大豆根分泌物活化难溶性铝磷的研究

在酸性红壤上，土壤有效磷含量低，大部分磷以难溶性磷形式存在，这是影响作物生产的重要限制因素之一。作物根分泌物活化难溶性磷的能力对改善其磷素营养具有重要意义。本文系统研究了大豆根分泌物对难溶性铝磷的活化效果，同时运用阴、阳离子交换树脂将根分泌物分成阴离子组分、中性组分和阳离子组分，活化结果表明．阴离子组分对铝磷的活化量显著高于中性组分和阳离子组分。运用分子膜把根分泌物分成大于8K、8～3．5K、3．5～1K和小于1K组分．发现对铝磷活化量最大的组分为小于1K根分泌物组分。另外．小于1K阴离子组分对铝磷的活化量为缺磷13．2mg／pot，供磷可达9．3mg／pot，分别占总根分泌物活化量的71％和57％。运用离子色谱仪对小于1K阴离子组分根分泌物测定表明，供磷和缺磷处理．根系均能分泌少量的柠檬酸和苹果酸，约占铝处理的10％～20％，但处理之间差异不显著。上述研究表明．除有机酸影响难溶性铝磷活化之外，根分泌物中可能还存在其它物质对铝磷活化有促进作用，相关研究正在深入进行之中。

Mobilization of Insoluble Aluminum Bound Phosphate by Soybean Root Exudates

On acidic red soils, low phosphate availability is one of the major limitations to crop production. Mobilization of insoluble phosphates by root exudates plays an important role in improving P nutrition of crops. In this study, mobilization of Al bound phosphate (AlP) by root exudates of soybean was systematically studied using anionic, cationic exchange resins, and molecular membrane of different molecular weight. Mobilization experiment indicated that AlP mobilization by anionic fraction of root exudates was significantly higher than those by cationic or neutral fraction. Among above 8K, 8~3.5K, 3.5~1K, and below 1K fraction, root exudates of below 1K fraction has the largest ability to mobilize AlP in comparison to other fractions of root exudates. Mobilized AlP by below 1K anionic fraction were 13.2 mg/pot and 9.3 mg/pot for P-deficient and P-sufficient treatment respectively, which represented 71% and 57% of the AlP mobilized by total root exudates. Analysis of root exudates of below 1K anionic fraction by ion chromatography indicated that a small amount of citrate and malate was exuded by both P-deficient and P-sufficient soybean roots, which took up 10%~20% of organic acid triggered by Al treatment. However, no difference of organic acid exudation was observed between P-deficient and P-sufficient soybean roots. The above results indicated that other unknown compounds in root exudates of soybean might enhance the mobilization of AlP except for organic acids. Related search is deeply on going.