The effects of salt stress on growth and biochemical parameters in two maize varieties

Abstract

The main objective of this study was to examine the influence of salinity on growth and biochemical parameters (NR activity, amino compound accumulation, protein content, some inorganic ion concentrations) of two varieties of maize (Limko and Koka). Salinity (75.0 mol • m^-3 NaCl and 37.5 mol • m^-3 Na₂SO₄) significantly reduced fresh and dry weights of the investigated maize varieties. NaCl induced higher reduction in biomass production than Na₂SO₄. Differences in salt tolerance between Limko and Koka were small.It was found that in both maize varieties the nitrate reductase activity decreased under salt stress (100 mol • m^-3 NaCl). This effect was more marked in the Koka variety than Limko. Decrease in nitrate reductase activity had no inhibitory effect on accumulation of protein and free amino compounds. Salinity treatment (100 mol • m^-3 NaCl) led to an increase in free amino compound contents in roots and shoots of both investigated maize varieties, but these changes were not very large. The highest increase in amino compound level was observed in roots of Koka and it was 2-fold higher than in control plants. Salt stress did not change soluble protein contents in Limko and Koka varieties with the exception of Limko leaves. There was significant increase in soluble protein content on leaves of Limko and it amounted 128% of the control. Salinity caused a great increase in leaf and root Na⁺ concentration and a decrease in case of Ca²⁺ and K⁺ contents. The declines in Ca²⁺ content in maize roots were 76 and 70% respectively for Koka and Limko roots. The fall in K⁺ concentration was high, but not so drastic as in Ca²⁺. In roots of Koka and Limko the reduction in K⁺ content was approximately 30%. Higher reduction in K⁺content showed shoots of Limko. In this case K⁺ content lowered to 49% of control.