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On March 11, 2005 Steve Tobletz posted the following: I have evaluated the Annals of Botany paper back from 1980... Just as suspected, it is in my unscientific opinion, total crap. This was verified when I threw a P. sanderianum leaf section under slide and found thousands upon thousands of stomates in a small section of leaf, and they were indeed closed. I have\ a microscope camera with which i will take pictures and make them available online if anyone cares. Steve Topletz Orchid friends: The test of stomatal opening/closing reported in the posting by Steve Topletz is, I am sorry to say, meaningless (OGD Vol. 7, Issue 115, #5). A stoma (stoma [Greek origin] is the singular term; stomata is the plural, NOT stomates) consists of two living guard cells of the leaf epidermis. They respond to certain environmental changes and change their shape which causes them to separate from each other in the midregion, thus creating a gap or hole through which water vapor and gases are exchanged between the intercellular spaces within the leaf and the external environment. The operative concept here is living cells. The procedure used by Mr. Topletz (who admittedly is not a scientist) imposed the following on his samples of P. sanderianum (Latinized binomials should be italicized Steve): A) “leaf section” which meant that he used a blade to cut the leaf thin enough to be able to view it with a microscope. B) He “threw” it “under slide” is not really clear. I presume he means he carefully placed it under a cover slip on a microscope slide. C) Implied but not stated was, “subjected to very high light conditions and possible change in temperature” as a consequence of illumination for observation under the microscope. Now, for “A” above, he severely mechanically damaged cells of the leaf. It is difficult to say which ones and how badly, but living cells do respond to being cut, even if it is their neighbors that are decapitated or cut open. The bottom line is that the tissue piece was seriously stressed by the method of specimen preparation. Next is “B” above. By placing the small piece of leaf (emphasis on piece) on a slide under a glass cover slip, no doubt enclosed in a liquid water environment, the leaf epidermis is not in the kind of environment that is normal and customary for its typical day-night functioning. The gas mixture of air (nitrogen, oxygen, carbon dioxide, water vapor, etc.) was replaced by liquid water (I assume, or else he did not describe his methods in sufficient detail). The bottom line is that the leaf epidermis was subjected to environmental stress due to the method of mounting the “live” piece of leaf tissue. “C” above, is self explanatory as described above. The bottom line is that the very act of observing the living tissue with the intense light in its stressed environment adds yet another stress. Finally, he does not state how many times he repeated his experimental observations, and whether he did so under different conditions. Given this laundry list of stresses and faults, one cannot draw any reliable conclusions about the real life behavior of guard cells (stomata) on the leaves of P. sanderianum or any other plant. Steve should understand that there is absolutely nothing personal about my comments. They are made in a constructive sense to set the record straight. But I would be very careful about calling other people’s (scientist’s) work “crap” when it is published in a refereed professional journal, and when you are admittedly a non scientist. The broader lesson to be learned from this limited example is that untrained nonscientists, who do not understand or adhere to the scientific method or to standard laboratory techniques and precautions should be hesitant to draw conclusions from data that may very well be faulty. If I were a stoma subjected to the conditions of Steve’s observations, and if I still had enough life left in me to do so, I would close up as tight as I possibly could, just to protect myself against the coming doomsday. Steve’s conclusion may be correct or it may be incorrect, but not because of the data he obtained. His data just don’t hold any water. Dr. Charles Bracker |
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