"What did parasitic plants do before the fall!?"
The question clearly implied that the holoparasitic plants
that I study (plants that are totally incapable of
photosynthesizing and rely totally on a host plant from
which they derive both water, minerals, and metabolites)
could not have existed with the life-history characteristics
they now possess before the fall when all of creation was
"good." The question caught me off guard and I realized
that I was ill prepared to defend any answer that I might
be tempted to give. Thus the renewed interest into
delving more heavily into the recent literature, discussions
at church, this group, etc...
Parasitic plants reveal a very interesting molecular
evolutionary trend difficult to account for in both the YEC
camp and I believe even for most PCs (I confess to having
a limited ability of defining the latter term and so may not
be justified in this claim). Classic studies of _Epifagus_
(Indian pipe) a holoparasitic (white) plant in the late 80's
(refs on request) revealed that they had lost more than
one third of their chloroplast DNA relative to other green
plants. The cpDNA is a remarkable "conserved" molecule
consisted of ca. 120 genes in almost the same order and
having extremely high sequence similarity (relative to
nuclear genes) among all land plants (mosses to flowering
plants). In the case of Epifagus the cpDNA genome has
lost major parts of the cpDNA most of which contained
genes for photosynthetic capability although retaining
some photosynthetic genes. Since this time several other
presumably unrelated holoparasites have been looked at
and they also have lost significant portions of their genome
and all have lost genes that have something to do with
photosynthesis. Significantly this loss of genes appears to
be stochastic as the specific genes lost in each case are
not the same. In several instances in the Orobanchaceae,
member species have lost the rbcL gene (the one that
produces the enzyme the incorporates CO2 into sugars
and is considered on of the most important enzymes on
earth) completely, or just a portion of the gene, or none of
it at all. Members of this family range from normal green
plants to partially parasitic plants (like mistletoes) to
holoparasites. Only the holoparasites exhibit reduced
cpDNA genomes or loss of functionality of particular genes
in the chloroplast. The evolutionary explanation for this
trend in cpDNA genomes is that hemiparasites (partially
parasitic plants that still photosynthesize be get water and
nutrients from the host) still place high selectional pressure
on maintaining the genome organization and genes of the
chloroplast because they still need to do photosynthesis
for survival. The holoparasites on the other hand do not
need the photosynthetic apparatus and so are discarding
the unneeded parts over time (differently in each lineage).
It is important to point out that many of these parasitic
plants maintain many photosynthetic genes that based on
sequence analysis would work perfectly in a normal green
plant. The question I posed down the line in conversation
as a response to the question "what did parasitic plants
do before the fall?" (because they weren't parasitic then)
was "What are plants doing with so many genes they don't
use?
Several hypotheses present themselves from several
perspectives:
1: YEC perspective:
A: Parasitic plants were not around before the fall
They were green plants at the time which
were affected by sin and parasitism was the result (either
an instantaneous "creation" or they diverged from regular
green plants but are still "of the same kind") and thus had
a normal cpDNA genome and has since then (6000-
10000years) been losing parts of the genome (The gradual
loss idea was the response that was given to me at the
time and it sounds reasonable to the untrained but would
go against all knowledge of the rates of mutation in
cpDNA)
An added complication to both the "special creation"
or "gradual divergence" theories is that many holoparasitic
plants require very specific (species) hosts and so had to
get through the flood together somehow.
## An additional note - Members of the
Orobanchaceae and some other holoparasites (_Cuscuta_
= dodder) have obvious affiliation to other green plants
upon morphological and molecular analyses and so the
level of divergence in their genome is at the level of
structural change and not really seen in actual sequence
divergence but the plants I work on (Rafflesiaceae,
Hydnoraceae, and Balanophoraceae) are so highly
divergent from all other flowering plants that their
relationships to other plants even at the Subclass level is
of much dispute and interestingly gene sequences of these
show that they have radically divergent genomes both on
the structural and sequence level. A cpDNA genome from
Rafflesia (the worlds largest flower) has yet to even be
identified and looks to possibly be completely absent thus
setting up a nice reductionist series from green plant to
hemiparasite to recent holoparasites to holoparasites with
complete loss of genomes. Although little fossil
information is available, they as well as sequence analyses
of nuclear genes support the Rafflesiaceae as being
extremely divergent from other plants and thus presumably
has been a holoparasite for a longer time accounting for
the increased portions of the genome lost.
If the above is due to gradual change since fall why
the highly contrasted cpDNA types. If special creation
then why have photosynthetic genes at the start at all.
B: There were parasitic plants in the Garden of
Eden.
Death only referred to animals and not to plants and
therefore plants death and even use of one plant by
another is not prohibited. Surely plants were "dying" as
Adam and Eve were chomping away.
1. In this case why did God create "from
nothing" parasitic plants with genes they never used and
presumably never will. Responses I've gotten here are
"maybe we just don't know what those genes do, we
haven't studied them enough, they might do something
else in these parasitic plants."
2. A second problem is that many of the
same observations with respect to divergence rates among
parasitic and non-parasitic animals show similar pattern to
those of plant parasites. The same questions about
animals could be asked as I am raising with plants with
the added complication to the YEC that they certainly
couldn't be parasitic before the fall.
What is raised in my mind is a question that I
should think would trouble the YEC: that no easy
distinction can be made between the plant and animal
world that would allow one to say that death is all right in
one situation but not alright in another.
2: EC Perspective
Parasitic plants are the result of evolution.
This would seem to the most obvious choice and is
certainly attractive to me but does raise one hairy point
regarding this theme of "death" with me I would appreciate
enlightenment on. With respect to mans mortality there
would be two options:
A: Man created immortal
Reading archived material with respect to the
origins of man it seems that some are willing to allow for
the immortality of man upon his creation (by whatever
means) and at the same time say animals could die and
that then sin brought "death" to Adam. I think that to be
consistent one would have to say that going from a state
of immortality, while at the same time having a fleshly
body and then entering into a condition allowing death
constitutes a fundamental biological change which is so
profound it must be one of the real "mysteries" that we
cannot understand. Why if sin can enact such a
fundamental change in the way matter and energy works
cannot it be used to say that all of nature could have
been fundamentally changed in the same way. Given this
argument the following argument (of YEC connection)
seems valid: that we cannot extrapolate back before the
fall because everything in our experience has been
changed in such a way that we cannot even imagine what
it was like before. There have been numerous reasons
discussed in this newsgroup why the last statement isn't
terrible desirable from both a "natural" and theological
view.
B: Man created mortal
If man was created mortal (either uniquely or by
evolution or variations thereof) then there doesn't seem to
be the problem presented in A except of course possible
theological problems which I would like to have some
discussion of because it is here that I think some real
analysis it still needed for progress to be made in my
mind. I would be interested in anyone who could point me
to passages that are significant to this question. Much of the
discussion of late would place many under this catagory but I am
interested in what the potential pitfalls may be that I have not
thought of and what needs further discussion.
3: Other scenarios that would fit under the umbrella of
Gap theories, Day-age theories etc could also be
expounded upon and I would like to here about.
discussion welcome,
Joel Duff
Postdoctoral Research Associate
Southern Illinois University
Carbondale IL 62901-6509
duff@siu.edu
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| |,___| "I am Homer of the Borg. You will be assimilated. Resistance
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