Category Archives: holiday plants

Epiphany Hidden in Fava Beans

January 6 is Epiphany, not a week into the new year and its tradition causes many Louisianians to abandon any resolutions related to gustatory moderation. I’m referring, of course, to the King Cake. In modern tradition, a King Cake is a circular pastry made of Danish-type dough, filled with fruit spread, cream cheese, flavored sugar or some combination thereof topped with an additional layer of icing decorated with purple, yellow and green colored sugar. There is a plastic baby, representing Jesus, inside, and the eater finding the slice with Jesus is charged with purchasing the next King Cake. This continues throughout the Carnival season. It truly is the decadence of Mardi Gras captured in cuisine.

King Cake via Wikimedia

Traditionally, the King Cake has slightly more humble origins. It has always been associated with Epiphany, the church holiday marking the visitation of the Three Kings to see the baby Jesus, but the recipe was not always the refined sugar freight train it is today. Think more bread and dried fruit. Before the advent of plastic trinkets, the baby Jesus was symbolized by the fava bean.

Vicia faba via Wikimedia

The fava bean (Vicia faba) or broad bean is a hardy legume that has been in cultivation for thousands of years. This low maintenance crop has been a source of quality protein for the human diet for just as long. Its class connotations have waxed and waned throughout history, but for some people it can trigger a potentially deadly anemia. The condition is so tightly linked to fava beans, it is known as favism.

The king is dead?

Favism is really just one manifestation of a deficiency in the enzyme Glucose-6-Phosphate Dehydrogenase (G6PD). This is the rate-limiting enzyme within the pentose phosphate pathway, which the cell uses to generate reducing power in the form of NADPH and glutathione as well as 5-carbon sugar groups to use as building blocks of DNA or amino acids. People can display a range of G6PD deficiency levels. This depends on the type of mutation and the relative amounts of the mutant G6PD expressed. This mutation is X-linked, which means you inherit it from your mother. Because males inherit only one X chromosome copy, if they get a defective version, they will always display some level of favism. Female carriers of the G6PD mutation can also show some deficiency as well. Even though female carriers contain two X-chromosomes (of which has a normal G6PD and the other has the mutant version), cells only need to use one copy. Relatively early in development, one copy of the X chromosome in each cell is silenced. Thus, there is a random inactivation of one copy of the G6PD gene in each cell; in some cases the mutant version will be inactivated, in others the normal version. This creates the potential for a range of G6PD deficiency to be observed even when the woman has one copy of a normal G6PD.

So how can fava beans wreak such havoc on basic human metabolism? Fava beans synthesize the alkaloid glycoside, vicine. This substance is a particularly powerful trigger for oxidative damage to the cells. In the red blood cells of G6PD deficient individuals, there’s just not enough reducing power within the cell to protect them from the build-up of hydrogen peroxide and other damaging reactive oxygen species. Consequently, the red blood cells burst open resulting in acute anemia.

Vicine chemical structure via Wikimedia

Long live the king!

How have this metabolic mutation and food crop coexisted for so long? It seems like nature and/or agriculture would select for one or the other. There are other beans out there, ‘Am I right?’ And how could a mutation in such a critical enzyme in central metabolism accumulate in more than 400 million people worldwide? The answer lies within another disease- malaria. The incidence of G6PD deficient versions is higher in individuals of African and Mediterranean descent. There is a working hypothesis that some level of G6PD deficiency offers a fitness advantage over normal individuals when it comes to malaria infections. When the Plasmodium parasite infects red blood cells, some amount of oxidative stress occurs. Because G6PD deficient individuals have a sensitivity to this stress, their red blood cells burst eliminating the parasite’s home. When you consider a population of red blood cells within a G6PD deficient individual infected by the parasite, it’s advantageous to be able to sacrifice some red blood cells in order to give the immune system the chance to clear the parasite. In normal individuals, all red blood cells are easy targets for the parasite, which can enter them and hide more effectively from the host’s immune system. It should be noted though that some malarial treatments given to G6PD deficient patients can be toxic themselves as they also generate a fair amount of oxidative stress.

G6PD deficiency is a relatively benign condition when it is diagnosed and certain oxidative triggers are avoided. So in the same way that it’s good to uncover a plastic Jesus in your King Cake, it’s good to know your G6PD variety. If you’re G6PD deficient, it’s not so good to uncover a fava bean. However, the complicated hidden interrelatedness of each of these things will lead to new epiphanies in malarial infections and their treatment.


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The Twelve Days of Christmas Plants

If you’re looking for a holiday related diversion, here’s a linkfest of my posts from last year on the Twelve Days of Christmas plants. Understand the plant science behind the traditions. Use these random facts to quickly change the subject when nosy but well meaning friends and family ask you uncomfortable questions.

