No abstract

The halophytic C 4 grass, Aeluropus littoralis, was cultivated under low (50 mM) and high (200 mM) NaCl salinity and inoculated with the arbuscular mycorrhizal fungi (AMF) Claroideoglomus etunicatum in a sand culture medium for 20 weeks. Shoot and root dry mass increased under salinity conditions up to 24 and 86%, respectively. Although the root colonization rate significantly decreased in the presence of salt, +AMF plants had higher biomass compared with -AMF ones only under saline conditions. Net CO 2 assimilation rate increased significantly by both salinity levels despite stable stomatal opening. In contrast, AMF-mediated elevation of the net CO 2 assimilation rate was associated with higher stomatal conductance. Unexpectedly, leaf activity of phosphoenolpyruvate carboxylase decreased by salinity and AMF colonization. Transpiration rate was not affected by treatments resulting in higher water-use efficiency under salinity and AMF conditions. Concentrations of soluble sugars and free α-amino acids increased by both salinity and AMF treatments in the shoot but not in the roots. Proline concentration in the leaves was higher in the salt-treated plants but AMF colonization did not affect it significantly. Leaf activity of nitrate reductase increased by both salinity and AMF treatments. Mycorrhizal plants had significantly higher Na + and K + uptake, while Ca 2+ uptake was not affected by salt or AMF colonization. The ratio of K:Na increased by AMF in the shoot while it decreased in the roots. Leaf osmotic potential was lowered under salinity in both +AMF and -AMF plants. Our results indicated that higher dry matter production in the presence of salt and AMF could be attributed to higher CO 2 and nitrate assimilation rates in the leaves. Higher leaf accumulation of soluble sugars and α-amino acids but not proline and elevated water-use efficiency were associated with the improved growth of A. littoralis inoculated with AMF.Additional key words: compatible solutes; net CO2 assimilation rate; nitrate reductase; phosphoenolpyruvate carboxylase; water relations.