Free proline levels in Ulva (Chlorophyta) in response to hypersalinity: Elevated NaCl in seawater versus concentrated seawater

Abstract

Changes in free proline concentrations following exposure to elevated NaCl in 35 psu artificial seawater (ASW) (an imbalance in ion ratio) or concentrated ASW (constant ion ratio) were investigated in the intertidal green alga Ulva fasciata Delile. When exposed to 55 psu achieved by adding NaCl to 35 psu ASW, free proline concentrations increased at hour 3 and reached a plateau after 12 h, whereas free proline concentrations in response to 55 psu achieved by concentrating ASW were constant during the treatment period. It is likely that an imbalance in ion ratio is a cue for the induction of a moderate accumulation of free proline in U. fasciata.