title: Arbuscular mycorrhiza mediates glomalin-related soil protein production and soil enzyme activities in the rhizosphere of trifoliate orange grown under different P levels.
abstract: Glomalin-related soil protein (GRSP) is beneficial to soil and plants and is affected by various factors. To address whether mycorrhizal-induced GRSP and relevant soil enzymes depend on external P levels, a pot study evaluated effects of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae on GRSP production and soil enzyme activities. Three GRSP categories, as easily-extractable GRSP (EE-GRSP), difficultly-extractable GRSP (DE-GRSP), and total (EE-GRSP + DE-GRSP) GRSP (T-GRSP), were analyzed, together with five enzyme activities (β-glucosidase, catalase, peroxidase, phosphatase, polyphenol oxidase) in the rhizosphere of trifoliate orange (Poncirus trifoliata) grown under 0, 3, and 30 mM KH2PO4 in a sand substrate. After 4 months, root AM colonization and substrate hyphal length decreased with increasing P levels. Shoot, root, and total biomass production was significantly increased by AM colonization, regardless of P levels, but more profound under 0 mM P than under 30 mM KH2PO4. In general, production of these three GRSP categories under 0 or 30 mM KH2PO4 was similar in non-mycorrhizosphere but decreased in mycorrhizosphere. Mycorrhization significantly increased the production of EE-GRSP, DE-GRSP and T-GRSP, soil organic carbon (SOC), and activity of substrate β-glucosidase, catalase, peroxidase, and phosphatase, but decreased polyphenol oxidase activity, irrespective of P levels. Production of EE-GRSP, DE-GRSP, and T-GRSP significantly positively correlated with SOC and β-glucosidase, catalase, and peroxidase activity, negatively with polyphenol oxidase activity, but not with hyphal length or phosphatase activity. These results indicate that AM-mediated production of GRSP and relevant soil enzyme activities may not depend on external P concentrations.
authors.affiliation: College of Horticulture and Gardening, Yangtze University, Jingzhou, Hubei, 434025, China, wuqiangsh@163.com.
authors.forename: Qiang-Sheng
authors.initials: QS
authors.lastname: Wu
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Ying-Ning
authors.initials: YN
authors.lastname: Zou
authors.forename: Xin-Hua
authors.initials: XH
authors.lastname: He
mesh_terms: D002957:Citrus / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology*; D005656:Fungal Proteins / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D038821:Mycorrhizae / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D010710:Phosphates / Q000032:analysis / Q000378:metabolism*; D058441:Rhizosphere; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D005656:Fungal Proteins; D006023:Glycoproteins; D010710:Phosphates; D012987:Soil; C573268:glomalin