Integrated effect of arbuscular mycorrhizal fungi and hydrogen peroxide on the root system of trifoliate orange seedlings

Abstract

The root-system architecture (RSA) is critical for plant growth and mineral absorption and is also easily affected by various abiotic and biotic factors including arbuscular mycorrhizal fungi (AMF). The present study evaluates the integrated effects of an AM fungus (Glomus versiforme) and exogenous hydrogen peroxide (0, 1, and 100 µM) on mycorrhizal development, growth, RSA, and carbohydrate allocation of trifoliate orange (Poncirus trifoliata) seedlings. Root mycorrhizal colonization and number of vesicles increased significantly on application of 1 µM H 2 O 2 but was notably inhibited by 100 µM H 2 O 2 . AMF colonization increased shoot and root fresh weight. A significant differences was seen with 1 µM H 2 O 2 but not with 0 or 100 µM H 2 O 2 . Inoculation with AMF notably increased RSA traits, including total length, surface area, projected area, and volume, with 0 and 1 µM H 2 O 2 but not with 100 µM H 2 O 2 . AMF significantly decreased the concentrations of sucrose and glucose in leaves treated with 0 and 100 µM H 2 O 2 , but notably increased the concentrations of sucrose and glucose in roots treated with 0 and 1 µM H 2 O 2 . The highest root sucrose allocation of AM seedlings appeared in the treatment with 1 µM H 2 O 2 . The results imply that a low concentration of H 2 O 2 (1 µM) acted as a signal molecule to stimulate the development of RSA and AMF, whereas a high concentration of H 2 O 2 (100 µM), which is regarded as a toxic molecule producing reactive oxygen species, interfered with the formation of RSA and AMs.