In the 1920s, Nobel Prize-winner Karl von Frisch showed that bees see colour. And we now know that pollinators perceive light between 300 and 600 nanometres. But we see different colours in response to a spectrum between 380 to 740 nanometres. So how does the way bees see colour differ from our perception?
Recently, scientists from the Indian Institute of Information Technology and Management, the University College and the Indian Institute of Space Science and Technology, Thiruvananthapuram, reported how humans and bee pollinators perceive floral colours.
The team selected fresh flowers of eighty-one species growing in and around Thiruvananthapuram and measured their floral spectral reflectances. Each flower species had a unique value. The wavelength varied between 350 and 700 nanometres. To test how the human eye perceives flower colours, the team used the universal colour space developed under the guidelines of the International Commission on Illumination.
They measured the mean reflectance values for the red, green, and blue regions of the spectrum, to which we are most sensitive. Since our response to different colours varies, the researchers used nonlinear modelling to relate our response to the variation in floral colours in terms of brightness, hue and chroma. And they found a dominance of red (52%) and yellow (43%) hued flowers.
To examine how the pollinator eye perceived the same colours, they illustrated floral colours in the form of colour hexagons. They measured the sensitivity of trichromatic reflectance for the ultraviolet, blue, and green regions of the spectrum, to which bees are more sensitive. They calculated the photoreceptor response of each receptor cell. Thus they found that blue-green (36%) and blue (25%) are the dominant floral colours perceived by bees.
The team found that the pollinators perceive the human-perceived white of Bauhinia acuminata as blue, and the human-perceived red colour of Saraka asoka as ultraviolet.
Pollinators associate floral colour with nutritional rewards. Understanding how insect pollinators perceive colour will provide insights into pollination ecology and help define strategies to ensure crop production mediated by pollinators.
Colour Res. Application 44 (3): 426-432 (2019)
Environmental Management and Policy Research Institute, Bengaluru
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