Unlocking Flowering: The Vernalization Process

Certain plants require low temperatures to initiate their flowering process, which is known as vernalization. This phenomenon was named after the Latin term "vernal," meaning "spring-like." The stimulus for vernalization is received by the shoot apex of a mature plant or plant embryo, rather than the leaves as in photoperiodism.

Vernalization requirements vary among plant species, but most occur between 0°C to 10°C, with a temperature of around 4°C being the most effective. The specific temperature and duration of exposure required for vernalization varies, and the plant part that must be exposed to low temperature also varies.

In some plants, moist seeds require several weeks of exposure to low temperature to initiate flowering, while recently germinated seedlings have a cold requirement in other plants. For some plants, low temperature exposure is an absolute requirement for flowering, while others will flower sooner with low temperature exposure but still flower at a late date without it.

Examples of plants with a low temperature requirement for flowering include biennials such as carrots and annuals like winter wheat. Without exposure to low temperature, carrot plants will continue vegetative growth indefinitely and not initiate sexual reproduction. The vernalin hormone, which induces vernalization, is actually gibberellin.

Both photoperiodism and vernalization serve to synchronize plant reproductive behavior with their environment, ensuring that the same species of flowers bloom at the same time for cross-pollination and genetic variability.