title: Respiratory responses of arbuscular mycorrhizal roots to short-term alleviation of P deficiency.
abstract: Arbuscular mycorrhizal (AM) root respiration can impose a respiratory sink on host reserves under low P conditions, but it is not known how AM roots respond to short-term supply of sufficient P. Therefore, the effect of P stress alleviation on the respiration of AM roots was investigated in 5-week-old tomato plants. Plants were inoculated with Glomus mosseae in sand culture and grown hydroponically in a low P (2 microM) nutrient medium for 3 weeks. P stress was alleviated by the supply of 2 mM P for 72 h. With P stress alleviation, the improved root P status coincided with a decline in AM fungal activity and a reduction in root CO2 and O2 fluxes of the AM plants. During P stress alleviation, the AM roots had lower concentrations of organic acids, derived from root-zone CO2 assimilation, in their root exudates. These results show that short-term alleviation of low P conditions in AM roots rapidly affects AM fungal symbiont activity, AM root respiration, and root-zone CO2-derived organic acid metabolism.
authors.affiliation: Department of Horticulture, Applied Sciences Faculty, Cape Peninsula University of Technology, P.O. Box 652, Cape Town, 8000, South Africa. alexvalentine@mac.com.
authors.forename: A J
authors.initials: AJ
authors.lastname: Valentine
authors.affiliation: Department of Horticulture, Applied Sciences Faculty, Cape Peninsula University of Technology, P.O. Box 652, Cape Town, 8000, South Africa.
authors.forename: A
authors.initials: A
authors.lastname: Kleinert
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002250:Carbon Radioisotopes; D018551:Solanum lycopersicum / Q000382:microbiology; D038821:Mycorrhizae / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D010758:Phosphorus / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology*
chemical_list: D002250:Carbon Radioisotopes; D002245:Carbon Dioxide; D010758:Phosphorus