What makes flowers different colors?

Pigments are responsible for many of the beautiful colors we see in the plant world. Dyes have often been made from both animal sources and plant extracts . Some of the pigments found in animals have also recently been found in plants.

Bilirubin is responsible for the yellow color seen in jaundice sufferers and bruises, and is created when hemoglobin (the pigment that makes blood red) is broken down. Recently this pigment has also been found in plants, specifically in the orange fuzz on seeds of the white Bird of Paradise tree. The bilirubin in plants doesn’t come from breaking down hemoglobin. (In animals hemoglobin is broken down to heme, and then converted to bilirubin.) Chlorophyll molecules have similar ring structures to those of heme, and it appears that breaking down chlorophyll can also yield bilirubin – or almost; the breakdown products require just one more step to produce bilirubin. It is fascinating to realize that the process of degradation starts the same way in plants as it does in our own bodies.

Major plant pigments and their occurrence

Pigment Common types Where they are found Examples of typical colors
Chlorophylls Chlorophyll Green plants Green
Carotenoids Carotenes and xanthophylls (e.g. astaxanthin) Bacteria. Green plants (masked by chlorophyll), vegetables like carrots, mangoes and so on. Some birds, fish and crustaceans absorb them through their diets Oranges, reds, yellows, pinks
Flavonoids Anthocyanins, aurones, chalcones, flavonols and proanthocyanidins Produce many colors in flowers. Common in plants such as berries, eggplant, and citrus fruits. Present in certain teas, wine, and chocolate Yellow, red, blue, purple
Betalains Betacyanins and betaxanthins Flowers and fungi Red to violet, also yellow to orange

Chlorophylls

Chlorophyll is green, and is responsible for the green color of foliage and leaves. More importantly, by enabling plants to produce oxygen during photosynthesis, it is critical to sustaining our life on earth. Chlorophyll has structural features similar to heme. Bilirubin, which produces a yellow color, has recently been found in plants.

Red, orange, and yellow plants, as well as other organisms, generally rely on carotenoids for their vivid colors.

Carotenoids

Carotene is a pigment that absorbs blue and indigo light, and that provides rich yellows and oranges. The distinctive colors of mango, carrots, fall leaves, and yams are due to various forms of carotene, as is the yellow of butter and other animal fats. This pigment is important to our diet, as the human body breaks down each carotene molecule to produce two vitamin A molecules.

Lycopene, canthaxanthin, and astaxanthin share a similar structure to carotene. The red tones of tomatoes, guava, red grapefruit, papaya, rosehips, and watermelon indicate the presence of lycopene.

Canthaxanthin produces the pink colors of flamingos, some crustaceans, salmon, and trout. In its synthetic form, it is used to ensure captive flamingos retain their coloring, as a red food colorant, and even as a tanning aid. Astaxanthin provides the red colors of cooked salmon, red bream, trout, lobster, and shellfish. In a live animal, astaxanthin is combined with a protein and is blackish in color. When boiled, the protein breaks down to unmask the true “lobster red” of astaxanthin.

Flavonoids

Flavonoids are the yellow plant pigments seen most notably in lemons, oranges, and grapefruit. The name stems from the Latin word “flavus,” which means yellow. Flavonoids in flowers and fruit provide visual cues for animal pollinators and seed dispersers to locate their targets. Flavonoids are located in the cytoplasm and plastids. Many of the foods that we eat, including dark chocolate, strawberries, blueberries, cinnamon, pecans, walnuts, grapes, and cabbage, contain flavonoids. These chemicals lower cholesterol levels, and many have antioxidant properties. Anthocyanins and proanthocyanidins, and the reddish-brown pigment theaflavin found in tea, act to create color, while most other flavonoids are visible only under UV light.

Flavonoids include red, purple, or blue anthocyanins, as well as white or pale yellow compounds such as rutin, quercetin, and kaempferol.

