SENSITIVE PLANT OR CARNIVORES
brya...@postoffice.pacbell.net
plants that I first encountered in Vieques, Puerto Rico. Not only do
the leaves fold in response to touch, but all of the leaves on the plant
will fold, in response to the touch; of a finger, a raindrop, a bug, or
even the wind on any part of the plant. I have long been curious about
how this information is transmitted throughout the plant. I'd really
love to be enlightened. To a lesser degree I'd like to know how the
carnivores respond. Please pardon my english, it is not my native
tongue. Thank you so very much.
Nick Moyes
under the leaf at the end of a branch. Set a stopwatch going as you do this,
or just start counting. . . . you really get the feel of a "nervous
stimulus" passing down the stem as leaf after leaf starts to close up - and
without any physical contact with the plant taking place.
For those of a nervous or caring disposition I can assure you that this is a
totally painless experiment, involving no cruelty. . . unless, that is, you
forget to blow the match out afterwards :-)
Nick Moyes
Derbyshire Biological Records Centre
Derby Museum & Art Gallery, The Strand,
Derby, DE1 1BS, England.
Tel (0)1332 716655 Fax: (0)1332 716670
home e-mail: ni...@nmoyes.freeserve.co.uk
Sandy
brya...@postoffice.pacbell.net wrote:
Hi, yes the sensitive plant is fascinating. Here is an extract about how
they work, from the book: The Private Life Of Plants, by David Attenborough.
"Sensitive mimosa manages to conceal its leaves in a way that is, literally,
electrifying. It is common throughout the tropics, sprawling across the
ground in clearings and along roadsides. Its leaves are feathery, with rows
of small leaflets rising from either side of its stems. Spread out in the
sunshine, they must look delicious to any hungry leaf-eating insect. But
then the grasshopper or a locust lands on them, the leaflets suddenly
disappear. Within seconds, they fold upwards to lie tight alongside the stem
so that what was obviously luxuriant foliage is suddenly reduced to nothing
more than a tangle of unappetising twigs. If in spite of this the insect
does not lose interest and starts to bite the plant, the leaves make a
second movement, downwards, which exposes the sharp barbs on the stems. The
grasshopper, baffled, hops away.
The mechanism that brings about this transformation is triggered by
minute electric currents, similar to those that pass along our own nerves.
The plant does not have such special power-lines to carry the current and
consequently its reactions are not nearly as fast as ours. nonetheless the
signal, transmitted along the ducts that carry its sap, can travel the whole
length of a foot-long stem within a second or so. The warmer the
temperature, the quicker the reaction will be. The base of each leaflet,
where it joins the stem, is greatly swollen. The cells within are turgid,
filled tight with liquid. When the signal arrives, those in the lower half
of the swelling immediately discharge their water which is equally swiftly
taken up by those in the upper half. And the leaf collapses downwards. So as
the signal travels along the stem, the leaflets fold up one after the other
like a line of falling dominoes. After such a defensive collapse, the plant
takes about twenty minutes to pump up its cells again and reopen its
leaflets to the sunshine so that they can resume their work of food
production."
That is a great book, and if you have it or can get hold of a copy, it also
mentions about the venus fly trap, and other carnivorous plants.
Sandy.
