Where does tropism collide?

In plant biology, a tropism is directional growth in which a plant organ bends toward or away from a stimulus such as light or gravity, driven by uneven elongation on the two sides of the organ. Darwin and Darwin's 1881 The power of movement in plants documented how shoots curve toward light and roots toward gravity and traced the response to a signal passed from the tip, laying the groundwork for the discovery of auxin. The referent is a stimulus-directed growth movement of a plant, measured by curvature toward a source, and it is a distinct construct from a virus's tissue preference or an animal's forced orientation, sharing only the root idea of a turning.[1]

Unit

The direction and degree of growth curvature relative to a stimulus

Recovery means

Not applicable

Measured by

Quantified by curvature angle over time toward or away from the stimulus direction

In comparative psychology, tropism was Loeb's theory that much animal behaviour is a forced orientation of the whole body by a stimulus, the same physico-chemical mechanism he saw in plants extended to explain movement toward light or chemicals without appeal to will or purpose. Loeb's 1918 Forced movements, tropisms, and animal conduct set out this mechanistic account of behaviour as directed response. The referent is a stimulus-forced orientation of an organism's movement, and it is a different construct from a plant's growth curvature or a pathogen's tissue targeting, carrying over only the meaning of being turned by an external pull.[2]

Unit

The orientation of locomotion forced by a directional stimulus

Recovery means

Not applicable

Measured by

Assessed by the heading of an organism's movement relative to the stimulus source

In virology and infection immunology, tropism (tissue or cellular tropism) is the set of host cells and tissues a pathogen can productively infect, set largely by which surface receptors the pathogen can bind and which intracellular factors it needs. Shenk's 1993 Virus and cell: Determinants of tissue tropism laid out how receptor use and host-cell permissiveness decide where a virus replicates. The referent is a pathogen's target-tissue range, which shapes disease pattern and the immune response it meets, and it is unrelated to a plant's bending toward light or an animal's forced movement, sharing only the idea of a leaning toward something.[3]

Unit

The range of host cell types a pathogen can productively infect

Recovery means

Not applicable

Measured by

Mapped by receptor usage, permissive cell panels, and the tissue distribution of infection