High and differential strontium tolerance in germinating dimorphic seeds of Salicornia europaea

Salicornia europaea, a highly salt-tolerant halophyte, is potentially resistant to other metals because plant stress tolerance partly relies on common physiochemical mechanisms. Large median seeds and small lateral seeds of S. europaea have high salt tolerance and display contrasting germination responses. Thus, we hypothesised that dimorphic seeds of S. europaea might also have high and differential strontium (Sr) tolerance during germination. Both types of seeds were incubated in different SrCl2 concentrations at 25 degrees C. 0-300 mmol L-1 SrCl2 did not significantly affect germination of median seeds. However, for lateral seeds, relatively high concentrations (>= 200 mmol L-1) dramatically inhibited germination. The simulated critical value (when germination percentage is 50%) was 502 mmol L-1 for median seeds and 224 mmol L-1 for lateral seeds. Dimorphic seeds of S. europaea are highly tolerant to Sr stress and large median seeds display higher tolerance. The results suggest that direct seeding of large seeds of S. europaea might be an effective method to remediate heavy Sr-polluted soils.