How and Why Did Flower Color First Evolve?
Flowering plants feature a wondrous array of colors, the primary purpose of which is to attract insect pollinators. But this may not have been the original function of flower color.
In a recent review published to the Journal of Experimental Botany, Dr. Paula J. Rudall, head of the Department of Comparative Plant and Fungal Biology at the Royal Botanic Gardens, Kew in the United Kingdom, suggests that anthocyanin pigments, one of the primary compounds that grants flowering plants their diverse colors, originally accumulated in plants to help protect growing tissues.
"Thus, the visual cue provided by colour in flower petals could have first evolved as a secondary effect," she writes.
Anthocyanin pigments first built up in gymnosperms, which predate angiosperms (flowering plants) and include conifers, cycads, and Gingko. These pigments gave some gymnosperms' seed cone bracts – specialized, scaly leaves – a red color, and also provided photoprotection, thermoregulation, or some sort of defense against herbivores, Rudall says. When angiosperms branched off from gymnosperms on the evolutionary tree, around 200 to 240 million years ago, flower color was co-opted as a way to attract insect pollinators. Subsequently, anthocyanins in the plants began producing purple and blue colors in addition to red. Other pigments like carotenoids also arose.
"Ultimately, both chemical and physical aspects of flower colour result from relatively late stages in a complex and interactive cascade of genes that control the entire process of flower development," Rudall concluded.
Source: Paula J. Rudall. Colourful cones: how did flower colour first evolve? J Exp Bot. 2019 Nov 12. pii: erz479. doi: 10.1093/jxb/erz479