Vigour/tolerance trade-off in cultivated sunflower (Helianthus annuus) response to salinity stress is linked to leaf elemental composition

Developing more stress-tolerant crops will require greater knowledge of the physiological basis of stress tolerance. Here we explore how biomass declines in response to salinity relate to leaf traits across twenty genotypes of cultivated sunflower (Helianthus annuus). Plant growth, leaf physiological traits, and leaf elemental composition were assessed after 21 days of salinity treatments (0, 50, 100, 150, or 200 mM NaCl) in a greenhouse study. There was a trade-off in performance such that vigorous genotypes, those with higher biomass at zero mM NaCl, had both a larger absolute decrease and proportional decrease in biomass due to increased salinity. More vigorous genotypes at control were less tolerant to salinity. Contrary to expectation, genotypes with a low increase in leaf Na and decrease in K:Na were not better at maintaining biomass with increasing salinity. Rather, genotypes with a greater reduction in leaf S and K content were better at maintaining biomass at increased salinity. While we found an overall trade-off between sunflower vigour and salt tolerance, some genotypes were more tolerant than expected. Further analysis of the traits and mechanisms underlying this trade-off may allow us to breed these into high vigour genotypes in order to increase their salt tolerance.