Pre-flowering heat stress cuts wheat yields but may shield crops from later heat damage
Field experiments in Spain found that wheat suffers greater grain yield losses when heat waves strike before flowering than after. However, an early heat wave appeared to trigger a priming effect that reduced losses from subsequent heat events. The study, published in the Journal of Experimental Botany, tested two modern wheat varieties across two growing seasons.
The study's experimental design relied on transparent field tents that generated controlled temperature increases via a greenhouse effect, with heat load standardized by measuring accumulated hourly degrees above a 32°C threshold. This allowed researchers to compare pre-flowering and post-flowering stress conditions on an equivalent thermal basis across two growing seasons.
Both modern wheat varieties tested—despite employing contrasting yield-building strategies—responded similarly to the heat treatments. The research team, led by scientists at the University of Lleida, emphasized that most prior heat-stress studies examined single events under controlled conditions rather than sequential stresses in actual field environments, making this the first documented evidence of antagonistic interactions between successive heat waves in field-grown crops.
This research could meaningfully inform agricultural planning as climate change extends heat wave seasons into critical wheat developmental windows. Farmers may use these findings to prioritize protective measures—such as irrigation scheduling or variety selection—around the pre-flowering period when grain number is established. Predictive crop yield models could also become more accurate by accounting for heat wave timing and priming effects, potentially helping stabilize food supplies and grain markets in regions increasingly exposed to extreme temperature events.