Barometric pressure and stomata

Tony Travis ajt at rri.sari.ac.uk
Wed Sep 30 07:09:10 EST 1992


In article <92830103032.MIN-LFBAa26899.bionet-news at uk.ac.daresbury> you wrote:
: Ok, I've done a cursory look in some of the literature and haven't found 
: any reference regarding efffects of barometric pressure  changes on the
: stomatal activity of plants. I'm specifically interested in fern, but
: would be satisfied to find anything on the subject. E-mail or repost, 
: I'll be waiting. Thanks in advance.

Are you asking about direct, or indirect effects?

The turgor pressure inside stomatal quard cells has been measured using
oil-filled glass micropippettes/needles and is large in comparison to
the changes in barometric presure that occur naturally (sorry - I don't
have any figures to hand, but this was work by Zeiger et al. in the
late '70s).

The pressure of surrounding subsidiary cells (or epidermal cells if the
fern doesn't have them) works against the turgor of the guard cell to
reduce opening.  If the subsidiary cells are killed by low pH
pretreatment the stomata open much wider (described in: Travis &
Mansfield 1977, Studies of malate formation in 'isolated' guard cells,
New Phytologist, 78, 541-546).

I think that direct effects are unlikely because turgor changes in the
surrounding cells would balance the effects on the guard cells.  The
mechanical interaction betwen the cells is complex but the subsidiary
cells are thought to have a mechanical 'advantage' due to the area of
the ventral wall of they have in common with the guard cell.

The indirect effects are likely to be profound!!

The partial pressure of CO2 and water vapour deficit of air is altered
by changes in presssure.  The feedback control mechanism regulating
water use efficiency in plants will adjust the stomatal apertures to
any changes that occur in either of these parameters.

There is also a feed-forward hypothesis of stomatal control that
postulates 'anticipatory' stomatal movements in response to changes
_outside_ the leaf.  In this hypothesis, the stomata respond far more
quickly than can be explained by negative feedback alone.

One other point is that bulk air movements will occur through open
stomata in response to a pressure gradient between air inside and
outside.  All in all, I think it's a *very* interesting area to be
investigating.

Please post responses - I don't want another email-only discussion ;-)

	Tony.
--
Dr. A.J.Travis,                       |  Tony Travis
Rowett Research Institute,            |  JANET: <ajt at uk.ac.sari.rri>
Greenburn Road, Bucksburn,            |  other: <ajt at rri.sari.ac.uk>
Aberdeen, AB2 9SB. UK.                |  phone: 0224-712751



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