WHAT IS THIGMOTROPISM? - BIOLOGY - 2025

The tigmotropismo is a biological quality by which a plant is mobilized to the touched be. It is a product of the ability to adapt and occurs in response to physical contact against a solid object, which obstructs the natural direction of growth.

This is a quality of plants, especially visible in those that bloom. However, some fungi are also capable of growing with thigmotropism.

The term has Greek roots and is a word composed of the prefix "tigmus", which means "to touch", added to the word "tropism", which means "turn".

Characteristics of thigmotropism in plants

All plants are capable of developing thigmotropism, although not all do it to the same extent. It occurs slowly, but its appearance is irreversible, even if the stimulus-object is withdrawn.

Thanks to thigmotropism, a plant can adapt and grow on a trunk, wall or any object that gets in its way. To do this, they develop a special organ that allows them to adhere to the support.

In botany, this organ is called a “tendril”. There are leaf-type tendrils, coming from the leaves; and there are tendrils of the caulinar type, coming from thin stems; so fine that they are not capable of producing flowers or leaves, but allow the plant to climb or crawl.

In the following video you can see the thigmotropism in the species Drosera burmannii:

Types of thigmotropism

There are two types of thigmotropism, positive and negative. They are not exclusive, so both can occur at the same time in the same plant.

Positive thigmotropism

It occurs when the plant grows around the object-stimulus, using it as a support to continue growing.

For it to occur, the presence of light is necessary, since the plant will grow looking for it. That is why this quality occurs especially in flowering plants.

Positive thigmotropism

In experiments carried out by Mark Jaffe with bean seed sprouts, while a plant was in contact with an object and in turn exposed to light, the stem looked for a way to use the object as a support to reach the light, while when performing the same test in the dark, the stem remained straight.

The Vine (Vitis Vinífera), the plant from which the grape is born, has tendrils that, when touching a support, are wound around it. Once rolled, they harden to achieve more grip and thus grow satisfactorily.

Another clear example of positive thigmotropism is in climbing plants and vines.

They have achieved a higher level of adaptation, since they expand on the surface of the object and sometimes end up depriving other plants of CO2 and light.

Negative thigmotropism

It occurs only in the roots of plants, especially when the roots are still fine and weak; its function is to avoid the object-stimulus. The roots are incredibly vulnerable to touch, so they deviate at the slightest resistance.

Negative thigmotropism

Negative thigmotropism is capable of canceling the proper geotropism of the roots. In experiments conducted by Charles Darwin with sprouted bean seeds, he found that upon contact with an obstacle, the root deviates from its natural vertical growth.

Classification of thigmotropism

Depending on the direction in which the plant or one of its parts rotates, it will be classified as dextrorotatory or left-handed thigmotropism.

Dextrorotatory thigmotropism

Occurs when the turn is oriented to the right side, clockwise.

Levorotatory thigmotropism

It is the opposite of dextrorotatory thigmotropism, it occurs when the plant rotates to the left side, taking an anti-clockwise direction.

References

1. Darwin, C. (2009). The movements and habits of climbing plants. Retrieved on August 17, 2017, from the Darwinian Library Web: 060.es.
2. Evert, RF, & Eichhorn, S. (2013). Raven: Biology of Plants. Houndmills: WH Freeman and company publishers.
3. Raven, P., Evert, R., & Eichhorn, S. (1992). Plant Biology. Barcelona: Reverté SA
4. Russell, PJ, Hertz, PE, & McMillian, B. (2017, 2014). Biology: The Dynamic Science, Fourth Edition. Retrieved on August 17, 2017, from Cengage Learning: cengage.com.
5. Vargas Rojas, G. (2011). General Botany: From mosses to trees. San José: Editorial Universidad Estatal a Distancia.