This series of posts will highlight the plants that help you celebrate the Yuletide season.
Kissing under the mistletoe is a Christmas tradition of yore when people would visit one another for parties during the holiday season and interact with one another without using an intermediary electronic device. Here’s everything you wanted to know about the plant that presides over passionate pecks. By the way, today’s post is brought to you by the letter P! Post puzzle: Try to find the theme word starting with ‘P’ for each paragraph below, and see if your answers are correct by scrolling to the bottom of the post (yes, past the references)*.
Depending on your continent, mistletoe can be either Viscum album (Europe) or Phoradendron serotinum (North America). Either way, mistletoe is a parasite. Yes, I’ve mentioned before that plants can be parasites. The large evergreen mistletoe globs residing in the forest canopy are actually feeding off of their tree hosts. Since they are green, they still perform photosynthesis (so they are only hemiparasitic and do not lead a completely shameful plant existence), but rely on their connection with the tree for water and mineral nutrients. This connection is called a haustorium (plant biology** word of the day), which penetrates into the host’s tissue (xylem and phloem, in this case), but doesn’t penetrate cell membranes. Even though mistletoe is an obligate parasite, relying on its host for its survival, infestation does not mean death for the host tree. Because water and nutrients may be cut off to a particular branch, which may suffer, the rest of the tree will survive without many ill effects. However, parasites can be problematic when the host plants experience stress.
Mistletoe may be fine as festive flora and even a somewhat benign forest parasite, but you should keep them off of your plate. Both American and European mistletoe varieties are poisonous. The entire P. serotinum plant contains phoratoxin, a toxalbumin which can cause gastrointestinal symptoms. You should also stay away from V. album (although the pretty pearly berries are less toxic) because it contains viscotoxins (aka viscumin). These protein poisons inhibit protein synthesis in your cells and cause particular problems with the digestive tract. So, as long as you aren’t serving mistletoe salad or spiking your punch with mistletoe berries, your guests should be safe.***
Despite their parasitic relationship with their hosts, mistletoe has a mutually beneficial relationship with certain bird species. The berries provide sustenance for the birds and the birds are useful seed dispersers for the mistletoe. This brings us to the decidedly unromantic origin of the common name ‘mistletoe,’ which translates from the Anglo-Saxon as ‘dung-on-a-twig.’ Bird poop is an ideal vector for dispersing mistletoe seeds onto the tree branches on which they must germinate. In a separate insurance policy to guarantee that the seeds stick to tree bark, mistletoe coats its pearl-like berries with a super-sticky substance called viscin. When birds eat or regurgitate them, they must clean their beaks by rubbing them into the bark leaving the viscin and mistletoe seeds. So, before you even brought mistletoe into your home, mistletoe was creating sticky situations (‘pasty predicaments’ is too much, right?).
Finally, mistletoe-related searches also bring up some interesting links to cancer treatments. Some clinicians use mistletoe extracts as palliative therapy in cancer patients to help alleviate the problematic side-effects of standard treatments (surgery, chemotherapy and radiation). Remember, the plants are poisonous, so DO NOT make your own mistletoe tea. These are prepared as for use as injections. However, as with many medicines, there is a fine line between poison and pharmaceutical. It should be noted that these effects are just beginning to be studied beyond anecdotal evidence, but there does seem to be an association with positive quality of life in conjunction with other treatments according to some studies. So far, these results have not been supported by well-designed clinical trials, but perhaps there is some biochemical potential in this plant.
I hope you were pleased with the particulars on this plant. If you find yourself in an awkward position under the mistletoe this holiday season, and you’d like to pass on the peck, try the following response. “I will not be pushed into passion under a poisonous, parasitic plant named after poop with possible pharmaceutical potential.” If you didn’t catch the answers to the post puzzle, keep scrolling down.
*In addition to kicking up the alliteration to level 11, it also means I will be taking the liberty of using a plethora of pesky parenthetical phrases (you have no idea how much I must reign myself in on a normal basis).
**The term is not restricted to the anatomy of parasitic plants, but also fungi. So, there’s your double dose of biology for the day.
***I should note, though, that sucking face with semi-random Yuletide visitors has its own dangers 😉
References and Links:
Post Puzzle Answers: Parasite, Poison, Poop, Possible Pharmaceutical