Internode Inhibition

Tony Travis ajt at rri.sari.ac.uk
Mon Feb 15 07:09:47 EST 1993


Martin Hughes (hughes at jp.go.riken.rkna50) wrote:
: [...]
: Well, after having "lurked" on this group since its inception, I
: finally feel confident enough to comment on something - and
: what is more to the point, in direct reply to something by the
: Great Tony!!!

Arf, arf!

Seriously, though: this group is what we make it, so don't hesitate to
post interesting/informative/funny articles about your work.

I'm an agricultural botany graduate, and I got my PhD in 1981 after
working for five years in Terry Mansfield's lab at Lancaster (UK) on
the ion-transport mechanism in stomatal guard cells.

Several interesting post-docs later (one of which took me into image
analysis) I work on the relationship between anatomical features and
nutritive value in forages and crops used to feed ruminants.

: Firstly, to answer the guys question.  Yes, GA biosynthesis inhibitors
: will work to decrease internode expansion.  Uniconazole or
: Paclobutrazol will do the job for you.  (Uniconazole is from a
: Japanese company-Sumi7 (a branch of Sumitomo - ICI sells
:  Paclobutrazol, maybe under adifferent name).  Can be applied 
: by spray, to the roots, or to seeds (with germinated radicles). Seeds
:  can be soaked for 1h in1mM (Uniconazole), followed by washing
: for 1h in water.  For further info (esp. for Paclobutrazol) see Plant
: Physiol. (1992) 100: 651-654.
: 
: And, as Tony said so will blue light.
: 
: And this, I think is the interesting point.  Several other things will
: also inhibit internode expansion.  Recently Frances et al. (Plant Cell
: 4: 1519-1530) noted the similar photomorphogenic phenotypes
: of their light-independant developing pea mutant with previously
: reported heat-shocked seedlings - in that both had (amongst
: their characteristics) reduced internodes.  Additionally, leaves 
: underwent development.  So, the question is, are all these causes
: (GA inhibitors, phytochrome transduction pathways and heat
: shock treatments) inter-related (and if so, to what level), or
: do they all serve to "trigger" the same (series of) responses
: in a trivial manner (after all, there are a limited number of things
: a plant can do in response to a stimulus!)?  Any thoughts?

I don't believe blue light is always a 'trigger' - I believe blue light
may also act directly on the ion-transport mechanism itself.

For example, if only 1% of the blue photons incident on the surface of
a guard cell are intercepted by pigments in an electron-transport chain
then the ion-transport mechanism (K+ influx) responsible for stomatal
movements could be driven directly (Travis, A.J. and Mansfield, T.A.,
1981, Light saturation of stomatal opening on the adaxial and abaxial
epidermis of Commelina communis, Journal of Experimental Botany, 32,
1169-1179).

The common factor in many plant responses to shock/hormones/etc. is the
effect these agents have on the cell membrane and transport processes
associated with it.  Low temperature treatment, for example, is known
to make cell membranes 'leaky' and so the cells lose electrolytes.  I'm
interested to know if mechanical stress has a similar gross effect on
membrane integrity in relation to 'hardening' of seedlings by brushing
prior to transplanting or handling generally.

In particular I'm interested to know if the changes in the plasticity
of cell walls associated with 'shortening' (actually, it's a reduction
in growth - the internodes don't get shorter: they grow less!) is in
any way related to the polymerisation of lignin precursors?  If it is,
then what is the underlying mechanism by which plants respond to
mechanical stimuli?

	Tony.
-- 
Dr. A.J.Travis,                       |  JANET: <ajt at uk.ac.sari.rri>
Rowett Research Institute,            |  other: <ajt at rri.sari.ac.uk>
Greenburn Road, Bucksburn,            |  phone: +44 (0)224 712751
Aberdeen, AB2 9SB. UK.                |    fax: +44 (0)224 715349



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