spinach vouchers --- a reply

[Joseph E. Laferriere]

   I have received several notes critical of my statement Sunday
concerning the necessity of vouchers for physiological studies. Most of
these have been sent to me directly, while only a few have been sent to
the whole list. My points seem to have been misinterpreted and/or taken
out of context. Please allow me to clarify.
   My note was in direct response to a direct question, and limited to
those conditions posited by the original questioner. Someone (I forget
who) complained that physiologists doing research on the mechamisms of
photosynthesis use supermarket spinach without making formal vouchers. My
assumption was that the physiologists in question were studying the
biochemical pathways involved in photosynthesis, rather than quantitative
measures of photosynthetic output. My comments were limited to this kind
of study.
   Yes, there are different varieties of spinach, and if one is doing a
comparative study of different varieties one would be seriously negligent
not to make permanent vouchers. Yes, environmental conditions can affect a
plant's growth, and if one is doing any kind of quantitative study one
would be seriously negligent not to grow the specimens in controlled
conditions. Yes, the grad student buying the spinach must be careful to
make certain she is purchasing Spinacia oleracea rather than Tetragonia
expansa. However, these are not the types of studies we were discussing.
If one is studying what enzymes and photoreceptors are involved in
photosynthesis, these are all probably the same for all varieties of
spinach, and may well be the same for all vascular plants.  This may not
turn out to be true, but we need to learn how photosynthesis works in one
plant before we can ask the question "Is it the same in others?" My
comments were limited to this type of scenario only.