Salinity and waterlogging tolerances in three stem-succulent halophytes (Tecticornia species) from the margins of ephemeral salt lakes

Tecticornia species are stem-succulent, perennial halophytes (sub-family Salicornioideae; Chenopodiaceae) that inhabit saline areas including the margins of ephemeral salt lakes in Australia. Based on zonation observed at salt lakes, species were hypothesised to differ in tolerances to salinity and/or waterlogging. Three Tecticornia species were grown in sub-irrigated or waterlogged sand culture with treatments from 10 to 800 mM NaCl, for 60 d in a glasshouse. Growth, tissue solutes, root porosity, root radial O-2 loss, and ethanol production, were assessed. The three species were salt tolerant; at 800 mM NaCl shoot RGR (ash-free) was reduced by 9% in T. indica, 22% in T. pergranulata and 39% in T. mellaria. Na+ and Cl- were the predominant osmotica in succulent stem tissues. Glycinebetaine was a major organic solute. T. pergranulata and T. indica were waterlogging tolerant; shoot RGR was reduced by at most 29% irrespective of salinity. Waterlogging tolerance in T. mellaria was variable (shoot RGR 8%-56% of controls) and some individuals died. T. pergranulata formed adventitious roots with aerenchyma, but the two other species did not. Anoxic tips of lateral roots produced ethanol. The three Tecticornia species are salt tolerant. T. pergranulata is also waterlogging tolerant and formed adventitious roots containing aerenchyma, traits consistent with growth on mud flats of salt lakes. T. indica was unexpectedly tolerant of waterlogging, whereas T. mellaria was less tolerant. Future work is needed to evaluate tolerances of inundation (i.e. submergence) and to higher salinity treatments.