Among the features that distinguish animals from plants, we can say that animals are heterotrophs —they do not carry out photosynthesis, but consume other living beings to obtain energy— and they move, while plants are autotrophs —they carry out photosynthesis— and they don’t move . These traits, however, are not always universal.
plant movements
Some animals sequester chloroplasts from the plants and algae they consume and can photosynthesize; there are others, like sponges, that do not move, are totally sessile, and in fact, do not have a nervous system.
Regarding plants, it is true that they all carry out photosynthesis, although some complement this autotrophic function with predation on animals, such as carnivorous plants. These are an obvious example that some plants can move , or at least some of their parts.
Actually, all plants have the ability to move part of their body based on external stimuli such as contact, light or gravity. This type of movement is called nastia —point movements, like the leaf of the Mimosa pudica tree, which closes on contact and reopens— or tropisms —continuous and prolonged movements, like the leaves of a plant seeking the sun—. But, if there is something that animals do and not plants, it is to move, right?
Neither.
plants that move
As was the case with movement, all plants can move through space at some point in their life cycle: when they are in fruit or seed form. What happens is that they do not do it voluntarily or directed, but are displaced by other factors, generally, the wind, the water or some animal .
Maple samaras —those fruits that look like helicopters when they fall— or poplar seeds —reminiscent of fluff— move by the action of the wind, something called anemochory . One of the seeds that best represents transport by water, or hydrochory , is the coconut, which colonizes new islands dragged by sea currents. Regarding transport by animals , there are fruits, such as thistles or burdocks, that adhere to the fur and fall at a certain distance from the mother plant. Others whose seeds resist passing through the digestive tract of the animal that eats them, and are deposited with the feces. These two processes are called exozoochory —the external one— and endozoochory —the internal one—.
But there are also plants that take advantage of these types of factors, not to transport their fruits, but to transport the entire plant or a fragment of it, so that it can take root elsewhere.
Steppe cursors —also called tumbleweeds— dry up, and in that state, lighter, they are moved by rolling on the ground thanks to the action of the wind, crossing steppes and deserts until they are deposited somewhere with water where they can rehydrate and rehydrate. ingrain. Other plants, such as tongue whip ( Galium aparine ) have tiny hooks along the stem and leaves, which adhere to animal fur similar to Velcro. When an animal brushes against the plant, part or all of it is uprooted and carried, until it falls to the ground and takes root again.
But there are plants that have an even more complex method of displacement. Plants that can almost be said to walk.
The palm tree that (almost) walks
We are talking about Socratea exorrhiza , although other species such as Iriatea ventricosa have shown a similar function. But, both in the title and in the previous sentence, a very specific and important nuance has been made, and that is that it can almost be said of this plant that it walks, but it does not do so per se . To understand the difference, we must first know how this species moves , and under what conditions.
These palm trees, native to American tropical forests, emit adventitious roots from the stem. In botany, the organ that arises in an atypical position is called “adventitial”; for example, as is the case, new roots that, instead of arising from previous roots or the root primordium, arise from the stem.
These adventitious roots are born only at the moment when the stem is in contact with the ground or very close to it; that is, when the plant has been knocked down . The previous roots that it had, that have been left behind, where the base of the stem used to be, now exposed, rot. The stem, for its part, thanks to these new roots that continue to nourish it, continues to grow in the opposite direction to gravity , straightening the plant again.
The end result is that, thanks to this process, the plant has moved a certain distance from where it was previously.
He almost walks, but he doesn’t really walk
There are notable differences between an organism that walks, and what these palms do. In the first place, when walking, anatomical parts are not lost to form new structures, something that does happen in these palm trees. And on the other hand, an organism that walks does so deliberately , with the intention of going somewhere, whereas in these plants it is totally incidental. It is not even due to stimuli or stress factors, as would happen with a nastia or a tropism; it does not move looking for moisture, nor escaping from a flood, nor with or against a slope; it only does so when the plant is knocked over by external causes, and it has no control over which direction it travels.
It is, in fact, an evolutionary adaptation, which prevents the palm tree from dying once it is uprooted from the ground and knocked down. A fascinating adaptation, but with the same meaning as steppe cursors or tongue whippers; a real displacement of a complete plant, but totally dependent on external factors —the wind in the stepipores, the animals in the tongue whipper, and in the case of the palm tree, the disturbance that uproots it from the ground—, and on which the plant you have no control.
References:
Avalos, G. et al. 2005. Stilt Root Structure in the Neotropical Palms Iriartea deltoidea and Socratea exorrhiza1. Biotropica, 37(1), 44-53. DOI: 10.1111/j.1744-7429.2005.03148.x
Pérez Morales, C. 1999. Morphology of spermatophytes. Ed. Celarayn.
