Effect of water-logging stress and nitrogen forms on roots of maize (Zea mays L.) plants at seeding stage | 淹涝胁迫和供氮形态耦合对苗期玉米根系的影响

Chinese. 研究苗期玉米根系对供氮形态和淹涝胁迫的适应特性，为玉米抗涝的氮营养生理调控提供理论依据。采用砂培模拟培养方法，比较研究2种水分条件（淹涝胁迫和非淹涝胁迫）以及不同供氮形态（NH+4-N（7.5 mmol/L(NH4)2SO4）、NO-3-N（7.5 mmol/L Ca(NO3)2）和NH+4+NO-3-N（7.5 mmol/L(NH4)2SO4与7.5 mmol/L Ca(NO3)2等体积混合）对苗期玉米根体积、根系气体体积、伤流液流量、根系脱氢酶活性、植株氮累积量及根系氮、磷和钾含量的影响。在非淹水胁迫条件下培养3周，玉米植株的叶及茎鞘干质量均以铵、硝混合处理最高；但在淹涝胁迫条件下，在玉米同一部位单一铵态氮处理的生物量抗淹涝系数（淹涝胁迫条件下的生物量/非淹涝胁迫条件下的生物量）最高，且均大于1，并以根系的生物量胁迫系数最高；而硝态氮处理的生物量胁迫系数均低于其他2种氮形态处理，且以根系的生物量胁迫系数最低，表明苗期玉米根系对不同供氮形态的响应与其耐淹涝胁迫能力密切相关。与硝态氮处理和铵、硝混合处理相比，铵态氮处理玉米的根系具有相对较高的根系气体体积，且其和根体积在淹涝胁迫条件下能保持同步增长，故铵态氮处理可维持稳定的根系孔隙度、单位质量根系活力以及根系氮、磷、钾含量，并提高其单株根系活力、伤流液流量、氮素吸收以及氮/磷、氮/钾和磷/钾，进而提高苗期玉米对淹涝胁迫的适应能力。在铵态氮营养条件下，苗期玉米根系对淹涝胁迫的适应能力相对较强。

English. The aim of the study was to provide a theoretical basis on water-logging tolerance by comparing the difference in root traits acclimatization to stress environment and form of nitrogen supply. Effect of water conditions (water-logging stress and non-water-logging stress) and nitrogen forms, supplied as 7.5 mmol/L (NH4)2SO4, 7.5 mmol/L Ca (NO3)2） and the mixture of 7.5 mmol/L (NH4)2SO4 and 7.5 mmol/L Ca (NO3)2 on roots volume, gas volume in root, amount of bleeding sap, roots dehydrogenase activity, amount of nitrogen accumulation, root nitrogen, phosphorus and potassium content of maize (Zea mays L.) plants at seeding stage was carried out by using sand culture experiment. The result showed that, under non water-logging stress conditions, the mixture of ammonium and nitrate improves the growth of maize plants over that with ammonium or nitrate alone, while stress tolerance of different parts of maize plants supplied with ammonium was higher than that with the other nitrogen forms, roots showed the highest dry biomass stress coefficient of different parts in ammonium fed maize plants, and the lowest in nitrate fed maize plants. That is to say, water-logging stress tolerance of maize plants supplied with different nitrogen forms depended on the response of the roots to water-logging stress in the experiment. Non water-logging stressed maize plants supplied with ammonium had much higher roots volume, gas volume in roots, and both of which increased in step with each other under water-logging stress conditions to keep relatively constant roots porosity, roots activity per roots biomass, nitrogen, phosphorus and potassium content, and at the same time, to enhance roots activity and amount of bleeding sap of total plant, nitrogen uptake, and the ratio of nitrogen content to phosphorus content, nitrogen content to potassium content and phosphorus content to potassium content, when compared with that of supplied with the other two nitrogen forms Therefore, it revealed that nitrogen form is a major factor affecting maize plants responses to water-logging stress, and negative effects of the stress were alleviated by ammonium rather than nitrate supply, with the higher roots porosity and facilitating increase in gas volume in roots.