菜豆根瘤菌对土壤钾的活化作用  

Mobilization of potassium from Soils by rhizobium phaseoli

作　　者：张亮[1] 黄建国[1] 韩玉竹[1] 吴叶宽[1] 

机构地区：[1]西南大学资源环境学院,北碚400716

出　　处：《生态学报》2012年第19期6016-6022,共7页Acta Ecologica Sinica

基　　金：中央高校基本科研业务费专项资金资助XDJK(2010D002);XDJK(2011C034)

摘　　要：以土壤为钾源,通过液体培养试验研究了8株菜豆根瘤菌对土壤钾的活化作用。结果表明,菜豆根瘤菌能释放大量的氢离子,使液体培养基的pH值大幅度降低,氢离子的浓度至少提高22倍以上。根瘤菌分泌有机酸的种类与数量因菌株不同而异,这些有机酸包括甲酸、乙酸、草酸、丁二酸、柠檬酸、苹果酸和乳酸等,其中全部菌株均能分泌草酸和苹果酸,大部分菌株能分泌乙酸。在接种根瘤菌的液体培养基中,可溶性钾含量显著高于不接种的液体培养基,土壤矿物结构钾则显著降低。由于土壤是培养基钾的唯一来源,故根瘤菌可促进土壤无效钾的溶解。相关分析表明,土壤矿物结构钾与有机酸分泌总量呈极显著负相关(r=-0.878**,n=9),与培养液pH值呈极显著正相关(r=0.863**,n=9),说明根瘤菌分泌的有机酸和氢离子可能溶解土壤无效钾。考虑到根瘤菌草酸分泌量大,络合钙、镁、铁、铝的能力强,且与有机酸分泌总量呈极显著正相关(r=0.870**,n=9),推测草酸分泌在活化土壤无效钾的过程中起重要作用。此外,根瘤菌分泌的有机酸电离产生的氢离子仅占培养液氢离子的4.15%—27.56%,推测根瘤菌直接分泌的氢离子可能是造成培养液pH值降低的主要原因之一。Potassium（K） is one of the most important essential elements for plant growth and function.However,both the concentration and the availability of K are very low in most soils.The chemical K supplemented through fertilization is rapidly adsorbed by soil minerals resulting in a 20%—35% of K use efficiency.Studies have found that rhizobia,which have the capacity not only to fix nitrogen from the atmosphere to contribute plant nitrogen nutrition,but also to mobilize soil K for plant use.As a result,the improvement of plant K use efficiency through some specific rhizobia to mobilize soil K has attracted much attention around the whole world.However,less information is available to illustrate the mechanisms how rhizobia could directly mobilize K from the soil.Eight strains of rhizobium sp.,which isolated from a gray brown purple soil in Chongqing,southern China and coded as R 01,R 02,R 03,R 04,R 05,R 06,R 07 and R 08,respectively,were grown a liquid medium to study their capacity to mobilize soil K.The medium contained 1L H2O,10 g mannitol,1.0 g yeast powder,0.5 g NaH2PO4,0.2 g MgSO4·7H2O,0.1 g NaCl,0.1 g CaCl2·6H2O and 4.0 mL microelement solution（each 1 L contained 5.0 g H3BO3 and 5.0 g Na2MoO4 dH2O）.Compared to the non-rhizobium control,concentrations of proton in the liquid media under all eight rhizobium treatments were increased by 22 times at least leading a significant pH decrease after 7 days of incubation.All rhizobium strains exuded oxalic acid and malic acid and most of them exuded acetic acid,but varied their capacity to exude succinic acid,formic acid,citric acid and lactic acid.Soluble K in the liquid medium was significantly higher whilst mineral structure K was significantly lower in the soil in the rhizobium treatments than in the non-rhizobium control.Mineral structure K in soil negatively correlated with total organic acids（r=-0.878＊ ＊,n=9）,but positively correlated with pH in the liquid medium（r=0.863＊,n=9）.So,rhizobia could mobilize soil K through the exudation of organic

关 键 词：菜豆根瘤菌 土壤 钾 

分 类 号：S154.3[农业科学—土壤学]