- SUBJECT: Detecting starch in Coleus
- DATE: 4/97
-
-
- Dear Biolabbers,
- In our freshman bio labs we do an experiment in which we stain the
leaves of
- a Coleus plant with an iodine solution in order to test for storage
of
- starch. A leaf is boiled in water to break the cell wall, then boiled
in
- ethanol to remove pigments, washed with water and then stained with
iodine.
- The problem is that the control leaves (plenty of water, sun, etc.)
hardly
- stain. The first time I ever saw this expt, it worked beautifully &
now I
- can hardly tell a difference between leaves that are supposed to stain
well
- and those which are not (e.g., light-starved). Any suggestions??
-
- Thanks,
- Dan
- ********************************
- Dr. Dan Murray
- Assistant Professor of Biology
- University of Texas-Pan American
- 1201 W. University Dr.
- Edinburg, TX 78539-2999
- phone: (210) 384-5098
- fax: (210) 381-3657
- email: dmurray@panam.edu
-
-
- Dan
- The Coleus leaves with white veriegated regions may work for you, as
these
- lack chloroplasts; whereas the green and red and orange areas of the
leaves
- have chloroplasts.
- David Crabtree
- Hillsdale College
-
-
- Green leaves should accumulate starch throughout the light period and
break
- it down in the dark. Therefore you should find the highest starch content
- at the end of the day. If your labs are in the morning you might not
see
- much starch. Alternatively, if the plants are not in direct sun, they
may
- not accumulate much starch. If plants are under continuous light they
tend
- not to accumulate much starch, presumable because they don't need it.
You
- might also want to test your iodine solution on some starch off the
shelf
- to make sure it works.
-
- Hope this helps.
-
- Jon
-
- -----------------------------------------------------------------
- Jonathan Monroe voice: 540-568-6649 (office)
- Department of Biology 540-568-6045 (lab)
- James Madison University fax: 540-568-3333
- Harrisonburg, VA 22807-0001 e-mail: monroejd@jmu.edu
- http://www.jmu.edu/biology/biofac/jmonroe/jmonroe.html
-
-
- You might want to do this with Geranium (Pelargonium) leaves instead.
It
- is fun to clip a design or a negative portrait of the student to the
leaf
- for a few days, then test for starch. The unexposed areas of the leaf
- won't stain and the exposed areas will. I believe both these ideas
were
- on biolab (or perhaps plant-ed) earlier this academic year.
- Janice
- ***********************************
- Janice M. Glime, Professor
- Department of Biological Sciences
- Michigan Technological University
- Houghton, MI 49931-1295
- jmglime@mtu.edu
- 906-487-2546
- FAX 906-487-3167
-
-
- I second that suggestion. Iodine sublimes, and an old solution just
won't
- work well.
-
- Maren
-
- Maren H. Brown, Ph.D. brownm@goliath.sunyocc.edu
- Professor of Biology office (315) 469-2405
- Onondaga Community College fax (315) 469-2593
- Syracuse NY 13215
-
-
- We have the best luck with 2 week old bean plants. --cmw
- Charlene M. Waggoner, Ph.D.
- Department of Biological Sciences
- Bowling Green, State University
- Bowling Green, OH 43403
-
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