小麦叶内硝酸还原的代谢库

随营养液中No_3~-浓度升高,叶片内No_3~-总量、代谢库大小(NIPS)及硝酸还原酶(NR)活性均升高,其中MPS与NK活性呈同步变化;No_3~-浓度达2.0mmol/L时,两者趋于稳值;若再增加NO_3~-浓度,则被吸收的NO_3~-积累于液泡中,而代谢库中NO_3~-含量(MPS)与NO_3~-总量之比有一定程度降低。低氮(NO_3~-浓度为1.0 mmol/L)情况下,反应液中无NO_3~-时,叶片内NR活性品种间有差异,但在50 mmol/L NO_3~-反应液中则品种间无差异;NK活性高的品种鲁麦8号及品种321叶内有大的NO_3~-代谢库,反应液中NO_3~-对NR活性刺激程度低,代谢库NO_3~-含量与叶NO_3~-总量之比高,而叶组织长时间反应过程中其NR活性衰减速率低。

The Metabolic Pool of Nitrate Reduction in Wheat Leaves

The total content of nitrate in wheat leaves, the nitrate reductase activity (NRA) in the absence of nitrate in assay medium, and the metabolic pool size (MPS) of nitrate increased with the increase of nitrate concentration in nutrient solution. NRA and MPS changed synchronously and reached their steady values at 2.0 mmol/L of nitrate. When the nitrate concentration increased to 2.5 mmol/L, most of the absorbed nitrate was accumulated in vacuoles, with little in cytoplasm, and the ratio of MPS to total nitrate decreased to some extent. This indicated that the content of nitrate in the metabolic pool regulated NRA in vivo in wheat seedling leaves. The nitrate reductase activity in seedling leaves of four wheat cultivars grown in nutrient solution with 1.0 mmol/L nitrate was assayed in vivo. The NRAs In leaves of cultivard studies were different in the absence of nitrate in assay medium, but such difference was not observed in the presence of 50 mmol/L nitrate in the assay medium. The NRAs of cultivars 321 and Lumai 8 were higher than those of Yangmai 3 and J13, and their nitrate contents in metabolic pool and ratios of MPS to total nitrate content in leayes were also higher. Less effects of nitrate in assay medium on NRA of cultivars 321 and Lumai 8 were observed, and NRA decreased more slowly during the incubation peroid. The differences of NRA among wheat cultivars were due to the different nitrate content in the metabolic. pool of leaves.