WOLFGANG SCHAD
Abstract. Concerning lunar periodicity in biology, we summarized all what has been observationally and experimentally found and published in scientific literature till 1996. We summoned up as many as about 600 living species (mostly animals) with identified lunar periodicities, functioning in a more or less endogenous manner. Here we give a short review about the occurrence in the plant kingdom. In Thallophytes 45 species have been described as well as 40 species of Angiosperms. In Prokaryonts no lunar rhythms could be found. Their individual life cycles do not reach the time span of at least comparable parts of a lunar day. Thus as in all Eukaryonts the occurrence of the cell nucleus constitutes specifically endogenous rhythms in plants as well as in the animal kingdom.
In Cyanobacteria no lunar periodical rhythms have been found. The life cycle of Procaryonta under adequate conditions is too short in relation to at least only parts of lunar rhythms. If ever such rhythms should be found in the dynamics of their populations, it seems very likely that they can be derived from environmental conditions. Only in the marine Cyanobacteria Synechococcum an endogenous factor of the circadian activity for nitrogen fixation could be found by Chen (1991), but that is a solar, not a lunar periodicity.
All eukaryontic cells and organisms are generally assumed to oscillate by interference of exogenous and endogenous factors, for a true cell nucleus in mutual interaction with the plasma is capable of what is called the inner clock. Already in 1938 Bracher found in Euglena limosa a vertical migration in the mud flats at the east coast of England not only in its circadian but also in its lundian behaviour, for only at daytime during low water it appears at the surface. It continues this rhythm also during removal from tidal influence for three days. In Dinophyceae several species of the genera Amphidinium, Gymnodinium, Polykrikos, Oxyrrhis, also in Chrysophyceae the species Chromulina psammobia and in Diatomeae 10 more species could be identified for the same manner to migrate to the surface of mud flats in order to assimilate during daytime and tidal low water (Figure 1). The species are:
Biddulphia aurita Pleurosigma aestuarii
Cylindrotheca signata Scoliopleura latestriata
Hantzschia virgata Stauroneis salina
var. intermedia Surirella gemma
Navicula ammophila Tropidoneis vitrae
Nitzschia colsterium
Earth, Moon and Planets 85–86: 405–409, 2001.
© 2001 Kluwer Academic Publishers. Printed in the Netherlands.
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Within multicellular plants about a dozen of species with moon-related perodicities in their reproduction could be found in the brown algae (Phaeophyceae), especially in such common genera as Dictyota, Fucus, Sargasso etc., which produce lundian, semilunar and lunar periods (Figure 2).
In green algae (Chlorophyceae) freshwater species of Pediastrum, Scenedesmus and the marine species Enteromorpha, Ulva, Halimeda and Halicystis show similar periodicities in reproduction as well.
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It is obvious that most of the addressed moon-related Thallophytes live in tidal zones of marine coasts and have obviously adapted to their environment to a more or less strict, genetically fixed amount.
The occurrence of moon-related rhythms in higher Spermatophyta, the Angiosperma, mostly being landplants, is therefore of special interest. In 1972 Giovanni Abrami reported his observations here in the Botanical Garden of Padova concerning the growth of several angiosperms during spring time in 1972. The growth, of course, depends on the temperature, being slow at cold weather and quick at warm time. But this correlation was more positive at new moon and more negative at full moon (Figure 3). Thus some investigated plants grow more independently from temperature during full moon. This lunar changes of temperature-related growth he found rather in dicots (5 observed species) than in monocots (2 observed species).
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Thus the capability to germinate is prepared by oscillating rhythms, partly being moon-related ones. In so far it is not surprising that several authors referred to better germination by several seed-plants two days before new moon, resulting in higher amounts of products for instance in agriculture (Kolisko, 1935, 1953; Spieß, 1990, 1993, 1994; Zürcher, 1992). The investigated species are:
Delphinium consolida Achillea spec.
Pisum sativum Lactuca sativa capitata
Phaseolus vulgaris Allium porrum
Brassica oleracea Hordeum spec.
Daucus carota Avena spec.
Levisticum officinale Triticum spec.
Melissa officinalis Zea mays
Solanum lycopersicum
Some results give hints to the time, when medicinal herbs should be picked. Rounds (1982) found a semilunar periodicity of neurotransmitter-like substances from heart-stimulating plants, applied to the cockroach (Periplaneta africana). The weakest stimulation by the extracts of the investigated plants was, when picked at short time before new and full moon, indicating a semilunar oscillation. The investigated species were:
Ulmus americana Forsythia spec.
Phaseolus vulgaris Lilium tigrinum
Geranium spec. Philodendron sagittifolium
Coleus blumei
In long-day-plants (Agrostemma githago, Iberis amara, Hordeum distichon, Triticum vulgare) the time span till flowering is prolonged to some days under the influence of moon light; whereas in short-day-plants (f.i. Soja hispida) the time span is delayed for some days under the same influence (Gaertner/Braunroth, 1935). In these cases moonlight can be contraproductive to sunlight.
In all chronobiology there is always the question whether the produced physiological rhythms are exogenous or endogenous. In the sixties Frank Brown junior plead for only exogenous causality, but Erwin Bünning guaranteed for endogenous factors sharing their contribution to the periodicities of living systems. Today three modes are differentiated:
Exo-Rhythms, Exo-Endo-Rhythms and Endo-Rhythms.
After the long discussion over half a century I would like to say that all chronobiological rhythms are always exo-endogenous, sharing their autonomous inner clock to some degree with the periodicity of the environment, both sides being connected by the long process of evolution. It is quite clear: Every organism has its own abilities, at least inherited from its ancestors. And on the other hand it is not a closed system, but part of the system of the environment itself. Thus its constitution is the cooperation of inner and outer systems. Concerning its rhythms there is only the question, if the concerned oscillation is more endogenous than exogenous or vice versa or in balance. But always both sides are involved, if investigated enough.
References
All citations in Endres, P. u. Schad, W.: 1997, Biologie des Mondes. Mondperiodik und Lebensrhythmen, Hirzel-Verlag, Stuttgart/Leipzig; English translation in work by Floris Books, Edinburgh.