Anthocyanins play a role in the colors of ripening fruit. They are found in most other plant parts and in most genera. Anthocyanin pigments take their color from the range of red, purple, or blue, depending on their pH. Blueberries, cranberries, and bilberries are rich in anthocyanins, as are the berries of the Rubus genus (including black raspberry, red raspberry and blackberry), blackcurrants, cherries, eggplant peel, black rice, Concord and muscadine grapes, red cabbage, and violet petals. Anthocyanins are partly responsible for the red and purple colors of some olives.

Proanthocyanidins are linked to the beige color of the broad bean seed coat, and also to shades of black, red, brown, and tan. Apples, pine bark, cinnamon, grape seed, cocoa, grape skin, and the grapes used to make most red wines all contain proanthcyanidin.

The yellow colors of flavonoid pigments can be found as chalcones (found in flowers and the organs of plants), aurones (found in flowers and some bark, wood, or leaves) and flavonols.

Betalains

Like carotenoids and flavonoids, betalains also seem to play an important role in attracting animals to flowers and fruit, and produce a similar range of colors. The betalains consist of two sub-groups, red-violet (betacyanin) and yellow to orange (betaxanthin) pigments. They only occur in a few plant families, and always independently of anthocyanins.

Betacyanins are established food colorants. Betalains give rise to the distinctive deep red of beetroot. The composition of different betalain pigments can vary, giving rise to breeds of beetroot that are yellow or other colors, in addition to the familiar deep red. The betalains in beets include betanin, isobetanin, probetanin, and neobetanin (the red to violet ones are known collectively as betacyanin). Other pigments contained in beet are indicaxanthin and vulgaxanthins (yellow to orange pigments known as betaxanthins). Betalains cause the crimson of Amaranthus flowers (class of Caryophylalles).

Interestingly, betalains are only found in one sub-group of flowering plants (Caryophylalles or Centrospermae). Bougainvillea, certain cacti, and amaranth are all examples of this family. These plants lost, or never acquired, genes for the synthesis of other plant pigments. Genes for the synthesis of betalains appear in unrelated fungi (such as Amanita muscaria) as violet and yellow pigments.

Betalains are close in structure and in their synthesis to the animal pigment group melanins, and to eulamelanins in particular.

We take colors for granted. They enrich our world and provide beauty every day. Colors come from pigments and most flower colors come from the pigments known as anthocyanins. These are classified as chemicals called flavonoids and result in pink, red, blue and purple coloring in flowers. Oranges and yellows are from a type of pigment called carotenoids. The next pigment you’ll probably recognize— Chlorophyll. It is the most commonly known because of all the greenery we see in our world—this abundant chemical puts the green in leaves, foliage and flowers.

A genom Is an organism’s genetic material. Chloroplasts are fixed in the genoms of every flower and plant. These are responsible for color. So what is a chloroplast? Dictionary definition: A plastid containing chlorophyll and other pigments, occurring in plants and algae that carry out photosynthesis.

You may wonder why some flowers are brightly colored and others are pale or dull? Well, think about those flowers and flowering plants who need the help of the birds and the bees to pollinate and reproduce. In order to attract bees, birds and other insects they typically have bright, bold, noticeable colors. They will also have fruits that taste sweet and probably smell nice, too. But for plants and flowers whose pollination is handled by the wind, they don’t need bright colors and their fruit tastes bad or has no taste at all. They may smell bad or have no scent – they aren’t trying to attract anyone!

Essentially, the amount of anthocyanin pigments produced by a flower determine its color, as well as its genetics and the location of the flower. Weather and soil conditions can affect the brightness or dullness of any certain flower or plant. If you want a beautiful flowering garden, you probably want to use bright, colorful flowers. Which flowers you choose to grow should depend on where you live. The Northeast United States can be harsh but summer can bring a beautiful array of colorful blooms. Ask your landscaping professional to recommend flowers for the space that you have available for planting. Certain flowers require more sun or more shade than others so explaining or showing your lawn and garden area to your landscaper will help them make the best selections for you.

