1998 Fiscal Year Final Research Report Summary
HORMONAL FACTORS DETERMINING A PREFERENCE IN GROWTH AND FILLING OF GRAINS AT DIFFERENT SPIKELET POSITIONS WITHIN THE PANICLE OF RICE.
| Project/Area Number |
08660012
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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 |
作物学
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| Research Institution | TOHOKU UNIVERSIYU |
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Principal Investigator |
NAKAMURA Teiji TOHOKU UNIVERSITY,FACULTY OF AGRICULTURE,RESEARCH ASSOCIATE, 農学部, 助手 (70155844)
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| Project Period (FY) |
1996 – 1998
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| Keywords | rice / grain / spikelet position / cytokinin / abscisic acid / grain growth / grain filling / source / sink ratio |
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| Research Abstract |
It is known that the grains at the lower spikelet positions within the panicle of rice (Oryza sativa L.) grew slowly during early growth, especially under reduced source/sink ratio conditions, and the lower growth rate of these grains was not caused by the limitation of carbohydrate supply, and was accompanied by reduction of endosperm cell number and final gram weight. Cytokinin application to roots through water culture solution during the grain filling enhanced the early growth of gram at the lower spikelet position. Direct application of abscisic acid (ABA) to the young grain at lower spikelet position enhanced its early growth, too. This growth promotion by cytokinin or ABA was not caused by the increment of carbohydrate supply. In addition, these treatments increased the final weight and endosperm cell number in grain at lower spikelet position. These effects strongly resemble the effects of the treatment increasing source/sink ratio. Foliar application of ABA enhanced the early growth and final weight of the grain at lower spikelet position. ABA levels in the grain at the higher spikelet position during early growth stage were higher than that in the grain at the lower spikelet position, significantly, and ABA levels in the grain at the lower spikelet position increased significantly by degraining treatment. But, there were no significant differences in grain cytokinin levels either between spikelet positions or treatments. These results suggest strongly that ABA contained in the young grain is transported from the leaf and acts as a growth promoter in natural grain development, and ABA levels in the young grains determine a preference in growth and filling of grains at different spikelet positions within the rice panicle.
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