Modification of the direction of growth, caused by some external influence, such as light; -- sometimes used for motion of an organism toward or away from an external stimulus, more properly called taxis.

Gr. tropos: to turn] • In plants, growth toward or away from a stimulus such as light (phototropism) or gravity (gravitropism).

the movement and response of plants as a result of light, gravity, water, or other causes

Long-term growth of a plant toward or away from a stimulus.

the bending or turning response of a plant caused by external stimuli.

The movement response of an organism to an external stimulus, such as heat or light.

The response of an organism to an external stimulus by turning or bending. ( BCFT)

an invariable response.

an involuntary orienting response.

Involuntary orientation by an organism or one of its parts that involves turning or curving by movement or by differential growth and is a positive or negative response to a source of stimulation.

a fixed, automatic, or inherited plant movement in response to a simuli

a growth movement whose direction is determined by the direction from which the stimulus strikes the plant

a growth response of a plant to an environmental influence

a growth response toward or away from a directional stimulus

a growth response toward or away from an environmental

a plant movement that is determined by the direction of an environmental stimulus

TRO-piz-um Plant growth toward or away from an environmental stimulus. 578

The movement of plant parts toward or away from a stimulus in the plant's environment. Plant movement in response to an environmental stimulus. PICTURE

(tropic): affinity or specificity for a particular target or stimulus.

(Gr. trope, a turning)  An involuntary plant response to a stimulus, in which a bending, turning or growth occurs, such as phototropism, geotropism or hydrotropism. The response may be positive (towards) or negative (away from) to the stimulus.

A growth response to a stimulus.

The turning or bending movement of an organism or a part toward or away from an external stimulus.

the movement of an organism in response to an external source of stimulus

A tropism 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.