Heatwaves affecting wheat before flowering can cause greater yield losses than those occurring afterwards. However, an initial exposure to high temperatures can activate protective mechanisms in the plant, better preparing it for subsequent heatwaves during the same season.
These are the main conclusions of research by Agrotecnio and the University of Lleida (UdL), published in the Journal of Experimental Botany. The study analyzes how the intensity, frequency, and timing of heatwaves interact and influence wheat yield.
Field experiments, conducted over two growing seasons with two wheat varieties, simulated heatwaves using transparent tents that increased diurnal temperature through a greenhouse effect. Results indicate that grain yield is more sensitive to pre-flowering heatwaves, primarily affecting grain number, while later heatwaves have a greater impact on grain weight.
“"Most studies have examined heat stress as a single event and often under controlled rather than field conditions. We investigated whether a prior heatwave could modify how wheat responds to a subsequent exposure during its development."
One of the most significant findings is that plants exposed to an initial heatwave before flowering showed less impact from a subsequent second heatwave compared to plants that only experienced this second exposure. This phenomenon, known as 'priming' or physiological memory, suggests that initial stress can activate lasting protective responses.
“"To our knowledge, this is the first evidence of this type of antagonistic interaction between successive heatwaves in field crops."
These results have implications for improving crop yield prediction models and designing more effective climate change adaptation measures. The study highlights the importance of protecting wheat during sensitive reproductive stages, particularly around flowering.
Although the research focuses on wheat, the investigators believe this response could be relevant for other temperate climate cereals such as barley, oats, or rye, although temperature thresholds and heat response may vary between species.