Your landscaper will also consider what type of soil you have or are using. Here’s an example of a flower easily affected by soil. The hydrangea blooms in shades of pink and purple when the soil pH is higher. If the pH is 5.5 or lower and aluminum is present in the soil, these flowers produce a bright blue bloom.

Flowers brighten our day and bring cheer to our home. When choosing flowers to plant in the ground or in pots, you will probably consider both color and scent—or maybe you’ll choose them just for looks. But be advised that the flower that looks the prettiest may not grow the best in your home. This is why garden professionals are a great source of information. The other thing you should tell them when asking for recommendations of what to grow is whether or not you want to attract birds, butterflies, bees or even specifically hummingbirds. They can advise you on which flowers will attract which critters. Enjoy your flowering world this spring and summer!

National Science Foundation – Where Discoveries Begin

Research News

Roses are red. Violets are blue. What gives flowers those eye-catching hues?

To find answers, scientists delve into the world of plant genetics

Knock-your-eyes-out red: A flowering plant native to Mexico called early jessamine or red cestrum.

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February 13, 2017

To solve the mystery of why roses are red and violets are blue, scientists are peering into the genes of plant petals.

“When you ask anyone how one flower is different from another, for most of us, color is the feature that first comes to mind,” says evolutionary biologist Stacey Smith of the University of Colorado Boulder.

Most people don’t think about why a flower is a particular color, but it’s an important question for biologists, says Prosanta Chakrabarty, a program director in the National Science Foundation’s (NSF) Division of Environmental Biology, which funds Smith’s research.

Smith and her team are “looking at the genetics of flower colors, and at changes in those colors over time,” Chakrabarty says.

It all comes down to biochemistry

In nature, flowers come in hues that span the rainbow.

“On a microscopic level, the colors come from the biochemical composition of petal cells,” Smith says.

Pigments are the main chemicals responsible. Plants contain thousands of pigment compounds, all of which belong to three major groups: flavonoids, carotenoids and betalains. Most flower colors come from flavonoids and carotenoids.

“In addition to giving flowers their colors, carotenoids and anthocyanins — which are flavonoids — have antioxidant and other medicinal properties, including anti-cancer, antibacterial, antifungal and anti-inflammatory activity,” says Simon Malcomber, a program director in NSF’s Division of Environmental Biology.

Malcomber says the research could show how plants evolved to synthesize the carotenoids and anthocyanins that produce red flowers. “The results could be used in future drug discovery research,” he says.

Much of Smith’s work is focused on understanding how changes in flavonoid and carotenoid biochemistry relate to differences in flower colors. She and colleagues conduct research on the tomato family, a group of about 2,800 species that includes tomatoes, eggplants, chili peppers, tobacco and potatoes.

“These domesticated species don’t have a terribly wide range of flower colors and patterns, but their wild relatives often do,” Smith says. “So we study wild, or undomesticated, species, which are most diverse in South America.”

Hot pursuit of red-hot color

Smith has had her share of adventures in the field — like the time she tried to find a plant with red flowers that lives at the base of a volcanic crater in Ecuador.

“It was my very first field trip, and I wasn’t super-savvy,” Smith says. “I took a bus to the outside of the crater, dragged my suitcase up to the rim then down into the crater, assuming there would be a village and a way to get out. There was neither. Thankfully, there was a park station nearby where I was able to stay overnight. I found the species in full flower in the forest the next day.”

Smith is currently in hot pursuit of an answer to the question: When did red flowers first appear in the tomato family? “We thought that red flowers might have evolved many times independently of each other because red-flowered species are scattered among many branches of this family tree,” she says.

Just 34 species in the entire tomato family, however, have red flowers.

“With such a small number, we can take samples of every one of these species to find out whether it represents an independent origin, and to determine the biochemistry of how it makes red flowers,” Smith says.

