Seed and transplanted adult plants from populations of Festuca rubra, collected from inland, salt-marsh and sand-dune sites were grown on culture solution with added sodium chloride. The growth of the populations of the three habitats was reduced differentially by salt. The salt marsh ecotype Festuca rubra ssp. litoralis was only slightly affected and the inland ecotype F. rubra ssp. rubra was severely retarded at 60 mM NaCl. The dune ecotype F. rubra ssp. arenaria had an intermediate tolerance. The tolerant ecotypes accumulated less sodium chloride as compared to the sensitive ecotype, suggesting that salt tolerance is caused in part by salt exclusion.In addition, the dune ecotype F.r. arenaria appeared to be more drought tolerant than the salt marsh ecotype. Abscission of salt-saturated leaves does not function as an adaptation to salinity in Festuca rubra.All three ecotypes accumulated proline with increased salinity. The response was most pronounced in the drought tolerant F.r. arenaria, indicating that proline accumulation is a response to osmotic stress rather than to ion-specific effects of salinity. The observed differences in salt tolerance may be explained by differential sensitivity to toxic effects of sodium chloride.The occurrence on a beach plain of closely adjacent populations of F.r. arenaria and F.r. litoralis, differing markedly in salt tolerance, is briefly discussed.

Juvenile plants of Plantago lanceolata and P. major ssp. major were grown on nutrient solution at optimal availability of nitrate as well as at various degrees of suboptimal nitrate availability. In the optimal treatment the nutrient solution contained 7.5 mmol NO per 1. In the various suboptimal treatments nitrate of the basic solution was replaced by sulphate, and nitrate was continually added during the experimental period. The rate of addition was exponential, according to the formula: [Formula: see text] (N=initial content of nitrogen in the seedling, RAR=relative addition rate, t=time in days). There were four suboptimal treatments corresponding to RAR's of 0.25, 0.20, 0.15 and 0.10 per day. In all cases plants were in steady state. The plant parameters as varied in the experimental treatments were related to the N concentrations (% fresh weight). Most relationships were linear. P. major attained a higher RGR than P. lanceolata at equal N concentrations. The root weight ratio was inversely proportional to the N concentration, and varied between 0.55 and 0.25. The N productivity (mg·(mg N)·d) with respect to shoot biomass was proportional to the N concentration, and higher in P. major. This difference is related to the lower N concentration of P. major. The N productivity with respect to root biomass was highest when the N concentration was reduced by about 50 per cent. The length of the root axis was inversely proportional to the N concentration, and greater in P. lanceolata. The ecological implications of the experimental results were discussed.

Abstract. Plantago major ssp. major and P. lanceolata were grown in solution culture with exponential nutrient addition rates. Compared with P. lanceolata, P. major major showed a higher shoot weight ratio (SWR, fraction of plant dry weight in the shoot) and a higher net assimilation rate (NAR, expressed on a leaf dry weight basis) at equal plant (PNC) and shoot (SNC) nitrogen concentration, respectively. No difference was observed in shoot nitrogen ratio (SNR, fraction of plant nitrogen in the shoot) against PNC between the two species. The effect of these differences in matter partitioning and NAR on plant growth was examined by using a growth model. The model assumed (1) that the SWR and SNR are a linear function of PNC and (2) that the NAR is a rectangular hyperbolic function of SNC. Curvilinear relationships were observed between relative growth rate (RGR) and PNC. P. major major had a higher RGR at equal PNC and, thus, a higher nitrogen productivity (NP) than P. lanceolata. Steady‐stale exponential growth was simulated for different nitrogen availability in the environment. P. major major had a higher RGR over the whole range of nitrogen availability but the difference attenuated with decreasing availability of nitrogen. The simulation also showed P. lanccolata having higher plasticity in the shoot/root ratio, which resulted from its higher variability in PNC.

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