Heat Stress Halts Plant Growth Via Phytochrome Pathway
Researchers show high temperatures reverse the thermomorphogenesis pathway in Arabidopsis seedlings, suppressing their growth.
Updated on Nov. 9, 2026 in Botany
Researchers demonstrated that heat stress suppresses growth in Arabidopsis seedlings by reversing the thermomorphogenesis pathway. Temperatures beyond the growth optimum reduce auxin levels, auxin signalling, and PIF4 abundance in cotyledons.
Why it matters
Understanding how plants shut down growth under heat helps explain how crops respond to rising temperatures. The findings identify the phyB protein as a central regulator of this response.
The study used Arabidopsis cotyledons and seedling hypocotyls, tracking auxin, PIF4 and phyB behavior at temperatures above the growth optimum compared with optimal conditions. Whether these molecular changes translate directly to field-grown crops was not addressed in the findings.
The details
Warm temperatures normally promote hypocotyl elongation by relieving inhibition of phytochrome B, which activates the transcription factors PIF4 and PIF7 to drive auxin synthesis. Under heat stress beyond the growth optimum, the researchers found this sequence reverses, shrinking phyB nuclear bodies and causing phyB to assemble into enlarged condensates.
The Big Picture
The study extends the established thermomorphogenesis model, in which warm temperatures promote elongation through phyB inhibition, by showing that heat stress beyond the growth optimum reverses the pathway. The reported condensate behavior of phyB is also seen in mammalian cells, pointing to a shared mechanism across kingdoms.
Findings on how heat shuts down plant growth could inform breeding of crops more tolerant of rising temperatures. Commercial application timelines were not addressed in the research.
The takeaway
Plants can switch from growth to stress mode when temperatures climb too high, and the phyB protein sits at the center of that switch. Tracking this pathway may help researchers develop crops that keep growing through heat.
Further reading
Explore more research on plant responses in our Botany section.
