"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 current discussion is in response to my question regarding a statement made in Lance Birk's Paphiopedilum Grower's Manual several times (and I posted a thank you for the discussion that somehow never showed up). The statement is that all Orchids have "fixed stomata that cannot close". He further says that this is how Orchids are able to absorb moisture and nutrients from humid air (intuition, and two terms of college level plant physiology suggests that transpiration at the leaf surface and vapor pressure would preclude this) . Though Steve's experimental observations may not pass muster for publication in a peer reviewed journal, that he observed closed stomata strongly implies that they are in no way "fixed". One assumes several minutes must pass before general desiccation of tissues closes even "fixed stomata"; and if stomata closed as a result of trauma to adjacent tissue or introduction to an unfamiliar environment (under a cover slip with water), they can in no sense be considered "fixed".
Just my two cents!
Dennis
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