Effect of arbuscular mycorrhizal fungal inoculation on root system architecture of trifoliate orange (Poncirus trifoliata L. Raf.) seedlings

Plant root system architecture is essential characteristics in relation to nutrient acquisition by root system from soil volume. Many environmental factors can affect the establishment of root system architecture, e.g. arbuscular mycorrhizal (AM) fungi. We inoculated the trifoliate orange (Poncirus trifoliata L. Raf.) seedlings with four AM fungal species in rhizoboxes, with non-inoculated seedlings as control. Using the WinRHIZO® image analysis system, the root system architecture of seedlings was characterized. Results indicated that AM colonization did not affect the tap root length, the average root diameter, the basal root growth angle in spite that four AM fungal species exerted differential influence on the plant growth. Contrastingly, AM colonization significantly reduced the total root length, the root volume, the root surface area, but promoted the formation of lateral roots of high order. In addition, AM colonization induced more fine roots and less coarse roots. To our knowledge, it is the first report on the influence of AM fungi on the distribution of root diameter size classes. The mechanisms and implication of AM fungi on root system architecture is discussed.