title: Mycorrhizal C costs and nutritional benefits in developing grapevines.
abstract: Arbuscular mycorrhizal (AM) C-costs in grapevines were investigated. Dormant vines rely on stored C for initial growth. Therefore AM colonisation costs would compete with plant growth for available C reserves. One-year-old grapevines, colonised with Glomus etunicatum (Becker and Gerdemann), were cultivated under glasshouse conditions. The C-economy and P utilisation of the symbiosis were sequentially analysed. AM colonisation, during the 0-67 day growth period, used more stem C relative to root C, which resulted in lower shoot growth. The decline in AM colonisation during the period of 67-119 days coincided with stem C replenishment and higher shoot growth. Construction costs of AM plants and root C allocation increased with root P uptake. The efficiency of P utilisation was lower in AM roots. The reliance of AM colonisation on stem C declined with a decrease in colonisation, providing more C for the refilling of stem carbohydrate reserves and shoot growth. Once established, the AM symbiosis increased P uptake at the expense of refilling of root C reserves. Although higher root C allocation increased plant construction costs, AM roots were more efficient at P utilisation.
authors.affiliation: Botany Department, University of Stellenbosch, Private Bag X1, 7602, Matieland, South Africa.
authors.forename: P E
authors.initials: PE
authors.lastname: Mortimer
authors.forename: E
authors.initials: E
authors.lastname: Archer
authors.forename: A J
authors.initials: AJ
authors.lastname: Valentine
mesh_terms: D000383:Agriculture / Q000191:economics; D003365:Costs and Cost Analysis; D005658:Fungi / Q000502:physiology; D038821:Mycorrhizae / Q000502:physiology*; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D027843:Vitis / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology*