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plant growth

Hugh Macaulay ar903 at FreeNet.Carleton.CA
Thu Jan 5 13:48:55 EST 1995

In a previous posting, Robert Mcgehee (TEJU87B at prodigy.com) writes:
> I am going to do my science report/project on plant growth hormones ie 
> auxins, gibberellins, cytokinins and possibly inhibitors: abscisic acid 
> and ethylene.  Currently I am doing research on the topics trying to 
> think of a good experiment (any suggestions would be GREATLY appreciated).
>   I don't seem to understand the role of auxins in phototropism and 
> geotropism.  First how are the auxins (and other hormones) transported 
> throughout the plant, is it through the tissues itself, being carried 
> from one cell to the other, or is it transported in the tubes that carry 
> the sap and water?  Is it correct that auxins respond to light and dark 
> by migrating over to one side of the plant;  and it responds to gravity 
> by migrating upward?  Next question:  supposedly if a plant is allowed to 
> grow in the darkness it will grow faster for a while than a similar plant 
> growing in full light.  Why is this, if the auxins are not migrating in 
> either case wouldn't the growth be the same?  Do the auxins migrate down 
> to the roots in the light, and if so how does this fit in with geotropism 
> (auxins migrate up).  Lastly if anyone can think of an experiment that 
> could possibly tie this together please tell.

Your questions are interesting and pertinent, but too broad to be answered
here, I think.

My advice to you would be to check out your nearest university library and
the scientific journals therein.  Good plant journals are Planta,
Physiologia Planarium, and Plant, Cell and Environment.  To find specific
topics, the librarian should be able to instruct you on the use of Science
Citations and other cross-referencing material. 

As far as the issue of plants in heterogeneous light conditions, check out
"Plants as competing populations of redundant organs" by Sachs. It's in
Plant, Cell and Environment, Vol. 16, p. 765 (1993).  The references
should take you further. 

Also, a very neat series of experiments that involve auxin and plant
wounding was done by M.E. McCully, and are written up in the journal
Protoplasma, Vol. 112, p. 143-166 (1982)

Power corrupts absolutely. Absolute power is kinda neat.
                                   -----Andy Jukes

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