Flowering mechanism A biological mechanism is proposed based on the information we have above. Light is the flowering signal of Arabidopsis thaliana. Light activates photo-receptors and triggers signal cascades in plant cells of apical or lateral meristems. Action potential is spread via the phloem to the root and more voltage-gated calcium channels are opened along the stem. This causes an influx of calcium ions in the plant. These ions bind to calmodulin and the Ca2+/CaM signaling system triggers the expression of GI mRNA or FT and CO mRNA. The accumulation of GI mRNA or GI-CO-FT mRNA during the day causing the plant to flower. References External links Plant hormones