AbstractSeeds ofLepidiumandSinapiswere germinated and grown for 3 days in different concentrations of Triton X‐100 (0.001–0.1 % v/v). The elongation of the primary root was slightly stimulated by low concentrations. In concentrations above 0.01 %, Triton inhibited root growth and forked root hairs developed. The hairs elongated both at the apex and at the base, exhibited protoplasmic streaming and activity of particulate non‐specific esterase. In contrast the growth of the hypocotyl of bothLepidiumandSinapisdiminished steadily in increasing concentrations of Triton. Triton also affected the percentage germination ofLepidium, which increased or decreased according to the concentration used. The changes in root growth and germination and the appearance of branched root hairs in abundance coincide with a change in the detergent solution from monomer to aggregated mole