Salinity responses of three halophytes from inland saltmarshes of Jaén (southern Spain)

•Better growth: F. pulverulenta >A. prostrata >P. coronopus.•Increase in Na+ and Cl−, and decrease of K+ in plants with saline excretion.•Greater increase of metabolite concentrations in the most tolerant plants.•A common signaling response (phenols and polyamines) in three halophytes. Soil analyses of three saltmarshes in Jaén province (southern Spain) indicated Sodic Solonchack type for Don Benito saltmarsh, and Sodic Calcixerepts for Barranco Hondo and Brujuelo saltmarshes. Three halophytes (Frankenia pulverulenta, Atriplex prostrata, and Plantago coronopus) from these saltmarshes were submitted to long (21 days) and gradual (0, 100, 200, and 300 mM NaCl) salinity stress, under hydroponic culture. The results of fresh mass, dry mass, root:shoot ratio, leaf water content, ion content, proline, total phenols, and polyamines (putrescine, spermidine, spermine and cadaverine) were examined to investigate the species’ responses to saline stress. Maximum biomass production and leaf water content was found between 100 and 200 mM NaCl in F. pulverulenta and at 100 mM NaCl in A. prostrata, while a decrease of these parameters was registered in P. coronopus as the salt concentration and salt-exposure time increased. In leaves, Na+ and Cl− accumulation increased with salt concomitant with a reduction of K+ in plants with salt excretion mechanisms (F. pulverulenta and A. prostrata), while high levels of ions were found with and without salt in P. coronopus. For osmotic adjustment, proline content proved important in F. pulverulenta and A. prostrata, while in P. coronopus this osmolyte decreased with salt, while phenols and polyamines increased in all three species. The highest levels in (Spermidine + Spermine): Putrescine ratio was related to the more salt-tolerant species. These results appear to indicate various adaptation responses to salinity. Rising levels of proline, phenols, and polyamines were related to better growth, which could contribute to different degree of tolerance and distribution of these species in saltmarshes.