Question

Thigmotropism is a plant response to a. light. d. gravity. b. cold. e. drought. c. touch.

Short answer

The correct answer is c. touch.

Step-by-step solution

Understand the Terminology

Start by understanding the term 'thigmotropism'. Thigmotropism is a response mechanism in plants that causes them to alter their growth to react to a touch stimulus.

Apply the Definition to the Choices

Next, apply this definition to the choices provided. You are looking for a stimulus that involves touch.

Select the Correct Answer

The correct option that matches with 'thigmotropism' is the stimulus brought about by 'touch'.

Key concepts

Plant Response

Plants, unlike animals, cannot move from place to place to react to their environment. However, they still exhibit remarkable responses to external stimuli. One such response is thigmotropism, which refers to a plant's growth response to touch. Plants adapt their growth patterns to maximize their chances of survival based on different types of stimuli. Thigmotropism is just one aspect of the broader category of plant responses that includes other stimuli like light and gravity. These growth responses are crucial for plant survival, helping them navigate their environment effectively, enhance support, or find more favorable positions for growth.
Plant response mechanisms involve complex signaling pathways. In thigmotropism, when a part of a plant, such as a tendril, comes into contact with a surface, it can trigger a cascade of biochemical events. These events lead to growth changes, allowing the plant to grip or climb. This sophisticated response system is one way plants ensure they remain anchored, supported, and correctly oriented, even in adverse conditions.

Stimulus

A stimulus is any change in an environment that elicits a response from an organism. In plants, stimuli can be numerous and varied. Thigmotropism specifically involves a physical touch stimulus. When a plant detects a mechanical stimulus, like touching a solid object, it can react by changing its growth. This is unlike responses to stimuli such as light or gravity, which involve different mechanisms but also influence plant development.
Plants perceive these stimuli through specialized cells. These cells can detect mechanical pressures or changes and then send signals throughout the plant. In thigmotropism, the stimulus of touch is vital for plants like vines and climbing plants. It helps them find solid structures to support their ascent, enabling them to reach sunlight and other resources necessary for their growth.

Touch Response

The touch response in plants is an intriguing aspect of their interaction with the environment. When a plant part experiences touch, a series of reactions are triggered, starting with the perception of the touch. For climbing plants, the touch of a solid surface instigates rapid growth on one side of the tendril or stem, causing it to coil around the object.
This coiling phenomenon is an excellent example of thigmotropism in action. It allows the plant to secure itself onto surfaces, which is essential for climbing plants like grapevines or peas. The touch response is not just about physical attachment but also includes hormonal changes that influence growth direction and speed.
In some cases, the touch response can be immediate, as seen in rapid responses like those in the sensitive plant (Mimosa pudica), where leaves fold quickly upon touch. However, in thigmotropism, the response usually involves a more gradual, directional growth pattern influenced by the continuous perception of touch.

Plant Growth

Plant growth is heavily influenced by how plants respond to environmental conditions and stimuli. In thigmotropism, the growth is directional, where the plant alters its growth toward or away from the stimulus of touch. This growth is typically enhanced on one side of the plant, causing bending or coiling.
Understanding how plant growth is regulated by thigmotropism also involves looking at growth hormones such as auxins. Auxins play a critical role in elongating plant cells, helping the plant grow towards or away from touch stimuli, depending on what benefits the plant. This fine-tuned growth coordination is essential for the plant to adapt to its surroundings.
Overall, plant growth is a dynamic process that enables adaptation and survival. Through mechanisms such as thigmotropism, plants can overcome physical challenges in their environment, making strategic use of available supports to reach optimal positions for sunlight and other growth-promoting factors.