Plant growth and tissue sucrose metabolism in the system of trifoliate orange and arbuscular mycorrhizal fungi

Mycorrhizal development is absolutely dependent on hexoses of the host plant from sucrose cleavage by sucrose-cleaving enzymes. A pot study evaluated effects of five arbuscular mycorrhizal fungi (AMF) species including Diversispora spurca, Funneliformis mosseae, Glomus versiforme, Rhizophagus intraradices, and Paraglomus occultum on growth performance, chlorophyll, sucrose, fructose and glucose concentrations, and sucrose-related enzyme (acid invertase, Al; neutral invertase, NI; sucrose synthase, synthetized direction, SS) activities in four-month-old trifoliate orange (Poncirus trifoliata) seedlings. All the inoculated treatments significantly increased plant height, stem diameter, leaf number, shoot and root fresh weight, total root length, root surface area, root volume, and chlorophyll a, chlorophyll b and total chlorophyll concentrations. In general, AMF inoculation markedly decreased leaf and root sucrose concentration and increased leaf and root glucose concentrations. AI, NI and SS activities in leaves were generally significantly higher in AM than in non-AM seedlings, whereas in roots AI, NI and SS activities were significantly lower in AM than in non-AM seedlings, except a significantly higher root SS activity in R. intraradicesand G. versiforme-colonized seedlings. Root AM colonization was significantly positively correlated with root glucose but negatively with root sucrose. These results indicated that AMF could regulate sucrose synthesis and cleavage of the host plant for AM development through affecting sucrose-related enzymes and chlorophyll concentration, thereby stimulating plant growth. (C) 2014 Elsevier B.V. All rights reserved.