A few months ago, I wrote a detailed article on philodendrons and their growing needs. And in one of my readings, I had noted the word “scototropism”. Hey! A word I’ve never heard of! So I had noted it down, promising myself to eventually push my research. I had to discover what a scototropist individual might be! My intention was twofold, because in botany, I teach phototropism and gravitropism. I thought it would be interesting to add the famous scototropism to the list. Then, my second intention was to introduce you, dear readers of this blog, to a brand new word!

So here I am in front of my favorite search engine which offers me… five results. Five? Of these, two Reddit articles whose encyclopedic value can be questioned (sorry!). I am usually a fan of Reddit discussion forums. Then, there was a brief mention of scototropism in a document discussing the hydraulic architecture of plants (thank you Mr. Frank Ewers). The fourth site offered a Dutch list of 13-letter words, probably there to mystify your opponent in a game of Scrabble. I was starting to lose faith. Luckily, the very last text was an article dating from 1968, written by Professor Husson, from the University of Dijon, in France! Thank you France! All is not lost!

Still in The Dark

Proud of this discovery, I dive into the tedious reading. I’m on the lookout for any information that Professor Husson could provide me on the subject of the increasingly mysterious scototropism.

And that’s how I discovered that Professor Husson was probably a Scrabble enthusiast too. There it is, THE word, along with about twenty other words, all followed with the suffix “tropism”. Nothing about its definition. Not even a little three-word sentence, like “The scototropism… exists.”

Looking for Answers in the Smallest Cracks

Impossible! There must be writings… somewhere. That’s when I searched the depths of literature to unearth a very fascinating text (read: rather weird), dating from 1885! It was here, in this speech presented to the Science Class of the Royal Academy of Belgium, that I found THE answer. (THE as in the only one!)

“This faculty of moving in the opposite direction of light to place oneself in the shade, opposed to heliotropism, could be designated under the name of scototropism.” – Edouard Morren

And that’s simply what scototropism is: loving little dark corners! In this famous text, the example of vanilla is cited, whose adventitious roots embed themselves in interstices. And in the case that originally interested me, the aerial roots of several species of philodendrons and monsteras behave this way. As soon as the root is long enough to have a certain “mobility”, it moves away from the light and looks for a crevice in which to insert itself. In my “incredibly numerous” readings on scototropism (not at all), I also learned something else. When they reach the ground, these roots, starting from the nodes along the stem, take over the absorption of water and minerals, making the original roots practically useless.

Despite the limited information available, the study of “tropisms” is still interesting because it introduces the notion of movement in plants. It is partly because of phototropism, which gives leaves and flowers the ability to turn towards the sun, that we have better understood how hormones work in plants. Indeed, the auxin influences cell growth and makes the leaf or flower develops faster on the dark side than on the sunny side. This is a well-known phenomenon in sunflowers. There are therefore, in the adventitious roots of certain tropical plants, hormones that encourage these roots to seek out small shaded corners. In this case, it is difficult to explain in more detail what mysterious hormones are at play to influence this particular movement of the roots.

In short, the mystery prevails in the dark depths of scototropism!