In 1880 appears a book in which plants are not passive creatures for which they are given by many. In his book on the power of movement in plants older Charles Darwin shows a passion for the sensory qualities of plants. He takes care of photo tropism and other mobile activities in the plant kingdom. Together with his son Francis Charles dedicates itself to numerous experiments that relate mainly carrot and carrot seed. He assumes that roots do not nourish plants only, but also sensory organs to light, humidity, pressure and gravity and determining on the basis of a favorable trajectory for chart the growth of roots. His focus is mainly on the tip of the radicle Darwin proposes to look at a plant as an animal inverted, with underground senses an underground "brain" and aboveground sexual organs.
Today's research shows that the end of a carrot on a slope running, like a creeping worm, looks for a weak spot in the substrate to settle optimally. At least when there is a root cap is present. Without root cap grow roots in a straight line, without touching the slope. Recent advances in molecular biology, cell biology, physiology and ecology confirm the picture of plants as sensitive and communicative beings, characterized by an active, problem-solving behavior. For example, their sensory role is confirmed by scientists who state that plant roots to be able to measure a 20-many environmental parameters, such as soil volume, nitrogen content, phosphorus content, salt content and the presence of toxins. Also, chemical signals from neighboring plants and micro-organisms are collected. In addition, consider neighboring roots or roots of the same plant, the same species or another species belong. After the measurement, the following observations so that an integration of the plants would be able to adapt to their environment. Thus, there is a sensory perception leading to changed behaviors and take "intelligent" decisions. Such a vision of plants is still disputed, however. Nevertheless show both the organs of plants and animals movement and touch, albeit generally at a different time scale and the latter is apparently difficult for some to grasp.
A concrete example of perception, communication, adaptation and social behavior in the vegetable world the relationship between acacia trees and a variety of antelope: the big kudu. In 1991 Post a scientific article about the sudden death of 3000 kudu in South African game parks. Because the dead animals show no signs of injury or parasites, their stomach contents are analyzed. Which is found to contain lethal concentrations of tannins. Kudus are, however, accustomed to these chemicals because they have to ask themselves often satisfied with leaves of acacia, which, like most trees, tannins produce when they are eaten. As a result of a dry winter period the foraging behavior of kudu in certain wildlife parks but so intense that the affected trees proceed to emit ethylene. In parks with low densities kudu, there is nothing to worry about. Ethylene is a volatile organic compound as a plant hormone which, among other things is able to ripen fruit. The emission of ethylene by acacias reaches tens of meters far and acts like a chemical SOS cloud, producing tannins from neighboring, non-eaten species within five to ten minutes drive up to deadly levels.
Some trees do not limit themselves to self-defense, but show a certain form of social and communicative behavior, using signal molecules. Smart enough to limit giraffes tend to infest not affected acacia against the wind, so they avoid the effect of the ethylene clouds. A similar process in the United States is emitting volatile organic compounds by conifers as the turned to repel bark beetles. Trees that are affected by these beetles appear up to 20 times more VOCs - especially monoterpenes - emit compared to healthy trees. Some researchers, these increased emissions associated with a kind of haze that reduces visibility, affects the environment and harm human health.
In 1990 it is determined that corn plant terpenes emit when they are eaten by the larvae of the katoenuil, a Mediterranean moth which nowadays is also found in Africa and Asia. Such VOCs attract parasitic wasps of the species Cotesia marginiventris. They then lay their eggs in the larvae of the moth, and the growing wasp larvae parasitize their hosts. Because the parasitized larvae eat less maize and can not reproduce this phenomenon can protect the corn plants, and result in increased seed production. Eventually the butterfly larvae death. A similar phenomenon takes place underground off. Root damage by the larvae of the corn rootworm notorious activates an enzyme that allows for the production of terpenes that attract nematodes. These also act as fatal parasites, which are slain beetle larvae inside.
The roots of most land plants are in contact with hyphae of fungi, which provide the plant minerals, water, and protection against pathogens in exchange for sugars. A phenomenon that is known as mycorrhiza. Sugars set fungi capable of expanding sometimes gigantic networks of mycelia, which are responsible for transporting water and food. Recently, it was shown that these underground structures may also serve as channels for the exchange of information between "connected" plants. Even if they belong to different species. This allows trees and other plants warn each other relatively quickly, as in the case of attack by aphids. Such a threat causes the production of VOCs such as methylsalicylic, allowing plants to repel aphids and attract their parasitoid enemies. When not by aphids affected plants, such effects only occur when they are connected by hyphae with or affected. This underground network allows neighboring plants able to develop defenses before an attack occurs. Networks of hyphae may therefore act as a kind of internet which both the behavior of herbivores as enemies can be influenced by means of a fast and efficient communication. The same networks could also facilitate the establishment of seedlings and influence the composition of plant communities.
Plants appear also able to sense magnetic fields. The geomagnetic field, which is the result of turbulence in the liquid metal outer core of the earth, it is therefore an unavoidable environmental factor for plants. The GMV protects the earth from harmful solar winds, but also influences biological processes such as germination, flowering, photosynthesis and the migration of birds. The GMV changes in the course of evolution and thus ensures stress factors that contributed to speciation and extinction. The increase in high-energy particles during reversal of the polarity can possibly contribute to mass extinctions. On the other hand, it was recently shown that periods of normal polarity - such as the current - overlap with the appearance of most of the families of flowering plants, which belong to the broad-leaved trees. To prove conclusively that the sensing of magnetic fields is a driving force needed to move more experiments, however. As research into the effect of "reversals" on certain genes from plants. The relationship between magnetic fields and numerous influences of these plants, however, is beyond dispute.
Geneticists often have to their surprise found that plants have more genes than animals. In light of the foregoing, this is not surprising. The life and survival of plants depends to a large extent on numerous, sometimes complex signal molecules and toxic substances, which are also called secondary metabolites can be mentioned. The ability of plants to produce signal and antibodies is partially inherited. But there's more to it. In 1999 did a team of biologists led by Ralph Toll Rian a remarkable discovery. In the renowned journal Nature describes how radish plants are exposed to their natural enemies. As expected, the radishes react by larger amounts of the toxin glucosinolate to create. But in doing so it does not remain. Offspring of stressed plants also produce large amounts of poison. Even without predators nearby. That is the most evolutionary biologists swallow. During life acquired properties through reproduction pass on to posterity, according to the classical Darwinism indeed impossible. As a violinist whose child comes into the world as a violinist. This is reminiscent of the ideas of Jean-Baptiste Lamarck and giraffes have long necks because they stretched beyond that generation after generation to reach the highest leaves of a tree.
Especially insights into the molecular genetics and the conclusion that evolution is the result of random changes in the DNA, which can sometimes lead to an advantage but are not influenced by the environment, meant the death knell for Lamarckism. But what about the radishes Toll Rian? Meanwhile, it became clear that the switching on or off of the activity of genes can be passed on to the offspring without leaving the DNA-code changes. The inheritable position of certain molecules surrounding the DNA to determine which parts are active. This is called epigenetic information. These changes more quickly than the more stable and DNA can be influenced by the environment in which a plant or animal grows up. That way heritable information may change in response to the environment and the prevailing selective pressure. For example, genes responsible for the production of glucosinolate be turned on in radishes and passed on to the next generation. . Lamarck undoubtedly chuckles from his grave.