AbstractSerial longitudinal and transverse sections were prepared from roots ofCucumis sativusandCucurbita maximathat had been exposed/sham‐exposed to 60‐Hz electric fields for 0–2 days. Field exposures were selected to produce a 10–20% or a 70–80% growth inhibition in whole roots of both species. Cortical cell length and diameter were measured using a microscope and eyepiece micrometer; measurements were conducted “blind”. In both species, inhibition of cellular elongation was associated with exposure to electric fields (EF). Cellular radial expansion was apparently unaffected by exposure to electric fields. The diameters of radially unexpanded or fully expandedC. sativuscortical cells were about 25–30% smaller than those of comparable cells inC. maximaroots. Previous studies of the relationship between rates of root growth and applied EF strength showed that the response thresholds ofC. sativusandC. maximadiffered by a similar relative amount. These results are consistent with the postulate that EF‐induced effects in roots are elicited by induced transme