Absorption experiments were conducted with tomato (Lycopersicon esculentum Mill. ‘VF-315’) seedlings using salts at the approximate ratio found in saline irrigation water (NaCl 41.9 mM, CaCl2 20.9 mM, and MgCl2 · 6H2O 10.5 mM) in combination with two herbicides. The osmotic pressure of this salt solution is 0.40 MPa (mega Pascal), which is equivalent to 4.0 bar or about 4.0 atm. EPTC (S-ethyl dipropylthiocarbamate) at 0.25 mM reduced the residual Na+, Ca2+, and Mg2+ content relative to the treatment with salts alone. CDEC (2-chloroallyl diethyldithiocarbamate) at 0.1 mM produced similar effects for Na+ and Ca2+. The addition of salts to either EPTC or CDEC induced significantly higher concentrations of total and residual herbicide in the tomato seedlings. The data suggest that salts reduce the tolerance of tomato to EPTC and CDEC by increasing absorption of the herbicides. The residual EPTC or CDEC in the tomato seedlings increased as the CaCl2 concentrations increased in the incubation medium. A strong linear relationship was found between the calcium content and EPTC or CDEC content in the tomato seedling tissue.

The combination of salts at the approximate ratio found in saline irrigation water, (NaCl 41.9 mM, CaCl2 20.9 mM, and MgCl2.6H2O 10.5 mM), with either 1 mM EPTC (S-ethyl dipropylthiocarbamate) or 0.1 mM CDEC (2-chloroallyl diethyldithiocarbamate) induced a greater reduction of root length, shoot length, and fresh weight of tomato (Lycopersicon esculentum Mill. ‘VF-315’) relative to either factor alone. The osmotic pressure of this salt solution is 0.40 MPa (mega Pascal), which is equivalent to 4.0 bar or ca. 4.0 atm. Similar results were found in lettuce (Lactuca sativa L. ‘Great Lakes–659’) using salts at 0.30 MPa (NaCl 31.4 mM, CaCl2 15.7 mM, and MgCl2.6H2O 7.3 mM) combined with either 0.75 mM EPTC or 0.2 mM CDEC. In tomato, the inhibition was additive for each parameter measured. In lettuce, however, the effect on fresh weight and shoot length was synergistic and the effect on root length was additive. Calcium chloride was the single salt component of the mixture, which when combined with either EPTC or CDEC, induced a significant reduction of root length, shoot length, and fresh weight in tomato relative to either factor alone. No additional reduction in growth was found in lettuce when each individual salt was combined with either EPTC or CDEC.