EFFECTS OF SALINITY ON GROWTH AND IONIC COMPOSITION OF COLEUS-BLUMEI AND SALVIA-SPLENDENS

The amenity species Coleus blumei and Salvia splendens were irrigated with increasing concentrations of NaCl under glasshouse conditions. Salt was either added to the plants from the seedling stage onwards at one of the following concentrations, 0, 30, 60, 120 or 180 mM NaCl up to six weeks (Expt. I), or, starting from 0 mM NaCl, the concentration was increased by 15 mM NaCl per week to a final concentration of 210 mM NaCl at 14 weeks (Expt. II). In Expt. I leaf number, leaf area, shoot and weight progressively decreased in Coleus. However, Salvia root and shoot weights showed a pronounced fall at 30 mM NaCl and total leaf abscission occurred at NaCl concentrations above 60 mM NaCl within six weeks. Leaf thickness increased in both species over the sampling period. Where there was a gradual increase in NaCl concentrations (Expt. II), growth of Coleus and Salvia was much less inhibited at concentrations of NaCl found to be inhibitory in Expt. I. In both the concentration of Na+ in the roots increased as the external concentration of NaCl increased and the shoots showed a delayed but eventually similar pattern to that of the roots. The K+ content in both species were reduced as the external NaCl increased. From the data reported here, Coleus was the more salt tolerant species.