Salt Accumulation and Physiology of Naturally Occurring Grasses in Saline Soils in Australia

Abstract

Salinity is a major soil contamination problem in Australia. To explore salinity remediation, we evaluated the concentrations of sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca) in roots and shoots and in the supporting soil of the naturally occurring grasses, Cynodon dactylon and Thinopyrum ponticum, at two salt-affected sites, Gumble and Cundumbul in central-western New South Wales, Australia. The physiological parameters of the two grass species, including net photosynthetic rate (Pn), stomatal conductance (gs), and intercellular CO2 concentration (Ci), were investigated using one mature leaf from C. dactylon and T. ponticum populations. Increasing salinity levels in the topsoil had a significant influence on Ci and gs, whereas no significant effect occurred on Pn in C. dactylon and T. ponticum. The Pn values in C. dactylon and T. ponticum were greater at Cundumbul than at Gumble. The greater Mg concentration facilitated greater Pn in C. dactylon and T. ponticum populations at Cundumbul than Gumble. With increasing salinity levels in the soil, Na accumulation increased in C. dactylon and T. ponticum. The ratio between K and Na was > 1 in roots and shoots of both populations irrespective of the sites. Bioaccumulation factor (BF) and translocation factor (TF) results revealed that K and Na translocations were significantly higher in T. ponticum than in C. dactylon, whereas Ca and Mg translocations were significantly higher in C. dactylon than in T. ponticum. Accumulation of Na, K, Mg, and Ca ions was higher in T. ponticum than in C. dactylon; therefore, we suggest that T. ponticum as a greater salt accumulator than C. dactylon could be used for revegetation and phytoremediation of the salt-affected soils.