Tolerance of roadside and old field populations of common teasel (Dipsacus fullonum subsp. sylvestris) to salt and low osmotic potentials during germination

Plants inhabiting degraded habitats must contend with stressful environments. However, their ability to adapt may be constrained by available genetic variation and genetic correlations between traits. Here, we examine the correlation between salt and drought tolerance in germinating seeds from contrasting populations of common teasel (Dipsacus fullonum subsp. sylvestris) growing on roadsides that experience high salinity due to de-icing salts, or growing in an old field site, remote from roadsides and free of salinity stress. We examined the contribution of drought and salinity tolerance to the tolerance of roadside conditions in seedlings from five maternal families from three roadside and three old field populations. Germination and early growth were compared under high salinity, low water potential set at 20.5 MPa with solutions of polyethylene glycol 8000, sodium chloride or vermiculite wetted to 20.5 MPa with distilled water. Root length and the emergence of cotyledons (where appropriate) were used as a measure of performance. Maternal families from roadside populations displayed greater tolerance of both high salinity and drought than families from old field populations. However, no maternal family possessed tolerance to both drought and salinity. Salt and drought tolerance during germination were not correlated, indicating that they are separate traits in this species.