From: ajt@doc.ic.ac.uk (Tony Travis)
Newsgroups: bionet.general
Subject: Re: Mechanical stress and lignification
Date: 8 Apr 92 18:33:29 GMT
Organization: Department of Computing, Imperial College, University of London, UK.

harper@convex.csc.FI (Rob Harper) writes:
: In <1992Apr6.171329.14957@doc.ic.ac.uk> ajt@doc.ic.ac.uk (Tony Travis) writes:
: 
: >: It was rather an interesting study.
: >Can you tell us the author, and was any of the work published?
: 
: She was a Polish research worker, who I am told has now gone to Malaysia.
: 
: From what I can remember mechanical stress could be viewed in two ways
: Thigmomorphogenesis and seismomorphogenisis. ( Wonderful scientific sounding
: words) In actual fact the former was defined by Jaffe in 1976 and refers to
: the retardation of growth caused by physical contact, and the latter refers
: to retardation induced by shaking or the wind Mitchell 1975
: 
: The masters thesis that I looked at was done at Helsinki University
: If you want the references then perhaps you could fax them at the number
: below. Department of Plant Production fax +358 0 708 5582

Thanks Rob, I will do that.  It amazes me that fax is so widely
accepted without any fuss, but that e-mail seems to be a major issue!

: Young tissue seems to be specifically sensitive to MS (Mechanical Stress)
: stimuli, and often brushing or shaking of plants can also be combined with
: nutrient hardening to produce sturdy plants that survive transplanting.
: 
: For example Cauliflour seedlings fed with low amounts of nitrogen and
: potassium are tougher and more compact. They have a dry matter % weight
: which is twice that of normal plants, and do not wilt after transplanting.

The response to nutrient levels is not surprising. There has been a lot
of work on the relationship between nitrogen application and lodging
resistance.  However, I didn't realise that shaking plants about was a
well known method of hardening seelings!

: With Tomatoes, MS causes a reduction in node and leaf number, shortening 
: of internodes, nodal swelling, deep greening of new leaves, and increased
: lateral branch development (Mitchell 1975) Beans that had been brushed and 
: rubbed were greatly hardened against breakage. The elastic strength of the 
: stems was related to the cellulose fraction in the stem fibre, and MS treated
: plants withstood bending of about 90 degrees whereas untreated controls broke
: due to slight bending. (Heuchert 1983)

It sounds to me that this work demonstrates that plants *do* adapt to
mechanical stress in a similar way to adaptation to other stresses.  I'm
interested to know if anything similar has been done with species that
are normally grown in the field such as barley or maize.

Have you any explanation of the mechanism by which mechanical stress
acts?  Could it, for example, be an indirect effect of disrupting the
vascular system (eg. by introducing embolisms) resulting in water stress?

: So the take home pay is that if you want to grow tough plants then get
: tough with them.

Yes, but if you want to eat them or, more particularly, if you want farm
animals to eat them you have got to be nice and gentle :-)

	Tony

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