Volume 6, Spring 2008 - Saddleback College

Fall 2007 Biology 3A Abstracts
4. EFFECT OF pH ON RATES OF CLOSURE IN VENUS FLY TRAPS (Dionaea Muscipula). Jason R.
Riggio Department of Biological Sciences, Saddleback College, Mission Viejo, California 92692
Venus flytraps are peculiar in the fact that they can close their leaves completely in times of under a
second. This does not seem very remarkable until one steps back and understands that plants do not
have any muscle tendons or a nervous system. Scientists are still not exactly sure how this phenomenon
occurs, however, the current (leading) hypothesis is a combination of acid growth, turgor pressure, and
rapid cell division. The hypothesis tested in this paper, the effect of two pH’s on the rate of closure of the
leaves, was simply to test the first part of the leading hypothesis, acid growth. This was done by picking
16 leaves or “traps” from four different plants and randomly placed into sixteen 10ml beakers, eight
beakers each filled with 5mL of HNO 3 , at a pH of four, and eight more each filled with 5mL of NaOH, at a
pH of 10. The leaves were left in the solutions for 24 hours and then timed on individual rates of closure.
Timing was done by use of digital camera and further analyzed on computer. Average rate of closure of
leaves in HNO 3 was 5.487(±0.654) seconds and average rate of closure in NaOH was 1.814 (±0,654)
seconds. Surprisingly, the leaves in the basic solution closed much more quickly than the leaves left in
the acidic solution, putting the leading hypothesis into question. Several factors may account for this
difference, such as age of the leaves or defective leaves.
5. EFFECT OF TEMPERATURE ON PHOTOSYNTHETIC RATE OF Elodea canadensis. Aubrey Michi
and Jeremy Ward. Department of Biological Sciences, Saddleback College, Mission Viejo, California
92692
We designed an experiment to measure the rate of oxygen production of Elodea canadensis at
various temperatures. We hypothesized that as temperature increased, photosynthetic rate would
increase. Three test tubes containing 0.1M NaHCO 3 solution and Elodea were kept in water baths of 5ºC,
22ºC, and 37ºC. A light was shined on the test tubes for 30 minutes and oxygen production was
measured by water displacement on each attached manometer. On average, during the 30 minute
interval, the Elodea in 5ºC water produced 0.10mL of oxygen; the plant in 22ºC water produced 1.03mL of
oxygen; and the plant in 37ºC produced 3.10mL of oxygen. Therefore, oxygen production increased with
an increase in temperature. This arises from the principle of Brownian Motion, which explains that the
random movement of molecules is related to their overall kinetic energy. We expect that an increase in
photosynthetic rate will continue with an increase in temperature until a limit is reached either due to the
stoma in the plant closing or the plant’s tissues denaturing from excessive heat. Nevertheless, our results
suggest that increases in environmental temperature, such as those caused by global warming, may
affect the photosynthetic rate of various aquatic plants.
6. THE EFFECT OF GUAVA Psidium guajava AGAINST Escherichia coli.. Anne Kathreane Ebol and
Hannah Rae Manuel. Department of Biological Sciences, Saddleback College, Mission Viejo, California
92692
The “poor man’s apple of the tropics”, guava, has been known to be a great natural remedy for
diarrhea in various countries. For this reason, an experiment was set up to find out the effectiveness
and strength of guava Psidium guajava leaves extract against one of the common bacteria that causes
diarrhea, Escherichia coli, also known as E. coli. The experiment aims to verify the efficacy of guava
extracts in combating bacteria and intends to find a nonchemical substitute to antiseptics in efforts to
prevent an increase in dangerous, resistant strains of bacteria. The strength of the guava extracts was
evaluated against the strength of isopropyl alcohol, a common household antiseptic, with a 91%
concentration. Water was used a determinant in bacterial growth inhibition. Cultures of Escherichia coli
were isolated in order to evaluate guava’s anti-microbial effect. After measuring inhibition zones, E. coli
showed about equal propensity to the isopropyl alcohol and the guava extract. The guava extract
returned an average inhibition zone of 1.1cm ± 0.15cm (±se), n=16, and the isopropyl alcohol returned
an average inhibition zone of 1.1cm ± 0.07cm (±se), n=24. The guava extract was not able to inhibit
bacterial growth entirely; however, according to the data collected, guava extract is just as strong as the
91% isopropyl alcohol when it comes to bacterial growth inhibition. There was no significant difference
in mean inhibition zones (p= 0.5; one-tail t-test).
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Saddleback Journal of Biology
Spring 2008