Mechanism of the Removal of Aluminum Toxicity for Plant by Chemically Modified Lignins

铝离子对植物的毒害作用在酸性土壤地区普遍存在，特别是失去了对铝离子毒害作用具有重要作用的腐殖质的良好表层土壤，其毒害作用更为严重。作者发现，通过自由基磺化和碱氧氧化改性的木质素具有与腐殖物质相似的功能。本研究的目的是找出化学改性木质素具有这些积极作用的机理，发现改性木质素中至少引入了四种不同类型的酸基团，即强酸基团、弱酸基团I - III。强酸性基团应是通过自由基磺化反应引入的磺酸基。弱酸组I似乎是芳香族羧酸，并且儿茶酚和粘康酸结构包括在弱酸组II中。通过添加铝，发现酸基团，特别是弱酸基团I的量增加，表明通过形成铝-木质素复合物释放酸性质子，这也通过1HAL-NMR证实<27>。

Toxic effect of aluminum ions to plants is generally observed in the area of acidic soil, and is particularly serious if the sound surface soil is lost in which humic substances have important functions to remove those toxic effect. The authors have found that chemically modified lignins by radical sulfonation and alkaline-oxygen oxidation have the functions similar to the humic substances. The aims of this research were to find out the mechanisms why the chemically modified lignins had those positive effect.It was found that at least four different types of acid groups were introduced into the modified lignins, namely strong acid group, weak acid groups I - III. Strong acid group should be sulfonic acid group introduced by radical sulfonation reaction. Weak acid group I seems to be the aromatic carboxylic acid, and catecholic and muconic acid structures are included in weak acid group II. By the addition of aluminum, amount of acid groups, particularly weak acid group I was found to increase indicating the release of acidic proton by the formation of aluminum-lignin complex, which was also confirmed by ^<27>AL-NMR.