Hydrotropism (hydro- `water`; tropism `involuntary orientation by an organism, that involves turning or curving as a positive or negative response to a stimulus`) is a plant`s growth response in which the direction of growth is determined by a stimulus or gradient in water concentration. A common example is a plant root growing in humid air b...
• (n.) A tendency towards moisture. • (n.) In a broader sense, any curvature or turning induced in certain growing plant organs under the influence of moisture.
(from the article `tropism`) ...by active movement or by structural alteration. Forms of tropism include phototropism (response to light), geotropism (response to gravity), ...
The growth or movement of an organism in the direction of water. The influence of an organisms growth or movements by the presence of water. ... (09 Oct 1997) ... 
(hi-drot´ro-piz-әm) tropism in response to the presence of water or moisture.
Hy·drot'ro·pism noun (Botany) A tendency towards moisture. 
Type: Term Pronunciation: hī′drō-trō′pizm, hī-drot′rō-pizm Definitions: 1. The property in growing organisms of turning toward a moist surface (positive hydrotropism) or away from a moist surface (negative hydrotropism).
hydrotropism 1. The turning of a plant toward or away from water. 2. The growth or directional response of an organism toward or away from water or moisture.
oriented growth in response to water.