Poinsettia length. The colored bracts—which are most often flaming red but can be orange, pale green, cream, pink, white, or marbled—are often mistaken for flower petals because of their groupings and colors, but are actually leaves. The colors of the bracts are created through photoperiodism, meaning that they require darkness (12 hours at a time for at least five days in a row) to change color. At the same time, the plants require abundant light during the day for the brightest color. The flowers of the poinsettia are unassuming and do not attract pollinators. They are grouped within small yellow structures
Basics of white flower colouration is a method to turn petunia flowers from white to transparent. The petunia flower is immersed into a flask of water, connected to a vacuum pump, after which the flower appeared colourless. The white colour is expressed by the air present in the vacuoles that absorb the light, without air the flower would lose the white colour. There is an increasing interest in flower colour, since some colorations are currently unavailable in plants. Ornamental companies create new flower colour by classical and mutation breeding and biotechnological approaches. For example white bracts in "Poinsettia" are obtained by high frequency irradiation. Basics