PLANT-GROWTH, METABOLISM AND ADAPTATION IN RELATION TO STRESS CONDITIONS .14. EFFECT OF SALINITY ON THE INTERNAL SOLUTE CONCENTRATIONS IN PHASEOLUS-VULGARIS

In response to salinity, remarkable changes in ion distribution and concentration, proline content, relative growth rate (RGR) and in transpiration rate were maintained in 4-week-old Phaseolus vulgaris plants. Thus increasing salinity levels in the growth medium induced a reduction in the RGR and in the rate of transpiration. In all of the plant organs, Na, Cl and proline concentrations increased continuously whereas K and Ca concentrations decreased with increasing salinity except in the second and third trifoliate leaves. The magnitude of increase in Na concentration in roots was more profound than in leaves. Moreover, Mg was almost unaffected by increasing salinity. On the other hand, desalinization of the growth medium increased the internal contents of K and Ca and largely decreased that content of Na in all of the plant organs. The present changes in the internal ion concentrations are discussed in relation to K - Na selectivity and ion transport in the plant.