This herbaceous perennial plant with a height of 30 to 150 cm comes from the tropical regions of South America, where it is considered a weed; at the same time, it is cultivated all over the world as a decorative one. Mimosa blooms from May to September with small purple inflorescences in the form of balls, which are located on long peduncles. Pollination occurs with the help of wind or insects, after flowering hook-shaped curved beans are formed.
A distinctive feature of the bashful mimosa is its reaction to a potential threat. When the roots are damaged, the plant emits a “cocktail” of toxic substances, including methanesulfonic, lactic, pyruvic acids and various sulfur compounds; this often leads to the poisoning of livestock in pastures.
Another amazing property that gave the plant its name was its ability to fold leaves in response to touch. The mechanism of this action is known to scientists. At the base of the petioles, water membranes are located, and sensory areas on the leaflets respond to pressure. When touched, the water rushes to the place of contact, and under this weight the leaves fold and fall down.
Recently, Australian scientists have discovered that the bashful mimosa is capable of self-learning. According to a study published in the journal Oecologia, mimosa "remembers" the characteristics of each contact, and if it does not pose a threat, it will not waste energy on folding leaves. This behavior is characteristic of animals: with the help of the nervous system, they not only receive information, but can also use it in the future. The behavioral response of a plant, taking into account the data accumulated by it, was described for the first time using this example.
It is interesting that bashful mimosa well distinguishes its potential enemy. In the course of the experiments, it was established: in those cases when a person touched its roots, the air was filled with a mixture of hydrogen sulfide and other substances, while contact with metal, glass and other objects did not trigger the mechanism for producing "chemical protection".
As a result, biologists have found another conceptual difference between the bashful mimosa and other representatives of the fauna: if the majority of plants using poison for their protection release it from their aboveground part, then the object of their study does this with the help of their roots, on which tiny nodules are located. Moreover: they not only produce poison, but also analyze the chemical composition of the environment, "making a decision" about the potential danger.