Vernalisation

Vernalisation is a plant’s developmental response in which prolonged exposure to winter cold induces flowering or the transition to reproductive growth. It is a common adaptation in temperate-zone species, especially winter annuals and many biennials, and is also observed in some perennials. In these plants, exposure to a chilling period ensures that flowering occurs in spring rather than during mid-winter.

Mechanistically, vernalisation involves the repression of flowering repressors through cold-induced pathways. In the model plant Arabidopsis thaliana, extended cold lowers the expression of FLOWERING LOCUS C (FLC), a major flowering repressor, via cold-responsive regulators such as VIN3 and associated chromatin changes. This creates a vernalization memory that persists after winter, allowing flowering to proceed during warmer spring conditions when other cues like photoperiod are favorable. In cereals and other crops, vernalisation involves different gene networks (for example VRN1 and VRN2) that enable or modify the flowering transition after cold.

The requirement for vernalisation varies among species, cultivars, and environments. Some plants have no vernalisation requirement and flower without cold exposure; others, particularly winter varieties, need a chilling period of weeks to months. Cold treatment can occur naturally in the field or be simulated in controlled environments, though the precise duration and temperature range are species-specific.

Vernalisation has major ecological and agricultural significance. It ensures flowering aligns with favorable spring conditions, influences seed production and crop yield, and is a central consideration in breeding programs aimed at temperate climates.