How to measure flower ultraviolet reflectance using digital photography

Abstract

AbstractAimsFlower ultraviolet (UV) reflectance strongly influences insects’ ability to detect flowers and locate pollen/nectar sources. Although included in the TRY database, the lack of a cost‐effective standardised method of measurement hampers the availability of information on this key floral trait. Digital photography and image processing allow for a novel approach to flower UV reflectance measurement that is both accessible and accurate.LocationEuropean semi‐natural grasslands.MethodsWe used a UV‐LED light and a mirrorless camera with a filter, which represents a low‐cost equipment for narrow emission/reflection photography (350–380 nm). Flowers were photographed with two standards of known reflection, and UV reflectance values were obtained using open‐source image processing software. We measured UV reflectance for 57 plant species typical of European semi‐natural grasslands.ResultsOur values substantially matched the categorical classes obtained by analogue photography available in TRY and showed a highly significant relationship with spectrophotometric measures.ConclusionsThe method proposed here overcomes the one based on analogue photography and subjective visual estimates, and represents an easy and low‐cost alternative to spectrophotometry. It may promote the standardised measurement of flower UV reflectance and broaden the information of this trait globally, meeting the needs of functional ecology and trait‐based community assembly studies.