Gebauer G, Melzer A, Rehder H
Institut für Botanik und Mikrobiologie der Technischen Universität München, Arcisstr. 21, D-8000, München 2, Germany.
Oecologia. 1984 Jul;63(1):136-142. doi: 10.1007/BF00379795.
With Rumex obtusifolius L., the influence of some environmental conditions on nitrate uptake and reduction were investigated. Nitrate concentrations of plant material were determined by HPLC, the activity of nitrate reductase by an "in vivo" test. As optimal incubation medium, a buffer containing 0.04 M KNO; 0.25 M KHPO; 1.5% propanol (v/v); pH 8.0 was found. Vacuum infiltration caused an increase of enzyme activity of up to 40%.High nitrate concentrations were found in roots and leaf petioles. Nitrate reductase activity of these organs, however, was low. On the other hand, the highest nitrate reductase activity was observed in leaf laminae, which contained lowest nitrate concentrations.In leaves, nitrate content and nitrate reductase activity exhibited inverse diurnal fluctuations. During darkness, decreasing activities of the enzyme were followed by increasing nitrate concentrations, while during light the contrary was true. In petioles diurnal fluctuations in nitrate content were observed, too. No significant correlations with illumination, however, could be found.Our results prove that Rumex obtusifolius is characterized by an intensive nitrate turnover. Theoretically, internal nitrate content of the plant would be exhausted within a few hours, if a supply via the roots would be excluded.
以钝叶酸模为材料，研究了一些环境条件对硝酸盐吸收和还原的影响。通过高效液相色谱法测定植物材料中的硝酸盐浓度，采用“体内”试验测定硝酸还原酶的活性。发现含有0.04M硝酸钾、0.25M磷酸氢钾、1.5%丙醇（体积/体积）、pH8.0的缓冲液作为最佳孵育培养基。真空渗透使酶活性提高了40%。在根和叶柄中发现了高浓度的硝酸盐。然而，这些器官的硝酸还原酶活性较低。另一方面，在叶片中观察到最高的硝酸还原酶活性，而叶片中的硝酸盐浓度最低。在叶片中，硝酸盐含量和硝酸还原酶活性呈现相反的昼夜波动。在黑暗中，酶活性下降后硝酸盐浓度增加，而在光照下则相反。在叶柄中也观察到硝酸盐含量的昼夜波动。然而，未发现与光照有显著相关性。我们的结果证明，钝叶酸模的特点是硝酸盐周转强烈。从理论上讲，如果排除通过根部的供应，植物体内的硝酸盐含量将在几小时内耗尽。
