Movement Physiology in Plants
Relocation Movements
Higher plants cannot move because they are attached to the soil by their roots. However, primitive plants and protozoa can be displaced, albeit slowly, by cytoplasmic movements. This phenomenon seen in primitive plants is of three types.
Amoebic Movement
This movement is seen in slime molds. Slime molds do not have a protective sheath on the cytoplasm. These creatures form extensions with pseudopods they remove from the cytoplasm. It can change place in line with these extensions.
Protoplasm Movement
In plant cells, the protoplasm is in constant motion under normal conditions. For example, when Elodea, an aquatic plant, is examined under a microscope after being kept in the sun for a while, the movements of the protoplasm can be observed in this plant that contains water. Protoplasm movements are of two types:
Rotation: Protoplasm always moves in the same direction, following the cell wall.
Circulation: It is the movement of protoplasm in various directions in multi-vacuum cells.
During the protoplasm movement, the organelles are displaced.
Immigration Movements
One-celled and some multi-celled organisms move around under the influence of various substances. This phenomenon is called taxis. The factors that enable living things to do this movement are light and chemical substances. Movement of a living thing under the influence of light is called phototaxis, and movement under the influence of chemical substances is called chemotaxis.
Let’s examine phototaxis with a simple experiment. Let’s take a glass of water from a puddle around you and cover it with a black cover. Let’s make a hole in the glass. Let’s wait like this for a few days. When we pull the black container from the glass, a greenish-orange appearance occurs in the part with the hole. It is seen that the algae in the water move to this part.
State Change Action
Plants cannot move like animals because they are attached to the soil by their roots. However, in order to benefit more from the environment they are in, they make changes in the situation.
Tropisms
State change movements can be related to the direction of the stimulus, in the direction of the stimulus or in the opposite direction to the stimulus. These movements are called tropism. In short, tropism is state-changing movements depending on the direction of the stimulus. It results from uneven growth due to the uneven distribution of growth hormone auxin. Tropisms are named according to the type of stimulus.
Phototropism: The auxin hormone secreted from the stem end of the plant is more on the side where there is no light. For this reason, auxin hormone accumulates less on the side where the light comes directly, and more on the side where the light does not come. As a result, growth is fast in the sunless regions and slower in the sun-exposed regions. In this case, it allows the plant to turn towards the sun. This is why the flowers placed on the edge of the glass turn their leaves towards the glass. If the plant turns an organ towards the light source, it is called positive phototropism, and if it moves away from the light, it is called negative phototropism.
Geotropism: It is the movement of change of state due to gravity of the plant.
Positive geotropism is seen in the root, while negative geotropism is seen in the stem.
Positive tropism in the root allows the plant to attach to the soil.
hydrotropism; It is a movement towards water. For example, the roots of the plants near the stream tending towards the water.
Traumatropism: It is the orientation movement of plants to the injury stimulus. If the root of the plant is injured, wound hormone is secreted in that area. As a result, the root tends to the opposite direction of the wound.
Chemotropism: Plant roots grow towards beneficial organic and inorganic substances in the soil. In the meantime, it gets away from harmful substances. The movement of the plant towards or away from chemical substances is called chemotropism.
Haptotropism: It is the reaction of the plant to the tactile stimulus. It is usually seen on wrapping stems. The plant continues to grow by wrapping it with the effect of haptotropism wherever it touches.
Irgan (nasties)
It is the movement that does not depend on the direction of the stimulus in plants. Regardless of which side the stimulus comes from, the reaction of the plant is the same. Nasti movements occur with sudden changes in turgor pressure. Nasti types are:
Photonasty: Movements caused by light in plants. In some plants, light causes flowers to close and open in darkness or shade. The movements of the stomata, which open and close with turgor changes, are also related to the light or dark of the day. An example of this phenomenon is the evening primrose plant. No matter where the light comes from, the flowers in the evening primrose close in high light and open in low light.
Seismonasti: Movements caused by shaking in plants. For example, mimosa leaves are closed by shaking, many plants throw their seeds away when touched, dandelion closes its leaves and hangs down when shaken.
Thermonasty: It is formed by the effect of temperature. For example, if tulip flowers that have not yet opened are brought to an environment 10-15 oC warmer than the environment they are in, the flower will open fully in a few minutes.
Tigmonastia: Occurs with tactile stimulus. An example of this is the fly trap plant. If an insect lands on the leaf of the fly trap, the leaves close with the effect of touching it.
Periodic Movements
Some movements seen in many plants differ between night and day. In many plants, the movements of hanging the leaves down at night, closing the flowers, blooming and erecting the leaves in the daytime continue rhythmically. These movements are called pedriodic movements. This event can be likened to a night’s sleep in humans. Periodic movements can be given as examples of movements seen in locust, acacia, and bean plants. While the leaves of the bean plant hang down at night, on the contrary, they tend upwards during the day. Periodic movements occur as a result of changes in turgor pressure. In many places, these movements are also called sleep movements.
Movement in Inanimate Tissues of Plants
Apart from the movements seen in living tissues of plants, some movements are also seen in inanimate tissues. Movements seen in inanimate tissues occur as a result of asymmetric swelling. The rotational movement in the fruit awn of the Dönbaba plant, the opening and closing movements in the old cones can be given as examples of the movement in inanimate tissues.
This movement seen in inanimate tissues is related to the humidity and drought of the air. Since swelling is not the same in all parts of the plant, it occurs in the form of twisting and twisting.