title: Blooming rhythms of cactus Cereus peruvianus with nocturnal peak at full moon during seasons of prolonged daytime photoperiod.
abstract: Cereus peruvianus (Peruvian apple cactus) is a large erect and thorny succulent cactus characterized by column-like (cereus [L]: column), that is, candle-shaped, appendages. For three successive years (1100 days), between early April and late November, we studied the flowering patterns of eight cacti growing in public gardens and rural areas of north and central Tunisia, far from nighttime artificial illumination, in relation to natural environmental light, temperature, relative humidity and precipitation parameters. Flower blooming was assessed nightly between 23:00 h and until at least 02:00 h, and additionally around-the-clock at ~1 h intervals for 30 consecutive days during the late summer of each year of study to quantify both nyctohemeral (day-night) and lunar patterns. During the summer months of prolonged daytime photoperiod, flower blooming of C. peruvianus exhibited predictable-in-time variation as "waves" with average period of 29.5 days synchronized by the light of the full moon. The large-sized flower (~16 cm diameter) opens almost exclusively at night, between sunset and sunrise, as a 24 h rhythm during a specific 3-4-day span of the lunar cycle (full moon), with a strong correlation between moon phase and number and proportion of flowers in bloom (ranging from r = +0.59 to +0.91). Black, blue and red cotton sheets were used to filter specific spectral bands of nighttime moonlight from illuminating randomly selected plant appendages as a means to test the hypothesis of a "gating" 24 h rhythm phenomenon of photoreceptors at the bud level. Relative to control conditions (no light filtering), black sheet covering inhibited flower bud induction by 87.5%, red sheet covering by 46.6% and blue sheet covering by 34%, and the respective inhibiting effects on number of flowers in bloom were essentially 100%, ~81% and ~44%. C. peruvianus is a unique example of a terrestrial plant that exhibits a circadian flowering rhythm (peak ~00:00 h) "gated" by 24 h, lunar 29.5-day (bright light of full moon) and annual 365.25-day (prolonged summertime day length) environmental photoperiod cycles.
authors.affiliation: a Faculté des Sciences de Bizerte , Laboratoire de Biosurveillance de l'Environnement, Université de Carthage , Zarzouna , Tunisie.
authors.forename: Mossadok
authors.initials: M
authors.lastname: Ben-Attia
authors.affiliation: b Unité de Chronobiologie , Fondation A de Rothschild , Paris , Cedex , France.
authors.forename: Alain
authors.initials: A
authors.lastname: Reinberg
authors.affiliation: c Department of Biomedical Engineering , Cockrell School of Engineering, The University of Texas at Austin , Austin , TX , USA.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Smolensky
authors.affiliation: a Faculté des Sciences de Bizerte , Laboratoire de Biosurveillance de l'Environnement, Université de Carthage , Zarzouna , Tunisie.
authors.forename: Wafa
authors.initials: W
authors.lastname: Gadacha
authors.affiliation: d Institut Supérieur de Biotechnologie Marine, Université de Monastir , Monastir , Tunisie.
authors.forename: Achraf
authors.initials: A
authors.lastname: Khedaier
authors.affiliation: a Faculté des Sciences de Bizerte , Laboratoire de Biosurveillance de l'Environnement, Université de Carthage , Zarzouna , Tunisie.
authors.forename: Mamane
authors.initials: M
authors.lastname: Sani
authors.affiliation: b Unité de Chronobiologie , Fondation A de Rothschild , Paris , Cedex , France.
authors.forename: Yvan
authors.initials: Y
authors.lastname: Touitou
authors.affiliation: e Département des Sciences de la Vie, Faculté des Sciences de Bizerte , Université de Carthage , Zarzouna , Tunisie.
authors.forename: Néziha Ghanem
authors.initials: NG
authors.lastname: Boughamni
mesh_terms: D029421:Cactaceae / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D008027:Light; D016081:Moon; D017440:Photoperiod; D018521:Plant Physiological Phenomena; D012621:Seasons; D013696:Temperature; D014416:Tunisia
keywords: Cereus peruvianus; annual rhythm; circadian rhythm; environmental light/dark cycles; flowering; lunar rhythm; moon light