Research conducted by a team at China Agricultural University has identified a promising approach to help crops adapt to rising temperatures by shifting their flowering times. The study, published on August 28, 2025, in the journal Seed Biology, reveals that “early-morning flowering” (EMF) can significantly enhance the reproductive success of vital crops, including sorghum, pearl millet, and indica rice, in the face of increasing heat stress.
The team analyzed temperature trends and the diurnal floret opening time (DFOT) of over 100 plant species. They discovered that shifting reproductive events to cooler early hours allows these crops to avoid the damaging midday temperatures that can hinder pollination and grain development. This natural adaptation strategy holds great potential for breeding climate-resilient varieties of essential crops such as rice, wheat, and maize.
Climate-induced heat stress has intensified over the past fifty years, with projections indicating that conditions will continue to worsen as the century progresses. Staple crops like maize, rice, and soybean often flower during peak summer heat, exposing them to temperatures that can disrupt reproductive processes. Traditional adaptation methods, such as altering sowing dates or enhancing biochemical tolerance, have proven inadequate in rapidly warming regions or multi-cropping systems.
Linking Flowering Habits to Heat Resilience
The researchers combined global climate records, field data, and molecular analyses to assess how rising temperatures affect crop reproduction and how diurnal flowering habits can mitigate heat stress. Between 2004 and 2023, daily maximum temperatures during hot seasons increased by an average of 1.25°C, with the duration of midday heat episodes extending by 1.08 hours. Notably, Africa recorded the highest mean maximum temperature at 34.0°C in 2023, while North America experienced the fastest rate of warming.
To evaluate biological adaptation, the team classified DFOT data from 102 flowering species into morning-, midday-, and night-flowering groups. Cereal crops exhibited significant differences in optimum flowering temperatures, with morning-flowering species thriving at 26.1°C, midday species at 22.3°C, and night-flowering varieties at 29.3°C. Among cereals, maize and indica rice, which bloom in the early morning, showed higher temperature thresholds for seed set compared to japonica rice.
Controlled experiments provided further evidence of the effectiveness of early-morning flowering. EMF wheat and rice varieties consistently achieved higher seed set under heat stress, while maize also benefited from earlier pollination. At the molecular level, genes such as OsMYB8 and EARLY MORNING FLOWERING 1 were found to regulate DFOT by modifying cell wall structures, with similar homologs identified in over 60 plant species.
Integrating EMF into Crop Management
The findings suggest that early-morning flowering serves as a robust, widely applicable mechanism for safeguarding crop reproduction against escalating climate-induced heat stress. By aligning flowering with cooler hours, plants can avoid issues such as pollen sterility, fertilization failure, and grain loss during heat episodes.
Beyond breeding, integrating EMF traits into crop management strategies could enhance the resilience of agricultural systems. Approaches such as precision sowing or even drone-assisted morning pollination could optimize growing conditions. This strategy would also benefit insect-pollinated species, as pollinators are more active in cooler morning temperatures.
Unlike traditional biochemical tolerance breeding, which struggles to keep pace with climate change, manipulating DFOT provides an immediate and practical adaptation strategy based on natural plant behaviors. The implications of this research extend beyond individual crops, offering a blueprint for developing climate-resilient agricultural varieties that can maintain stable yields in increasingly unpredictable environments.
The study received funding from various sources, including the National Key Research & Development Program of China and the National Science Foundation of China, highlighting the importance of collaborative efforts in addressing global food security challenges.
This research underscores the critical need for innovative approaches to agriculture as climate change continues to impact crop production worldwide.
