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

铝离子对植物的毒害效应一般在酸性土壤中观察到，如果失去了良好的表层土壤，尤其是腐殖质对去除这些毒害作用具有重要作用的表层土壤，铝离子对植物的毒性作用尤为严重。作者发现，经自由基磺化和碱氧氧化处理后的木质素具有与腐殖质相似的功能。本研究旨在探讨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，即强酸基、弱酸基I-III，其中强酸基应为自由基磺化反应引入的磺酸基。弱酸性基团I似乎是芳香族羧酸，弱酸基团II包括儿茶酸和弱酸结构。铝的加入增加了酸性基团的数量，特别是弱酸性基团I，表明铝-木质素络合物释放了酸性质子，这也得到了~&lt；27&gt；AL-核磁共振的证实。

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.