缺磷对紫云英根系分泌物产生及难溶性磷活化的影响

Effect of P Deficiency on the Emergence of Astragalus L.Root Exudates and Mobilization of Sparingly Soluble Phosphorus

【目的】探讨紫云英根分泌物对难溶性磷活化、吸收能力,以及不同紫云英基因型对难溶性磷活化差异。【方法】采用Hoagland营养液培养并收集紫云英根分泌物,经旋转蒸发仪减压、浓缩后,进行难溶性磷活化试验,利用高效液相色谱(HPLC)测定分泌物中有机酸成分及含量。【结果】缺磷胁迫下,不同基因型紫云英根半径减少,而根冠比和根比表面积较供磷有显著提高。紫云英根系分泌的有机酸有草酸、酒石酸、柠檬酸、苹果酸等,但主要为草酸;缺磷条件下,不同基因型紫云英分泌草酸存在显著差异,且各有机酸分泌量显著高于供磷时的分泌量。闽紫1号、浙紫5号和闽紫6号分泌的各种有机酸量明显高于余江大叶和弋江籽分泌的量。缺磷和供磷下,紫云英根系分泌物对难溶性Al-P和Fe-P都具有一定的活化能力,其活化值(P)分别为36.40-157.39μg.g-1、32.20-139.42μg.g-1,缺磷根系分泌物对难溶性磷的活化量高于供磷处理,而且Al-P的活化能力略高于Fe-P。通过活化模拟试验,也证实不同有机酸可活化难溶性Al-P、Fe-P且差异显著。【结论】缺磷胁迫能促进紫云英分泌有机酸,显著增加对难溶性磷的活化效果;基因型之间紫云英对磷的活化效果差异较为明显,显现出紫云英品种间的差异性;栽培紫云英有利于改善南方红壤地区缺磷土壤磷素养分循环。然而科学地评价有机酸对Al-P和Fe-P的活化能力还有待于进一步研究。

【Objective】 The objective of this study was to investigate the mobilization and uptake capacity of sparingly soluble phosphorus by root exudate of Astragalus L.,and genotypic variation of different Astragalus L.in activation of sparingly soluble phosphorus.【Method】 Hoagland nutrient solution culture was carried out to collect root exudate and test the mobilization of sparingly soluble phosphorus via concentrated vacuum rotary evaporator,and the content of organic acids was analyzed by high performance liquid chromatography（HPLC）.【Result】 Under the condition of P-deficiency stress,root radius from different genotypes of Astragalus L.reduced,while the root-shoot ratio and root surface area were significantly higher than P-supply.Root exudates were oxalic acid,tartaric acid,citric acid,malic acid and so on,but it mainly exuded oxalic acid.Under the condition of P-deficiency,secreation of oxalic was significantly different among variou genotypes,and the amout of organic acid secretion was significantly higher than P-supply.Minzi 1,Zhezi 5 and Minzi 6 in organic acid secretion were significantly higher than Yijiangzi,Yujiangdaye.Root exudates on insoluble Al-P and Fe-P had certain activation capacity under P-deficiency and P-supply.The activation P values for Al-P and Fe-P were 36.40-157.39 μg·g^-1,32.20-139.42 μg·g^-1,and P-deficient root exudates on sparingly soluble phosphate was higher than P-supply,and activation capacity of Al-P was slightly higher than Fe-P.Through the activation of simulation experiment,it was confirmed that organic acids could mobilize sparingly soluble Al-P and Fe-P,and the difference was significant.【Conclusion】 Under P-deficiency stress,Astragalus L.exudated organic acids,which could significantly mobilize sparingly soluble phosphate.There were obvious differences among various genotypes,showing differences between Astragalus L.varieties.Cultivating Astragalus L.could be used to improve soil P-deficiency nutrient cycling in red soils region of southern China,but further research should be carried out to scientifically evaluate organic acids on the activation capacity of Al-P and Fe-P.