ABSTRACT The benefits promoted by arbuscular mycorrhizal fungi (AMF) to forest species seedlings include higher growth rate, better nutrition, and higher survival rates. Inoculation with AMF may facilitate revegetation of degraded lands, although it depends on symbionts and environmental conditions, such as soil P availability. In this sense, the lack of information justifies the carrying out of studies of this nature. We investigated the dependence and responsiveness of two forest species native to the Atlantic Forest, Pseudobombax grandiflorum and Bauhinia forficata, to different AMF inocula (isolated AMF species, Dentiscutata heterogama, DH, Gigaspora margarita, GM, Rhizophagus clarus, RC, mixed inoculum with these former three AMF species, MI) compared to the uninoculated control (UC), combined with different P doses applied to the substrate (0, 24, 71, 213, and 650 mg kg -1 ), under greenhouse conditions. We evaluated root colonization, growth, and nutritional variables for Pseudobombax grandiflorum and Bauhinia forficata, 112 and 116 days after sowing with pre-germinated seeds, respectively. Native forest species exhibited different degrees of mycorrhizal dependence. The highest mycorrhizal dependence of P. grandiflorum seedlings was indicated by significant benefits, both growth and nutritional, promoted by innoculation treatments, under fertilization with the intermediate dose of P (213 mg kg -1 ). In fact, under this P dose, seedlings responded to a maximum increase in biomass in the GM treatment and maximum concentration of P and N in the shoots in the UC and DH treatments, respectively. The lowest mycorrhizal dependence of B. forficata seedlings was highlighted by significant growth benefits promoted by inoculation treatments under the lowest doses of P (24 or 71 mg kg -1 ). Under this P dose, we observed seedlings with maximum value of the root:shoot ratio in most of the types of inoculation and also higher values of biomass and height in the MI treatment. The responsiveness in terms of increase in growth and nutritional variables varied depending on the forest species, the dose of P applied to the substrate, and the AMF type of inoculum used. Root biomass and total dry biomass, mainly, should preferably be included in future studies with the same objective as the present study, as they were more relevant to point out the differences between treatments, in comparison with the variables associated with nutritional variables.
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