| Autor: |
Kitao M; Hokkaido Research Center, Forestry and Forest Products Research Institute, Hitsujigaoka 7, Sapporo, 062-8516, Japan. kitao@ffpri.affrc.go.jp., Agathokleous E; Hokkaido Research Center, Forestry and Forest Products Research Institute, Hitsujigaoka 7, Sapporo, 062-8516, Japan.; Key Laboratory of Agrometeorology of Jiangsu Province, Institute of Ecology, School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing, 210044, China., Harayama H; Hokkaido Research Center, Forestry and Forest Products Research Institute, Hitsujigaoka 7, Sapporo, 062-8516, Japan., Yazaki K; Department of Plant Ecology, Forestry and Forest Products Research Institute, Matsunosato 1, Tsukuba, 305-8687, Japan., Tobita H; Department of Plant Ecology, Forestry and Forest Products Research Institute, Matsunosato 1, Tsukuba, 305-8687, Japan. |
| Abstrakt: |
Constant mesophyll conductance (g m ), and two-resistance g m model (involved in resistances of cell wall and chloroplast), where g m reaches maximum under higher CO 2 concentrations, cannot describe the phenomenon that g m decreases with increasing intercellular CO 2 concentration (C i ) under relatively higher CO 2 concentrations. Yin et al. (2020) proposed a g m model, according to which the ratio of chloroplastic CO 2 concentration (C c ) to C i is constant in the two-resistance g m model, which can describe the decreasing g m with increasing C i . In the present study, we investigated the relationship between C c and C i in leaves of Japanese white birch by using simultaneous measurements of gas exchange and chlorophyll fluorescence under various CO 2 concentrations, light intensities, and during progressive drought. Across the range of ambient CO 2 from 50 to 1000 μmol mol -1 , and light intensities of 50 to 2000 μmol m -2 s -1 , measured under well irrigation, the ratio of C c to C i kept constant. During the progressive drought, overestimated C i due to stomatal patchiness and/or cuticular transpiration was empirically corrected (threshold: stomatal conductance < 0.08 mol H 2 O m -2 s -1 ) from the A/C i response measured under adequate irrigation. The ratio of C c to C i during progressive drought (predawn leaf potential reached ≈ - 2 MPa) also remained constant irrespective of soil drying rate in various pot sizes. The present study suggests the involvement of some physiologically regulative mechanisms to keep C c :C i ratio constant, which might act on g m in addition to the physical interaction of diffusive resistances in the cell components. |
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