Experiment 1: Effects of pH on Radish Seed Germination
Natural soil pH depends on the parent rock material from which it was formed and processes like climate. Soil pH is a measure of the acidity or alkalinity of the soil. Acidic soils are considered to have a 5.0 or lower pH value whereas 10.0 or above is considered a strong basic or alkaline soil. The pH of soil affects the solubility of nutrients in soil water and thus it affects the amount of nutrients available for plant uptake. Different nutrients are available under differing pH conditions.
In this experiment we will look at the effect of pH on the germination and growth rate of radish seeds in order to determine the range of pH tolerance for the seed. Acidic or basic water will be used in order to stimulate acidity or alkalinity in soil.
2 mL 4.5% Acetic Acid (Vinegar), C2H4O2 Permanent Marker (3) 5 cm Petri Dishes 3 pH Test Strips Radish Seed Packet Ruler 2 mL 15% Saturated Sodium Bicarbonate (Baking
Soda) Solution, NaHCO3 *Paper Towel Sheets (cut to fit into the petri dish) *Scissors *Sunny Location *Water *You Must Provide
1. Use the permanent marker to label the top of each of the three petri dishes as Acetic Acid, Sodium Bicarbonate, or Water.
2. Carefully cut three small circles from the paper towel sheets. The circles should comfortably fit within the bottom of the petri dish.
3. Place the circles in the dishes, and wet them with approximately 2 mL of each respective solution (acetic acid, sodium bicarbonate, or water).
4. Gently press the reaction pad of three, pH test strips onto the wet paper towels. Record your data in the first row of Table 1.
5. Arrange 10 radish seeds on each paper towel in each petri dish. Make sure the seeds have space and are not touching. Then, place the top of the petri dish on the bottom.
6. Place the petri dishes in a sunny or well-lit, warm place. Be sure to keep the paper towels moist for the length of the experiment with the appropriate solution if any of the towels dry out.
7. Observe the seeds daily for seven days, and record the number of seeds that germinate in Table 1. Note when the seeds crack and roots or shoots emerge). On the seventh day, record the lengths of radish seed sprouts (mm or cm).
|Table 1: pH and Radish Seed Germination|
|Day and Initial pH||Acetic Acid||Sodium Bicarbonate||Water|
1. Compare and construct a line graph based on the data from Table 1 in the space below. Place the day on the x axis, and the number of seeds germinated on the y axis. Be sure to include a title, label the x and y axes, and provide a legend describing which line corresponds to each plate (e.g., blue = acetic acid, green = sodium bicarbonate, etc…).
2. Was there any noticeable effect on the germination rate of the radish seeds as a result of the pH? Compare and contrast the growth rate for the control with the alkaline and acidic solutions.
3. According to your results would you say that the radish has a broad pH tolerance? Why or why not? Use your data to support your answer.
4. Knowing that acid rain has a pH of 2 – 3 would you conclude that crop species with a narrow soil pH range are in trouble? Explain why, or why not, using scientific reasoning. Is acid rain a problem for plant species and crops?
5. Research and briefly describe a real world example about how acid rain affect plants. Be sure to demonstrate how pH contributes to the outcome, and proposed solutions (if any). Descriptions should be approximately 2 – 3 paragraphs. Include at least three citations (use APA formatting).
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