How do Spring plants know when to bloom

With buds bursting early, only for a mild winter to turn Arctic and wipe them out, we are witnessing how warm weather can trigger flowering, even out of season, and how important it is for plants to blossom at the right time of year. In research published in the journal Nature, scientists from the John Innes Centre on the Norwich Research Park have identified the switch that accelerates flowering time in response to temperature. With warm air, a control gene, called PIF4, activates the flowering pathway, but at lower temperatures the gene is unable to act. "What is striking is that temperature alone is able to exert such specific and precise control on the activity of PIF4," said Dr Phil Wigge. Previously, it has been shown that PIF4 is vital for controlling other aspects of plant responses to warmth, for example growth, but this is the first time that the gene has been shown to be necessary for the activation of flowering by temperature. Flowering is activated by a special molecule, called Florigen. Florigen is activated by many signals, including the longer days of spring. Some plants rely more on temperature, others more on daylength to control key stages in their life cycle such as leaf emergence and flowering. This is reflected in the old saying "Ash before Oak, you're in for a soak; Oak before Ash, you're in for a splash."