Can Plants feel pain?

[Rich Young]

In article <B.Hamilton.184.2EE2A54A at irl.cri.nz> B.Hamilton at irl.cri.nz (Bruce Hamilton) writes:
>The following exchange is occurring in nz.general and alt.folklore.urban,
>mainly between a vegetarian and an opponent. 
>
>While not wishing to get involved in either side, it did set me wondering 
>whether the presence of a nervous system is a prerequisite for feeling pain, 
>and whether any communication system that causes an organism to 
>respond to an adverse stimulus could be considered "pain"  - ( not 
>necessarily just electrical, but chemical - either internally, or externally - 
>by the release of volatile chemicals that other plants recognise ) 
>that causes an organism to respond to an adverse stimulus could 
>be considered "pain". 
>
>The timescale isn't important, and I vaguely remember some simple 
>microscopic organisms that were considered either plant or animal, did they 
>have to show they responded negatively to adverse stimuli to be classed as 
>animal?.   
>
>I'm not certain that such a subject is relevant to bionet.plants,
>but if any reader knows of a fairly accessible, reputable, 
>reference - I would appreciate email of the reference. 
>
>Apologies if this is off topic, suggestions of a more appropriate group
>are welcome, as is reference to a FAQ on this - if there is one. 
>
>             Bruce Hamilton 

	The starting point of the exchange seems to have been "The Secret
	Life of Plants", which we can safely dismiss as not worth much
	beyond a temporary entertainment value, but the subject is argued
	in deadly earnest by proponents of so-called "ethical" vegetarianism
	and animal rights philosophy.  In rec.food.veg and talk.politics.
	animals, it comes up about once every two months...or perhaps more
	often.

	There are two distinct facets to the argument, as it is usually 
	developed.  The first is a semantic one which retreats to the
	human-centered definition of the word "pain" found in most 
	dictionaries...and from this standpoint, it is virtually certain
	that plants do not, indeed, "feel pain."  It is this facet that
	"ethical" vegetarians and AR advocates most often seek to exploit,
	but it is clearly not a direct addressing of the issue....it is
	merely defining the question out of existence.

	The second facet is far more challenging, since it deals with moral
	and biological significance rather than semantics.  To address this,
	one must first define pain, its significance to an organism, and
	the significance of reactions to it, as well as the moral signifi-
	cance of inducing it.  [Even then, one will not have silenced the
	true believer, because the conversation will then turn to the
	deprivation caused a "sentient" being by premature death, but that's
	another matter.]

	At its base, pain can be viewed as a warning to the organism that
	experiences it, that it's life and/or ability to propagate its
	genetic heritage is under threat.  It can be argued that organisms
	are essentially [as some wag once said] "DNA's way of making more
	DNA."  Virtually ALL organisms have sensory mechanisms that are
	aimed at warning the individual of threats to life and/or repro-
	duction, thus, while plants probably can't "feel pain" (as defined
	in human dictionaries), plants can certainly sense their environment
	and react in ways that are clearly intended to minimize threats to
	life and/or reproduction: threats that humans would interpret as
	painful.  In other words, whatever one chooses to call it, plants
	certainly experience the *functional equivalent* of that which we
	humans call "pain", as do essentially all other organisms.

	Having settled that, one must consider (assuming one remains 
	interested) whether consciously inducing these responses in plants
	is the moral equivalent of consciously inducing them in humans
	[as well as cute, furry, non-human creatures].  Can one "torture"
	a plant by making it waste its resources and energy on self-protec-
	tion rather than directing to toward reproduction?  There is ample
	evidence of systemic response in plants to external threats, as
	I'm sure many researchers in the field of botany would agree.
	Wildon has published evidence of an electrical signalling system
	in plants similar to the epithelial conduction system found in
	several "lower" animals (NATURE 360:62-65; 1992); others have
	published evidence of intra-plant chemical signalling systems and
	have even found intriguing indications that plants may even signal
	to each other (an interesting lay review can be found in Science
	News, Dec. 22/29, 1990, pp. 408-410).

	However simple plants may seem as viewed from our position of
	evolutionary complexity, we should not fall into the trap of
	thinking plants to be simply "passive green things."


-Rich Young

(The view expressed herein should not be assumed to be that of my employer.)