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Nastic movment

Nastic movements are plant movements that are independent of external stimuli and are controlled by internal mechanisms. There are two types of nastic movements: growth movements which are permanent, and turgor movements which are temporary and reversible. Some examples of specific nastic movements include nyctinasty, which is the opening and closing of plant organs in response to day and night cycles. Seismonasty is the movement of plants in response to physical disturbances like touch or wind. Thigmonastic movements occur in response to touch but without regard to the direction of the stimulus, as seen in insect-trapping plants. Hydronasty is the movement of plants in response to atmospheric moisture.

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Nastic Movements Dr. V. I. Kahalkar Department of Botany M. G. College, Armori
Nastic Movements • The plant movements which are independent of the external stimulus are called ‘nastic movements’. These will be no bending curvature toward or against the direction of stimulus in nastic movements . The direction of response is predetermined by internal control mechanism (within the tissue). These plant responses can be either growth movements or turgor movements . Growth movements are permanent (irreversible), while turgor movements are temporary and reversible.
1 Nyctinasty: • The sleep movements (opening and closing) of plant organs due to day and night periods of daily rhythm are called ‘nyctinastic movements’. Ex. Leaves and flowers. Leaves of many nyctinastic plants open during day time and close (sleep) during night time . Nyctinastic movement caused by change in light intensity is called photonasty, while that is caused by change in temperature is ‘thermonasty’.
2 Seismonasty: • Movement in plants or plant parts in response to touch or physical contact with regard to the direction of stimulus is called Seismonasty. The mechanical disturbance such as shaking, wind, rain drops and intense heat or burning also cause Seismonastic movement. Ex. the leaflet of Mimosa pudica rapidly folds and bends in response to external stimulus touch or heat.
Thigmonastic or Haptonastic • The plant movement in response to touch or physical contact but without regard to the direction of stimulus is called Thigmonastic movement. Thigmonastic movement are present in insectivorus plant that show movement of trap leaves, when they come in contact with any insect. Ex. Dionaea. Droscera.
• Hydronasty:- Plant movements in response to atmospheric moisture or humidity is called Hydronasty. Ex. Opening and closing of of some flowers. • Epinasty and hyponasty :- the plant part show curvature due to more cell division in one specific region. If the curvature is on upper side then it is called Epinasty. Ex. Leaves curve upwards because more growth is present on lower side. If the curveture is on lower side then it is called hyponasty. Ex. Thalamus and petals curve towords downwords as more growth can be observed on upper side.
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