1992 Fiscal Year Final Research Report Summary
Analysis for the process of leaf senescence and the causes promoting its senescence in crop plants.
| Project/Area Number |
02454039
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
作物
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| Research Institution | Tokyo University of Agric. & Tech. |
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Principal Investigator |
ISHIHARA Kuni Tokyo Univ. of Agric. & Tech. Agronomy, Professor, 農学部, 教授 (70014925)
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| Co-Investigator(Kenkyū-buntansha) |
OOKAWA Taiichiro Tokyo Univ. of Agric. & Tech. Agronomy, Assistant Professor, 農学部, 助手 (80213643)
HIRASAWA Tadashi Tokyo Univ. of Agric. & Tech. Agronomy, Associate Professor, 農学部, 助教授 (30015119)
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| Project Period (FY) |
1990 – 1992
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| Keywords | Leaf Senescence / Cytokinin / Conjugated Zeatin / Rice / Exudation / Mass Spectrometry / High Yielding Cultivar / 品種間差 |
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| Research Abstract |
It was reported that the yield in Akenohoshi (a high yielding rice cultivar) was about 1780 kg/ha higher than that in Nipponbare (a Japanese standard cultivar), and that Akenohoshi had a higher dry matter production capacity compared with Nipponbare. This was attributed to the maintenance of a higher net assimilation rate during the ripening period in the former. The higher net assimilation rate of Akenohoshi resulted from a slower leaf senescence than that of Nipponbare at the ripening stage. To clarify the cause of the slower senescence in Akenohoshi, changes in exudation rate and cytokinin activities in the exudates were measured in two varieties of rice. The exudation rates of Akenohoshi, the leaves of which remained green for a longer time, were higher than those of Nipponbare after the booting stage. Cytokinin activities in the exudates of Akenohoshi were higher than those of Nipponbare during the ripening period. Cytokinins in the exudates collected during the middle of the ripening stage were analyzed with mass spectrometry using deuterium-labeled standards. trans-Zeatin, trans-ribosylzeatin, and N^6-isopentenyladenosine were detected in the hydrolysates of highly polar fractions("conjugated zeatin") in the exudates of both cultivars. Therefore, we suggest that conjugated zeatin is an important form of cytokinin during the ripening stage. The level of each of the cytokinins in Akenohoshi was higher than that in Nipponbare.
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