4种外生菌根真菌对难溶性磷酸盐的溶解能力

以红绒盖牛肝菌(Xerocomus chrysenteron)、美味牛肝菌(Boletus edulis)、黄须腹(Rhizopogen luteous)和劣味乳菇(Lactarius insulsus)4种外生菌根真菌为对象,在纯培养条件下比较它们对4种难溶性磷酸盐[Ca_3(PO_4)_2、Ca_(10)(PO_4)_6(OH)_2、FePO_4·4H_2O和AlPO_4]的溶解能力,以探讨外生菌根真菌对难溶性磷酸盐的溶解作用及其影响因素.结果表明:(1)4种外生菌根真菌均能在Ca_3(PO_4)_2为唯一磷源的NBRIP平板上生长,但生长速率明显不同,且红绒盖牛肝菌生长速率最快.(2) 4种菌根真菌对4种磷酸盐的溶解能力存在显著差异,红绒盖牛肝菌发酵液可溶性磷含量大多显著高于对照和其他菌根真菌,对磷酸盐的溶解能力最强.(3)4种菌根真菌发酵液可滴定酸度(2.30～46.00 mmol·L~(-1))和pH(4.57～6.99)与其溶磷量分别呈极显著正相关(r=0.991**)和极显著负相关(r=-0.939**).(4)4种外生菌根真菌均能分泌乙酸、柠檬酸和反丁烯二酸,且它们分泌有机酸总量(14.14～1 537.46 mg·L~(-1))与其溶磷量呈显著正相关(r=0.998*).研究发现, 4种外生菌根真菌发酵液可滴定酸度、pH和有机酸的种类与含量是影响其溶解Ca_3(PO_4)_2能力的主要因素;红绒盖牛肝菌的溶磷能力较强,具有应用于中国土壤缺磷地区造林的潜力.

Ability of Dissolving Insoluble Phosphate by Four Ectomycorrhizal Fungi

To study the ectomycorrhizal fungi on the dissolution of insoluble phosphate and its possible influencing factors,we used four strains of ectomycorrhizal fungi,Xerocomus chrysenteron,Boletus edulis,Rhizopogen luteous and Lactarius insulsus,to compare their phosphate-dissolving ability in vitro.The results showed that all the four ectomycorrhizal fungi could grow on the solid plate of NBRIP with Ca_3(PO_4)_2 as sole phosphate source,but having different growth rates.It was found that there were significantly different in dissolving these phosphates of Ca_3(PO_4)_2,Ca_(10)(PO_4)_6(OH)_2,FePO_4·4H_2O and AlPO_4 after culturing 14 days.The amounts of soluble P in the broth of Xerocomus chrysenteron were significantly higher than that of control and other ectomycorrhizal fungi.The titrable acidity of the broth(2.30～46.00 mmol·L~(-1)) was found to be significantly positively correlated to the amounts of soluble P (r=0.991**).Nevertheless there was a negative correlation between the final pH values of the broth and the amounts of soluble P(r=-0.939**).The kinds and concentrations of organic acid were determined by HPLC,all the four strains of ectomycorrhizal fungi were able to excrete Acetic,Citric and Famaric acid.However,significant differences existed between the total of organic acid and the phosphate-dissolving capacity (r=0.998*).The main factors influencing dissolving phosphate on Ca_3(PO_4)_2 included the titrable acidity,pH value and organic acid excreted by ectomycorrhizal fungi.Therefore,Xerocomus chrysenteron,which had larger phosphate-dissolving ability,is the most promising fungus for afforestation at P-deficient areas in China.