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Plants aren’t equipped with the locomotor system like humans or other animals. However, that doesn’t mean they cannot be active or use movement as a strategy for survival or even catching prey. Let’s take a look at some amazing examples of plant movement.
Tropism – Plant’s reaction to conditions
Tropism is essentially a plant’s alteration of growth due to environmental conditions. This kind of movement is irreversible – once the plant grows or turns a certain way, it cannot go back to a previous shape. There are many types of tropism, depending on the factor that indicates the change.
Mechanism
Tropism is a crucial mechanism that helps plants adapt to environmental changes. The reaction takes a while and consists of three steps. First, there are stimuli, which change the most optimal place for a plant to grow. Next, the change is noted by the plant’s receptors, and the chemical response begins. The hormone that regulates the plant’s growth- auxin – moves and stops the growth in a certain part of the plant. Afterward, the sprig elongates in a different direction and bends.
Types of tropism
There are as many types of tropism as there are stimuli that can affect a plant’s growth. The most common one is phototropism- reaction to sunlight. When a plant detects sunlight, auxin moves to the shady part of the plant. As a result, the sprig moves towards the light. Conversely, if a stimulus is negative, the plant can move away from it. For example, if someone often walks or touches one side of the plant, it will grow away to the other side. Similarly, plants can react to gravity, chemicals, temperature, or even electric field. Therefore, tropism is essential for a plant’s adaptation to various conditions, making it crucial for survival.
Plant movement unrelated to growth
Nastic Movements and Taxis
Opposite to tropism, nastic movements aren’t always associated with a plant’s growth, and they don’t depend on the stimuli’s direction. Another type of plant movement is taxis. Taxis is a directed, independent movement towards or away from the stimuli. Similar to tropism, both types are classified depending on the type of stimuli that generates a response. A great example of a nastic movement is epinasty, which occurs when the top of the plant grows faster than its bottom (for example, a heavy flower or a fruit develops). As a response, the plant bends down to be able to hold additional weight.
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Strategy for spreading seeds
Many plants use various chemical mechanisms to create a stimulus that will push the seed away, enabling the plant to spread its offspring. Some species even developed a mechanism similar to a catapult. The fastest catapulting plant is bunchberry dogwood. Scientists concluded that when the flower’s petals open with an explosive force, it can reach a speed of up to 24 kilometers per hour. The explosion throws the grain 2.5 cm into the air. That is ten times the height of the plant! The wind carries the seeds away from that point, and they can grow further away from the mother plant.
Carnivorous plants
All plants are autotrophic, which means they transform the energy from the light into energy necessary for metabolic processes. However, some plants get minerals and other elements from animals. Even though not all of them move, many species demonstrate a unique strategy of catching prey. Some strategies involve plant movement, while others are related to realizing special substances.
Catching prey
There are over seven hundred species of carnivorous plants worldwide, and many traps evolved independently from one another. Venus flytrap uses “a snap trap.” When an animal enters the leaves, they snap together and trap it inside the plant. Afterward, the plant begins digesting the prey with enzymes synthesized by the leaves. The reaction time of the plant is only 0.5 milliseconds! That happens because highly specialized hairs on the surface of the leaves detect even the slightest pressure and movement. After detection, they send an electrical signal across the plant, which makes the leaves close.
