Symbiosis with AMF and leaf Pi supply increases water deficit tolerance of woody species from seasonal dry tropical forest

Abstract

In seasonal dry tropical forests, plants are subjected to severe water deficit, and the arbuscular mycorrhizal fungi (AMF) or inorganic phosphorus supply (P_i) can mitigate the effects of water deficit. This study aimed to assess the physiological performance of Poincianella pyramidalis subjected to water deficit in combination with arbuscular mycorrhizal fungi (AMF) and leaf inorganic phosphorus (P_i) supply. The experiment was conducted in a factorial arrangement of 2 water levels (+H₂O and -H₂O), 2 AMF levels (+AMF and -AMF) and 2P_i levels (+P_i and -P_i). Leaf primary metabolism, dry shoot biomass and leaf mineral nutrients were evaluated. Inoculated AMF plants under well-watered and drought conditions had higher photosynthesis and higher shoot biomass. Under drought, AMF, P_i or AMF+P_i plants showed metabolic improvements in photosynthesis, leaf biochemistry and higher biomass compared to the plants under water deficit without AMF or P_i. After rehydration, those plants submitted to drought with AMF, P_i or AMF+P_i showed a faster recovery of photosynthesis compared to treatment under water deficit without AMF or P_i. However, plants under the drought condition with AMF showed a higher net photosynthesis rate. These findings suggest that AMF, P_i or AMF+P_i increase the drought tolerance in P. pyramidalis, and AMF associations under well-watered conditions increase shoot biomass and, under drought, promoted faster recovery of photosynthesis.

Keywords: Caatinga; Chlorophyll a fluorescence; Gas exchange; Mycorrhiza; Phosphorus; Plant biochemistry.