Phytochromes have unique properties that enable them to switch between two stable states that sense red and far-red light. The light is actually detected by a specialized pigment that sits within a pocket on the protein. Red and far-red light, says Forest, have the effect of reversibly changing the structure of the pigment in the pocket, which then flips a switch on the protein to trigger the events of growth and development.
Intriguingly, the phytochrome has the ability to store the light it has detected, initiating a response days after it is sensed, Vierstra says. "This memory allows the plant to predict where the light will come from each day and measure the length of daylight so that they flower in the correct season." By deducing the architecture of the phytochrome protein, according to Vierstra and Forest, it may be possible to engineer and introduce into crops phytochromes that respond to different wavelengths of light, or are more or less active. These changes, in turn, could allow plants to grow under different climate regimes or flower at different times of the year, for example.
Gaining precise control over flowering events, says Vierstra, is a key to the success or failure of most crops, as most of what we eat comes from seeds and fruits produced by flowers. In another scenario, it may be possible to dampen the role of phytochromes in crop plants to avoid having them compete with each other for light when grown close together in a field.