She and other biologists traveled from Brazil to Colombia to Mexico to track down red flowers and measure their pigments. “We found surprising patterns,” Smith says, “including that nearly every red-flowered species represents a new origin of the color, so red flowers have evolved at least 30 different times.”

While the researchers expected that flowers would be red due to the presence of red pigments, they found that plants often combine yellow-orange carotenoids with purple anthocyanins to produce red flowers.

“Our studies are now aimed at tracing the entire genetic pathway by which plants make flower colors and identifying genetic changes to see if there are common mechanisms,” Smith says.

The scientists want to know, for example, what changes have taken place since flowers first became red.

Answers in a petunia

“We’re focusing on a single branch of the tomato family , creating an evolutionary history and conducting measurements of gene expression, pigment production and flower color,” says Smith.

Petunias and their colorful relatives are good choices for this research, according to Smith.

“Most of us have seen the tremendous variation in petunia colors at our local nurseries, and indeed, petunias have served as models for studying flower color and biochemistry for decades.”

Few people, though, are aware of the variation in petunias’ wild relatives, most of which are found in Argentina and Brazil. “We’re harnessing this natural diversity, as well as genetic information already available from ornamental petunias, to reconstruct the evolutionary history of flower colors,” says Smith.

“If earlier studies taught us anything,” she adds, “we shouldn’t expect flowers to play by the rules.”

Will roses always be red, and violets blue?

— Cheryl Dybas, NSF (703) 292-7734 [email protected]

  • Scientist Stacey Smith collecting plant samples near Tambo de Viso in central Peru.
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  • The flowers of Brugmansia sanguinea are a vibrant blood-red, hence the plant’s name.
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  • Microscope view of a red Calibrachoa flower’s petal.
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  • The flowers of the Jaltomata plant are awash in red nectar at the bases of their flowers.
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  • Researchers found extensive color variation in this single flower species in Bolivia.
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Investigators
Stacey Smith

Related Institutions/Organizations
University of Colorado Boulder

Related Awards
#1553114 CAREER: Testing The Predictability of Flower Color Evolution at a Phylogenetic Scale in the Petunieae Clade (Solanaceae)
#1413855 Evolution and diversification of red flowers: Testing the macroevolutionary causes of rarity
#1355518 Mechanisms of convergent flower color evolution above and below the species level

Total Grants
$1,641,071

How Flowers Get Their Color, Shape and Smell

To understand the nature and beauty of flowers, one must begin with a scientific principle known as co-evolution. Many people have revered flowers since antiquity for their beautiful colors, wide array of symmetrical shapes, and fragrant scents; however, a flower does not possess these qualities simply to appear pleasing to humans. Flowers have an intricate relationship with pollinators, such as bees, birds, bats, and even the wind. This relationship has resulted in flowers evolving with various colors, shapes, and smells that ensure their survival, as these qualities are attractive to their pollinators. To appreciate the marvel that flowers truly are, a closer look at their relationship with pollinators is required.

They say a rose by any other name would smell just as sweet, and that saying is just as true in the animal kingdom as it is in the world of literature. Flowers, also known as angiosperms, rely upon their scent in order to attract pollinators. Pollinators are agents or hosts that deliver pollen from a male flower to a female flower, thereby allowing a flower to reproduce. Without pollinators, nearly 90% of the world’s flowers would cease to exist. The interdependence between flora and their pollinators is crucial to the survival of flowers. The scientific community has shown that a flower’s scent is used to attract specific pollinators. Additionally, science has shown that individual pollinators are lured to a flower particularly due to its specific scent, giving more evidence of the relationship between flowers and the insects, birds, and bees that pollinate them.

Like scent, flowers also rely upon their shape when attracting pollinators. While scent may be used to draw a pollinator to the flower, each flower’s individual shape has evolved to allow for the pollination process. Scientists point to this as another example of co-evolution, which is how flowers and their pollinators evolved at the same time and share mutual characteristics that create a working relationship. Co-evolution comes about when two species are dependent upon one another for survival.

