North Central Forest Experiment Station, U.S. Department of Agriculture, Forest Service, 54501, Rhinelander, Wisconsin, USA.
Planta. 1976 Jan;128(3):185-93. doi: 10.1007/BF00393227.
The ability of a developing cottonwood (Populus deltoides Bartr.) leaf to export (14)C-labeled assimilates begins at the lamina tip and progresses basipetally with increasing LPI. This progression indicates that portions of leaves function quasi-independently in their ability to export (14)C-photosynthate. Although most of the exported radioactivity was recovered in the petiole as water-80% alcohol-soluble compounds, there was also substantial incorporation into the chloroform and insoluble fractions. This observation indicates that assimilates translocated from the lamina are used in structural development of the petiole. Freeze substitution and epoxy embedding were used to prepare microautoradiographs for localization of water-soluble compounds. Radioactivity was found in all cell types within specific subsidiary bundles of the petiole. However, radioactive assimilates appeared to move from the translocation pathway in the phloem toward active sinks in the walls of the expanding metaxylem cells. Translocation in the mature xylem vessels was not observed.
发育中的三角叶杨（Populus deltoides Bartr.）叶片输出（14）C 标记同化物的能力始于叶尖，并随 LPI 的增加向基端推进。这种推进表明叶片的部分区域在输出（14）C-光合产物的能力上具有准独立性。尽管大部分输出的放射性物质都以水-80%酒精可溶化合物的形式回收在叶柄中，但也有大量放射性物质掺入到氯仿和不溶性部分中。这一观察结果表明，从叶片中转运的同化物被用于叶柄的结构发育。使用冷冻替代和环氧树脂包埋来制备水可溶性化合物的微自动放射性自显影。在叶柄的特定次级束的所有细胞类型中都发现了放射性。然而，放射性同化物似乎从韧皮部的转运途径向正在扩张的木质部细胞壁中的活跃汇处移动。在成熟的木质部导管中没有观察到转运。
