Mike Weber asks for ideas for a plant lab.
My experience has been that students find plants that act
like people interesting. They like plants that move, so I
have found using the sensitive plant (Mimosa pudica), Venus
fly trap (Dionaea muscipula), and sundew plants (Drosera)
stimulates interest. Plants with diurnal leaf movements,
such as the prayer plant (Maranta leuconeura), or bean
plants, are also useful. While these phenomena are not
easily investigated in a traditional classroom laboratory
setting, students with medical interests may relate well to
a discussion of the various mechanisms responsible for
movement (including action potentials shown by some
species), and the concept of circadian rhythms. It is easy
to make comparisons between these characteristics in plants,
vs. those in humans. I grow all of these plants in our
college greenhouse. Many students have never actually seen
these plants move, or looked up close at the pulvini,
trigger hairs, etc.
I have found that my students enjoy laboratory work using
hormones or other growth regulators, because they can see
dramatic changes in the plants over a few days or weeks, and
can relate to hormones because animals have them. Examples
of hormone laboratory exercises are easily found in most lab
manuals. I have found that the following usually always
work, and can be related to practical uses (crop yields,
Christmas tree shape):
1. addition of various concentrations of gibberellic acid to
genetically dwarf pea plants.
2. Coleus plants kept intact or with the apex removed, to
demonstrate lateral growth inhibition.
3. Coleus plants with various proportions of the leaf blades
removed (0 to 100%), to determine how much of the leaf blade
must remain intact to avoid abscission of the petiole.
4. application of differing amounts of red and far-red light
to study phytochrome and seed germination (this topic has
been discussed previously in plant-ed).
Because the movements and hormones are physiological topics,
they could be combined into one physiology lab session.
Mike Gross
Dept of Biology
Georgian Court College
Lakewood, NJ 08701
gross at georgian.edu
