| 研究実績の概要 |
野生1年草オオオナモミと作物イネの葉群動態を葉の平均滞留時間と光合成生産効率に着目して調べた。オオオナモミは密度を変えて育成し、群落内光環境の違いが植物の成長と繁殖をとおして葉群動態に与える影響を解析した。イネについては葉、シュート、個体の各レベルで窒素利用効率を解析した。野生1年草に比べて高いイネの収量窒素利用効率は、高い窒素生産力に起因し、平均滞留時間に差がないこと、乾物成長量に対する収量割合にも大きな差は見られないことを明らかにした。
Leaf dynamics: leaf mean residence time and photosynthetic efficiency
We studied leaf dynamics with respect to mean residence time and photosynthetic efficiency using cockleburs and rice. Cockleburs were grown at two densities and the effects on leaf dynamics of light gradient within a canopy and of nitrogen sink strength were studied. Light gradient was stronger in a dense stand due to mutual shading, while nitrogen sink strength was stronger in an open stand due to higher branching and reproductive activities. Nitrogen use efficiency (NUE) in rice plants was analyzed at leaf, shoot, and whole-plant level, with factorization into nitrogen productivity (NP) and mean residence time (MRT). No significant difference was found in MRT and harvest index between rice and wild annuals. The high NUE in rice was ascribed solely to its high NP. Because of high opportunity costs of reducing NP, MRT may not be increased further in rice. By contrast, high NUE in perennials was due to high MRT. Their NP was as low as wild annuals'.
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