Mechanical stress and lignification

Tony Travis ajt at doc.ic.ac.uk
Thu Apr 2 13:08:42 EST 1992


mwfolsom at hydra.unm.edu (Mike Folsom) writes:
: [...]
: 
: Such a heavy question for April's fool day -  

I realised the date when I posted the question ;-)

It _is_ a serious question though!

: Oh well, since you insist - 
: 
: Have you buzzed through the plant defense literature?  Seems 
: to me that lignification is one of the mechanisms plants use 
: to defend against pathogens.  Now how different is this from the     

No, but you are right because I have seen reference to this in the
'physiology' literature in relation to lignification and turgor
maintenance during water stress.

: production of lignin in response to mechanical stress?  I seem to 
: remember that people who do research in the area of plant 
: defense mechanisms often use mechanical techniques, e.g. 
: sandpaper, grinding powerders, etc, to induce plant responses.  
: I guess I'm wondering if the same techniques used to analyze 
: plant defense responses could be applied to the questions   
: which interest you.
: 
: Are we on the same wavelength?

Yes we are.

The mechanical techniques you mention are intended to breach the cuticle
aren't they?

What I'm interested in knowing is do varieties that exhibit resistance
to lodging damage (falling over) have genetic characteristics that
result in thicker and more lignified cell walls, or do they have the
ability to adapt to mechanical (bending) stress by increasing the rate
of cell wall deposition and/or lignification in response to a
mechanical stimulus such as the load from leaves in the canopy blowing
about in the wind.

I studied forestry many years ago and I remember that trees produce
'reaction' wood if the soil they are growing in gives way making the
trunk lean over.  The wood is produced at the point of greatest
mechanical stress and is not simply a geotropic response.  I'm
interested to know if this is a response to a mechanical stimulus like,
for example, the response of Mimosa pudica to the impact of raindrops
on its leaves (I'm not suggesting it is the same mechanism though).

We are investigating the differences in anatomy of maize varieties in
our lab, but we are using samples from mature plants.  I wondered if
some of the differences we see are evidence of adaptation.  This is
important because lignification, in general, reduces the usefulness of
crop plants that are used to feed animals.

If plants can be selected for their ability to adapt to mechanical
stress when lodging is likely, the extent of lignification would be
reduced under conditions where lodging is less likely to occur because
the mechanical stress would be absent.  At present, varieties that are
known to resist lodging damage are thought to do so because of more
robust anatomy (thicker and more lignified sclerenchyma in particular).

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



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