Salinity tolerance mechanisms of grasses in the subfamily Chloridoideae

Forage grasses and turfgrasses are increasingly being subjected to salinity stress, due to accelerated salinization of irrigated agricultural lands wo rldwide, and to increased use of reclaimed and other secondary water source s for irrigating turfgrass landscapes. The objective of this study was to e xamine salinity responses of a number of important forage and turfgrass gen era in the subfamily Chloridoideae in attempt to gain understanding of sali nity tolerance mechanisms operating in this subfamily. Grasses were exposed to salinities up to 600 mM NaCl in solution culture. Salinity tolerance de creased in the following order: Distichlis spicata var. stricta (Torr.) Bee tle > Sporobolus airoides (Torr.) Torr. > Cynodon dactylon (L.) Pers. = Zoy sia japonica Steud. > Sporobolus cryptandrus (Torr.) A. Gray. > Buchloe dac tyloides (Nutt.) Engelm. > Bouteloua curtipendula (Michx.) Torr. Relative r oot length (RL) and relative root weight (RW) increased under saline condit ions, relative to control, in salt tolerant grasses. Leaf sap osmolality, N a+, Cl-, and proline concentrations were negatively correlated and glycineb etaine was positively correlated with salinity tolerance. Bicellular salt g lands were observed on leaves of all species. Salinity tolerance was positi vely correlated with Na+ and Cl- salt gland secretion rates. Within the sub family Chloridoideae, salinity tolerance was associated with saline ion exc lusion, facilitated by leaf salt gland ion secretion, and with accumulation of the compatible solute glycinebetaine.