Subject: Mimosa, expert help

From: [email-masked]
Date: 6 Oct 1995 18:15:00 +0100

Dear Phil:
The leaves (and leaflets) of Mimosa pudica (the sensitive) have at the base of
their stalk a particular organ called pulvinus (you can see it) which is made
of fleshy tissue that has the capacity to loose or take up water from the
surrounding tissues. When the internal side of the pulvinus loose water and
the external get it the leaflets close, in the reverse case the leaflets open.
In the case of the main leaf stalk the situation is a little different because
they get down when the plant is touched because the external part of the pulvi-
nus is loosing water. Normally the leaflets close at sunset and reopen at dawn
because they have a sort of a clock in the pulvinus cells (entrained by light).
Anyway, when somebody touches the plant the leaflets close and the leaves drop
under the action of an electric impulse started in the part of the organ that
has been touched. They will reopen in about 15 minutes however.
Be careful anyway since the leaves of the sensitive close because the plant
doe not like to be touched and be eaten by herbivorous, it can't however dis-
tinguish between animals and men !
Cherles Darwin wrote a beautiful book about plant movements and about the
sensitive behaviour. It is a pity that so few scientists today read it and
are interested in studying this plant, because the intrinsic mechanism of the
movement is not known. They just know that potassium ions are involved. But
what activate and deactivate the postassium pumps !
Good luck with your son.

A nice weekend to all plant lowers!

Fernando from Rome

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From: [email-masked] (Sean Stinson)
Date: 18 Oct 1995 23:40:17 GMT

[email-masked] wrote:
 They just know that potassium ions are involved. But
: what activate and deactivate the postassium pumps !
Sean replied,
	I'm not an expert in plants, but what makes you 
think the pumps are turned off and on.  I would assume
that the pumps are constantly pumping and that K+ channels
are opened allowing free movement K+ ions.  From what I
know of physiology cells can't survive without the Na-K pump.
I would also one step further and guess that there is an
ocsillation of [K+], subthreshold to cuasing turgidity.
	I recognize that your not an expert either but
I would be interested to know why you think the pumps are
activated and deactivated.