Alpine pennycress in UV light. Coloured photograph showing moderate ultraviolet (UV) reflecting properties of alpine pennycress flower petals (Noccaea caerulescens). Blue represents UV reflectance, dark areas represent UV absorption. The UV pattern, known as a 'nectar guide' is thought to attract pollinating insects. This image was created with a digital camera adapted to filter and detect UV light waves. The resulting image is monochrome since UV light has no true colour. It was coloured on a computer. See image B826/803 for same image seen in normal daylight.