Nastic Movement in Plants

Plants are known to be fixed in place with their roots in the earth and hence unable to migrate from one location to another. They don't demonstrate motility in general, but they can move individual portions or organs of a plant, such as shoots, roots, and leaves when they are exposed to stimuli such as light, gravity, chemical compounds, water, and touch. Plant hormones enable these motions to occur under the effect of stimuli. We will discuss one of the essential plant movements in this article, namely, what is nastic movement, its types, and examples.

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What is a Nastic Response?/ What is Photonastic Movement?

To define what is a nastic response or photonastic movement, these are plant movements that occur in response to environmental stimuli, but unlike tropic movements, the direction of the response is independent of the stimulus direction. Nastic movements are some of the most remarkable plant movements. These include the carnivorous Venus Flytrap leaf closing as it takes prey and the mimosa leaf folding when disturbed.

Examples of Nastic Movement:

1. The Venus flytrap, which captures insects, is probably the most well-known nastic movement. Mechanoreceptors (movement-detecting receptors) are three sensitive hairs on the inside surface of the trap, and two of them must be triggered in succession for the trap to close. This disables the need to react to falling twigs and debris.

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2. In the morning, the leaves of the prayer plant rotate downward to a horizontal posture, increasing light exposure, then upward at night, limiting water loss. This reaction to darkness is called nyctinasty.

3. When the leaves of the Mimosa pudica plant are touched, they fold up. Touch is the stimuli in this case.

Types of Nastic Movement

Plants have five different forms of Nastic movements.

The four types are 1) Seismonastic Movements, 2) Photonastic Movements, 3) Thermonastic Movements, 4) Nyctinastic Movements, and 5) Thigmonastic movements.

1. Seismonastic Movements

Mechanical stimuli such as contact with a foreign body, quick wind, and raindrops, among others, cause these movements. Many plants' stigmas, stamens, and leaves display seismonastic movements. For example, leaflets movements are seen in Mimosa pudica, Biophytum sensitivum, and Neptunia, among others. Certain plants, such as Mimulus, Martynia, and Bignonia, have stigma lobes that wrap the pollengram as soon as it falls over them. Berberis, Portulaca, and Opuntia stamens react promptly to any insect when touched by the body. The size of the seismonastic movement is determined by several parameters, including the stimulus's intensity, the plant's vigour and age, and the time since the last stimulation.

2. Photonastic Movements

Fluctuations in the intensity of light can cause these movements. Flowers from a variety of plants show this type of movement. Many flowers bloom when the sun rises higher in the sky and close as the sun sets lower in the sky. Cestrum nocturnum flowers bloom at night and close with the light of the day.

3. Thermonastic Movements

Temperature fluctuations cause these types of movements. Thermonastic flower movements are common. Such flowers bloom when the temperature rises and close when the temperature drops. Thermonastic and photonastic movements are sometimes seen together. Differential growth or changes in turgor on the upper and lower sides of the petiole, leaf blade, or perianth portion may be the mechanism in both types of responses.

4. Nyctinastic Movements

These are usually referred to as 'sleeping movements.' Some authors have categorised such movements as photonastic or thermonastic movements. The cycle of day and night causes these movements. Some plants, such as Enterobium, clover, and oxalis, have leaves that grow nearly horizontal throughout the day, then droop and close in the evening, not to rise again until the next morning.

5. Thigmonastic movement

Thigmonastic movement is the non-directional movement of a plant in reaction to contact with an object. The tentacles of insectivorous plants' leaves, such as Drosera and Dionaea, display variation in a movement when they come into contact with an insect. An insect's stimulus touch is relayed to the entire leaf, causing all of the tentacles to bend around the bug.

Difference Between Nastic Movement and Tropic Movement

Plants move in reaction to a stimulus. Plant growth is separated into two categories: 1) Tropic Movements and 2) Nastic Movements. To comprehend What is tropic and nastic movement, you must first understand the differences between these two motions, which are detailed below for your convenience.

1. Unlike tropism, the direction of the response in nastic movement is independent of the stimulus's orientation.

2. Tropic movements are slow in comparison to other movements. Nastic movements are fast movements.

3. Tropic motions are induced by the organ's cell divisions. The shift in the turgor pressure of the cells in the organ causes the nastic motions.

4. In contrast to tropism, which is based on differential growth, nastic mobility is based on osmotic changes.