For example, the yucca plant is pollinated by the yucca moth. The plant’s shape is such that only the yucca moth’s mouth may pollinate and feed from it. The mutual relationship is so perfectly matched that science has concluded that the two species evolved simultaneously while adapting to one another. Another example of floral shapes that highlight co-evolution is the relationship between acacia trees and acacia ants. While ants do not serve as pollinators, they have a close, mutual relationship with the tree, and in exchange for receiving food, they act as defenders for the species.

Hummingbirds pollinate many plants, and one can see the effects of co-evolution. Hummingbirds have very long, narrow beaks, and the flowers they pollinate have very deep, narrow tubes in the center. This allows hummingbirds to insert their beaks into the flower, thereby stimulating the reproductive center and allowing for pollination. The relationship between flower shapes and their mutual pollinators cannot be overlooked.

Another striking example of co-evolution is found in the wide array of colors exhibited by many flowers. The scientific community has shown that certain pollinators are attracted to a flower’s individual color or lack of it. In fact, some flower colors are so dominant when it comes to attracting pollinators that hybrid colors fail to attract as many pollinators. It might be easiest to think of flowers wearing colors as a woman who wears makeup to attract a mate. Flowers that depend upon insects, birds, or bees for pollination appear in bright, vivid colors. These colors help the flower stand out and be noticed. Interestingly, flowers or grasses that depend upon the wind for pollination do not appear in bright colors but are rather dull in hue. These flora types do not need to attract attention in order to reproduce.

Scientists have shown that certain pollinators are attracted to individual flower species depending upon the color and will show preference to particular shades. The interrelationship between flowers and their pollinators is truly a marvel of the diversity and magnificence of life.

Written By Ava Rose.

Color In Flowers – Where Does Flower Pigment Come From

Flower color in plants is one of the biggest determinants for how we choose what to grow. Some gardeners love the deep purple of an iris, while others prefer the cheerful yellow and orange of marigolds. The variety of color in the garden can be explained with basic science and is pretty fascinating.

How Do Flowers Get Their Colors, and Why?

The colors you see in flowers come from the DNA of a plant. Genes in a plant’s DNA direct cells to produce pigments of various colors. When a flower is red, for instance, it means that the cells in the petals have produced a pigment that absorbs all colors of light but red. When you look at that flower, it reflects red light, so it appears to be red.

The reason for having flower color genetics to begin with is a matter of evolutionary survival. Flowers are the reproductive parts of plants. They attract pollinators to pick up pollen and transfer it to other plants and flowers. This allows the plant to reproduce. Many flowers even express pigments that can only be seen in the ultraviolet part of the light spectrum because bees can see these colors.

Some flowers change color or fade over time, like from pink to blue. This informs pollinators that the flowers are past their prime, and pollination is no longer needed.

There is evidence that in addition to attracting pollinators, flowers developed to be attractive to humans. If a flower is colorful and pretty, we humans will cultivate that plant. This ensures it keeps growing and reproducing.

Where Does Flower Pigment Come From?

Many of the actual chemicals in flower petals that give them their different colors are called anthocyanins. These are water-soluble compounds that belong to a bigger class of chemicals known as flavonoids. Anthocyanins are responsible for creating the colors blue, red, pink, and purple in flowers.

Other pigments that produce flower colors include carotene (for red and yellow), chlorophyll (for the green in petals and leaves), and xanthophyll (a pigment that produces yellow colors).

The pigments that produce color in plants ultimately come from genes and DNA. A plant’s genes dictate which pigments are produced in which cells and what amounts. Flower color genetics can be manipulated, and has been, by people. When plants are selectively bred for certain colors, plant genetics that direct pigment production are being used.

It’s fascinating to think about how and why flowers produce so many unique colors. As gardeners we often choose plants by the flower’s color, but it makes the choices more meaningful with an understanding of why they look the way they do.

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