Pedosphere 25(4): 501–511, 2015 ISSN 1002-0160/CN 32-1315/P c  2015 Soil Science Society of China Published by Elsevier B.V. and Science Press Salt Accumulation and Physiology of Naturally Occurring Grasses in Saline Soils in Australia Mohammad S. I. BHUIYAN 1,2 , Anantanarayanan RAMAN 1,2,∗ , Dennis S. HODGKINS 1 , David MITCHELL 3 and Helen I. NICOL 1 1 Soil Research Group, Charles Sturt University, Orange NSW 2800 (Australia) 2 Graham Centre for Agricultural Innovation, Wagga Wagga NSW 2650 (Australia) 3 Orange Agricultural Institute, NSW Department of Primary Industries, Orange NSW 2800 (Australia) (Received June 24, 2014; revised December 17, 2014) 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 (g s ), and intercellular CO 2 concentration (C i ), were investigated using one mature leaf from C. dactylon and T. ponticum populations. Increasing salinity levels in the topsoil had a significant influence on C i and g s , whereas no significant effect occurred on P n in C. dactylon and T. ponticum. The P n values in C. dactylon and T. ponticum were greater at Cundumbul than at Gumble. The greater Mg concentration facilitated greater P n 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. Key Words: bioaccumulation factor, intercellular CO 2 concentration, net photosynthetic rate, phytoremediation, revegetation, soil contamination, stomatal conductance, translocation factor Citation: Bhuiyan M S I, Raman A, Hodgkins D S, Mitchell D, Nicol H I. 2015. Salt accumulation and physiology of naturally occurring grasses in saline soils in Australia. Pedosphere. 25(4): 501–511. INTRODUCTION Metal contamination in soils is a major issue throughout the world. Metals, particularly the heavy metals such as cadmium (Cd), zinc (Zn), and lead (Pb), mostly from industrial sources, inflict immense changes to the soil environment (e.g., Mani et al., 2014, 2015). Salinity, too, is one of the major soil contamination problems across the world, due to human-induced landscape-scale changes of land use and modification of soil properties by human activi- ty (Rengasamy, 2006). In Australian landscapes, dry- land salinity (e.g., New South Wales, South Australia) and transient salinity (e.g., Western Australia) pre- dominate with nearly 17 Mha of land affected (Ren- gasamy, 2006). Salinity in New South Wales (NSW) is known to affect 0.062 Mha of productive agricultural land and in the central-western region of NSW 0.04 Mha (DECCW, NSW, 2009). For restoring the saline land, drainage and plant-based remediation are the two major options (Hajkowicz and Young, 2005). Drainage is energy and cost intensive, site specific, and can not be deployed in extensively salinity-affected areas (Barrett-Lennard et al., 2005). An alternative viable salinity-mitigation option is the establishment of salt- tolerant vegetation (Dickinson et al., 2009). Several studies (Qadir et al., 2007; Ravindran et al., 2007; Rabhi et al., 2009, 2010) have indicated that plant- based remediation is a well-established option for recla- mation and restoration of salt-affected land throughout the world. For restoring saline land, two plant-based strategies are currently being considered: 1) genetic manipulation of plant species for greater salinity tole- rance and 2) utilization of naturally occurring salt- ∗ Corresponding author. E-mail: araman@csu.edu.au.