Department of Agricultural Biochemistry, East Campus, University of Nebraska, Lincoln, Nebraska 68583-0718.
Plant Physiol. 1983 Nov;73(3):740-5. doi: 10.1104/pp.73.3.740.
The distribution of (14)C in photosynthetic metabolites of two naturally occurring higher plants with reduced photorespiration, Moricandia arvensis and Panicum milioides, in pulse and pulse-chase (14)CO(2) incorporation experiments was similar to that for the C(3) species, M. foetida and Glycine max. After 6 seconds of (14)CO(2) incorporation, only about 6% of the total (14)C fixed was in malate and aspartate in both M. arvensis and P. milioides. The apparent turnover of the C(4) acids was very slow, and malate accumulated during the day in M. arvensis. Thus, C(4) acid metabolism by M. arvensis and P. milioides had no significant role in photosynthetic carbon assimilation under the conditions of our experiments (310 microliters CO(2) per liter, 21% O(2), 1100 or 1900 micromoles photon per square meter per second, 27 degrees C).After a 36-second chase period in air containing 270 microliters CO(2) per liter, about 20% of the total (14)C fixed was in glycine with M. arvensis, as compared to 15% with M. foetida, 14% with P. milioides, and 9% with G. max. After a 36-second chase period in 100 microliters CO(2) per liter, the percentage in glycine was about twice that at 270 microliters CO(2) per liter in the C(3) species and P. milioides, but only 20% more (14)C was in glycine in M. arvensis. These data suggest that either the photorespiratory glycine pool in M. arvensis is larger than in the other species examined or the apparent turnover rate of glycine and the flow of carbon into glycine during photorespiration are less in M. arvensis. An unusual glycine metabolism in M. arvensis may be linked to the mechanism of photorespiratory reduction in this crucifer.
在脉冲和脉冲追踪 (14)CO(2) 掺入实验中，两种自然发生的低光呼吸高等植物 Moricandia arvensis 和 Panicum milioides 的光合作用代谢产物中 (14)C 的分布与 C(3) 种 Moricandia foetida 和 Glycine max 相似。在 (14)CO(2) 掺入 6 秒后，两种 M. arvensis 和 P. milioides 中只有约 6%的总 (14)C 固定在苹果酸和天冬氨酸中。C(4) 酸的表观周转率非常缓慢，在 M. arvensis 中，苹果酸在白天积累。因此，在我们实验的条件下（310 微升 CO(2) /升，21% O(2)，1100 或 1900 微摩尔光子/平方米/秒，27°C），M. arvensis 和 P. milioides 的 C(4) 酸代谢在光合作用碳同化中没有重要作用。在空气中进行 36 秒的追踪期后，空气中含有 270 微升 CO(2) /升，M. arvensis 中总 (14)C 固定的约 20%在甘氨酸中，而 M. foetida 为 15%，P. milioides 为 14%，G. max 为 9%。在 100 微升 CO(2) /升的 36 秒追踪期后，C(3) 种和 P. milioides 中甘氨酸的百分比约为 270 微升 CO(2) /升的两倍，但 M. arvensis 中甘氨酸的 (14)C 仅增加 20%。这些数据表明，要么 M. arvensis 中的光呼吸甘氨酸池大于其他检查的物种，要么甘氨酸的表观周转率和光呼吸过程中碳进入甘氨酸的流量在 M. arvensis 中较低。M. arvensis 中异常的甘氨酸代谢可能与该十字花科植物光呼吸还原的机制有关。
