Abstract: Annual Populus×euramericana Neva was applied as the studying material, and the magnetic device was used to manage the 1/2-Hoagland nutrient solution containing 0 or 100 mol·L^-1 Cd(NO₃)₂·4H₂O four groups performed in our study. The nitrogen content, nitrogen key metabolic enzyme activity, amino acid content and root morphological characteristics in different tissues were measured by lab analysis, aiming to explore the effect of magnetic treatment of irrigation water on nitrogen metabolism in Populus×euramericana Neva seedling stage under cadmium stress. The results were as follows: The content of $NH_4^+$-N, $NO_3^-$-N, and TN in leaves increased by magnetic treatment when exposed to cadmium stress. Similarly, $NH_4^+$-N and TN content in the roots was also promoted by the magnetization, while $NO_3^-$-N content was decreased. The activities of NR, NiR, GR, GOGAT in the leaves, and the enzyme activities of NR, GS and GOGAT in the roots were stimulated by the magnetic treatment under Cd stress. On the contrary, the activity of NiR in roots was inhibited by the magnetization. The magnetization improved the synthesis of Cys and Gln in leaves, and reduced the content of Glu and Gly when stressed to Cd conditions. Meanwhile, magnetization promotes the synthesis of Cys, Glu, Gln and Gly in the roots. The magnetic treatment induced a promotion in the root system and was beneficial to the formation of root morphology by Cd exposure. The above results indicated that magnetization can regulate the absorption and transportation of mineral nutrients by affecting root morphology. The synthesis of nitrogen assimilation and free amino acids can be improved by stimulating the key enzyme activity of nitrogen metabolism, which is of great significance for poplars to adapt to the stress conditions performed by the heavy metal.

Key words: cadmium stress, magnetization, nitrogen metabolism, enzyme activity, free amino acids

摘要： 为探究磁化水灌溉对镉(Cd)胁迫下杨树幼苗营养代谢的影响,以一年生欧美杨Ⅰ-107(Populus×euramericana Neva)幼苗为研究对象,通过磁化处理含Cd(NO₃)₂·4H₂O的1/2 Hoagland营养液浇灌幼苗,测定不同组织的氮素含量、氮素关键代谢酶活性、关键氨基酸含量以及根系形态特征。结果表明,磁化水灌溉使得Cd胁迫下叶片中铵态氮($NH_4^+$-N)、硝态氮($NO_3^-$-N)和全氮(TN)含量增加;同样磁化处理也促进根系中$NH_4^+$-N和TN含量升高,但降低了根系中$NO_3^-$-N含量。磁化水灌溉有利于提高叶片中硝酸还原酶(NR)、亚硝酸还原酶(NiR)、谷氨酰胺合成酶(GS)和谷氨酸合成酶(GOGAT)活性,同时提高根系中NR、GS活性,但对根系中NiR和GOGAT活性有明显的抑制作用。磁化水灌溉促进了Cd胁迫叶片半胱氨酸(Cys)、谷氨酰胺(Gln)的合成,但对谷氨酸(Glu)和甘氨酸(Gly)合成有明显的抑制作用。另外,磁化作用均促进了Cys、Glu、Gln和Gly在根系中的合成。磁化水灌溉可促进杨树根系形态建成。综上可知,磁化水灌溉可通过影响根系形态来调节根系对矿质养分的吸收和运输,可通过刺激氮素代谢关键酶活性来提高氮同化和游离氨基酸的合成,这对于提高杨树对镉污染土壤的适应能力具有重要意义。

关键词: 镉胁迫, 磁化作用, 氮素代谢, 酶活性, 游离氨基酸