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2213262465_f22f073c8d_m.jpgThe Biology of Moonlight?

The moon may have effects on animal behavior (see here for example), but does it affect plants?

Last time I introduced the scientific literature on the subject by referring to a 1946 paper by Beeson (see ref. 1 below) published in the journal Nature. In this paper Dr. Beeson divided the information regarding the moon’s effects on plants into three categories: (a) myth or beliefs, (b) experiments by people believing in biodynamics, and (c) professional plant scientists with no ties to biodynamics.

Let’s see what’s out there from group (c), starting with the sunlight reflected by the moon.

Is Moonlight Bright Enough to Affect Plants?

moon_plant.jpgFrom laboratory experiments, it’s known that light intensities as low as 0.1 lux (approximately 0.01 foot-candle) during the night can influence photoperiodic time measurement in some plants and animals.

Yet the intensity of light from a full moon on a cloudless night may reach 0.3 lux at latitude of 50′, and more than three times this value in tropical regions.

This fact led E. Bunning and his colleagues (ref 2 below) to inquire whether moonlight can disturb time measurement. Surprisingly, their investigations revealed that some plants have adaptive mechanisms that apparently prevent moonlight from interfering with photoperiodism.

Photoperiodic perception occurs in the leaves. In the leguminous plants soybean, peanut, and clover, “sleep movements” change the position of the leaves from horizontal during the, day to vertical at night. This behavior reduces the intensity of light falling on the leaf surface from an overhead lamp (an “artificial moon”) by 85% to 95%, to an intensity below threshold for interference with time measurement.

In some nyctinastic plants such as Albizzia, Sainanea, and Cassia, leaflets not only orient vertically at night, but also rotate on their axes so that paired leaflets fold together, with the upper surfaces shading each other, an interesting behavior in view of the fact that the upper surface is more sensitive to light breaks than is the lower surface.

Albizzia.jpgSome long-night plants (a.k.a., short-day plants) flower most prolifically when grown with low intensity light (approximately 0.5 lux) rather than complete darkness during the night. In these plants, moonlight probably increases the number of flowers produced by a short-day regime.

However, flowering of Pharbitis nil (Morning Glory) plants was slightly inhibited by exposure to the light of the full moon for 8 or more hours with a single dark period of 16, 14 or 13 h. It is suggested that in the natural environment moonlight may have at most only a slight delaying effect on the time of flower induction in short-day plants (see ref. 3 below).

In a brief review, Wolfgang Schad (ref. 4) cites evidence for the effects of moonlight on biological rhythms in plants. He is co-author of the book Moon Rhythms in Nature: How Lunar Cycles Affect Living Organisms.

Bottom Line: Although it is not clear why low light intensities affect flowering more than darkness, these examples provide some rational basis for the belief of planting particular seeds by the light of the full moon. Another full moon one lunar cycle later could have effects on flowering.

References
1. Beeson, C.F.C. (1946) “The moon and plant growth.” Nature vol. 158, pp. 572-573. (PDF)

2. Bunning, E. and I. Moser (1969) “Interference of Moonlight with the Photoperiodic Measurement of Time by Plants, and their Adaptive Reaction.” Proceedings of the National Academy of Sciences (USA) vol. 62, pp. 1018-1022. (PDF)

3. Kadman-Zahavi, A. and D. Peiper (1987) “Effects of Moonlight on Flower Induction in Pharbitis nil, Using a Single Dark Period.” Annals of Botany vol. 60, pp. 621-623.

4. Schad, W. (1999) “Lunar influence on plants.”, Earth, Moon, and Planets vol. 85-86, pp. 405-411. (PDF)

Next Time: Does the moon’s gravity affect plants?

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11 Responses to “Does the Moon Affect Plants? Part 2: Moonlight and Biorhythms”

  1. Doris Fornefeld says:

    Good day to you,

    we have an almond tree, approx 15 -20 yrs old, that has a twisted stem, i.e. it turns like a corkscrew. We live in Gauteng, RSA.

    A farmer here in South Africa told my husband that it follows the moon, being one of only a few kinds of trees that behaves in this way.

    Can you give me more information in this regard?

    With kind regards,

    Doris Fornefeld

    • howplantswork says:

      Hello,
      You ask very interesting question. Though it would be wonderful to imagine that the moon caused the contorted growth of your tree, there is no scientific evidence that I’m aware of that the moon has such an effect on plant growth.

      There is, however, plenty of scientific evidence that this type of contorted or “corkscrew” growth is due to an inheritable genetic mutation. (See the following link, for example: http://www.springerlink.com/content/m41872726w4n2753/ )

      As I understand it, the corkscrew-type growth in stems is due to one side of the stem growing a bit faster than the other. I’m sure you’ve seen the common example of this in the curling of bean or pea tendrils around adjacent stems or a support. For an example, go to this webpage http://plantsinmotion.bio.indiana.edu/plantmotion/movements/nastic/nastic.html and select “Morning glory twining” from the menu on the left.

      I hope this answered your question (and dare I say that the farmer may have been having a bit of fun with your husband.)

      Thank you for your question.

      Richard Stout

  2. kazumasoju says:

    :) this is some amazing things, thank you

  3. Abdul Khalil Afghani says:

    Hello!
    I am from Afghanistan.
    I need some information about the ” Moon light effect on the growth of plants” , if having some detailed information pleased send me.

    thanks

    • plantguy says:

      Hello,
      What I know I’ve summarized here in the HowPlantsWork blog.

      I think a brief answer to your question is:

      At the present time there is no scientific evidence supporting the idea that moonlight affects plant growth, with the possible exception of the timing of flowering in some plant species.

  4. mevlut says:

    hı;
    ı’m mevlut.ı’m universty student in Turkey.
    ı research about the effect of moonlight on trees.
    can you help me ?
    thanks

  5. Leila says:

    hello ;
    has there been any research on the effect on moonlight on plants with silverly color leaves vs. the green ones.. i am curious merely because of the way they look under the moonlight; it appears, to me , that they might have a certain quality that links them to the moon. ?? maybe
    thank you for your post ;

    • plantguy says:

      I am unaware of any reported research regarding your very interesting observation.
      Plants with unusual leaf pigments may indeed be more sensitive, and thus more responsive, to moonlight.
      Thanks for your question.

  6. Leila says:

    i’ve also recently heard that moonlight effects the ripening of the tomato, seemed to be secondary knowledge.
    google proved it right ‘

    • plantguy says:

      I’ve also heard the claim that moonlight promotes tomato ripening stated as a “fact” by a so-called “master gardener”.
      However, I’ve never been able to find any reliable scientific evidence to support this claim. So, I presume it’s just an example of “…reiterations of peasant beliefs, myths and rules, both ancient and modern,…” (Beeson, from Ref. 1 above).

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