Photosynthetica 2015, 53(4):572-584 | DOI: 10.1007/s11099-015-0131-4

Physiological responses of halophytic C₄ grass Aeluropus littoralis to salinity and arbuscular mycorrhizal fungi colonization

R. Hajiboland^1,2,*, F. Dashtebani², N. Aliasgharzad^1,3

¹ Center of Excellence for Biodiversity, University of Tabriz, Tabriz, Iran

² Plant Science Department, University of Tabriz, Tabriz, Iran

³ Soil Science Department, University of Tabriz, Tabriz, Iran

The halophytic C₄ 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-colonized (+AMF) plants had higher biomass compared with plants without AMF colonization (-AMF) only under saline conditions. Net CO₂ assimilation rate increased significantly by both salinity levels despite stable stomatal opening. In contrast, AMF-mediated elevation of the net CO₂ assimilation rate was associated with a 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 Ca²⁺ 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 CO₂ 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.

Keywords: carotenoids; chlorophyll content; compatible solute; gas exchange; growth parameters; water relations

Received: September 17, 2014; Accepted: January 19, 2015; Published: December 1, 2015Show citation