Question

what is nastic movement?​

Answer 1

Answer:

Nastic movements are non-directional responses to stimuli, and are usually associated with plants. The movement can be due to changes in turgor or changes in growth. Decrease in turgor pressure causes shrinkage while increase in turgor pressure brings about swelling.

Answer 2

Answer:

★ Nastic Movement : It is the induced movement of curvature of any plant part or organ, which is influenced by intensity of external stimulus.

➠ Characteristics of Nastic Movement :

• This is induced movement of curvature.
• This is influenced by intensity of stimulus.
• Nastic movement occurs due to variation in turgor pressure.
• It occurs in matured parts of plant body.
• It is mostly positive (+ ve) movement.

➠ Types Of Nastic Movement :

◘ Nastic movement can be classified into five main types :

❶ Photonasty : The induced movement of curvature in plants, that is controlled by the intensity of light, is called photonasty.

Example : Petals of sunflower open widely in bright daylight, but they close during the evening.

❷ Thermonasty : The movement of curvature in plants induced by temperature of the surroundings, is called thermonasty.

Example : Tulip flowers open their petals when temperature is very high during the midday. As soon as the temperature drops, the petals close eventually.

❸ Chemonasty : The movement of curvature in plants, which is induced by strength of any chemical substance, are called chemonasty.

Example : Tip of young tendrils bend in contact with chemicals like ether, chloroform etc., the leaf tentacles of sundew bend very fast to capture any insect, when it sits on the leaf. The proteins of the insect body stimulate this movement.

❹ Seismonasty : The induced movement of curvature in plants, which is stimulated by touch, friction, vibration or any kind of mechanical impact, are called seismonasty.

Example : The touch-me-not plant fold at once, if these are touched gently. In case of stronger impact, the whole leaf droops.

❺ Nyctinasty : The induced movement of curvature in plants, which is controlled by the intensity of both light and heat, are called nyctinasty.

Example : Leaves of Oxalis, babool etc. spread widely in hot and bright sun in midday, but fold in late afternoon as the intensity of heat and light decreasing.