Darkinduced

Darkinduced, often written with a hyphen as dark-induced, is an adjective used in biology to describe processes that are initiated or regulated by darkness. It denotes responses whose onset follows a reduction or absence of light rather than the presence of light.

In plants, dark-induced responses include dark-induced leaf senescence, a process in which extended darkness accelerates the degradation of chlorophyll and macromolecules, leading to tissue yellowing and nutrient remobilization. Darkness also suppresses photosynthesis-related gene expression and can alter growth patterns, stomatal behavior, and energy balance. Mechanistically, the absence of light shifts metabolism from photosynthetic carbon fixation toward respiration and catabolism and can involve signaling pathways linked to hormonal changes, including abscisic acid and ethylene.

Outside of plants, dark-induced phenomena have been reported in some fungi, algae, and bacteria, where darkness modulates sporulation, pigment production, or gene expression in species-specific ways. These reports are heterogeneous and depend on organism, experimental conditions, and the duration of darkness.

Research and interpretation: researchers study dark-induced processes by comparing specimens kept under controlled darkness with light-treated controls, often using transcriptomic, metabolomic, and physiological readouts. The term emphasizes an induction by darkness rather than a response to light, but care is needed to distinguish truly dark-induced effects from circadian-phase–dependent changes or secondary consequences of energy limitation.

See also: photomorphogenesis; circadian rhythm; senescence; photoperiodism.