The colourful life of flowers

Abstract

Flowers are the flagship structure of angiosperms (flowering plants). This spectacular innovation has probably contributed in a significant way to the extraordinary success of angiosperms, which today make up 90% of land plant species. Flowering plants display a beautiful and spectacular diversity of floral forms that results largely from the diversification of reproductive strategies, including co-adaptation with pollinators. One of the most spectacular variations concerns flower colour, with an almost endless range of shades varying from pure white to near black. In many plants, floral colours contrast with the rest of the plant, and are generally produced by the presence of pigments other than chlorophyll, although in some cases colour is created by light-reflecting structures. The biosynthetic pathways of carotenoids, anthocyanins and betalains, the three main classes pigment, have been deciphered. In many species, flower colour plays a key role in pollination as a visual cue to attract biotic pollinators. Although petals are often the most colourful and showy part of the flower, there are many exceptions, including examples where bracts are showier than the flowers themselves. Colour is usually stable within a species, resulting from adaptive processes linked to plant-pollinator relationships. The evolutionary and genetic mechanisms involved in flower colour shifts have been described in several taxa, providing insights into some of the processes that have shaped the diversity of flowering plants.

Anthocyanin and Flavonol Glycoside Metabolic Pathways Underpin Floral Color Mimicry and Contrast in a Sexually Deceptive Orchid

“…Brightly colored flowers are the norm in diurnally pollinated plants, ensuring visibility to pollinators against the background, with flower colors spanning the UV and visible spectrum. In addition to bright colors, many flowers display contrasting color markings, spots, and lines, which serve as “nectar guides” for pollinators, with some markings only visible to pollinators that can perceive UV light ( Davies et al, 2012 ; Glover et al, 2013 ; Nadot and Carrive, 2021 ).…”

Identification and Quantification of Bioactive Compounds in Organic and Conventional Edible Pansy Flowers (Viola × wittrockiana) and Their Antioxidant Activity

“…Flavonoids, in addition to their functions to help plants adapt to their surrounding environment, have also been correlated with numerous health benefits in humans, including antioxidant, antimicrobial, and anticancer activities [ 29 , 31 ]. Organic pansy flowers contained significantly more flavonoids than conventional flowers, with flavonoid contents of 293.7 mg/100 g F.W.…”

“…Edible flowers can combine a few scopes: nutritional, decorative, and pro-healthy properties such as antioxidants in chronic disease prevention and oxidative stress diminishing [ 29 , 30 ]. Flowers contain numerous bioactive compounds, such as carotenoids (orange and red colorants), xanthophylls and flavonoids (yellow colorants), anthocyanins (purple, pink, and red colorants), and chlorophylls (green colorants), therefore they have such beautiful colors [ 31 , 32 , 33 ].…”

Molecular Phylogeny, Character Evolution, and Biogeography of Hydrangea Section Cornidia, Hydrangeaceae

“…Flower color polymorphisms are generally attributed to three major groups of pigments other than chlorophyll, i.e., betalains, anthocyanins, and carotenoids (Grotewold, 2006 ; Lagorio, 2013 ; Nadot and Carrive, 2021 ). Anthocyanins are most widespread in angiosperms (Grotewold, 2006 ) and change unpigmented white flowers to a diverse mosaic of colors, including yellow, orange, red, pink, purple, or blue (Zhao and Tao, 2015 ; Nadot and Carrive, 2021 ). Besides the pigmentation itself, transposable element activity is well-known to change floral color as well, such as in Ipomoea (Clegg and Durbin, 2000 ).…”