Acclimation to high salinity in the invasive CAM plant Aptenia cordifolia

Background: Invasive species, such as Aptenia cordifolia, grow rapidly in different habitats, colonising large areas of soil surface. However, mechanisms of acclimation to salt stress have not been explored thus far in this obligate CAM plant. Aims: We evaluated the capacity of this species to withstand salt stress in terms of growth, photoprotection and changes in phytohormones. Results: This species was not only very resistant to extreme salinity (up to 650 mM NaCl) in the short term (14 days) but also to high salt concentrations (150 mM NaCl) in the longer term (42 days); improvements in leaf water status and fresh biomass production were also observed. This occurred concurrently with an increase in zeatin levels, while concentrations of other phytohormones were unaffected. Furthermore, plants were able to maintain the F v/F m ratio above 0.80 indicating little damage to PSII for 42 days at 150 mM NaCl, or above 0.50 for 14 days at extreme salinity (up to 650 mM NaCl). Conclusions: We conclude that A. cordifolia has not only evolved mechanisms to adapt to high salinity, but it is able to take advantage of such conditions by increasing leaf water content and fresh biomass production, which underpin its ecological competence in saline environments.