The discovery explains the mechanism of this memory --a sort of biological switch -- and how it can be inherited by offspring, say the researchers at the John Innes Centre led by Prof Martin Howard and Prof Caroline Dean.
Prof Dean said: "There are quite a few examples that we now know of where the activity of genes can be affected in the long term by environmental factors. And in some cases the environment of an individual can actually affect the biology or physiology of their offspring but there is no change to the genome sequence."
The researchers used the example of how plants "remember" the length of the cold winter period in order to exquisitely time flowering so that pollination, development, seed dispersal and germination can all happen at the appropriate time.
Prof Howard said: "We already knew quite a lot about the genes involved in flowering and it was clear that something goes on in winter that affects the timing of flowering, according to the length of the cold period."
Using a combination of mathematical modelling and experimental analysis the team has uncovered the system by which a key gene called FLC is either completely off or completely on in any one cell and also later in its progeny.
They found that the longer the cold period, the higher the proportion of cells that have FLC stably flipped to the off position. This delays flowering and is down to a phenomenon known as epigenetic memory.