No abstract

The inland distribution of Plantago maritima in Ireland and Britain is strongly western and generally associated with base-rich soils or with flushes in more acidic upland soils. Plants from an eastern Irish salt marsh and from an inland population growing on shallow calcareous soils in east County Clare, Ireland, were grown in culture solutions with a range of seawater dilutions (10-100%) and nitrogen (2.8-140 ppm N) concentrations added as ammonium nitrate. A low nitrogen supply (2.8 ppm N) resulted in very low dry matter production but with increased nitrogen, plant growth increased, even of inland population plants in 50% seawater. Some inland plants survived 100% seawater, but growth was much reduced. The relatively high salinity tolerance of this inland population is discussed.

SUMMARYTwo experiments on the interaction between salinity and nitrogen supply were carried out on the halophytes Armeria maritima and Plantago maritima. Water potential values ranged from -016 MPa to -5-OMPa and nitrogen from 028 to 280 mg 1"' N. An increase in nitrogen above 2 8 mg T' N in the medium in all cases resulted in an increase in growth, though this was not so great at higher salinities. Armeria growth rate was optimal at a higher nitrogen concentration than Plantago and Armeria also accumulated nitrogen in shoots with increasing salinity. Plantago root nitrogen concentrations increased with increased nitrogen.Both species accumulated sodium in shoots, but in Armeria concentrations were lowest in the highest nitrogen treatments. Potassium was redistributed from shoots to roots with increasing salinity.Two populations oi Plantago from the salt marsh were examined. Differences in growth response and flowering time were observed. A third, inland population otPlatitago showed reduced vigour in water potentials lower than -2-5 MPa.

No abstract