Plant nutritional physiological studies on husk leaf size for failoring ideo-type of high-yielding corn

某些玉米（Zea mays L.）基因型产生谷壳叶（从谷壳延伸出的薄片），在单位面积的基础上，谷壳叶比秆叶对粮食生产贡献更多的光合作用。然而，壳叶的叶面积是有限的。关于壳叶面积的变化我们所知甚少。从细胞成分合成的角度探讨了影响叶面积扩大与叶片发育的因素和壳叶大小的基因型差异。试验1，叶片发育的影响：通过田间试验定量测定了出丝前9天（DBS）至出丝期间细胞壁中甲醇（MeOH）可溶性组分（胞浆）和^<13> c标记的光合产物的含量。N-19 × X-15处理的燧石玉米穗叶（Fl）在^<13>CO_2 - 8 DBS下处理。结果：(1)4 DBS时，壳叶在最大叶面积的8%时达到最大表观光合速率的一半；(2)在9DBS时，果皮叶中非主要碳水化合物的主要成分为meoh可溶性部分的中性糖（68%），而半纤维素和纤维素部分的非主要碳水化合物含量较少。然而，在吐丝时，半纤维素和纤维素组分中的糖含量分别增加了23%和56%。(3)结果^<13>CO_2标记表明，在谷壳叶快速发育过程中，meoh可溶性组分减少，半纤维素组分波动，纤维素组分增加。试验2，基因型差异对谷壳叶大小的影响：采用田间种植的3个谷壳叶大小不同的燧石玉米纯系进行了类似的试验。结果：(4)燧石玉米基因型X-15的壳叶面积较大，主要是由于快速膨大持续时间较长，膨大率高于其他基因型。(5)胞浆组分中的优势糖种为葡萄糖（GIc），而半纤维素组分中的优势糖种为木糖（Xyl）和阿拉伯糖（Ara）。(6) ^<13>CO_2标记实验表明，在谷壳叶快速发育过程中，细胞质中Xyl的^<13>C原子百分比保持在较低水平，而半纤维素中的^<13>C原子百分比显著增加，且在X-15中增加更为明显。这表明，在半纤维素的合成过程中，羟基起着重要的作用，导致了更大的壳叶面积。少

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 … More 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