Fuzzy stems. Why?

Monique Reed monique at mail.bio.tamu.edu
Tue Nov 21 10:14:13 EST 2000


Well, now we know what happens when they don't make botany and
horticulture students take physics...

M. Reed

David Kirschtel wrote:
> 
> Monique Reed wrote:
> 
> > Hairs on a stem or leaves can a)provide insulation b)make the air
> > layer around the plant more turbulent and slower-moving so water loss
> > is less,
> 
> I'd have to take issue with this. If the hairs a far enough apart to
> induce turbulence then the result will be to decrease insulation and
> increase water loss. Turbulence is a mixing phenomenon. In a fully
> developed tubulent flow profile there is effectively zero velocity
> gradient, the average velocity next to the surface will be the same as
> at all distances from the surface. The innerlayer/ viscous sublayer/
> boundary layer has been eliminated. This region of relatively stagnant
> air near the surface is what provides the insulation. If on the other
> hand the hairs are relative densely packed they will produce skimming
> flow over the top of the hairs, effectively creating a new elevated
> surface and extending the region of stagnant air around the surface of
> the plant. This is what will increase insulation and reduce water loss -
> the absence of turbulent flow near the surface of the plant.
> 
> 
> ------------------------------------------------------------------------
>       David Kirschtel * kirschte at pilot.msu.edu * 517.432.0898
>     112 N Kedzie Lab * Mich State Univ * E Lansing, MI * 48824






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