Effect of Acid Rain on Germination of Plant Seeds 346 BOT Amal Alghamdi Background: • Pollution from burning fossil fuels included nitrogen and sulfur compounds. • They combine with water vapor in the atmosphere to form low pH solutions, like sulfuric acid and nitric acid. When this water falls to the ground it is called acid rain. It affects any organism living there, especially plants. • It can damage forest, crops, soil, and buildings. Background • "Acid rain" is a popular term referring to the deposition of wet (rain, snow, sleet, fog, cloudwater, and dew) and dry (acidifying particles and gases) acidic components • Distilled water, once carbon dioxide is removed, has a neutral pH of 7. Liquids with a pH less than 7 are acidic, and those with a pH greater than 7 are alkaline. CHEMICAL PROCESSES • Combustion of fuels produces sulfur dioxide and nitric oxides. They are converted into sulfuric acid and nitric acid. • Gas phase chemistry • In the gas phase sulfur dioxide is oxidized by reaction • SO2 + OH· → HOSO2 • HOSO2· + O2 → HO2· + SO3 CHEMICAL PROCESSES • In the presence of water, sulfur trioxide (SO3) is converted rapidly to sulfuric acid. • SO3 (g) + H2O (l) → H2SO4 (l) • Nitrogen dioxide reacts with OH to form nitric acid: • NO2 + OH· → HNO3 ACI D RAI N CYC LE Seed Germination • Seed germination is the growth of a plant inside its pod. • All developed seeds have an embryo inside. • Water, oxygen, light, and certain temperatures are required for seed germination. Example: EFFECT OF ACID RAIN ON SEED GERMINATION OF RICE • The germination test showed that seed germination was absolutely inhibited at pH 2.0 for three species, Rice and wheat seeds germinated abnormally at pH 2.5. • Inhibition index of shoot and root length of three kinds of seeds decreased in relation with increased pH values. Aim In this investigation, you will perform an experiment to simulate and test the effect of acid rain on the germination of plant seeds. How does acid rain affect the germination of seeds? Materials: • • • • • • • • Monocotyledons seeds, as wheat and lentils. Dicotolydons seeds as beans, . Cotton bags, filter paper, Hydrochloric acid (HCl), and Sodium hydroxide (NaOH). Water. pH meter Foriceps. Pipettes. Procedure • A filter paper and cotton should rinse with each pH and placed in the bottom of separate petri dish. • Seeds (20 monocotyledons and 10 cotyledons) were placed separately on the paper and covered with cotton soaked in each pH and the lid was placed on top. • All plates were observed over a week period. • The investigation include: the rate of germination and/or the amount of seeds that germinated. Hypothesis:• How do you think the seeds placed in each pH of will germinate? • compared to seeds placed in normal water (pH=7) ? • In addition, the experiment will show whether or not the acids have a corrosive on the seeds. Nuber of seeds germinated Data 12 10 8 replica 1 replica 2 replica 3 6 4 2 0 2 5 7 pH Value 9 12 Discussion • The hypothesis stated that the seeds soaked in water (pH=7) would germinate first. • However, all of the seeds sprouted after 48 hours, but the number varied for each solution. References • "Acetic Acid." EdInformatics. N.p., n.d. Web. 29 Nov. 2009. <http://www.edinformatics.com/ math_science/science_of_cooking/acetic_acid.htm>. "Acid Rain Experiments- Experiment 7- Observing the Influence on Acid Rain on Plant Growth." Environmental Protection Agency. U.S. Environmental Protection Agency, 8 June 2007. Web. 20 Nov. 2009. <http://www.epa.gov/acidrain/education/experiment7.html>. Carpi, Anthony. "Acids and Bases: An Introduction." Vision Learning. N.p., 2003. Web. 29 Nov. 2009. <http://www.visionlearning.com/library/module_viewer.php?mid=58>. Cummins, R. Hays. "Final Presentation of the Effect of Acid Rain on Plants." Jr. Science. Miami University, 10 Dec. 2008. Web. 20 Nov. 2009. <http://jrscience.wcp.muohio.edu/nsfall02/ FinalArticles/FinalPresentationofTheEff.html>. Holt, S. A. "How to Grow Mint Indoors." eHow.com. N.p., n.d. Web. 13 Nov. 2009. <http://www.ehow.com/how_4493938_grow-mint-indoors.html>.