Classic experiments suggested that a floral stimulus, florigen, could move across a graft from an induced plant to a noninduced plant and trigger flowering. Recent evidence using Arabidopsis has recently shown that florigen is probably A) a phytochrome molecule that is activated by red light. B) a protein that is synthesized in leaves, travels to the shoot apical meristems, and initiates flowering. C) a membrane signal that travels through the symplast from leaves to buds. D) a second messenger that induces Ca++ ions to change membrane potential. E) a transcription factor that controls the activation of florigen-specific genes.