Have the students brainstorm and / or
research types, sources and effects of water pollution. Identify
one type of water pollution as acid rain and ask students to identify
how this might affect the world around us (buildings, plant growth,
cars,...) Scientific background: Seeds are in a period of dormancy
and germination is the resumption of growth - this occurs generally
if there is an increase in temperature and a presence of water;
light or external nutrients are not required as seeds store energy
in the form of carbohydrates. During germination, cells actively
oxidize the carbohydrates during cellular respiration to provide
energy for metabolism and growth. Adverse conditions (i.e., acidic
environment) interfere with cellular respiration to hamper or
prevent seed germination.
Explain to the students that as Agricultural
Scientists they have been asked by local farmers to investigate
changes in plant growth (their crops). They have rain water samples
suspected to be acidic to test on one specific organism. Explain
the experiment to the students highlighting the presence and importance
of a control group, and the need for precision and consistency
in their work. Have all of the students create a testable hypothesis
about the experiment. Note: This experiment could be done as
a full-class demonstration or in individual groups, depending
on time and material availability.
Organize the students in groups of 2-3
and have each group prepare a set of seeds for germination:
Scientific method: Divide a paper towel into two pieces. Saturate
each towel with either water or vinegar by placing them into separate
beakers or cups containing equal volumes of each liquid. Remove
the towels and spread 5-10 radish seeds over the surface of each.
Roll the towels snugly into a tube and slip into a separate sandwich
ziploc bags. Seal the bags and leave them in a warm environment
for 2-4 days. Open the bags after 24-48 hours to the towels are
still moist. If necessary, add more liquid to each bag: the amount
of liquid added to both towels should be the same throughout the
experiment. Opening the bags will also allow for an exchange of
air, replenishing oxygen, which will assist rapid cellular respiration.
Have students check the pH of each bag with pH paper.
Scientific fact: pH (vinegar) = 3, pH (water) = 6-7
Have students check the seeds periodically
for about three or four days for both germination and moistness.
Students should record final observations after a period of 3-4
days including a description and a diagram of the seeds. Note:
those in vinegar should show no significant germination compared
to the water-treated seeds.
