What is geotropism?

What Does geotropism Mean

The geotropismo is a kind of tropism : a displacement or tilt orientation performing a sessile organism (which is fixed on the substrate) to respond to a stimulus. In this case, the tropism in question is produced by the force of gravity.

The gravity is a force exerted by the planet Earth on all the bodies found on its surface. The earthly center attracts all objects with mass, which are acted upon by this force. Plants, in this framework, respond to gravity through geotropism.
Also called gravitropism , geotropism is a reaction to the intensity of the gravitational field . The roots of the plants, in order to fulfill their functions, grow towards the interior of the Earth , sinking into the substrate; the stems, on the other hand, develop their growth upwards, spreading on the surface.

Different concentrations of auxin allow plants to develop geotropism. This plant hormone or phytohormone is responsible for regulating the growth of the plant, promoting cell development. Depending on how the auxin is concentrated, the specimen grows in one way or another.
When geotropism accompanies the force of gravity , we speak of positive geotropism (the roots). On the other hand, if the geotropism is opposite to gravity, it is a negative geotropism (the stems).
Geotropism, in short, allows plants to develop, subsist and reproduce. With negative geotropism, stems and leaves develop in the air and can photosynthesize thanks to sunlight; With positive geotropism, the roots move in the same direction as gravity to access the nutrients and water they need.
Returning to the concept of auxin , we can say that it is a set of phytohormones , which are also known as plant hormones , and are the substances that plant cells produce. They are generally found in leaves and their action on other types of cells is equivalent to that of a chemical messenger.
The main function of auxin in the regulation of development is the elongation of plant cells. The synthesis of these hormones takes place in the apical meristem of the stem , a meristematic tissue (that is, it is responsible for growth) that is located at the tip of the plant, in particular in the area of ​​division and expansion of cells, and gives rise to stems, leaves and flowers.

Precisely at the core of the definition of geotropism is this group of plant hormones, which reaches its maximum level at the apex and decreases as it moves away from it.
In the geotropism of the hypocotyls (the germinating part of the seed ) of soybeans, it has been proven that small messenger RNAs are involved (the ribonucleic acid that carries the genetic code from the DNA of the cell nucleus to some ribosome located in the cytoplasm), which are known by the name SAURs . The synthesis of SAURs requires the addition of auxins for their stimulation.
The expression of SAURs in soybean sprouts that grow in a vertical direction is symmetric , while for those with horizontal growth, the expression is modulated so that they accumulate especially in the basal half of the hypocotyl. In this way, the response that gives rise to the curvature of the organ and the increase in verticality of the plant begins. This is just one example of geotropism that demonstrates the complexity of the processes that take place in living things, no matter how small.

Go up