| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1998: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1997: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
Some corn (Zea mays L.) genotypes produce husk leaves (laminae extending from the husk) which on a per unit area basis, contribute more photosynthate to grain production than culm leaves. However, leaf area of the husk leaves is limited. Little is known about the changes in husk leaves area. Factors affecting leaf area expansion in relation to leaf development and genotypic difference in husk leaf size were examined in terms of cell component synthesis.
Experiment 1, Effect of leaf development : A field experiment was conducted to quntify methanol (MeOH)-soluble fraction (cytosol) and incorporation of ^<13>C-labeled photosynthate in cell walls from nine days before silking (DBS) to silking. The ear Leaf of flint corn (Fl of N-19 by X-15) was subjected to ^<13>CO_2 eight DBS.Results : (1) The husk leaf attained half its maximum apparent photosynthtic rate when it had 8% of its maximum leaf area at 4 DBS.(2) At 9DBS, neutral sugars in the MeOH-soluble fraction accounted for most of non-st
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arch carbohydrates within the husk leaf (68%) , while hemicellulose and cellulose fractions showed low figures. At silking, however, sugars in the hemicellulose and cellulose fractions increased by 23% and 56%, respectively. (3) Results ^<13>CO_2 labeling suggest that during rapid husk leaf development, MeOH-soluble fraction decreases, while the hemicellulose fraction fluctuates, and cellulose fraction increases.
Experiment 2, Effect of genotypic difference in husk leaf size : Similar experiment was conducted using field- grown three flint corn pure lines differing in husk leaf size. Results : (4) A flint corn genotype, X-15 showed a greater husk leaves area mainly due to a longer duration of the rapid expansion and a higher expansion rate than other genotypes. (5) The predominant sugar species in the cytosol fraction was glucose (GIc), however in the hemicelllose fraction, xylose (Xyl) and arabinose (Ara) were more dominant than other sugars. (6) ^<13>CO_2 labeling experiment indicated that during rapid husk leaf development, ^<13>C atom % in Xyl remained low in the cytosol, while it increased remarkably in the hemicellulose, and the increase was more pronounced in X-15. These suggest that Xyl plays an important role on synthesis of hemicellulose, which leads to a greater husk leaf area. Less
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