中文摘要：

钾在缓解植物铵毒害的过程中起着重要的作用。本文研究了高铵（30mmol／L）条件下，不同铵钾比（7．5：I和150：1）对拟南芥（C01-0）主根、侧根以及地上部生长的影响。结果表明：30mmol／LNHj条件下，高铵钾比（150）处理显著加重了拟南芥铵毒害现象，地上部和根系生长所受的抑制作用更为明显并导致更严重的氧化胁迫。相比低铵钾比水平，在高铵处理下，高铵钾比使得拟南芥主根伸长量降低57．4％，侧根数量减少33．3％，而地上部鲜重减轻69．9％。DAB（3，3’-二氨基联苯胺，3，3’．diaminobenzidine）叶片染色结果表明，不加铵处理下，外源不同钾水平（O．2和4．0mmol／L）对拟南芥叶片的氧化胁迫作用没有显著差异；而高铵处理下，相比低铵钾比处理，高铵钾比显著增加了叶片中过氧化氢的含量，加重了其氧化胁迫。伊文思蓝（Evansblue，EB）染色结果表明，不加铵处理下，外源不同钾水平对拟南芥地上部和根部的膜透性没有显著差异，而高铵处理下，高铵钾比显著增强了拟南芥地上部和根部的膜透性，表明其对细胞的伤害程度加重。可见，高铵抑制拟南芥根系和地上部生长，高铵钾比则会加重这种抑制，其原因除了高浓度钾能减少植物对铵的吸收外，可能与高铵钾比条件加剧了植物的氧化胁迫有关。因此，适宜的铵钾比在植物应对铵毒害的过程中发挥重要作用。

英文摘要：

Potassium plays an important role in the process of protecting plant species from ammonium toxicity. In the present study, primary root, lateral root （LR） and shoot developments of Arabidopsis wild type （Col-0） were analyzed under excessive NH4＋ （30 mmol/L） with two concentration ratios of NH4＋/K＋ （7.5 and 150） in agar medium. The results showed that under high ammonium condition （30 mmol/L）, high NH4＋/K＋ ratio （150） increased the ammonium stress, inhibited the shoot and root development and aggravated the oxidative stress compared with low NH4＋/K＋ ratio （7.5）. Compared with the low NH4＋/K＋ ratio, the highNH4＋/K＋ ratio inhibited the primary root elongation by 57.4%, the relative number of LRs by 33.3% and the shoot fresh weight by 69.9% under the high ammonium condition. The results of DAB （3, 3＇-diaminobenzidine） staining of leaf indicated that compared with no ammonium treatment, the different external K~ levels （0.2 and 4.0 mmol/L） did not show significantly different effects on shoot oxidative stress of Arabidopsis; while under the high ammonium condition, the highNH4＋/K＋ ratio further increased the H202 content of leaf and aggravated the oxidative stress compared with the low NH4＋/K＋ratio. Evans blue （EB） staining showed that the different external K＋ levels did not show significantly different effects on shoot and root membrane permeability of Arabidopsis in the treatment without ammonium; while the high NH4＋/K＋ ratio significantly enhanced shoot and root membrane permeability under the high ammonium condition. All the results indicated that high ammonium inhibited the development of shoot and root of Arabidopsis, and the inhibition would be enhanced by the high NH4＋/K＋ ratio. In addition to the reduction in the absorption of ammonium by the plants due to presence of high concentration of potassium, the reason may be also ascribed to the exacerbated oxidative stress by the high NH4＋/K＋ ratio. Therefore, appropriate NH4＋/