Colouring agents in yellow and white flowered papaver radicatum in Northern Greenland

Abstract

In the extreme north, Papaver radicatum s.l. occurs in a yellow and in a white-flowered type. The more severe the weather conditions the higher the frequency of the white phenotype. The colouring agents in the petals are all flavonol glucosides; in the yellow flowers gossypitrin (1) and herbacitrin (2), in the white ones the kaempferol glucoside astragalin (3). Only astragalin shows UV reflection, which is valuable in attracting insect pollinators, so very likely the presence of astragalin may be responsible for the success of the white-flowered type under suboptimal weather conditions. We were unable to confirm the hypothesis that the yellow colouring agents, gossypitrin and herbacitrin, should be more costly to produce than the white one, astragalin, as an investment in order to obtain the higher temperature observed in yellow flowers. The distribution pattern with high frequency of the yellow-flowered poppies where the likelihood of sunshine is high, may have other reasons than carbon allocation to the colouring agents. Yellow flowers are more showy than white ones, and although this in general benefits pollination it may also increase the risk of herbivory. White flowers are at the same time believed to escape herbivory and obtain a better pollination under dull weather conditions, due to the UV-reflection by astragalin.