Outlaw W H, Fisher D B
Department of Botany, University of Georgia, Athens, Georgia 30602.
Plant Physiol. 1975 Apr;55(4):699-703. doi: 10.1104/pp.55.4.699.
Leaflets of Vicia faba were pulse-labeled with (14)CO(2) to follow the subsequent movement of photosynthate between leaf tissues. Samples were taken during a (12)CO(2) chase, quick frozen, freeze-substituted, and embedded in methacrylate. Paradermal sections provided tissue samples consisting only of upper epidermis, palisade parenchyma, spongy parenchyma and veins, spongy parenchyma, or lower epidermis. Most CO(2) fixation occurred in the palisade parenchyma, but its (14)C content declined rapidly after labeling. Concomitant with the decline of activity in the palisade parenchyma, there was an increase in activity in the spongy parenchyma and upper epidermis and a slow increase in the lower epidermis. Activity in the palisade parenchyma and spongy parenchyma eventually reached similar levels and remained constant. Tissue samples containing veins were consistently the most radioactive, and activity in those samples showed a decline. Very little change occurred in the insoluble fraction from any tissue. The results support previous assumptions regarding the pathway of assimilate transport to the veins, and demonstrate the rapidity of such transport. Sucrose is apparently the principal mobile compound.
用(14)CO(2)对蚕豆叶片进行脉冲标记，以追踪光合产物随后在叶片组织间的移动。在(12)CO(2)追踪期间取样，快速冷冻，冷冻置换，并包埋在甲基丙烯酸酯中。平周切片提供了仅由上表皮、栅栏薄壁组织、海绵薄壁组织和叶脉、海绵薄壁组织或下表皮组成的组织样本。大部分CO(2)固定发生在栅栏薄壁组织中，但标记后其(14)C含量迅速下降。与栅栏薄壁组织中活性下降相伴的是，海绵薄壁组织和上表皮中的活性增加，而下表皮中的活性缓慢增加。栅栏薄壁组织和海绵薄壁组织中的活性最终达到相似水平并保持恒定。含有叶脉的组织样本始终是放射性最强的，且这些样本中的活性呈现下降。任何组织的不溶性部分变化很小。这些结果支持了先前关于同化物向叶脉运输途径的假设，并证明了这种运输的快速性。蔗糖显然是主要的可移动化合物。