The Twelve Days of Christmas Plants


1. The Christmas Tree

2. Chestnuts

3. Poinsettias

4. Holly

5. Peppermint

6. Mistletoe

7. Grapes

8. Greens and Black-eyed Peas

9. Sugarcane

10. Oranges

11. Pomegranates

12. Boswellia sacra and Commiphora myrrha


If you’re craving even more holiday nerdery or you’ve already used my random facts as diversion tactics last year, check out The 2014 Chemistry Advent Calendar over at the Compound Interest blog. Or check out these Yuletide plants gone global you’ve probably never heard of from the John Innes SVC blog.



A Green Deal for Black Friday

It’s Black Friday. The blog may have been dark for the last couple of weeks while I’ve been busy with my day job, but today I have a special deal for all my readers. I’ve been writing about the holiday plants we use in our celebrations for the past year and now you can have all of those posts to yourself in convenient downloadable PDF format*. All this plant science for the low, low price of absolutely free! How’s that for a green Black Friday Deal?

Here is the link to download:

Holiday Plants: An Autotrophic Almanac



*Sorry, the Youtube video links don’t work any more, but the rest of the links are still hot.

Plant Skulls

snapgdragon seed pod skull dragons skullIf you didn’t know this was a plant science blog, you might think these were macbre trophies of some ancient tribe. This isn’t so much an appropriate plant costume for Halloween as it is an interesting confluence of floral anatomy and human propensity for recognizing facial forms.

Snapdragons or Antirrhinum sp. are a colorful staple of summer gardens. We’re more used to seeing them look like this image with tall inflorescences boasting clusters of ruffled flowers in a variety of color schemes.

Antirrhinum majus Credit: Michael Apel via Wikimedia Commons

What’s responsible for this spooky transition from delicate flowers to haunting faces? It all comes down to the snapdragon’s flower structure and its bilateral symmetry. The skulls are really the seed pods of the plant after the flowers have been pollinated and the petals have withered away. Dissecting the flowers in their prime shows the ovary at the base of the bloom. The pollen-containing stamens and the style emerge from the orifices in the ovary. These structures leave behind gaping holes that look like a mouth and eye sockets.

Snapdragon flower anatomy

Snapdragon flower anatomy

The striking resemblance of these seed pods to human skulls has led to their association with supernatural powers. They were purported to help women stay young and beautiful as well as protect humans of all ages from witchcraft and evil spirits. I don’t have any scientific evidence of that, but if you’re looking for new ideas for botanical Halloween decorations that go beyond cucurbits and mums, dried snapdragon stems with seed pods make a wicked wreath.


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Flying Duck Orchid

Caleana major off the Elvina Track, Ku-ring-gai Chase National Park, Australia Credit: Peter Woodard via Wikipedia

Today’s featured floral form is Caleana major, an orchid from Australia. It looks like a duck. It flies like a duck when the wind blows, but it’s just a flower. Why would an orchid develop such an elaborate costume? The answer is again pollination.

While this may look like yet another case of autotroph posing as heterotroph, it’s not the one you think. Caleana major’s flowers are designed to attract male sawflies. When the flies enter the larger ‘body’ portion of the flower, the ‘neck and head’ portion of the flower snaps closed behind them. For about a minute or so, the sawflies buzz around in a slight frenzy and become coated in pollen. This ensures that flower pollinates itself and any pollen remaining on the fly travels with it to the next flower.

Closed Flying Duck Orchid Credit: Peter Woodard via Wikipedia

The secret to this strategy is the sensitive ‘neck’ strap of the flower. This portion can sense when a fly has landed within the bottom part of the flower and trigger a response to have the ‘head’ snap closed. This trigger must also be reversed on a relatively short timescale to release the captive fly. He just needs enough time to be coated in pollen but none the worse for wear (unlike other carnivorous plants that intend on killing their insect victims with triggered mechanical responses).

This is an painting of Caleana major by Ferdinand Bauer, based on a drawing by him of material collected at Sydney in September 1803. It first appeared as Plate 8 in Stephan Endlicher’s 1838 Iconographia. It was scanned from Plate 13 of Mabberley, D. J. (1984) Jupiter Botanicus. via Wikipedia

There must be some interesting biochemistry underneath that response, not to mention the developmental gymnastics that must occur to make flowers that look like flying ducks. I’m not sure scientists will figure out these tricks because Caleana major cannot be cultivated outside its native environment. Because of its novel form and potential popularity with orchid enthusiasts, experienced growers have tried to grow it under greenhouse conditions, but with little success. It is speculated that a symbiosis with another microorganism in the soil of its native habitat is necessary for growth.



