Photosynthetic Carbon Metabolism in an Amphibious Sedge, Eleocharis baldwinii (Torr.) Chapman: Modified Expression of C4 Characteristics under Submerged Aquatic Conditions
Photosynthetic Carbon Metabolism in an Amphibious Sedge, Eleocharis baldwinii (Torr.) Chapman: Modified Expression of C4 Characteristics under Submerged Aquatic Conditions
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DOI：
10.1093/oxfordjournals.pcp.a078754
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发表时间：
1995-03
影响因子：
4.9
通讯作者：
A. Uchino;M. Samejima;R. Ishii;O. Ueno
中科院分区：
文献类型：
--
作者：
A. Uchino;M. Samejima;R. Ishii;O. Ueno
本文研究了马蹄（Eleocharis baldwini（Torr.）对莎草科两栖无叶植物查普曼的陆生和沉水形态进行了研究。解剖观察的秆，这是光合作用的器官，在这种植物中，揭示了陆地形式的Kranz类型的解剖结构，而淹没的形式有一个内部结构，这是类似于沉水水生植物，减少的数量和大小的束鞘细胞和维管束和相对发达的叶肉细胞。在14 C脉冲12 C追逐实验与陆生形式，80%的总fixed 14 C被纳入C4二羧酸后，10秒的脉冲。在120秒的追踪过程中，C4酸的放射性迅速下降，而蔗糖中的放射性增加到36%。在浸没的形式，64%和30%的总fixed 14 C被纳入C4酸和磷酸酯，分别为10秒的脉冲后。这些化合物的放射性在120秒追踪期间下降相对缓慢。在叶绿素的基础上，参与NAD-ME亚型的C4光合酶的比活性高的陆地形式，而它们之间的C3和C4植物的淹没形式的中间。1，5-二磷酸核酮糖羧化酶的活性是1.5倍，在淹没的形式比在陆地形式。而碳酸酐酶活性则相反。从叶肉细胞和维管束鞘中提取的可溶性蛋白质的Western印迹分析表明，核酮糖1，5-二磷酸羧化酶/加氧酶蛋白存在于叶肉细胞以及在维管束鞘细胞中，后者的水平较高，虽然磷酸烯醇式丙酮酸羧化酶和丙酮酸，Pidikinase蛋白仅限于叶肉细胞。在淹没的形式，昼夜波动水平的苹果酸观察到显着的固定CO2在夜间。然而，苹果酸的日变化小于CAM植物的报道。这些数据表明，陆地形式ofEleocharis baldwinii固定大气CO2基本上通过C4途径，而淹没形式固定无机碳通过一个复杂的代谢系统，类似于一个中间体之间的C3和C4代谢与CAM样配置文件。
The photosynthetic characteristics ofEleocharis baldwinii(Torr.) Chapman, an amphibious leafless plant in the Cyperaceae, were investigated in both the terrestrial form and the submerged form of the plant. Anatomical observation of the culm, which is the photosynthetic organ in this plant, revealed that the terrestrial form has the Kranz type of anatomy, whereas the submerged form has an inner structure that is similar to that of submerged aquatic plants, with a reduction in both the number and the size of bundle sheath cells and vascular bundles and relatively well developed mesophyll cells. In14C-pulse12C-chase experiments with the terrestrial form, 80% of the total fixed14C was incorporated into C4dicarboxylic acids after a 10-s pulse. The radioactivity in the C4acids decreased rapidly, while that in sucrose increased to 36% during a 120-s chase. In the submerged form, 64% and 30% of the total fixed14C was incorporated into C4acids and phosphate esters, respectively, after a 10-s pulse. The radioactivity of these compounds decreased relatively slowly during a 120-s chase. The specific activities on a chlorophyll basis of C4photosynthetic enzymes that are involved in the NAD-ME subtype were high in the terrestrial form, while they were intermediate between those of C3and C4plants in the submerged form. The activity of ribulose 1,5-bisphosphate carboxylase was 1.5 times higher in the submerged form than in the terrestrial form. By contrast, the activity of carbonic anhydrase exhibited the reverse tendency. Western blot analysis of soluble proteins extracted from the mesophyll cells and the bundle sheath strands of the terrestrial form demonstrated that ribulose 1,5-bisphosphate carboxylase/oxygenase protein was present in the mesophyll cells as well as in the bundle sheath cells, with a higher level in the latter, although phosphoenolpyruvate carboxylase and pyruvate, Pidikinase proteins were restricted to the mesophyll cells. In the submerged form, diurnal fluctuations in levels of malate were observed with significant fixation of CO2at night. However, the diurnal changes of malate were smaller than those reported for CAM plants. These data indicate that the terrestrial form ofEleocharis baldwiniifixes atmospheric CO2essentially via the C4pathway, while the submerged form fixes inorganic carbon via a complex metabolic system that resembles an intermediate between C3and C4metabolism in association with a CAM-like profile.