Abstract: 1.Plants use light as a source of both energy and information. Plant physiological responses to light, and interactions between plants and animals (such as herbivory and pollination), have evolved under a more or less stable regime of 24-hour cycles of light and darkness, and, outside of the tropics, seasonal variation in daylength.
2.The rapid spread of outdoor electric lighting across the globe over the past century has caused an unprecedented disruption to these natural light cycles. Artificial light is widespread in the environment, varying in intensity by several orders of magnitude from faint skyglow reflected from distant cities to direct illumination of urban and suburban vegetation.
3.In many cases artificial light in the nighttime environment is sufficiently bright to induce a physiological response in plants, affecting their phenology, growth form and resource allocation. The physiology, behaviour and ecology of herbivores and pollinators is also likely to be impacted by artificial light. Thus, understanding the ecological consequences of artificial light at night is critical to determine the full impact of human activity on ecosystems.
4.Synthesis. Understanding the impacts of artificial nighttime light on wild plants and natural vegetation requires linking the knowledge gained from over a century of experimental research on the impacts of light on plants in the laboratory and greenhouse with knowledge of the intensity, spatial distribution, spectral composition and timing of light in the nighttime environment. To understand fully the extent of these impacts requires conceptual models that can (i) characterise the highly heterogeneous nature of the nighttime light environment at a scale relevant to plant physiology, and (ii) scale physiological responses to predict impacts at the level of the whole plant, population, community and ecosystem.

Abstract: Photoperiodic regulation of physiology, morphology, and behavior is crucial for many animals to survive seasonally variable conditions unfavorable for reproduction and survival. The photoperiodic response in mammals is mediated by nocturnal secretion of melatonin under the control of a circadian clock. However, artificial light at night caused by recent urbanization may disrupt the circadian clock, as well as the photoperiodic response by blunting melatonin secretion. Here we examined the effect of dim light at night (dLAN) (5lux of light during the dark phase) on locomotor activity rhythms and short-day regulation of reproduction, body mass, pelage properties, and immune responses of male Siberian hamsters. Short-day animals reduced gonadal and body mass, decreased spermatid nuclei and sperm numbers, molted to a whiter pelage, and increased pelage density compared to long-day animals. However, animals that experienced short days with dLAN did not show these short-day responses. Moreover, short-day specific immune responses were altered in dLAN conditions. The nocturnal activity pattern was blunted in dLAN hamsters, consistent with the observation that dLAN changed expression of the circadian clock gene, Period1. In addition, we demonstrated that expression levels of genes implicated in the photoperiodic response, Mel-1a melatonin receptor, Eyes absent 3, thyroid stimulating hormone receptor, gonadotropin-releasing hormone, and gonadotropin-inhibitory hormone, were higher in dLAN animals than those in short-day animals. These results suggest that dLAN disturbs the circadian clock function and affects the molecular mechanisms of the photoperiodic response.