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Is garlic smart?

neilgrif at uctvax.uct.ac.za neilgrif at uctvax.uct.ac.za
Thu Apr 7 04:14:56 EST 1994

>>It never ceases to amaze me how smart the garlic in my refrigerator is.
>>Every year, like clockwork, the bulbs I bought last year (for food
>>purposes) begin to sprout in mid-March.  I keep my garlic in the
>>refrigerator (which I have found stores MUCH better than identical bulbs
>>left in a cool dark place), so it is not really exposed to light.  In the
>>refrigerator the garlic stays in a vegetable bin, and never sees the sun.
>>Does anyone have an idea of how garlic knows when it is time to grow?
>>Many plants depend on degree days, photoperiod, etc., but my garlic
>>should not be affected by these given that they are in the refrigerator.
>>Their sprouting implies to me a biological clock, odd for a plant, but
>>then, garlic is an exceptional plant!

> I don't know abouth biological clocks (A bit unlikley) but I have found that
> whenever I go home in my vacs my garlic and onions (both in the lilly fam.)
> sprout, i.e. christmas easter and summer.
> By the way I know that various lenghts of chilling induce germination in many
> seeds, I don't know how this applies to bulbs but it must have some effect
> take snowdrops for example, 5-6 months of chilling and off they go.

An endogenous rhythm, or cycle controlled by a biological clock, has
been detected in several plants (e.g. _Goniaulax_, _Pyramimonas_,
_Mimosa_). Any paucity of known endogenous rhythms might be more of an
indication of a lack of research in that field!

Seriously though, living in a refrigerator should not deprive an
organism of all cues of passing time. Though it is dark and cool most
of the time, the door will tend to be opened more frequently during
the period that the householder is awake. When the door is opened,
some light should reach the garlic (is the vegetable tray
light-tight?), either from an internal light or external room
lighting. As the stimulus required to "set" any endogenous oscillator
can be very small, that light leak (or temperature drop?) might be
enough for an endogenous clock in the garlic. Light cues are often
very important in setting endogenous rhythms. In circumstances of
regular stimulation that I hypothesize, a true biological clock (a
timekeeper that functions in the absence of a regular stimulus) is not
necessary for the garlic to be aware of passing time.

Though I know little about garlic except as a food, a period of
chilling  is unlikely to stimulate shooting in the example given here
unless the garlic is only purchased and refrigerated in, say,
October. If garlic is purchased and refrigerated at any other time of
year, 5-6 months chilling would cause sprouting at another time.


rhubarb, rhubarb
Neil Griffin                    Tel: (+27-21) 650-3402
Botany Department               Fax: (+27-21) 650-3726
University of Cape Town         Internet: griffin at botany.uct.ac.za
Private Bag                               neilgrif at uctvax.uct.ac.za
7700 Rondebosch

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