Cultivars of Triticum aestivum differing in resistance to AI were grown under aseptic conditions in the presence and absence of AI and polypeptides present in root exudates were collected, concentrated, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Upon exposure to 100 and 200 NM AI, root elongation in AI-sensitive cultivars was reduced by 30 and 65%, respectively, whereas root elongation in resistant cultivars was reduced by only 15 and 30%. Accumulation of polypeptides in the growth medium increased with time for 96 to 120 h, with little additional accumulation thereafter. This pattern of exudation was virtually unaffected by exposure to 100 p~ AI in the AI-resistant cultivars Atlas 66 and Maringa, whereas total accumulation was reduced in sensitive cultivars. Changes in exudation were consistent with alterations in root elongation. AI-induced or AI-enhanced polypeptide bands were detected in Atlas 66 and Maringa after 72 h of exposure to AI. Increased accumulation of 12-, 22-, and 33-kD bands was observed at 75 p~ AI in Atlas 66 and 12-, 23-, and 43.5-kD bands started to appear at 50 PM AI in Maringa. In the Alsensitive cultivars Roblin and Katepwa, no significant effect on polypeptide profiles was observed at values up to 100 p~ AI. When root exudates were separated by ultrafiltration and the AI content was measured in both high molecular mass (HMM; >10 kD) and ultrafiltrate (