AP BIOLOGY

Detailed explanation-1: -These movements are non-directional responses to the stimuli. These movements are independent of the direction of the stimulus. These movements can be due to changes in turgor or growth. E.g. the response of the touch-me-not (Mimosa pudica) plant to touch.

Detailed explanation-2: -The movement of plant due to touch is known as a thigmotropic movement. Thigmotropism is a directional growth movement which occurs as a mechanosensory response to a touch stimulus. For example, once a shoot touches a suitable support, it grows towards the surface it is touching.

Detailed explanation-3: -●The movement of the plant part in response to an external stimulus in which the direction of movement is not determined by the direction of stimulus is defined as the nastic movement. ● The folding up of leaves belonging to a sensitive plant such as Mimosa pudica is an example of nastic movement.

Detailed explanation-4: -Nastic movements are non-directional responses to stimuli (e.g. temperature, humidity, light irradiance), and are usually associated with plants. The movement can be due to changes in turgor. Decrease in turgor pressure causes shrinkage while increase in turgor pressure brings about swelling.

Detailed explanation-5: -Nastic Responses are non-directional responses to the intensity of a stimulus. Because nastic responses are non-directional they cannot be described as positive or negative. Thigmonasty. Nastic responses are usually faster, reversible movements rather than growth responses.