2000 Fiscal Year Final Research Report Summary
Effects of water and light environment on photosynthesis of trees distributed in temperate forest at different insertion levels
| Project/Area Number |
10640617
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
生態
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| Research Institution | Nara Women's University |
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Principal Investigator |
FURUKAWA Akio Nara Women's University, Faculty of Science, Professor, 理学部, 教授 (10124356)
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| Co-Investigator(Kenkyū-buntansha) |
FUJINUMA Yasumi National Institute for Environmental Studies, Research Coordinator, 地球環境研究センター, 研究管理官 (10219032)
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| Project Period (FY) |
1998 – 2000
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| Keywords | Viburnum awabuki / Photosynthesis / Midday depression / Stomatal conductance |
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| Research Abstract |
The diurnal changes in net photosynthetic rates, stomatal conductance and the environmental factors were determined in Viburnum awabuki K.Koch using a portable photosynthetic system (LI-COR, LI-6400). The rates of net photosynthesis thus obtained were plotted against PAR (Photosynthetically Active Radiation) and the forenoon photosynthetic rates were higher than the rates obtained in the afternoon. The tree height was ca.3 m, so the water supply from roots to leaves might not be limited, though the highest resistance for water supply is in the root surface. To confirm this hypothesis, we measured the photosynthetic rates of cut stems and got the results that photosynthetic rates were not reduced in the afternoon. If the reduction of net photosynthetic rates in the afternoon is caused by the stomatal closure by high water saturation deficit and/or lowered water potential of leaves, the enrichment of CO_2 concentration might overcome the deficiency of CO_2 supply to chloroplasts. Then, we measured the diurnal changes in net photosynthetic rates at 1500 μmol CO_2 mol^<-1>. The depression of photosynthetic rates in the afternoon was not observed but the rates were higher than the rates detected in the forenoon. These results suggest that the stomatal closure and the limitation of CO_2 supply to chloroplasts should be the main factor causing the depression of photosyntheis in the afternoon. Furthermore, by highering the CO_2 concentration inhibits the photorespiration rates and enhanced the photosynthetic rates while leaf temperature was high in the afternoon.
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