Influence of N source on rate of Cl, N, Na and K uptake by cucumber seedlings grown in saline condition

The influence of two N sources, NO3 alone and NH4+NO3 (2:1) in the external medium on fluxes of Cl, N, Na and K calculated from the total nutrient content per unit root dry weight, were investigated using cucumber (Cucumis sativus) seedlings grown in saline conditions. The N source affected the fluxes of the above ions very differently: (a) when only NO3 was added, the rate of Cl uptake was inhibited whereas the rate of K absorption was stimulated; and (b) by contrast, the presence of NH, in the N source enhanced Cl uptake and inhibited K uptake. The effect on the rates of Na and N uptake was more complex and salinity dependent. The potassium: sodium ratios (K:Na) and potassium: sodium selectivity ratio (S., ) in roots and shoots in relation with the treatments are also presented. Possible reasons of the N source effect on the processes implicated with the response of plants to salinity are also discussed.