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Biological Chemistry

Periodic Graphics

Periodic Graphics: The chemistry of plant flowering

Chemical educator and Compound Interest blogger Andy Brunning explains the chemistry of flowers and their colors and scents.

by Andy Brunning, special to C&EN
March 14, 2021 | A version of this story appeared in Volume 99, Issue 9


A three-column infographic focusing on various aspects of flower chemistry. 

The first column examines what makes plants bloom. Plants flower when they detect environmental signals, such as changes in day length and temperature. The substance that triggers flowering is known as florigen. For decades, it was a hypothesized substance, but recent research has identified a protein, flowering locus T, that travels from leaves to a plant's shoots and helps initiate flowering.

The second column looks at the pigments that give flowers their color. These pigments come from three families. Most red, blue, and purple flowers get their color from anthocyanins. Carotenoids are responsible for red to yellow hues in some flowers. Some flowers in the Caryophyllales order get their red and yellow colors from betalains. 

The third column examines flower aroma. Flower petals emit volatile organic compounds (VOCs) to deter herbivores and attract pollinators. These aroma compounds come from three key chemical classes. Terpenoids are derived from isoprene and are often the most abundant VOCs. Green leaf volatiles are derived from fatty acids and are also emitted by leaves. Phenylpropanoids are a range of aromatic compounds synthesized from phenylalanine.
Credit: Andy Brunning

To download a pdf of this article, visit

References used to create this graphic:

Choi, Charles Q. “A Blossoming Field of Research: How Florigen Is Transported to Create Flowers.” PLOS Biol. (April 2012). DOI: 10.1371/journal.pbio.1001311.

Des Marais, David L. “To Betalains and Back Again: A Tale of Two Pigments.” New Phytol. 207, no. 4 (Sept. 2015): 939–41.

Grotewold, Erich. “The Genetics and Biochemistry of Floral Pigments.” Annu. Rev. Plant Biol. (June 2006). DOI: 10.1146/annurev.arplant.57.032905.105248.

A collaboration between C&EN and Andy Brunning, author of the popular graphics blog Compound Interest

To see more of Brunning’s work, go to To see all of C&EN’s Periodic Graphics, visit


This graphic was updated on March 17, 2021, to correct the example of a phenylpropanoid aroma compound. β-Damascone is not a phenylpropanoid; it's a degradation product of a carotenoid. We replaced it with 2-phenylethanol.



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