Internode inhibition

Thomas Bjorkman Thomas_Bjorkman at
Mon Feb 15 15:48:47 EST 1993

In article <1993Feb15.173832.28738 at> Tony Travis,
ajt at writes:
>My interest in this topic concerns the differences between weak-strawed
>and stiff-strawed crop varieties in relation to yield, nutritional
>value and susceptibility to lodging.
>Do you think is would be a practical proposition to select varieties
>that are able to _adapt_ to mechanical stress?  If so, the partitioning
>of assimilates into vascular tissue that I believe is an important
>factor in reducing the yield of stiff-strawed varieties could be
>avoided without the risk of losing the entire crop because of lodging
>as often occurs in higher yielding weak-strawed varieties.

The pea tendrils curve the same way whatever the direction of the
stimulus--it is a nastic movement.  The curvatrue is set in  the
structure of the tissue, the mechanical stimulus triggers it but provides
no directional information.

Regarding lodging in grains, I am not sure that the mechanical adaptation
would be effective.  The stiffening would have to occur suring stem
elongation to accomodate a stress occurring much later during seed fill. 
Therefore the plant would have to make the stem stiff enough for some
future condition, and one might as well put it in the constitutive
program.  Having the growing point at the bottom could be a problem, but
I wonder aht would happen if one were to start flexing the stem a little
each day starting at the boot stage.  Seems easy enough to try.

Now that I've shown how little I appreciate the subtleties of your
research, I'll tell you about a similar case that does seem to work.  I
am working with tomato transplants that are grown about 10 mm on center. 
They get crowded and elongate for the usual reasons.  The stems are not
very strong since they are supporting eachother, so that on transplanting
in the field, they do break off fairly easily.  Stroking the canopy slows
the growth by about 20% and makes the stems somewhat tougher.  The stems
are also slightly thinner and the leaf area is smaller than the controls.
 However, putting up an impediment for the plants to push against for a
few hours a day makes the stems tougher and thicker without reducing the
leaf area.  Apparently the stimuli are interpreted differently.  

One question I am actually doing research on is how the tomato interprets
different kinds of petting. :-).  If only William Proxmire were still in
the Senate, I'd be a shoo-in for the Golden Fleece award--even though
this is a money issue for on American industry.

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