Stomatal movements depend on interactions between external night light cue and internal signals activated by rhythmic starch turnover and abscisic acid (ABA) levels at dawn and dusk

Yellow poplar (Liriodendron tulipifera L.) is a widespread hardwood tree of great ecological and economic value. Light pollution caused by excessive and indiscriminate exposure to artificial night light has emerged as a new risk factor due to its adverse effects related to energy waste, sleep disorders, anthropogenic habitat disturbance, and perceptual disorder of daily and seasonal rhythms in wildlife. However, it remains unknown how associations between artificial night light and stomatal behaviors controlled by internal signals are established. After continuous exposure to artificial light at night over 3 years, leaves in the experimental set-up were measured for stomatal movements, starch turnover, endogenous abscisic acid (ABA) levels, and chloroplast ultrastructure during the growing season. Yellow poplar showed dynamic changes in stomatal movement, starch turnover, and endogenous ABA levels in response to day/artificial night light cycle, resulting in reduction of circadian phase-shifting capacity at both dusk and dawn and normal chloroplast development as compared with natural night. Nighttime light exposure may act as a major factor for disorder of circadian and circannual rhythms as well as physiological and ultrastructural repressor in plants, via a modification of the perceived photoperiod. Our study suggests that these dynamic responses can provide advantageous insights that complement the current knowledge on light pollution.