spinach in physiological studies

Jerry Bricker lcjbrick at ANTELOPE.WCC.EDU
Mon Jul 29 16:25:30 CDT 1996

On Sun, 28 Jul 1996, Joseph E. Laferriere wrote:

> On Sun, 28 Jul 1996, Automatic digest processor wrote:
> > From:    Jerry Bricker <lcjbrick at ANTELOPE.WCC.EDU>
> There are two types of experiments a physiologist can perform: 1) a
> broad-based survey comparing numerous taxa, or 2) an in-depth study of the
> detailed inner workings of a single species or genus. What you witnessed
> was one of the latter.
>    The reason we know so much about genetics of Drosophila and the
> physiology of E. coli is that they have been the subjects of the second
> type of research. These types of studies are immensely valuable in giving
> us a basis from which to work. Once we turn our attention to another
> genus, we can assume that similar things happen there as happen with
> Drospohila, which we already know so well. Perhaps this will turn out to
> be false, but at least we know what questions to ask. If we used only a
> broad-based approach in physiology, we would never know the details of
> how one narrow taxon works.
>    With respect to the spinach, it probably would not make any difference
> if the material were grown in the lab or on the farm. Spinach, like most
> crops grown in momocultures, has a very narrow genetic base, so on the
> level the physiologists are working there is probably not much variation.
> Hence it would be a waste of time and money to grow the things in
> carefully controlled environments, and a waste of herbarium space to have
> hundreds of sterile spinach vouchers. I agree that if they stray from
> commonly recognized garden crops, vouchers become essential.
>   Physiologists have different needs than systematists, and you have to
> respect those differences.
I must respectfully say that I still am not convinced.  Spinach,
cabbage, tomatoes and other garden crops may have a large degree of
genetic uniformity but there is still a fair amount of genetic variation
that exists in those cultivars.  Even if one were to eliminate the issue
of variability and its documentation, the issue of environmental
factors remains.  You are correct that both E. coli and Drosophila have
been used successfully for studies by geneticists and physiologists for
years.  I must point out, however, that both organisms are raised by the
researcher in a controlled environment.  He/she knows what factors have
been included in the media (no small item for pleiomorphic organisms
such as bacteria) and any extraneous situations the study subjects may
have been exposed.
        Spinach and other leaf crops grown in northern Mexico and the
central Valley of California are by no means as predictable as E. coli
and Drosophila maintained in the lab.  Exposure to varying types of
herbicides and pesticides are a fact of life for spinach.  If a person is
studying a photosynthetic or protein pathway influenced by an herbicide
what real conclusions can be drawn?  Let us not forget the example of how
methanol's influence on plant growth was discovered.  A graduate student
(sorry, his name slips my mind) noticed that in some algal cultures he
was working with there was vigorous growth.  Over time he began to
associate this with how he was setting up his cultures.  He would
sterilize the test tubes by flaming them with alcohol.  Occasionally in
his haste a small amount of liquid would be left in the bottom of the
tube.  Sure enough, the methanol was having an effect on the
photosynthetic mechanism.  He talked his father (a cotton farmer) into
allowing him to do some controlled field studies on various (cotton,
watermelons, etc.) crops.  The feature of methanol enhancement of
photosynthetic carbon fixation held up in most of the plants he studied.
This led to a fair amount of excitement among agricultural scientists and
lit a fire under his carreer.  He later proposed that methanol effects
certain key elements of photosynthesis
(it has been years since I attended one of his seminar so the details
have long cleared the soft tissue of my brain).  The point here is that
if methanol produces such drastic changes in photosynthesis then should
one not assume that an herbicide may also produce similar effects?
        My understanding of the scientific
method is that a researher must account for as many variables as possible
and work to control them.  I am not a physiologist but I have great
respect for the work they do.  My point was that controlling as many
elements of a study as possible is the prudent thing to do.  Such control
may be more tedious but that's life.  Maybe expecting voucher
specimens from physiologists is unrealistic but I believe that when they
consider the possility it raises the quality of science being done.


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