Day Night Cycling

Day-night cycling refers to terpene and cannabinoid expression patterns that fluctuate based on light exposure and circadian rhythm conditions. Cannabis plants under controlled photoperiods often display measurable shifts in volatile compound production—certain monoterpenes and sesquiterpenes may increase during light hours while others peak during darkness. This phenomenon reflects the plant's natural metabolic response to environmental timing rather than a fixed genetic trait. Breeders and researchers monitoring terpene profiles have documented these rhythmic variations across different cultivars, though expression intensity varies significantly by genotype and growing conditions. Understanding day-night cycling helps growers and breeders interpret terpene testing data more accurately and recognize that single-timepoint lab samples may not capture the full volatile profile.

Breeders tracking terpene stability across photoperiods can identify genotypes with consistent or predictable cannabinoid and terpene expression. This knowledge informs selection strategies for cultivars grown under different lighting schedules and helps explain phenotypic variation in otherwise genetically identical clones.