Abstract: The phytochrome gene family play a critical role in mediating photothermal responses during Arabidopsis thaliana seed germination. Here we evaluated the germination rates of phyA, phyB, phyC, phyD, and phyE single mutants under 12 different light and temperature regimes, using wild-type (Col-0) seeds as controls. Our results indicate that phyA mutant seeds germinate under red light but are inhibited under far-red light and high temperatures (35°C). phyB mutant seeds germinate at low (15°C) and moderate (25°C) temperatures under both white light and far-red light, but not at high temperatures (35°C). phyC mutant seeds show consistent germination across all conditions except under white light at high temperature (35°C). Both phyD and phyE mutant seeds germinate at low (15°C) and moderate (25°C) temperatures, and under red and white light, but not at high (35°C) temperature, darkness or far-red light. These observations suggest that phyB, phyC, and phyD mutants may have impaired integration of light and temperature cues, whereas phyA and phyE mutants appear to maintain this integrative function. Overall, our findings demonstrate that mutations in phytochrome genes can modify seed germination adaptability to varying environmental conditions.

Key words: phytochrome, Arabidopsis, seed germination, light quality, temperature, ecological adaptability