菌丝室接种解磷细菌Bacillus megaterium C4对土壤有机磷矿化和植物吸收的影响

通过30μm尼龙网将根盒分成根室和菌丝室,菌丝室中的低磷土壤施加75 mg P/kg土壤的植酸钙,研究了菌丝室土壤中丛枝菌根(AM)真菌Glomus intraradices和解磷细菌Bacillus megaterium C4对有机磷的矿化和吸收.结果表明,在试验条件下,植酸钙的溶解性很低,对土壤溶液有机磷的贡献不大.接种解磷细菌C4提高了土壤中磷酸酶的活性,减少了土壤中有机磷的含量.但是,由于存在解磷细菌与AM真菌对磷的竞争,解磷细菌矿化出的磷大部分被自身利用,AM真菌的生长受到抑制,解磷细菌对植物磷营养的改善没有表现出显著的贡献.

The effects of inoculation with phosphate solubilizing bacteria Bacillus megaterium C4 in the AM fungal hyphosphere on soil organic phosphorus mineralization and plant uptake

To study the interactions between arbuscular mycorrhizal(AM) fungus and phosphate solubilizing bacteria(PSB) and their effects on soil organic phosphorus(P) utilization in the hyphal compartment soil,maize(Zea myas L.) plants were grown 8 weeks in sterilized soil(brunisolic soil) in a two compartmented rhizoboxes.The rhizobox was composed of a compartment for root growth(root compartment) and a compartment separated from the root compartment by 30 μm nylon mesh,which can allow the fungal hyphae penetration but prevent the root from growing through(hyphal compartment).Glomus intraradices was inoculated in root compartment of all rhizoboxes.PSB Bacillus megaterium C4 at the concentration of 108 CFU/mL were inoculated in the hyphal compartment.Each rhizobox received 20 mg P/kg of KH2PO4 in the root compartment and 75 mg P/kg of phytin in the hyphal compartment. The results showed that inoculation with PSB C4 in the hyphal compartment soil had no significant influence on mycorrhizal colonization but decreased hyphal length density.The pH in AM treatment was higher than that in the control treatment but close to C4 treatment.The phosphatase activity in AM treatment was similar to the control treatment but significantly lower than that in C4 treatment.NaHCO3 extractable organic and inorganic P contents in AM treatment were similar to those in the control treatment.But both of them decreased significantly in C4 treatment.The biomass and P content of maize in AM treatment were much higher than those in the control treatment,but similar to C4 treatment.The results showed that NaHCO3 extractable organic P content in the hyphal compartment after experiment was 4.4 mg P/kg in the control treatment which was close to the initial soil content of 3.9 mg P/kg.Neither inoculation with AM fungus nor PSB C4 increased the P content,indicating that the solubility of phytin under the experimental condition was lower and didn′t have significant contribution to the soil effective organic P.By supplying NO-3-N in the hyphal compartment soil,AM fungi raised soil pH but had no influence on the phoshpatase activity.Inoculation with C4 increased phosphatase activity but didn′t change soil pH,indicating that C4 added the mount of phosphatase in the hyphal compartment soil.The NaHCO3 extractable organic P content in C4 treatment was much lower than that in AM treatment.NaHCO3 extractable inorganic P content in the C4 treatment soil was also significantly lower than that in the AM treatment but the total P content of maize didn′t increase.The hyphal length density decreased after inoculation with C4,and the number of C4 was 5×106 CFU/g soil,indicating that the soil must have provided it with P.So the bacterium C4 immobilized part of soil P to decrease the P uptake by AM fungal hyphae.As a result,the hyphae length density may decrease and P uptake of maize may not increase after inoculation with PSB C4.