Flower development in spring: plants, cells, and molecules 

Plants flower in response to seasonal changes of day length. Movement of the so called FT protein from leaves to the shoot apex is required for this response. On arrival, FT participates in the florigen activation complex (FAC) which directly binds to genes involved in flowering and activates their transcription. The first action of FT activity at the apex of the plant is an increase in size of the shoot apical meristem followed by initiation of flower primordia. We describe the function of FAC proteins and their role in regulating transcription factors that control meristem size.