COMPUTER INTERFACING AND PHOTOSYNTHESIS
Doug Herman, Biology Teacher , East High School, Sioux City, IA. 51106
I have been trying for some time to locate usable interfacing equipment for measuring
some of the variables that indicate to students that photosynthesis is taking place
in plants. Biology teachers all familiar with the classic tests for starch and sugar
in the leaves of geraniums left in the light and dark for 24 hours.
These labs were designed using Vernier probes and software to measure variables in
photosynthesis such as temperature, light, oxygen pressure, and pH. Although this
set-up was done using a PC, the Mac environment should work nicely as well. I am
in the process of working and designing some ways to use the newer TI82/85 and CBL technology
from Texas Instruments to gather this same data.
The TI82/85 and CBL should give the biology teacher more hardware and some flexibility
in the laboratory that computers might not offer. Any biology teacher who has successfully
used this technology might consider sharing your ideas with those of us just getting started.
BASIC EQUIPMENT NEEDED
Vernier Probes for pH, temperature, pressure and light.
PC or Mac with game ports or open serial ports
Serial Box Interface & Data Logger Software(Vernier) or
Software for each probe for PC or Mac
NOTE: 1. Probes can also be used with ULI interfaces from Vernier and their other newer
MPLI unit. These are not yet in our lab.
250ml flask and 1-2 hole rubber stopper
- The Vernier probes can now be interfaced through the new
CBL technology from Texas Instruments.
0.25% Sodium Bicarbonate dissolved in pond water
1000ml of beaker of water
Elodea plants are placed in 200ml of aquarium water with 0.25% Sodium bicarbonate
dissolved in it. Mix the sodium bicarbonate in the aquarium water so the resulting
solution is 25%. Place a healthy sprig of Elodea in the flask with the pH probe and
temp. probe cords fit through the stopper. The rubber stopper will need to be slit in order
to accomodate the cords of the probes. Follow the software directions for probe calibration
and taking readings. The stopper of the flask will need to be sealed to prevent gas loss and a 150 watt bulb is used to illuminate the plant. Students can study
the variable of light intensity in the experiment by adjusting the distance the plant
is from the light. During several minutes of readings data is collected on pH and
temperature in the flask. I have had students use color light filters in front of the flask
to show how wavelength of light