Question

What is the nastic movement? Give one example of each.

Answer 1

Every plant has their way of responding to the environment and different stimuli of nature whether (change in climate, long days, short days, rains, temperature and pressure in the surrounding), etc.

Complete answer: Nastic movements are known as non-directional responses to stimuli (e.g. temperature, humidity, light irradiance), and are mostly associated with plants. The movement can be due to a change in the turgor pressure. The decrease in turgor pressure results in shrinkage, while the increase in turgor pressure causes swelling. Nastic movements are different from tropic movements in that the direction of tropic movements depends on the direction of the stimulus, whereas the direction of nastic movements is not dependent on the stimulus's position. The tropic movement is a growing movement, but nastic movement may or might not be a growing movement. With an increase in the intensity of the stimulus, the rate or frequency of these responses also increases.
The different types of nastic movement are as follows:
a) Epinasty: It is the downward-bending from growth at the top, for example, the bending down of a heavy flower.
b) Photonasty: It is the response to light, Most petals of flowers open in the daylight and close in the evening in response to the intensity of the light.
c) Nyctinasty: It is the movements at night or in the dark, the petals of a flower closed at dusk and the sleep movements of the leaves of many legumes occurs.
d) Chemonasty: It is the response to chemicals or nutrients, shutting of the Venus flytrap.
e) Hydronasty: It is the response to water, coiling of tendrils or twiners when comes in contact to objects for support.
f) Thermonasty: It is the response to temperature between 5 and 10°C. Crocus flowers open up in a few minutes due to the relative increase in the growth rate of the inner side of the petals.
g) Seismonasty: It is the response to shock, thigmonasty include many species of the leguminous subfamily Mimosoideae, actively carnivorous plants such as the Dionaea and a wide range of pollination mechanisms.
h) Geonasty/gravinasty: It is the response to gravity, the bending of long leaves or barks (when the strength of the plant is not enough either to support them against gravity); The upward growth of a plant (against gravity) and generally the downward movement of roots (with gravity).

Note: Nastic movement is generally caused by elastic changes in the size of special motor cells within the plant tissue. These changes are generally produced by changes in the osmotic pressure due to an influx or efflux of ions that cause water to move in or out of the cells.