Movement Due to Growth Explained: Types & Examples

We often think that plants have no sense organs, so it will not be possible for them to show movements but it is not true. Although our plants have no sense organs, they show some movements in response to different factors. These factors are sun, gravity, pressure, water etc. Plants just recognize these factors and then with respect to these factors they respond. These factors on the basis of which they produce a response are known as stimuli, calling them more precisely to be environmental stimuli. Like humans, plants also respond to the changes that occur in the environment. These actions are regulated by the plants by using their hormones. These hormones, in turn , affect plant growth. Here in this article you are going to learn the basic information about the plants moments

Plants are rooted in one place, and cannot move from one place to another physically. But plants still exhibit motion by using hormones under stimuli influence. This movement is found when the two regions of a plant expand unequally.

For example:

Some plants, such as the pea plant, use tendrils to climb up other plants or fences. Those tendrils are touch-sensitive. The part of the tendril in interaction with the object does not grow as quickly as the part of the tendril away from the object when they come in contact with any supports.

This instigates the tendril to circle around and therefore cling to the object. More generally, by rising in a particular direction, the plants respond to stimuli gradually. Because this development is lateral, it appears as though the plant is growing.

Just like these tendrils are sensitive to the sense of touch, there are many other examples in plants that depend upon other examples. The most common example that we can see everyday is of sunflower plants. The plant, if a sunflower, changes its position constantly as the sun changes its position throughout the day. This example will give you more insight on the topic of plant movement. Further details are discussed below.

Depending on their growth there are two types of Movement in Plants. They are Tropic and Nastic movements

Tropic Movement:

When the external stimulus path determines the direction of the response in the form of growth it is called tropism. Thus, tropism is a part of a plant's directional growth motion. 

Tropic Movement of Plants can be of two types, it can be either in the direction of the stimulus or they can be in the direction away from the stimulus.

 So, if a plant's growth is in the direction of stimulus, it's called positive tropism.

If a plant's growth is in the opposite direction, or away from stimulus production, it is called a negative stimulus.

Types of Tropic Movements:

There are five stimuli like light, gravity, chemical, water and touch in the environment. There are five types of movement like phototropism, geotropism, chemotropism, hydrotropism and thigmotropism based on five stimuli.

Basically each kind of movement is dependent upon the type of stimulus they have like for light, we have phototropism, for stimulus of gravity we have geotropism, in response to chemical the Movement of Plant is chemotropism, in response to water it is hydrotropism and in response to touch, it is thigmotropism. All these movements are explained in detail in the article below.

Phototropism:

Movement of any plant part towards light is known as phototropism. In case, if the development of a plant's stem or any part of a plant is towards light, not only this even if it's movement is towards light it will be called as positive phototropism.

While if we talk about movement of a leaflet or stem or any other part of a plant away from the light it will be referred to as negative phototropism.

Geotropism:

When a section of a plant falls in reaction to gravity, geotropism is called that. That means geotropism is the movement of  plant parts in response to gravity. Mostly geotropism is positive geotropism rarely seen in the cases of negative geotropism.examples, a plant's roots move downward, so they show positive geotropism and stem moves upward, so it shows negative geotropism.

Chemotropism:

It is called chemotropism when a plant part moves in response to a chemical stimulus. The stimulus here is chemical in nature. In chemotropism, the movement of a plant's part is either towards the chemical or away from it. In order to do this these movements are positive or negative  chemotropism.For example, during fertilization in a flora, the growth of a pollen tube towards the ovule is called positive chemotropism.

Hydrotropism:

It is called hydrotropism, when a plant element moves in response to water. The trigger here is Water. Positive hydrotropism is the movement of the plant towards the water source while negative phototropism refers to its movement away from the source of water. A plant's roots move towards water, so that they show positive hydrotropism.

Thigmotropism

When a part of a plant shows directional motion in response to an object's touch it is called thigmotropism. For instance, a plant's tendrils climb towards any support that they touch. The movement of the plant's part toward the sense of touch is called positive thigmotropism while the movement away from touch is known as negative thigmotropism.

Nastic Movement:

If the direction of response in a plant isn't determined by stimulus direction, it's called nastic motion. Nastic movement is not plant-based directional movement.

Whatever the direction of the stimulus, all the parts of the plant move equally in the same direction in nastic motion. This type of movement usually occurs in leaves, flower petals, etc.

There are two types of Nasty movements. They are:

• Thigmonasty

• Photonasty

Thigmonasty:

The movement of a part of a plant in response to an object's touch is called thigmonasty. In this case the motion of a part of a plant is non – directional.

An example of thigmonasty is the responsive plant mimosa pudica which is also known as touch-me-not. If we touch this plant's leaves they immediately fold up and droop down.

This is the most common example of thigmotropism as you can easily find the touch me not, plant in your gardens or herbal garden around you for your study about the touch me not plant.

Photomonasty:

The motion of a part of a plant, usually flower petals, is called photonasty in response to light. Non-directional movement. In photonasty the stimulus is light. Examples of photonasty include dandelions and moonflowers.

Growth movements are the opening and closing of flower petals as a response to light. This is ììroot, stem or root shows differential growth.

The hyphae of the fungi are chemotropic.

Examples of Nasty movements:

Diurnal leaf movement and insectivorous plant response to prey, such as the Venus fly trap.

In all the above mentioned examples you can observe photonasty movements that are basically  the plant's movement or response to a particular stimulus.

Key points:

Despite their static nature, plants move due to their growth, accordingly they are divided into two types :   Tropic Movements and Nasty movements.

Tropic Movements: growth dependent Movement in Plants is seen

Nasty movements: Growth independent Movement in Plants is seen.

Types of Tropic Movements are phototropism, geotropism, thigmotropism, hydrotropism, and chemotropism, which are based on five stimuli present in the environment.

Basically these different types of moments are on the basis of the stimulus that they receive and how they interpret or perform action just in order to that particular stimulus.

Types of Nasty moments are thigmonasty and Photonasty.