800px-Socratea_exorrhiza_leaf Smartse modified

Socratea exorrhiza: plants also learn to walk!

This time I am going to present the plant that is becoming famous worldwide, the walking palm (Socratea exorrhiza). It has always been said that plants do not move from their place, but the nature surprises us once again with an example like this. Then, you can view more of this extraordinary plant.

INTRODUCTION

The walking plant, Socratea exorrhiza, is a palm tree (Arecaceae) that lives in the rainforest of Centre and South America. It can reach to 25 meters of height and 16 centimetres of diameter, but it is usually around 15-20 meters of height.

Socratea exorrhiza, walking palm
The walking palm at los Puentes Colgantes near Arenal Volcano, Costa Rica (Photo taken by Hans Hillewaert).

Along with the orchids and other herbs, palm trees are the most abundant plants in tropical forests. But the palms are very curious as they have arboreal morphology: tree height and measures. But, no truly secondary growth is developed, i.e., they haven’t tissues for the increase in thickness of the roots, stems and branches. This means that, if the plant grows in height, it has to be a mechanism that can support its own weight. And we know that is not due to the thickness of the stem, which is pretty slim. So, what is the mechanism? And how does it work?

STILT ROOTS

Many arborescent palms, i.e., that are not trees but similar, develop a set of aerial roots. These are characterized by being located above ground level. This is the case of the Walking palm (Socratea exorrhiza) and other palms (such Iriartea deltoidea). Stilt roots are generally very numerous and high.

Socratea exorriza
Stilt roots (Photo taken by Ruestz).

STILT ROOTS’ FUNCTIONS

The functions performed by these roots have been and are still a debate. Still, it has been proposed that they can provide different benefits.

First, their presence allows greater stability and support of the stem, which can grow faster. This is very interesting, because in tropical forests light is a very powerful limiting factor. And the fact that the plant can reach higher heights, spending less energy in developing a thick trunk or underground roots that stabilize, makes this specie more competitive. But, while providing stability, it has not been shown to result in an advantage to grow in slope.

On the other hand, it is also thought that roots let colonize (expand to) new places that contain many large organic wastes, generally branches or dead trunks of other trees. This is because the roots can avoid them by moving over them.

In addition, it has been found that the stilt roots increase the plants’ survival when tropical storms are violent (as explained in the next section) and also facilitate their own aeration when floods occur. Still, it has not been confirmed that they allow the palm to grow in marshy places.

Although it has been begun to possess an extensive knowledge, all functions of these very singular roots of palm trees are still unknown. Even so, it should be mentioned another function discovered on the Walking palm, which is precisely what allows the plant to “walk”.

HOW DOES THE WALKING PALM WALK?

Socratea exorrhiza is known as the Walking palm and this is because it can change its position for two reasons. Although the second, presented below, is what gives rise to its common name.

The first, known since more time ago, it is quite common due to strong tropical storms. It’s caused when the palm is in normal position (phase 1 of the image) and then is knocked down by another tree or branch and it’s flattened (phase 2 of the image). Once above the soil, the palm has the ability to regrow and recover, thanks to the development of new stilt roots on the old stem; while the old stilt roots die (phase 3 of the image). Finally, the organism grows again, but having changed its place (phase 4 of the image). Therefore, the palm can survive even when it’s lying over the ground and still can recover itself.

Socratea exorrhiza  diagram
Smartse – Bodley, John; Foley C. Benson (March 1980). Stilt-Root Walking by an Iriateoid Palm in the Peruvian Amazon. Biotropica (jstor: The Association for Tropical Biology and Conservation) 12 (1): 67-71

The second case has been discovered more recently and it is the reason why this plant has become popular nowadays. It is believed that its roots grow towards areas where there is more light; while on the other side, the roots die. So, the stem changes its place very slowly, but each year the displacement can reach up to 1 meter.

Simon Hart’s explicative video (Youtube Channel: Harold Eduarte).

As you have seen, plants never cease to amaze. Reaching as curious cases like this. Remember, if you liked it, please don’t forget to share in different social networks. Thank you.

REFERENCES

  • Notes of Forest Ecology, Degree of Environmental Biology, UAB.
  • Avalos, Gerardo; Salazar, Diego; and Araya, Ana (2005). Stilt root structure in the neotropical palmsIrlartea deltoidea and Socratea exorrhiza. Biotropica 37 (1): 44–53.
  • Avalos, Gerardo and Fernández Otárola, Mauricio (2010). Allometry and stilt root structure of the neotropical palm Euterpe precatoria (Arecaceae) acroos sites and successional stages. Ametican Joranl of Botany 97 (3): 388-394.
  • Goldsmith, Gregory; and Zahawi, Rakan (September–December 2007).The function of stilt roots in the growth strategy of Socratea exorrhiza (Arecaceae) at two neotropical sites. Revista de Biologia Tropical 55 (3–4): 787–793.
  • Zotz, G.; Vollrath, B. (2003).The epiphyte vegetation of the palm Socratea exorrhiza – correlations with tree size, tree age and bryophyte cover. Journal of Tropical Ecology 19

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