Abstract: Effect of cadmium stress on nitrogen uptake and activities of some enzymes related to N metabolism was compared between weedy rice and japonica rice cultivar Koshihikari with a hydroponic experiment under four Cd levels, i.e. 0, 01, 1.0 and 5.0 μmol/L with ammonium nitrate as N source. Cd concentration and accumulation in both shoots and roots of the two rices increased dramatically with increasing Cd level. However the extent of the increase varied with the rice genotypes. Under high Cd levels (1.0 and 5.0 μmol/L), weedy rice had lower Cd concentration and fewer Cd accumulation in roots than Koshihikari, while in shoots the case was just opposite, indicating that more Cd was translocated to shoots in weedy rice than in Koshihikari, and the shoots of weedy rice were more capable of detoxifying Cd than those of Koshihikari. N concentration, accumulation and the activities of nitrate reductase, glutamicoxalacetic transaminase and glutamatepyruvate transaminase decreased markedly with increasing Cd level. There was a clear difference in the extent of the decrease between the two rices. In general, the inhibition of N uptake and N metabolism-related enzymes was relatively less for weedy rice than for Koshihikari. It was proved that weedy rice had stronger tolerance to Cd toxicity than Koshihikari and there is a close association between performance of these N metabolism related enzymes and Cd toxicity tolerance.

Key words: cadmium, weedy rice, nitrogen metabolism, cultivated rice, enzyme activity

摘要： 在水培条件下，以杂草稻和粳稻越光为材料，研究了Cd胁迫对水稻氮吸收和氮代谢酶活性的影响。Cd处理设0、01、10和50 μmol/L 4个水平，以硝酸铵为氮源。结果表明，两种水稻的植株Cd含量和积累量均随溶液Cd处理水平的提高而显著增加，但增加程度两水稻材料存在着明显的差异，在较高Cd水平（10和50 μmol/L）下，杂草稻根系Cd含量和积累量低于越光，但地上部呈相反的趋势，表明杂草稻根系吸收的Cd转运至地上部的量高于越光，揭示出杂草稻地上部具有较强的解毒能力。植株氮含量、积累量以及氮代谢有关酶，如硝酸还原酶、谷草转氨酶和谷丙转氨酶等活性随着Cd处理水平的提高而下降，但Cd胁迫对这些参数的抑制程度两水稻材料之间存在着明显差异，总体上对杂草稻的抑制作用较弱。表明杂草稻对Cd的耐性要强于越光，且几种氮代谢酶活性变化与Cd耐性存在着一定的相关。

关键词: 镉, 杂草稻, 氮代谢, 栽培稻, 酶活性