Question

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

Answer 1

Hint: Plants exhibit varieties of movements which can be in the form of bending, twisting or elongation of different plant parts or organs. There are broadly two kinds of movements, the first one is called the Tropic movement which is a growth dependent movement that occurs in the direction to a particular stimulus. The second one is the Nastic movement which is a growth independent movement that occurs independent of the direction of any stimulus.

Complete answer: Nastic movements are a type of plant movement which occurs due to various environmental stimuli like temperature, humidity, light but unlike tropic movement do not occur in the direction of the stimuli. The rate of this movement increases as the intensity of the stimulus causing it also increases. This movement majorly takes place in leaves, petals of flowers. Types of nastic movement and their examples are as follows-
Seismonastic movement- this type is caused by mechanical stimuli such as touch, wind, raindrops, etc. this movement is mostly seen in stigmas, stamens and leaves. Examples include Mimosa pudica, Neptunia.
Photonasty movement- this type of movement occurs in response to light and is mostly observed in flower petals. Examples include Dandelion flower, Moonflower.
Thermonastic movement- this type of movement occurs due to changes in temperature. Sometimes the plants open with rise in temperature and close with fall in temperature. Examples include Rhododendron.
Nyctinastic movement- this movement is caused due to both changes in light and temperature. It is also known as the Sleeping movement. Examples include most leguminous plants.
Thigmonasty movement- this movement is caused in response to contact with an object. Examples include Drosera, Dionaea.

Note: Plants don’t move from one place to another like animals. Their roots are fixed in soil but they do show certain kinds of movements in response to a variety of stimuli that is ultimately helpful for them.