Salt Tolerance in the HalophyteHalosarcia pergranulatasubsp.pergranulata

Halosarcia pergranulata (P. G. Wilson) subsp. pergranulata is a member of the Salicornioideae and is native to Australia. Salt tolerance in H. pergranulata subsp. pergranulata was assessed by growing plants for 83 d at seven NaCl concentrations from 10 to 800 mol m −3 . Shoot biomass was greatest for plants grown at 10 to 200 mol m −3 NaCl, while at salinities of 300 mol m −3 or higher it was inhibited. There was little increase in succulence in response to NaCl, and it even declined at the highest salinities. The K + [ratio]Na + molar ratio in succulent shoot tissues decreased from 0.30[ratio]1 in plants grown at 10 mol m −3 NaCl to 0.02[ratio]1 in plants at 600 mol m −3 , due to a three-fold increase in tissue Na + concentration and a five-fold decline in tissue K + . The osmotic potential of sap (π sap ) in the expanding shoot tissues remained −1.7 to −2.5 MPa below the πof the root medium. Na + plus Cl − contributed 56 to 80% of the π sap in plants grown at 10 to 800 mol m −3 NaCl. These findings show that H. pergranulata subsp. pergranulata has a high degree of NaCl tolerance, and that studies on solute compartmentation at the cellular level are required to elucidate the mechanisms by which this species tolerates very low tissue K + :Na + ratios.