Research conducted by scientists from John Innes Centre (JIC), in
collaboration with colleagues in Hungary and France, shows that
vernalization is influenced by warm conditions as well as cold, and a much
wider temperature range than previously thought.

Vernalization is the process by which plants require prolonged exposure to
cold temperature before they transition from the vegetative state to flower.
The study began as an exploration into how variance in ambient temperatures
might influence flowering regulation in winter wheat. But it unexpectedly
uncovered an "extreme vernalization response". Before the study, it was
thought that vernalization only happened up to a maximum of about 12°C. The
researchers found that the true temperature was much higher.

The researchers exposed a panel of 98 wheat cultivars and landraces and to
temperatures ranging from 13 to 25°C in controlled environments. Normally,
when vernalization is complete, plant growth is accelerated under warm
temperatures. However, one cultivar, named Charger, did not follow this
standard response. Gene expression analysis showed that the wheat floral
activator gene (VRN-A1) was responsible for this trait. Further experiments
showed that expression of genes that delay flowering is reactivated during
high temperatures of up to 24 °C, showing that vernalization is not only a
consequence of how long the plant experiences continuous cold.

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