Two near-isogenic lines of the wheat variety Lance having Glu-D1a (HMW-GS 2 + 12) and Glu-D1d (HMW-GS 5 + 10) were subjected to several regimes of heat stress. In 200 1, the temperature regimes were (i) 20/16 (day/night, degrees C from planting to maturity, (ii) 20/16 except for a 3-day heat treatment of 35/20, 25 days after anthesis and (iii) 20/16 until 25 DAA, after which plants were subjected to 40/25 until maturity. In 2002, treatments (i) and (iii) were the same while treatment (ii) used a temperature of 40/25 degrees C for 3 days at 25 DAA. Seed was collected at 3-day intervals starting from 16 days after anthesis and analyzed for protein composition by SE-HPLC. The line with the Glu-D1d allele showed an earlier polymerization of glutenin than its allelic counterpart and a higher molecular weight of glutenin at maturity, this being deduced front measurements of the percentage of unextractable polymeric protein. It is postulated that the timing and rate of glutenin polymerization, and the timing of high temperature application may be the key factors contributing to an explanation of the effect of heat stress on functionality. (c) 2008 Elsevier Ltd. All rights reserved.