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.