Response of maize (Zea mays L.) to rimsulfuron under salt conditions

Investigations were carried out to determine the possible interaction between salinity (60 mmol*dm-3 NaCl) and phytotoxicity of herbicide Titus 25 DF (sulfonylurea herbicide containing active ingredient rimsulfuron). The herbicide was added to the nutrient solution at two concentrations - 1 or 100 nmol*dm-3. After 7 days of cultivation in the nutrient solution determined were the growth parameters and some biochemical compounds (photosynthetic pigments, total protein and free amino compounds content). The combined action of 1 nmol*dm-3 rimsulfuron and salt caused a reduction in plant biomass accumulation, but this reduction was due to the salt itself. In the presence of 100 nmol*dm-3 rimsulfuron, growth inhibition of maize roots was very high and salinity did not modify herbicide toxicity. However, reduction in maize shoots growth equalled the sum of the reductions caused by each particular factor applied separately (additive effect). The reduction in shoot fresh weight reached 64%. The investigated stress factors induced a significant increase in amino compounds, with the exception of maize roots grown under NaCl plus 100 nmol-dm-3 rimsulfuron. The concentration of total protein in maize roots diminished under NaCl and 100 nmol*dm-3 rimsulfuron, although in the other cases, it did not change distinctly in comparison to the control. All factors, with the exception of NaCl, induced a slight increase in protein contents in maize leaves. Stress factors did not change significantly the total chlorophyll concentration, however, carotenoid content was markedly reduced. Nevertheless, the combined action of 100 nmol*dm-3 rimsulfuron and NaCl caused a 10% increase in carotenoid content as compared to the control plants. In conclusion, salinity did not change the toxicity of the herbicide applied in low dose (1 nmol*dm-3), but it did increase herbicide toxicity at high concentration (100 nmol*dm-3) regarding the maize shoots.