Re: Plant Hormones

I heard Preston Littleton clapping one hand out there. Since it doesn't
take much applause for a ham actor to come back on stage, here is the
write-up on plant hormones. A second post will follow.
> 
> Jim Hawes wrote:
> >
> > There is a subject that we occasionally encounter in our hosta reading
> > or hosta discussions....plant hormones, also called growth  regulators.
> > We think we know or understand what they are and what they do in hosta
> > plants. But do we? I must confess I am often baffled by the role of the
> > various hormones. When considered alone, their roles seem simple but
> > when inter-relationships are studied, hormones are complex indeed.
> >
> > Much is known about them because extensive research has been conducted
> > by literally hundreds of investigators during the last 100 years. Plant
> > hormones are substances which are synthesized in all plants and perform
> > specific functions such as regulation of plant growth and development of
> > entire plants, promotion or inhibition of growth of specific cells,
> > tissues, organs or systems, flowering, fruit and seed production,
> > propagation, dormancy, emergence and other growth phenomena in plants.
> >
> > The natural hormones include auxins, cytokinins, Gibberillins, ethylene
> > and Abscisic Acid. In the next post I will attempt a simple
> > overview summary of each plant hormone before overall questions, answers
> > and comments begin . Conclusions to be drawn on this subject will come
> > at a much later time. I hope that Robins  will have many questions or
> > bits of information to contribute over an extended period of time. Let's
> > try to be open and free in our written email discussions to exchange the
> > vast store of knowledge and experience that has been acquired. Not
> > everyone on the Robin is a scientist but everyone is a gardener who can
> > benefit from more knowledge about plant hormones. So don't delete...YET.
> >
> > First a little history about plant hormones. In 1880, Charles Darwin,
> > the Father of the Theory of Evolution, along with his son Francis, was
> > one of the first to make scientific inquiries into the nature of plant
> > hormones. Working with Canary Grass coleoptiles he found that there was
> > a substance produced in the tips which controlled whether or not the
> > tips bent toward light when present. Some fifty years later, a Dutch
> > physiologist named Went, working with oat coleoptiles and pea epicotyls
> > arrived at similar conclusions, representing the classical research
> > which proved the existence of substances we now know to be auxin type
> > hormones. 
> >
> > Later investigators ( for example, Thimann, working and publishing with
> > Went) identified the naturally produced auxins as Indoleacetic Acid.
> > Since that time other  synthetically produced growth regulating
> > substances (Indolebutyric Acid, Napthalene Acetic Acid,2-4 D Dichloro-
>   phenoxyacetic Acid and others) have been found which have
> > similar characteristics in  promoting or inhibiting growth of plant
>   cells and tissues. Many of these substances are used for facilitating
> > the rooting of cuttings of all kinds. The scientifc literature on this
> > subject is profound but worth investigating to get an appreciation of
> > the quantity of research done to date. Such research is the basis for
> > worldwide efforts in the propagation of hundreds of economic  crops in
> > commercial nurseries of many countries of the world. Hormones play
> > a role in propagation of Hostas, especially in modern tissue culture
> > laboratories.I anticipate that our discussions will cover some aspects
> > of use of hormones in tissue culture propagation, with Robin members
> > having tc experience sharing it with us. I encourage wide participation.
>   Jim Hawes   hawesj@gcnet.net

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