The science behind chilling hours requirement for temperate fruit trees ?

[am77494]

A number of temperate climate fruit trees (apples, pears, …) and vegetables require chilling hours to flower / bear fruits.

Vernalization

Chilling requirement

So, what’s going on at the biochemistry level ? What does the chilling hours (1000, 500, …) requirement translate to at a cellular level ?

[Darren_Garrison]

It is right there in your first link:

At the molecular level, flowering is repressed by the protein Flowering Locus C (FLC), which binds to and represses genes that promote flowering, thus blocking flowering.[3][13] Winter annual ecotypes of Arabidopsis have an active copy of the gene FRIGIDA (FRI), which promotes FLC expression, thus repression of flowering.[14] Prolonged exposure to cold (vernalization) induces expression of VERNALIZATION INSENSTIVE3, which interacts with the VERNALIZATION2 polycomb-like complex to reduce FLC expression through chromatin remodeling.[15] The epigenetic silencing of FLC by chromatin remodeling is also thought to involve the cold-induced expression of antisense FLC COOLAIR[16][17] or COLDAIR transcripts.[18] Vernalization is registered by the plant by the stable silencing of individual FLC loci.[19] The removal of silent chromatin marks at FLC during embryogenesis prevents the inheritance of the vernalized state [20]
Since vernalization also occurs in flc mutants (lacking FLC), vernalization must also activate a non-FLC pathway.[21] A day-length mechanism is also important.[9]

[am77494]

My bad - thank you