The importance of phytochromes in plant growth lies in their role as photoreceptors that detect light. They regulate various physiological processes, such as seed germination, flowering, and stem elongation, in response to changes in light quality and quantity. Phytochromes exist in two interconvertible forms: Pr, which absorbs red light, and Pfr, which absorbs far-red light. The balance between these forms allows plants to adapt to their environment, optimizing their growth and reproductive success under varying light conditions.