The effect of saline hypoxia on growth and ion uptake in Suaeda maritima

Abstract

The widely occurring annual halophyte Suaeda maritima experiences fluctuating salt and oxygen concentration during tidal cycles in salt marshes and shows tolerance of extreme hypoxia. The effect of saline waterlogging on growth and ion accumulation was investigated in tanks in a glasshouse where tidal flow was simulated, and in an aerated and hypoxic saline nutrient solution in a controlled environment cabinet. Laboratory data were compared with data from a survey of growth in two salt marshes. Plants in the nutrient solution grew equally well in the alternative nitrogen sources, NO3– and NH4+. Hypoxia, produced in the nutrient solution by nitrogen bubbling in the absence of turbulence and using stagnant agar, reduced root growth; hypoxia in waterlogged pot media in the glasshouse also reduced shoot growth and net K+ uptake but increased net uptake of Na+ and Cl–. 22Na+ influx into shoots was only significantly reduced by hypoxia when combined with a sudden increase in salt concentration to 200 mM NaCl. S. maritima appears to be well adapted to tolerate severely hypoxic growth conditions.