Because plants are “rooted” to the place where they germinate, they don’t move. Indeed, it’s become almost a cliche to describe plants as displaying a “sessile life-style”, especially when contrasting them to animals.
But are all plants necessarily sessile organisms, never moving from the spot where they were “born”?
Well, if you’ve read the title of this post, then you already know the answer to this question is: No.
One of the most well-known plants that defies the “sessile life-style” rule is the so-called Walking Palm.
The key structural features of this plant that allows it to move are its “stilt roots”. These are adventitious support roots that grow down from lateral branches, branching in the soil.
By extending such stilt roots to one side or another, the palm tree moves laterally or “walks” through the forest. But why would it want to do so?
Some hypothesize that this “strategy” likely increases the “walking” palm’s ability to relatively rapidly (timeframe = a year, for example) exploit light gaps in the forest, compared to other trees.
Others think that this also allows the palm to right itself if knocked over by a fallen tree (see a diagram here illustrating this).
Below is a YouTube video that nicely describes the nature of the “walking” palm tree.
“Slithering” Toward the Sun
Question: What would you call a plant that germinates on the tropical forest floor, then grows upward toward the sun on the trunk and branches of a tree, and, when it reaches full sunlight, it causes the oldest portion of its shoot to die?
Answer: A “secondary hemiepiphyte“. (Perhaps a better answer: A “nomadic vine” – see Ref. 1 below)
Whichever name you prefer, these plants start their life as ground-dwelling flowering plants. Like other vines, the plant then climbs the host. But the plant eventually loses its connection to the soil and becomes an epiphyte.As pointed out by Mark W. Moffett (National Museum of Natural History, Smithsonian Institution) in a letter to The New Yorker: “One such nomad is the philodendron in your dentist’s waiting room. In a rain forest, some philodendrons remain a few yards in length and yet they meander through a tree’s canopy, acting like a snake searching for a place to bask. The plant grows small leaves and long thin stems to move quickly when in shade, changing over to the thick stems and large leaves when it reaches a patch of sunlight.”
Moffett continues: “The results are fantastical: when a canopy-dwelling plant, such as an orchid, falls from a tree, it’s likely to perish in the understory shade. But the philodendron simply uncoils itself, crawls over to the nearest tree trunk, and climbs up again.”
Another important observation noted by Moffett:
“Both walking trees and nomads change locations without muscles. Taking advantage of the “modular” strategy Pollan describes, they grow in the direction of motion while leaving their trailing parts to die.“
In this most interesting twist on “phototropism”, these nomadic “walking” and climbing plants are able to follow the sun by actually growing themselves, bodily, into the light.
And now on a bit more whimsical note, I present for your consideration: “Plantas Nómadas” (English translation = “Nomadic Plants”).
The creation of the Mexican artist Gilberto Esparza, these Nomadic “Cyborg” Plants live on the top of robots (think Mars rovers, but smaller) that roam around sucking up polluted water and converting it to energy using microbial fuel cells.
You can visit the Plantas Nómadas website for more photos and information about these nomadic cyborg plants.
1. Zotz, G. (2013) “‘Hemiepiphyte’: a confusing term and its history.” Annals of Botany, doi: 10.1093/aob/mct085; First published online: April 14, 2013. (Full Text)
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