Impact of Funneliformis mosseae on the growth, lead uptake, and localization of Sophora viciifolia.

On the basis of a pot experiment under lead (Pb) stress, we investigated the effects of an arbuscular mycorrhizal (AM) fungus (Funneliformis mosseae) on the growth and Pb uptake of Sophora viciifolia L., and explored the Pb localization in AM roots using transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The results showed that high Pb levels (500 and 1000 μg/g) inhibited the growth of S. viciifolia seedlings. Compared with the noninoculation treatment, F. mosseae inoculation decreased the Pb concentrations above- and belowground by 61.0% and 15.2%, when exposed to Pb at a concentration of 1000 μg/g. The root length, fork number, tip number, surface area, and volume of mycorrhizal S. viciifolia were higher than those of the corresponding nonmycorrhizal plants. These parameters of mycorrhizal plants increased by 220%, 219%, 157%, 225%, and 278% when plants were exposed to Pb at 1000 μg/g compared with nonmycorrhizal plants. The ratio of root length with diameters between 0-0.2 mm to the total root length significantly increased under Pb stress, and F. mosseae inoculation significantly reduced the ratio. Under Pb stress, F. mosseae increased the ratios of root length with 0.61-0.8 and 0.81-1.0 mm diameters to the total root length, indicating that F. mosseae tended to thicken the roots of S. viciifolia under Pb additions. The combined results of TEM and EDS indicated that Pb deposited in not only plant cells but also the cell walls and vacuoles of the AM fungal intracellular hyphae, thus revealing the subcellular-level mechanism of AM fungi in alleviating the Pb toxicity to the host plant.