“STRUCTURAL COLOR in flowers, such as the iridescence exhibited by hibiscus trionum and tulipa kauffmanniana petals is determined by surface diffraction gratings that consist of ordered striations or ridges…cellulosic CLCs (cellulose chiral liquid crystals) are responsible for plant surface nanostructures and iridescent colors.”
http://www.sciencedirect.com/science/article/pii/S2215038214000077