Hi, Malia,
Depending on the timing of the measurements relative to changes in air
temperature and sunlight exposure, such temperature differences are easy to
imagine without there being any "cooling" mechanism. If the gall is a
large mass, it will have a much lower surface-to-volume ratio than a thin
leaf blade, and will therefore exchange heat with the environment more
slowly. Overnight, even the thick gall will equilibrate with the cool
nighttime air temperatures. The following day, sunlight and the warm
daytime air will warm up the thin leaf very rapidly and the thick gall more
slowly. If the measurements are made before a daytime equilibrium is
reached, the gall will be cooler. This would also apply to circumstances
of shifting patterns of sun and shade throughout the day. Of course,
depending on the timing, during cooling periods the gall would measure
warmer than the leaf.
Did the sources you found specify the timing and conditions under
which the measurements were made?
By the way, virtually all land plants have cooling mechanisms, most
significantly evaporative cooling, but this would favor leaf tissue over
gall tissue.
Martin M. Meiss
2012/4/17 R. Malia Fincher <[email protected]>
> I have been unsuccessfully (but briefly) searching the literature for
> incidences of plants and/or galls on plants cooling themselves
> substantially
> below ambient temperature. I have run across a fungal gall, with an
> associated gall midge larva, that is 6-10 degrees C colder than normal
> leaves and the ambient air temperature. I am aware of the capacity of
> certain plants to warm themselves, but this is the first time that I have
> encountered cooling. Is anyone familiar with such a phenomenon?
>
> Thank you,
> Malia
>
> R. Malia Fincher, Ph.D.
> Assistant Professor
> Samford University
> Department of Biological and Environmental Science
> 800 Lakeshore Drive
> Birmingham, Alabama35229
> [email protected]
> 205-726-2928
> Fax 205-726-2479
> Office 133 Propst Hall
>
>
