leaf marking

Ross Koning koning at ECSUC.CTSTATEU.EDU
Wed Dec 3 09:08:02 EST 1997


At 8:39 AM -0500 12/3/97, Kathleen Archer wrote:
>Does anyone have a good method for marking positions on growing leaves?
>I'm planning some simple leaf growth measurement experiments for first year
>students, and every non-water soluble marking pen I have seems to damage
>the tissue (i.e. Sharpie-type pens). Any ideas would be much appreciated.
>Kathleen Archer

Hi Kathleen!

I have marked stems and roots with ultra-fine
Sharpie markers and have not observed any
toxicity (I have used corn roots, but a range
of species for marking stems).  I have not done
leaf markings and so that may explain why I
haven't seen the problem.

My students HAVE had difficulty keeping the
ultra-fine marker working (especially in marking
roots) and then have pressed too hard and crushed
tissue in an effort to force the pen to mark.
This was caused by the pen picking up water from
the plant surface.  I try to get them to think of
"painting" the marks rather than "drawing" the
marks, and show them to run the Sharpie on a
paper towel between strokes to be sure the ink
is flowing well and water has been absorbed out
of the tip.  When they get the "knack" of that
it has gone well...but our marks have been small
dots along a root or stem so the exposure to the
ink has been limited and the solvents evaporate
exceedingly quickly.

Before I used ultrafine Sharpies, I worked with
India ink.  One way to do that is to mount two
machine screws (buy ones with threads to match
the desired mark spacing) through a piece of strap
metal. You can then run cotton thread between the
threads of the two screws to achieve proper spacing.
Then you can paint the threads (or dip the apparatus)
with India ink and then lightly touch the organ to
be marked.  The only reason I abandoned this method
was the messiness of it...the pens keep the ink
contained.

If area is of interest, one could use some coarsely
woven cotton fabric, dip it in ink, blot briefly, and
then lay it on the leaf surface and lift cleanly.  You
could even try some fiberglass screening for coarser
markings.

I think India ink is fairly non-toxic compared to the
organic solvents used in Sharpie markers.  I don't
remember all the ingredients but the black is simply
lampblack carbon and the ink is water-based.  There are
some binders but I don't remember if they are anything
other than protein.

Good Luck!

ross

________________________________________________________________
Ross Koning                 | koning at ecsu.ctstateu.edu
Biology Department          | http://koning.ecsu.ctstateu.edu/
Eastern CT State University | phone: 860-465-5327
Willimantic, CT 06226 USA   | fax: 860-465-4479
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