Introduction
Since the begining of the Industrial Age, pH levels of water in the atmosphere have dropped. This is caused by the release of sulfur dioxide and nitrogen oxide, which are made as byproducts from burning fossil fuels. Once in the atmosphere, these chemicals react with water, oxygen, and oxidants to form sulfuric acid and nitric acid. The reaction creates what's known as acid rain and normally only forms in high clouds. Normal rain has an average acidity of approximately 5.6, while acid rain has an acidity of approximately 4.3. This difference in acidity could be detrimental to a plant's health. The change in soil pH can severely damage the cell structure, stop processes from occurring, and kill the plant. The pH of the soil can also affect the microorganism activity. Microorganisms work with the roots to help absorb nutrients in the soil, and without their presence, the plant might have nutrient deficiencies. Another result of pH change is it can create mineral levels that can be toxic to the plant, such as increasing solubility of aluminum, which represses plant growth at an very high rate.
This project will test the effect of different acidities on the germination of lentil seeds. The vinegar/water solutions created will mimic the affect of acid rain on plants. I will compare the effect of 3 different solutions and water on the plants, ten seeds in each solution. Plants will be measured 3 days after the experiment is first started and every 2 days for 14 days. I will then compare the averages of each plant in different solutions. My research suggests that the plants in less acid solutions will thrive compared to the plants in a solution with a higher acidity.
Materials
1 package of 40+ lentil seeds
1 Gal of distilled white vinegar
1 Gal of distilled water
1 role of paper towels
1 role of plastic wrap
1 role of thin string or floss
1 metric ruler
1 syringe with mL markings
3 sealable mason jars
3 pH testing strips
40 small plastic cups
40 rubber bands
Procedure
1. Mix 60 mL of water and 20 mL vinegar to make 80 mL of solution in a mason jar. This will make solution 1.
2. Measure the acidity of the solution.
3. Take 8 mL of the original solution and put it into another mason jar. Mix it with 72 mL of water. This creates solution 2 with a pH of approximately 1 point higher than the first solution.
4. Repeat step 2 with the new solution
5. Repeat step 2 and 3 using solution 2. This will create solution 3.
6. Label ten cups each: Water, 1, 2, and 3
7. Place one paper towel in each cup; add the indicated solution to each towel (the towel should be moist but not dripping wet)
8. Wrap a seed in each towel and place plastic wrap over the top of the cups so it goes on all side, then seal the cups using the rubber bands
9. On day 3, take the seeds out and measure growth of root and stem. Place the string along the growth to account for curvature while measuring; mark the farthest advance of the plant on the string from the tip of the main root repeat to tip of the stem. Measure the growth and record the length in in cm.
10. Reseal the cups and repeat step 9 every two days for 14 days
11. Calculate the cumulative average growth of each plant type on every day plants are checked
Results
Solutions used in this experiment had pH levels as follows; solution 1 pH of 3, solution 2 pH of 4, solution 3 pH of 5, distilled water pH of 7. The results indicate that the plants in the solutions with the highest acidities (solution 1 and 2) did not grow at all, while the plants in the solutions with lower acidities (water and solution 3) thrived. As the graph reflects, the plants in solution 3 grew approximately 10% more than the plants in water. While performing the experiment, I observed that the that the plants grown in the more acidic solution 3 were more fragile compared to the plants grown in pure wate
Discussion
Lentil seeds flourish in a pH of approximately 7. Seeds in solutions 1 and 2 failed to germinate due to the acidity levels of the solutions in which they were placed. The pH of the solutions were too low for the plants to handle, which resulted in failure of germination. While the plants in solution 3 still developed, the frail structure of its roots and stem can be attributed to the pH of the solution. Although the plants grown in water grew 10% less than the plants grown in solution 1, the plants grown in water produced stronger stronger stems and roots. The difference in growth could be attributed to the failed growth of two plants grown in water and one plant grown in solution 3. Without these outliers, the average growth per plant in each solution would average approximately 11 cm.
Conclusion
The results suggest that acid rain has a negative effect on the growth of plants. As the atmosphere becomes more polluted, the pH of atmospheric water will continue to decrease. Unless we are able to limit the use of fossil fuels, acid rain will continue to harm plants. I could advance the experiment in the future by using more plants and using solutions with a wider range of pH levels, such as using basic solutions. The data ultimately supported my hypothesis that the plants grown in the solutions with a lower pH and would not grown as well in the solutions with a high pH.
Works Cited
https://hort.purdue.edu/newcrop/afcm/lentil.html
http://www2.gsu.edu/~mstnrhx/EnviroBio%20Projects/AcidRain/definition.html
http://jrscience.wcp.muohio.edu/nsfall05/LabpacketArticles/TheEffectofpHontheGrotwho.html