Leaf surface of Asparagus Fern

Richard Winder rwinder at PFC.Forestry.CA
Fri May 7 11:03:20 EST 1993

(BIOHEAD) writes:

(Text deleted)

>Second, to get the surface area of the small needle-like appendages, one
>could xerox the shoot, and laboriously cut out all the needle images, then
>weigh the cut-outs and use a weight of xerox paper / leaf surface area
>conversion factor. I'd use an enlarging xerox to make the copies of needle
>leaves large enough to be manageable.

This is too laborious for large studies- almost as tedious as image analysis

>At trade exhibits, I have seen a machine that measures surface area of
>ROOTS by having samples floating in a dish of water, leaving a light
>sensor to calculate how often light was intercepted by a root fragment.
>Such a machine should be able to handle a dish full of Asparagus needles
>as easily as it does a dish of root segments.

You probably don't even have to bother with a machine.  Use a slide projector
or some other bright lamp as a source and  a large diameter cardboard tube as
a light guide.  For a sensor, use a silicon photocell (Currently ca. $5.00 - 
$10.00 Canadian) hooked up to a cheap multimeter (Currently ca. $30.00 
Canadian).  Dangle the sample and some standards in front of the tube and 
measure amps (not volts).  If sensitivity is not what you want, it is fairly
simple to construct a simple op-amp circuit to do the trick.  Since the 
largest commonly available photocells are ca. 10cm in diameter, leaves larger
than that would have to be cut up before measurement.  A dark room would also
be helpful.

I would be wary of using weight/area correlations.  They tend to be unreliable
if there are treatment differences (sun vs. shade, etc.) which affect vigor
and morphology.  -RSW

  RICHARD WINDER                    Title: Visiting Fellow
  Forestry Canada                   Phone: (604) 363-0600
  Victoria, B.C.                    Internet: RWINDER at A1.PFC.Forestry.CA

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