How do plants perceive their surroundings

Plants: Reading sample: What plants know

The green creatures perceive their environment with amazing precision - albeit completely different from animals or humans

For a long time, biologists agreed: Plants are simple creatures and, unlike animals, are incapable of such complex sensory functions as seeing, hearing, tasting, smelling and feeling. But recent research shows that many plants perceive their environment amazingly precisely, communicate with one another - and even have a kind of memory. How exactly they recognize touch, sound, light, smells and tastes is still largely a mystery. One thing is certain: you do it.

When they exposed the parasite, he went looking for a victim within days. One end of his thread-like body was stuck in the earth, while the tip of his torso twisted in different directions, stretching itself further and further. The worm-like creature seemed to be probing its surroundings.

And soon she found what she was looking for. Slowly she made for the victim who was not far from her. Finally she reached his body, embraced him.

Then she stuck her suction organs in and feasted on its juices.

The parasite had attacked a young tomato tree. And the attacker wasn't an animal. But about a plant - the devil's thread.

This floral drama took place in a laboratory at Penn State University in Pennsylvania in 2006. The researchers wanted to find out how the parasites make their host plant. Because they have no externally visible sense organs.

So what leads them to their prey?

In their experiments, the scientists used rows of devil's twists on tomatoes - and 80 percent of the experiments resulted in an attack.

If, on the other hand, the researchers placed artificial (albeit deceptively real-looking) perennials next to the parasites, there was no reaction.

And if the attackers had the choice between a container with an odorless solution and one with the intensely fragrant extract of tomatoes, they would grow towards the latter - so they clearly followed the odor.

The devil's twine, as the US scientists were able to prove for the first time, locates its host plants via their vapors, it can smell - a sensory achievement that researchers have long believed only animals to be capable of.

Cuscuta pentagonaThe scientific name of the test object is a winch: an inconspicuous, pale plant without leaves, only a few millimeters thick. It can branch out in many ways and even overgrow entire trees.

When fully grown, it has neither roots nor the ability to produce enough sugar by means of photosynthesis to supply itself. It is therefore dependent on finding and tapping other crops. However, it is so successful that it is one of the ten most devastating agricultural plagues in the United States.

As impressive as the sense of the devil's twine may seem, it is by no means an exception among plants, but rather an exemplary example of what plants can achieve. Because their repertoire of sensory abilities is enormous.

For centuries, plants were seen as simple, largely insensitive beings, as automatons programmed for mere growth. They seemed little more than a food resource. For what purpose, according to the prevailing view of biologists, should sensitive sensors serve them? The ability to perceive the environment precisely, the scholars almost exclusively ascribed to more complex animal organisms.

And it is no wonder that this point of view persisted into the last decade of the 20th century: The differences between animals and plants seem to be far more important than what they have in common.

If one considers the nutritional strategies alone, the contrasts are evident.

Here the animals, which mostly eat plants or other animals and have developed extremely keen senses in order to be able to find their food.

There the plants, which usually produce their own nutrients with the help of the sun. As a result, over the course of millions of years, most plants have enlarged the surface of their outer shell in order to capture as much light as possible.

They have developed the ability to expand the plant body by the same elements over and over again - for example, to let branches and leaves grow so that the light yield increases. Botanists therefore suspected for a long time that the plants could at best register the intensity of the sun, but otherwise hardly have sensitive sensory organs.

Because even if they saw a threat, they couldn't escape it.

But the picture has been changing for a good 15 years. Researchers use high-tech instruments to penetrate deeper and deeper into the sensory world of flora. They scorch foliage from bushes and then measure the electrical currents in their branches. They lower probes into tree trunks to intercept ultrasonic waves. Analyze the finest hormone concentrations in the foliage.

And there has been a paradigm shift in their assessment of the plant senses.

The new - downright revolutionary - finding is: Anyone who is stuck in the ground and can barely move must really grasp what is happening around them.

Many puzzles still remain. But botanists are now realizing that plants can smell, taste, hear, see, and feel in their own way, and they use highly specialized detectors to do this. And those biologists who research how these sensors work gain access to a long-hidden cosmos.

You decipher the secret life of plants.

You can read the whole article in GEOkompakt issue No. 38 "The secret life of plants"

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