Osmotic concentration and pH may inhibit the seed germination and radicle growth of lettuce. At 25 milliosmols, an aqueous solution of Hoagland, sodium chloride, and sucrose exhibits over 50% inhibition on the radicle growth of lettuce. However, mannitol solution reveals 50% inhibition only at concentrations above 125 milliosmols. The pH range of from 4 to 8 has only slight significant effect on the radicle growth of lettuce. Interaction between pH and osmotic effects is not evident. Compared with aqueous plant extracts, the nutrient solutions give less inhibition. The results of this study can be used as an indication of a solution of which the cause of inhibition is due to one or both of the aforementioned effects, or due to a phytotoxic effect.