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Some floral forms make you wonder if they know something we don’t. Take Calceolaria uniflora for example.

When photographed at just the right angle, these slipper-shaped blooms look like the face of an alien wearing beats headphones and holding an empty white tray as a peace offering. Calceolaria is native to the southernmost portion of South America in Tierra del Fuego whose rocky alpine terrain could also be confused with an inhospitable planet in another solar system.

Cacleolaria uniflora Credit: Butterfly voyages serge Ouachée via Wikimedia

If it isn’t an orange alien, what exactly are we looking at? The stalk-like eyes are the stamens, which contain the pollen-producing anthers at the end. The petals of the flower are asymmetrical such that there is a large lower lip and a much smaller upper portion. The green sepals are even larger than the upper part of the petals giving the illusion of halo or headset. The lower lip of the slipper contains a prominent folded appendage in white, a striking contrast from the other features.

Calceolaria uniflora colony Credit: Thomas Mathis via Wikimedia

The purpose for this elaborate costume isn’t mimicry, it’s attraction. But they are phoning home for E.T., they’re setting the table for birds. Birds are a part of many plants’ reproductive strategies and it’s usually in the form of oil and nectar producing floral structures that entice hummingbirds and other small birds over for a drink. Even other Calceolaria species produce nectar for their bee pollinators, but not C. uniflora. In this case, the white tray and larger lower lip of the flower are edible. Birds eat the tray and slipper portion of the flower while the upper portion dusts the top of their heads with pollen. As the birds move from flower to flower, pollen is transferred as well.

Calceolaria uniflora with missing trays Credit: Javier Martin via Wikimedia

There are many other examples of plants using edible portions of themselves in their reproductive strategy. Seed dispersal by the animals that eat them is the whole point of fruit. However, the case of C. uniflora, where the plant offers up part of itself as a meal before seed production seems out-of-this-world risky to me.



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Dracula (Orchids)

Dracula radiosa Credit: Eric in SF via Wikimedia

If you thought we were done talking about plant costumes, you were wrong. While the title may lead you conjure images of vampires with fangs and dark cloaks, orchids of the Dracula genus look decidedly like something else- an adorable monkey face! I admit it’s a strange nexus of nomenclature and form; nevertheless, today’s post will be appropriate for all audiences.

Dracula simia Credit: Dick Culbert from Gibsons, B.C., Canada via Wikimedia

Dracula orchids won’t be found in Transylvania. These blooms are native to the cloud forests of Ecuador, growing in rainforests at elevations of ~3000 – 6500 feet. They were given their name by botanist Carlyle Luer in 1978. The name was inspired by the dark burgundy to black petals that curve up like the stiff collar of a vampire’s cloak. The petals also taper off into sharp points reminiscent of infamous vampire fangs.

Dracula vampira Credit: Eric Hunt via Wikimedia

But back to the real costume, why would a flower need to look like a monkey? If you’ve been paying attention to the last few posts, you can probably guess that the answer has something to do with pollination. However, it’s not quite as obvious as the Orphys bee orchid connection- these flowers are not trying to entice monkeys over for pollen transfer. From what scientists have been able to decipher so far, these flowers aren’t really wearing a monkey costume so much as they are wearing a mushroom costume. Take a closer look at the floral structure posing as the monkey’s snout. These lightly colored and highly ridged structures look very similar to mushrooms found nearby on the rainforest floor. Check out this link with images for a close-up comparison.

Yes, a perfectly good autotroph in mycological masquerade. It’s not just looks either. Again, orchids dig deep into their biochemical repertoire to create a specialized perfume to go along with the visual effect. All of these smells and visual cues serve to trick small flies into coming to their flowers for pollination purposes. The flies prefer real mushrooms as a food source and place to lay their eggs, but are fooled by the Dracula orchids.

Still, this botanical mushroom costume looks an awful lot like a small monkey’s face. I don’t think scientists have completely uncovered all of Dracula’s secrets when it comes to floral form. Investigations are still underway to tease apart the factors of shape, coloration, and scent. Of course, it’s still possible that the rest of the costume isn’t exclusively for the flies. The faces may serve to deter other would-be herbivores from eating the plants. If you were an insect or another small mammal, wouldn’t you think twice before walking over for a bite if that face was staring back at you? I know I would.

Dracula cordobae Credit: Javier Martin via Wikimedia

If you’re interested in learning more about the ecology of cloud forests and the scientists that study it, check out the link below for a trailer for the Cloud Forest Project documentary film.



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