Arbuscular mycorrhizal fungi and foliar phosphorus inorganic supply alleviate salt stress effects in physiological attributes, but only arbuscular mycorrhizal fungi increase biomass in woody species of a semiarid environment

Abstract

Salinity may limit plant growth especially in arid and semiarid regions. Arbuscular mycorrhizal fungi (AMF) and the supply of inorganic phosphorus (Pi) could alleviate the negative effects of such stress by improvement in stomatal conductance, photosynthesis and biomass. The aim of this study is to evaluate the ecophysiological performance of Cenostigma pyramidale (Tul.) E. Gagnon & G. P. Lewis (Fabaceae) in a greenhouse under salinity conditions in combination with the supply of AMF and leaf Pi. The experiment was conducted in a factorial design considering two levels of salinity (+NaCl and -NaCl), two levels of AMF (+AMF and -AMF) and two levels of leaf Pi supply (+Pi and -Pi). The variables gas exchange, leaf primary metabolism, dry biomass and nutrients were measured. Plants with AMF under non-saline conditions presented a high photosynthesis and biomass. In saline conditions, AMF promoted lower decrease in photosynthesis, high shoot dry matter and low content of leaf and root Na+ and Cl-. Plants treated with leaf Pi increased biomass and photosynthetic pigments under both conditions and accumulated more Cl- in shoots under salinity conditions. When combined, AMF * Pi increased photosynthesis only in non-saline conditions. Plants under salinity conditions without AMF and Pi had higher decreases in gas exchange and high content of Cl- in roots. Therefore, C. pyramidale plants improved their metabolism under both growth conditions in the presence of AMF, Pi or a combination of both. However, the greatest increases in growth and tolerance to salinity occurred in the isolated presence of AMF.

Keywords: Caatinga; chlorophyll fluorescence; gas exchange; leaf biochemistry; mycorrhiza; phosphorus.