuating light conditions, which should be considered in assessing the leaf carbon gain of understory plants in low-light environments.
authors.affiliation: Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Tsukuba, Japan tomimatsu.hajime@nies.go.jp.
authors.forename: Hajime
authors.initials: H
authors.lastname: Tomimatsu
authors.affiliation: Center for Education and Research in Field Science, Agricultural Faculty, Shizuoka University, Ohya, Shizuoka, Japan.
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Iio
authors.affiliation: Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba, Japan.
authors.forename: Minaco
authors.initials: M
authors.lastname: Adachi
authors.affiliation: Forest Research Institute Malaysia, Kepong, Selangor, Malaysia.
authors.forename: Leng-Guan
authors.initials: LG
authors.lastname: Saw
authors.affiliation: Forest Research Institute Malaysia, Kepong, Selangor, Malaysia.
authors.forename: Christine
authors.initials: C
authors.lastname: Fletcher
authors.affiliation: Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Tsukuba, Japan.
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Tang
mesh_terms: D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D053958:Dipterocarpaceae / Q000378:metabolism*; D008027:Light; D008296:Malaysia; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D065947:Rainforest; D036226:Seedlings / Q000378:metabolism; D014197:Trees / Q000378:metabolism
chemical_list: D002245:Carbon Dioxide; D002244:Carbon
keywords: dynamic photosynthesis; elevated CO2; induction efficiency; lightfleck; tropical trees