A study by CIRAD has shown for the first time that despite its very low intensity, moonlight affects coffee trees on a molecular level, and disrupts their circadian clock.
The French research organization said it believes it could be in the interests of the horticultural and related sectors to control the effect on crops of this type of light. The results of the study* were published in the journal BMC Plant Biology.
Science has previously shown that moonlight and the lunar cycle can affect the biological cycles of living organisms. Plants are particularly sensitive to local gravimetric variations caused by the moon rotating around the earth, which affect their growth and development. This explains why farmers, gardeners and foresters have planted and harvested according to the moon’s cycle. But what about the light reflected by the moon?
CIRAD said it was “very surprised” that moonlight also affects plant development. It was while studying the circadian cycle of coffee trees and the way it is disrupted by climate change that a team led by Benoît Bertrand and Hervé Etienne noticed the atypical expression of some of the major genes in the circadian clock during the night.
The plants were sampled on the day of the spring solstice, during a full moon. This sparked the researchers’ curiosity, and they decided to study moonlight and attempt to reproduce it, in controlled conditions.
“What we found was that plant photoreceptors saw low-intensity wavelengths of light in moonlight as strong environmental signals,” said Jean-Christophe Breitler, a geneticist at CIRAD.
“By analysing the transcriptome of coffee trees, that is, the range of genes expressed, every three hours for 24 hours, under new moon and full moon conditions, we showed that 3,387 of the 25,574 known genes in the coffee transcriptome were differentially regulated.
“Our analysis of the differentially regulated genes seems to show that coffee trees see moonlight as a form of stress. It disrupts not just the genes in the circadian clock, but also many others controlled by them, such as genes linked to photosynthesis, lipid biosynthesis, growth control, and response to oxidative and heat stress.” In short, the results showed that moonlight may ‘stress’ coffee trees, although the over-expression of some genes suggests that the effect on growth is mainly positive.
Work is continuing to fully understand the effect of this type of light on plants, notably on their growth, which could be particularly useful for horticulture and gardening.
*Full moonlight-induced circadian clock entrainment in Coffea arabica. BMC Plant Biology.
J-C Breitler, D Djerrab, S Leran, L Toniutti, C Guittin, D Severac, M Pratlong, A Dereeper, H Etienne and B Bertrand.