Stoma density and pollution
The materials required for this science fair project:
- 15 pine trees at locations with different concentrations of automobile traffic. For example, you could locate trees in the city, at the city fringe, and in the country. You should ensure that all the trees are of the same species
- 3 bottles of clear nail polish
- A roll of clear cellophane tape, 2cm wide
- 15 glass slides
- A microscope
- 15 plastic bags
- A black marker pen
- A car and a driver
- GPS (global positioning system) equipment, or a good map
1. For this science fair project, the independent variable is the concentration of traffic at the location of the pine trees. The dependent variable is the number of stomata on the surface of their leaves. This is determined by viewing the leaf under a microscope and counting the number of stomata. The constants (control variables) are the size of the trees, the age of the leaves, the size of the leaves and the size of the tape.
2. 5 pine trees at each of 3 different locations are selected for this experiment. The pine trees should be about the same age and height. The concentration of traffic near the site of the trees is observed for 4 hours (ensuring that you include peak hour traffic) and the average number of vehicles that pass by the site, per hour, is recorded in the table below. At each of the 3 locations, perform your traffic counting during the same block of time. For example, if you choose to observe traffic between 2 to 6 pm, you should do so for all three locations.
3. Samples of 2 leave clusters from each of the 15 pine trees are collected. The leaves collected from each tree should be about the same size and of the same level of maturity. The plastic bags are labeled according to the location of the trees and the leaf samples are placed in a bag. The leaves are brought back to the lab.
4. Place the individual pine leaves immediately adjacent to each other. Using the transparent nail polish, a 2cm x 2cm area is painted on the bottom of each leaf (pick the a dense part of the leaf cluster) . The nail polish is left to dry and a piece of cellophane tape is placed over the nail polish. Peel off the cellophane tape and the skin of the leaf will come off with the cellophane tape. The tape is placed over a glass slide and viewed under a microscope. Count the number of stomata viewed under the microscope.
5. The average number of stomata for the leaves from each pine tree is calculated and recorded and the results are shown in the table below.
Basic safety requirements