Grand Rapids Variety of Lettuce Produces Seeds That Will Not

Essay

Grand Rapids variety of lettuce produces seeds that will not germinate unless they are exposed to light. Phytochrome is also involved in that exposure to red light stimulates germination and far-red light inhibits germination. However, the effect of red light can be reversed by an immediate exposure to far-red light--and vice versa. You design an experiment in which you expose seeds of Grand Rapids lettuce first to red light, then immediately to far-red light, and then immediately to red light again. Would these seeds germinate? Use your knowledge of the phytochrome molecule to explain your reasoning. What if the seeds were exposed first to red light, then immediately to far-red light, then immediately to red light again, and then immediately to far-red light again?