What is thigmotropism in plants?

Thigmotropism in plants is the directional growth response to physical contact or touch.

Thigmotropism is a type of tropism, which is a biological phenomenon that involves the growth or movement of an organism in response to an environmental stimulus. In the case of thigmotropism, the stimulus is touch or physical contact. This response is particularly noticeable in climbing plants, such as ivy or vines, which grow in the direction of a support structure when they come into contact with it.

The mechanism behind thigmotropism involves the plant's cells on the side that is in contact with the object undergoing a change. This change is typically a reduction in growth rate, causing the plant to curve towards the object. This is due to the redistribution of auxins, a type of plant hormone, from the side of the plant in contact with the object to the other side. The increased concentration of auxins on the untouched side stimulates cell elongation, causing the plant to bend towards the object.

Thigmotropism is an adaptive response that allows plants to grow in environments where space is limited or where support is needed for growth. It enables plants to maximise their exposure to sunlight, which is essential for photosynthesis, and to anchor themselves securely in their environment. This response is not limited to climbing plants; roots also exhibit thigmotropism when they grow around rocks and other obstacles in the soil.

In summary, thigmotropism is a growth response in plants triggered by touch or physical contact. It involves a change in the distribution of plant hormones, leading to differential growth rates on different sides of the plant, causing it to bend towards the object it is in contact with. This response is an adaptation that allows plants to navigate their environment effectively.