Full moonlight (FML) induces stress response and enhances post germination growth of Brassica juncea (mustard)

Beyond the myth, many creatures on earth sense solar radiation reflected by the moon. Moonlight and the lunar cycle can affect the behavior of vertebrate and invertebrate species including reproduction, communication, foraging, and predation. Rhythmic exposure to moonlight is believed to affect the life cycle of plants, from seed germination to fruit maturation and dispersal. In traditional lunar farming ‘above ground crops’ are commonly planted between the new moon and the full moon while ‘below ground crops’ are between the full moon and the next new moon; though these lunar farming practices have no solid scientific support. Here we addressed the effect of full moonlight (FML) on post germination growth of Brassica juncea (mustard, an above ground crop). Accordingly, 10-day-old seedlings were exposed to FML for three consecutive nights (5h each night, starting a day before FML) and their growth parameters were recorded after 1 and 2 weeks and compared to dark-exposed plants. The results showed that seedling performance (shoot and root dry and fresh weights) after 1 week or 2 weeks was significantly improved under FML compared to dark. Metabolic analysis showed that exposure of seedlings to 5h FML resulted in an increase in stress metabolites including salicylic acid, a plant hormone implicated in the defense against a variety of biotic and abiotic stresses, and in amino acids (valine, proline, serine). It appears that FML serves as a signal that induces a stress response, which in turn enhances post-germination growth under normal, unstressed conditions.