Salinity effects on photosynthetic pigments, proline, biomass and nitric oxide in Salvinia auriculata Aubl.

Abstract Aims: Effects of salt stress on the physiology of Salvinia auriculata were investigated. Method Plants were supplemented with 0, 50, 100 and 150 mmol L-1 NaCl and incubated for 5 days. NO content was evaluated after 2 hours and 5 days. Photosynthetic pigments, proline and nutrients were analyzed after 5 days. Major Results Higher chlorophyll a content was observed in plants treated with 50 mmol L-1, decreasing in higher NaCl concentrations, while chorophyll b content decreased with increasing NaCl concentrations. Exposure to 50 mmol L-1 NaCl increased biomass, while higher concentrations caused loss of biomass. Ca, K and Mg decreased with increasing NaCl concentrations, and the Na/K ratio was significantly increased at 150 mmol L-1 NaCl. Proline increased significantly at 150 mmol L-1. Extracellular NO content increased after 2 hours, with significantly higher NO concentrations in roots observed at 50 mmol L-1. Decreases in NO content were observed after 5 days. Conclusions The results indicate that moderate salinity induces NO production earlier during incubation, probably associated to signaling for the production of compounds that assist in stress tolerance. At higher concentrations, this tolerance is reduced. This allows for further understanding of the physiological and biochemical mechanisms associated with the adaptation of this macrophyte to saline conditions, which, in turn, affect this species ecology and distribution in coastal areas