De-vernalization - when heat erases flower induction

De-vernalization is the process leading to the delay or total inhibition of flowering in vernalized plants. This phenomenon takes place after planting under high temperatures and its meaning is the actual reversion of flower induction acquired by the plant during cold exposure. De-vernalization occurs in both annual and perennial plant species and can even be used as a means to avoid flowering, like in onion. How can this happen? The mechanism of de-vernalization has been elucidated in only a small number of plants, like wheat and Arabidopsis, revealing differential expression of master flowering inhibitors achieved by epigenetic modifications. Typically, bulbs and corms grown for flower production undergo appropriate forcing and vernalization treatments in the summer and are planted in autumn. In these crops, the occurrence of de-vernalization generating a delay or complete revocation of flowering is increasing, due to the constant rise in autumn temperatures. These features have a major detrimental effect on flower production, yet the regulation of de-vernalization in flowering bulbs is far from being elucidated. In bulbs and corms, higher temperatures at planting severely reduce germination and sprouting rate. In corms, such as anemone and buttercup, de-vernalization can lead to a total arrest of meristem development. In lily, de-vernalization is linked with an increase in glycerol content in the bulb. Glycerol and/or its metabolites also induce the upregulation of genes linked to dormancy and to the downregulation of flowering-promoting genes. In the context of climate changes and in view of the damaging interactions of higher temperatures with flowering-promoting pathways, it is important to further explore the regulation of de-vernalization in bulbs and corms.