VFT closing in CO2

Scott T. Meissner (smeissne@prairienet.org)
Wed, 8 Mar 95 07:27:11 CST

I am not sure if the closing of a VFT is really due to water
loss through photosynthesis. My understanding is that the
closing was due to the movement of ions and organic acids
out of the cells into the cell wall space, and the water
was following by osmosis. Photosynthesis would take
quite long, and water is at 55.5 molar, the highest
concentration of anything in a plant, so it would take
a long time to knock the water concentration down. But
moving the ions out, through ion channels in the cell
membranes would allow water to follow by osmosis; the
cell loses volume, and the trap folds. Later on the trap
could reopen by taking the ions up again, and the water
would again follow by osmosis.
How the CO2 comes into this I am not sure. But it
could form carbonic acid (H2CO3) and this would acidify the
cell wall space... Perhaps that triggers the loss of ions from
the trap. This would be fairly easy to check. A few drops of
an acidic solution, like vinegar, should drop the pH as well, and
aught to close the trap. Another way to check is to shade the VFT
and see if it will close in dim/dark conditions. If the water has to
be reduced by photosynthesis to shrink the cells and close the trap
then it should depend on light, and not happen in the dark.
Anyone got any extra VFTs to try these experiments out on
and report back? Mine suffered from heat stress a few weeks ago
and are still recovering.

Aure Entuluva!

Scott T. Meissner	Division of Science and Mathematics
			McKendree College, 701 College Rd
			Lebanon, IL 62254
Tel:  (618)  537-6934   E-mail:  smeissne@prairienet.org