define tropisms
Home Â» Morphogenesis Â» Cellular differentiation Â» Physiological Â» Pigmentation Â» Tropism. Definition. noun, plural: tropisms. A movement or growth response of a cell or an organism to a stimulus, which may either be positive or negative depending on the source and kind of stimulation. Supplement. A tropism is generally an involuntary orienting response of an organism to a stimulus.