杉木根际固氮菌筛选及其溶磷性与分泌IAA特性研究

我国特有速生用材林主要造林树种杉木的人工林地衰退问题日益严重,但对杉木甚至木本植物根际促生菌的作用及其分离与利用等研究还很少报道.利用Ashby培养基和固氮酶乙炔还原测定法从杉木根际土壤中分离到了16株固氮能力较强的菌株,并在蒙金娜培养基上鉴定了溶磷圈、用钼锑钪比色法测定了有机磷和无机磷的溶磷能力、用Salkowski比色法测定了IAA分泌量.结果表明:16株菌中有5株固氮酶活性大于150 nmol.mL-1.h-1,最高的NGJ-4达264.7 nmol.mL-1.h-1,NGX-5次之,为237.4 nmol.mL-1.h-1.8株解无机磷,其中NGJ-8、NGJ-4和NGX-3的有效磷增量分别为182.7、158.4和133.9mg.L-1,但都无明显解有机磷能力.有5株菌解有机磷,但能力都较小,最大的NGX-5有效磷增量也仅为46.1 mg.L-1,且不具有解无机磷能力.大部分菌株都能分泌生长素,有6株菌分泌能力较强,培养液上清中IAA浓度大于20 mg.L-1,其中NGX-5、NGJ-3、NGJ-4和NGJ-8分别为35.8、32.1、27.8和27.7 mg.L-1.综合这些结果,菌株NGJ-4、NGX-5和NGJ-8兼有固氮、解磷和分泌IAA等3种最强或较强能力,在多功能微生物菌肥研制中具有重要利用价值.

Screening of Nitrogen-fixing Bacteria in Rhizosphere of Cunninghaimia Lanceolata and Investigation on Their Properties of Phosphate-solubilizing and IAA-producing

Chinese fir(Cunninghaimia Lanceolata) is a main tree species of planted fast-growing forest in China.The problem on rapid reduction of soil fertility resulted from nutrient consumption of chinese fir plantation still remains to be solved since the studies on screening and application of rhizosphere bacteria of chinese fir with growth-promoting effect are rarely reported.In our study,16 strains of nitrogen-fixing bacteria are isolated from rhizosphere soil of chinese fir by measurement of nitrogenase activities using acetylene reduction assay after culturing in Ashby medium.Their abilities of dissolving inorganic and organic phosphorus are evaluated by dissolving phosphate zone on Menkina media and molybdenum blue spectrophotometry.IAA-producing abilities of the strains are measurated by the Salkowski colorimetry.The results indicate that 5 strains show high potential of nitrogen fixing with nitrogenase activity of over 150 nmol·mL-1·h-1.NGJ-4 has the highest nitrogenase activity(264.7 nmol·mL-1·h-1) and NGX-5 takes the second place(237.4 nmol·mL-1·h-1).There are 8 strains with abilitiy of dissolving inorganic phosphorus.The available phosphorus increments of NGJ-8,NGJ-4 and NGX-3 are 182.7,158.4 and 133.9 mg·L-1,respectively,which can’t dissolve organic phosphorus.There are 5 strains with low dissolving organic phosphorus abilitiy.The highest available phosphorus increments derived from organic phosphorus is only 46.1 mg·L-1 of NGX-5.Most of the strains can secrete IAA.The first 5 strains have a high IAA concentration of more than 20 mg·L-1 in supernatant of bacteria solution.The IAA concentration levels of NGX-5,NGJ-3,NGJ-4 and NGX-3 are 35.8,32.1,27.8 and 27.7 mg·L-1,respectively.Consequently,NGJ-4,NGX-5 and NGJ-8 integrated prominent nitrogen-fixing,phosphorus-dissolving and IAA-producing can be utilized in developing multiple-effective microbial fertilizer.