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The gliadin content and composition at harvest play a critical role in governing wheat flour properties and uses. The effects of two major environmental factors, temperature and nitrogen (N) supply, on gliadin accumulation were studied using a sequential extraction method coupled with RP–HPLC separation, in order to understand the variations observed at harvest. The thermal effects after anthesis were studied at canopy level in transparent climate tunnels in 1997 and 1998 under natural light. The N effects were studied in field experiments in 1997. An increase in temperature after anthesis induced an increase in the rate of gliadin accumulation per day, and a decrease in the duration of accumulation in days. The effects of the temperature were greater on the α, β-gliadins than on the ω- and γ-gliadins. Increased N nutrition increased the rate and duration of accumulation both in days and degree-days (˚Cd). The level of N nutrition before anthesis governed the effects of N supply at anthesis. The accumulation of ω-gliadins was relatively more affected by the N supply than the α-, β- and γ-gliadins. The final composition of gliadins was a function of the rate of accumulation and of the duration of synthesis, determined by the dates of onset and cessation of synthesis. We concluded that the dynamic allocation of N between different gliadin fractions, described in terms of thermal time, could be useful for modelling gliadin content and composition of wheat.

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