| The need for salinity tolerant turfgrasses is increasing because of the increased use of effluent or other low quality water for turfgrass irrigation. Greenhouse container and hydroponic experiments were conducted to determine the relative salinity tolerance, growth characteristics, and physiological responses (especially water and ion relations) of ‘Challenger’ Kentucky bluegrass (Poa pratensis L.) (KBG), ‘Arid’ tall fescue (Festuca arundinacea Schreb) (TF), ‘Fults’ alkaligrass (Puccinellia distans (L.) Parl.) (AG), and saltgrass (Distichlis spicata (Torr.) Beetle) (SG). Salinity treatments applied for 8 weeks using 1NaCl:1CaCl2 solution at 2.0, 4.7, 9.4, 14.1, 18.8, and 23.5 dS/m. Based on data on shoot dry mass, KBG, TF, AG, and SG experienced a 50% shoot growth reduction at 5.5, 14.2, 23.0, and 34.5 dS/m, respectively, suggesting the ranking of salinity tolerance was SG > AG > TF > KBG. Leaf firing of KBG, TF, and AG increased as salinity increased, but no injury was noticeable in SG. Salinity caused root cortex cells to collapse, in KBG at 14.1 dS/m and in TF at 23.5 dS/m. Alkaligrass and SG only had a few cell collapses at 23.5 dS/m. Osmotic adjustment (OA) occurred in all species under salinity stress. However, in KBG and TF, the contribution of Na + and Cl− to OA increased and became the major contributors at high levels of salinity, whereas Na+ and Cl − contributions to OA in SG were maintained at stable levels as salinity increased from 4.7 to 23.5 dS/m. As salinity increased, the contribution of unidentified osmolytes to OA increased in SG and decreased in KBG and TF. The ability to maintain a K+/Na+ ratio close to or above 1 appeared to be important for these grasses to tolerate high salinity. Saltgrass, AG, TF, and KBG could maintain a shoot K+/Na + ratio of 1 when salinity levels were less than 22.3, 13.6, 7.4, and 3.7 dS/m, respectively. Salt glands present in SG, root growth stimulation of SG and AG, maintenance of high root to shoot ratio in TF, synthesis of compatible solutes, regulation of ion concentrations, and maintenance of high K+/Na+ ratio in shoots are important salinity tolerance mechanisms among these grasses. |
