Movement in plants

Details about Types of Movements in plants

1. Plant Movement Plant movements can be defined as the changes in the spatial orientation or conformation of an organ or its parts. Plant movements include movements toward light, opening and closing of flowers, growth of developing roots in search of water and nutrients, etc. Plant Movements: Movement refers to the act of moving or changing its position. When organisms move from one place to another, then it is called locomotion which is seen in animals. Plant shows movements but not locomotion. But as plants are fixed with their roots at one place, locomotion is not possible in them. However, in plants, we can see different types of movement for their growth, development and reproduction. Some of the examples of Plant Movements are the downward growth of roots, opening and closing of stomata, opening of petals, etc. Let us have an overview of different types of plant movement shown by plants.

2. Movements of Locomotion It refers to the movement of the whole plant body from one place to another. Like that of male gametes of Bryophytes and Pteridophytes . Male gametes here are flagellated and move from one place to another, i.e. from the male reproductive part to the female gamete. This type of movement can be autonomic (spontaneous) or paratonic (induced). i . Autonomic movements a. Ciliary Movements – This type of movement is seen in some organisms having cilia or flagella. Like movements seen in Chlamydomonas , Volvox , etc. b. Amoeboid Movements – This type of movement is due to the formation of pseudopodia. Like in Amoeba, amoeboid movement is seen to capture food. c. Cyclosis - It refers to the protoplasmic movement of a cell. It can be rotational movement or circular movement. Example- Chara , Hydrilla exhibit rotational movement while trichomes or staminal hairs of Tradescantia (spiderwort) shows protoplasmic movement in a circular manner.

3. ii . Paratonic (Induced) movement or Tactic movements It refers to the movement of locomotion which is due to external stimulus. This type of movement is directional. a. Phototactic - Here, external stimulus is light. Light induces locomotion in certain organisms like Chlamydomonas that have flagellated structure. It swims towards the light. Other examples can be seen in the case of Euglena, which is considered as a link between plants and animals. It has a plant-like structure called the chloroplast. So if the light is there, it moves towards light and can perform photosynthesis. If the light is not there, then it will start eating other organisms like animals. b. Chemotactic- Here, external stimulus is chemical, i.e. Chemicals are responsible for the movement of the plant. Example- Male gamete of Bryophyte fern moves from anthredium to archegonium due to chemicals secreted by archegonium . Chemical secreted here is sucrose and malic acid produced by archegonium . c. Thermotactic - Here, external stimulus is temperature. Cells with flagella move towards the warmer temperature because the enzymatic activity is optimum in warmer conditions. Example- This can be seen in Chlamydomonas that will move towards the warmer side called positive thermotaxis while if the temperature is too high, then it will move away from the high temperature and is called negative thermotaxis .

4. 1. Nutation – This type of movement is seen in growing tips of vine or tendril. In this, there are differences in the growth of different parts of the plant. When tendril is given support, its side, which is attached to the support, grows at a slower rate than the part or side of the tendril which is away from the support, i.e. part of the tendril which away from the support will grow at a faster rate, which results in bending and twining of the plant around that support. 2. Nastic – There occur differences in the growth of different surfaces of organs of plants. Like if movement occurs due to the fast growth of the upper surface of the organ of a plant, then this type of movement is called epinastic movement. If movement occurs due to the fast growth of the lower surface of the organ of a plant, then this type of movement is called hyponastic movement. b. Paratonic (Induced)- This type of movement of curvature is caused by external stimuli. It is further divided into the following two types:- i . Tropic (Growth movements) or Tropism- These movements are directional. Movements can be towards or away from the stimulus. 1. Geotropic – It refers to the tropic movement which occurs in response to gravity. Here gravity acts as an external stimulus. These types of movements are called geotropic movements, and the phenomenon is called geotropism. It can be positive or negative geotropism. Like we can take the example of the growth of roots. This movement is taking place towards the gravity so-called positive geotropism. In contrast, the growth of the stem is away from gravity, so it shows negative geotropism.

5. 2. Phototropic – It refers to the tropic movement which occurs in response to light. Here light acts as an external stimulus. These types of movements are called phototropic movements, and the phenomenon is called phototropism. Like bending the stem of a growing plant towards the light source. 3. Thigmotropic – It refers to the movement of plants in response to touch. This movement is directional, and the movement is called thigmotropic movement and, the phenomenon is called thigmotropism . Like movement curling of tendril of Passiflora around a support. Fig: Response of ‘Tendril’ to Touch

6. 4. Chemotropic – Movement in response to the chemicals are called chemotropic movement and the phenomenon is called chemotropism. E.g. growth of pollen tubes. 5. Hydrotropic – Growth movements in response to the water are called hydrotropic movements and the phenomenon is called hydrotropism. Growth of roots towards the source of water shows hydrotropism. 6. Thermotropic – If the tropic movement occurs due to the stimulus temperature, then that type of movement is called thermotropic movement. 7. Aerotropic – If air is the stimulus and growth is due to this stimulus, then it is called aerotropic movement, and the phenomenon is called aerotropism . ii. Nastic (Variation movements)- These movements are not unidirectional. 1. Photonastic – Here, stimulus is a change in light intensity. This movement is seen in the noon flowers, in which flowers open up in sunlight and then closes when the intensity of light decreases. 2. Nyctinastic – It refers to the rhythmic nastic movements which occur due to day and night. Some of the legumes close their leaves at night and open up during daylight. This is called sleep movement. 3. Thermonastic – It refers to the non-directional movement of plants in response to temperature. Flowers open up as the temperature increases. E.g. The leaves of Oxalis triangularis fold up as temperature decreases. 4. Thigmonastic or seismonastic – This type of movement occurs in response to touch. Like in ‘Touch me not’ plant. As soon as we touch the leaves of this plant, a chemical is released, which is transported through the xylem and phloem to the pulvinus (swollen base of the leaves). Once the chemical reaches the pulvinus , the inner cells actively loose K+ ions to the outer cells. As a result of which the inner cells will become hypotonic, and outer cells become hypertonic.

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