Effect of NaCl and KCl salts on the growth and solute accumulation of the halophyte Atriplex nummularia

Atriplex nummularia plants are able to grow well in the absence of significant amounts of Na+. Medium levels of salinity (100 mM NaCl or KCl) did not cause substantial inhibition of growth but increasing concentrations of salt induced a progressive decline in length and weight of the plants. This inhibition was significantly higher in KCl grown plants than in NaCl grown plants. In addition, although it has been proposed that both K+ and Na+ are involved in the osmotic adjustment of plants in response to high soil salinity, we show that Na+ ions contribute more efficiently than K+ ions to perform this function. Our results also indicate that most of the osmotic adjustment of the plant was due to the accumulation of inorganic ions. The strong inhibition of Rb+ transport caused by internal sodium suggests that this cation could be efficiently used by the plant and, as a consequence, the transport of other monovalent cations is down-regulated.