Question

3 differences between tropic and nastic movement

Answer 1

Nastic movements are non-directional responses to stimuli (e.g. temperature, humidity, light irradiance). The movement can be due to changes in turgor or changes in growth. 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. The rate or frequency 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). Nastic responses are usually associated with plants." Tropism Movement: "A tropism (from Greek, tropos, to turn) is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in response to an environmental stimulus. In tropisms, this response is dependent on the direction of the stimulus (as opposed to nastic movements which are non-directional responses). Viruses and other pathogens also affect what is called "host tropism" or "cell tropism" in which case tropism refers to the way in which different viruses/pathogens have evolved to preferentially target specific host species, or specific cell types within those species. The word tropism comes from the Greek trope ("to turn" or "to change"). Tropisms are usually named for the stimulus involved (for example, a phototropism is a reaction to light) and may be either positive (towards the stimulus) or negative (away from the stimulus).
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