Nastic movements are non-directional responses to stimuli (e.g.

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

, light

irradiance In radiometry, irradiance is the radiant flux ''received'' by a ''surface'' per unit area. The SI unit of irradiance is the watt per square metre (W⋅m−2). The CGS unit erg per square centimetre per second (erg⋅cm−2⋅s−1) is often used ...

), and are usually associated with

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae excl ...

s. The movement can be due to changes in

turgor Turgor pressure is the force within the cell that pushes the plasma membrane against the cell wall. It is also called ''hydrostatic pressure'', and is defined as the pressure in a fluid measured at a certain point within itself when at equilibri ...

. Decrease in turgor pressure causes shrinkage while increase in turgor pressure brings about swelling. Nastic movements differ from tropic movements in that the direction of tropic responses depends on the direction of the stimulus, whereas the direction of nastic movements is independent of the stimulus's position. The tropic movement is growth movement but nastic movement may or may not be growth movement. The rate or

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

of these responses increases as intensity of the stimulus increases. An example of such a response is the opening and closing of flowers (photonastic response), movement of euglena, chlamydomonas towards the source of light. They are named with the suffix "-nasty" and have prefixes that depend on the stimuli: * Epinasty: downward-bending from growth at the top, for example, the bending down of a heavy flower. * Hyponasty * Photonasty: response to light * Nyctinasty: movements at night or in the dark * Chemonasty: response to chemicals or nutrients * Hydronasty: response to water *

Thermonasty Thermonasty is a nondirectional response in plants to temperature. It is a form of nastic movement, not to be confused with thermotropism, which is a directional response in plants to temperature. A common example of this is in some ''Rhododendron' ...

: response to temperature * Seismonasty: response to shock * Geonasty/gravinasty: response to gravity *

Thigmonasty Thigmonasty or seismonasty is the nastic response of a plant or fungus to touch or vibration. Conspicuous examples of thigmonasty include many species in the leguminous subfamily Mimosoideae, active carnivorous plants such as Dionaea and a wide r ...

/seismonasty/haptonasty: response to contact The suffix may come from Greek νάσσω = "I press", ναστός = "pressed", ἐπιναστια = "the condition of being pressed upon".

References

External links

'Daisy - 'Day's Eye or Eye of the Day'.
Physiology Articles containing video clips {{Botany-stub de:Pflanzenbewegung#Nastien und Tropismen

See also

References

External links