Housley T L, Schrader L E, Miller M, Setter T L
Department of Agronomy, University of Wisconsin, Madison, Wisconsin 53706.
Plant Physiol. 1979 Jul;64(1):94-8. doi: 10.1104/pp.64.1.94.
The influence of stage of development (preflowering versus flowering) in nodulated and nonnodulated soybeans (Glycine max [L.] Merr. cv. Wells) on partitioning of (14)C into assimilates following exposure of a soybean leaf to (14)CO(2) by both steady-state and pulse-labeling techniques was studied. Blades on the second fully expanded leaf from the stem apex were exposed to (14)CO(2). Radioactive assimilates were extracted from source leaf blades, petioles, and stems (both the path up and path down from source leaf), were separated into neutral (sugars), basic (amino acids), and acidic (organic acids, sugar phosphates) fractions by ion exchange chromatography. The basic fraction was further resolved using thin layer chromatography and the percentage of radioactivity recovered in each amino acid was determined.The distribution of radioactivity in the neutral, basic, and acidic fractions of the source leaf blades was significantly different from that of the transport path (petiole and stems). About 70% of the radioactivity in source leaf blades was recovered in the neutral fraction, whereas about 90% of the recovered radioactivity in the path was in the neutral fraction. (14)C-Aminoacids constituted 8 to 17% and 2 to 7% of the recovered radioactivity in source leaves and paths, respectively. Recovered (14)C in organic acids ranged from 13 to 20% and 2 to 7% in source leaves and paths, respectively. Partitioning of (14)C-assimilates among the neutral, basic, and acidic fractions was not affected by the presence of nodules or flowers. However, when steady-state labeling was compared to pulse labeling, a significantly lower percentage of (14)C was recovered in the neutral fraction with a concomitant increase in the basic fraction. Asparagine-arginine, serine, glutamate, gamma-aminobutyrate-alanine, and aspartate accounted for 69 to 85% of the recovered radioactivity in the basic fraction from the various treatments. [(14)C]Serine was significantly higher in pulse-labeling experiments, whereas glutamtate and proline were higher with steady-state labeling. [(14)C]Serine was significantly higher in nonnodulated plants than in nodulated plants, whereas gamma-aminobutyrate-alanine was significantly higher in preflowering plants as compared to flowering plants.
研究了结瘤和未结瘤大豆(大豆品种威尔斯)发育阶段(开花前与开花期)对通过稳态和脉冲标记技术将大豆叶片暴露于(^{14}CO_2)后(^{14}C)在同化物中的分配的影响。从茎尖数第二片完全展开叶的叶片暴露于(^{14}CO_2)。从源叶片、叶柄和茎(从源叶向上和向下的路径)中提取放射性同化物,通过离子交换色谱法将其分离为中性(糖类)、碱性(氨基酸)和酸性(有机酸、糖磷酸酯)组分。使用薄层色谱法进一步分离碱性组分,并测定每种氨基酸中回收的放射性百分比。源叶片的中性、碱性和酸性组分中的放射性分布与运输路径(叶柄和茎)的放射性分布显著不同。源叶片中约70%的放射性在中性组分中回收,而在运输路径中回收的放射性约90%在中性组分中。(^{14}C) - 氨基酸分别占源叶和运输路径中回收放射性的8%至17%和2%至7%。有机酸中回收的(^{14}C)在源叶和运输路径中分别为13%至20%和2%至7%。(^{14}C) - 同化物在中性、碱性和酸性组分之间的分配不受根瘤或花的存在的影响。然而,当将稳态标记与脉冲标记进行比较时,中性组分中回收的(^{14}C)百分比显著降低,同时碱性组分增加。天冬酰胺 - 精氨酸、丝氨酸、谷氨酸、γ - 氨基丁酸 - 丙氨酸和天冬氨酸占各种处理碱性组分中回收放射性的69%至85%。在脉冲标记实验中,([^{14}C])丝氨酸显著更高,而在稳态标记中谷氨酸和脯氨酸更高。在未结瘤植物中([^{14}C])丝氨酸显著高于结瘤植物,而与开花植物相比,开花前植物中的γ - 氨基丁酸 - 丙氨酸显著更高。