Introduction
Acid rain is precipitation that contains higher levels of nitric and sulfuric acids. This type of rain occurs as a result of pollution caused by human activities, such as factories, power plants, and cars. The main pollutants that contribute to the formation of acid rain are sulfur dioxide (SO2) and nitrogen dioxide (NO2). When these pollutants interact with substances in the atmosphere, they create acid rain. Unlike regular rainfall, which has a pH of 5.6, acid rain has a lower pH value below 5. This acidic nature poses a threat to plant life. Acid rain’s corrosive properties disrupt various cellular processes in plants, leading to cell death or impaired functionality. This environmental problem significantly impacts ecosystems and raises concerns within society due to our heavy dependence on agriculture amid a global population exceeding 7 billion people.
The purpose of this lab is to study the impact of acidic and basic environments on radish plants in order to gain insight into the potential harm caused by acid rain in agricultural production, which ultimately affects society. The goal is to examine how different pH levels of buffer solution introduced into the soil affect the height of Raphanus sativus plants. The observation period for this experiment is from Tuesday, April 10, 2012, to Friday, April 13, 2012. The independent variable being tested is the pH level of the buffer solution added to the soil, while the dependent variable being measured is the height from base to tip. Various variables including water and buffer solution volume, room temperature, light exposure, soil mass and type, water source (tap water), and plant container size and type will be controlled.
Materials and Apparatus
- radish (Raphanus sativus) seeds (6)
- soil (100g)
- planting pot (3)
- buffer solutions of pH 2.35, 4.0, 7.25, 10, and 7 (30mL)
- graduated cylinder (1)
- beaker (100mL)
- tap water
Procedure
- 100g of soil was placed into each planting pot, making sure the soil was not dense or compressed.
- In each planting pot, two holes, 3.8cm deep, were made into the soil.
- One radish seed was placed into each hole. Then, the seeds were covered with soil, making sure the soil was not compressed.
- 10mL of tap water was evenly distributed in the soil for each planting pot. The plants were watered in this method every two days.
- After the plants grew to a minimum of 0.5cm, each radish plant was measured and recorded in the data chart. Qualitative observations were made and recorded.
- Each plant pot was named “Controlled”, “Acidic”, and “Basic”, respectively. The plants were named “A” and “B” in each plant pot.
- 10mL of pH 2.35 was evenly distributed around the soil of Plant A in the Acidic plant pot. 10mL of pH 4 was evenly distributed around the soil of Plant B in the Acidic Plant Pot.
- 10mL of pH 7.25 was evenly distributed around the soil of Plant A of the Basic plant pot. 10mL of pH 10 was evenly distributed around the soil of Plant B of the Basic plant pot.
- Steps 7 to 8 were repeated for the next three days. The heights of the plants were measured and recorded during these steps. Qualitative observations were recorded during said steps.
Qualitative Observations and Analysis
Day 1
Both controlled soil plants (A and B) and acidic soil plants (A and B) exhibit healthy characteristics. These include supple, herbaceous stems covered in soft, white trichomes. The plants are light green in color and have multiple small, plump leaves with pinnate venation arranged in whorls. In contrast, basic soil plants (A and B) also appear to be stunted in height. Nevertheless, they retain supple and springy stems covered in trichomes, and maintain a light green color.
Day 2
The plants in Controlled Soil (A and B) have experienced significant growth in height. They now have larger leaves that are connected to the stem by thicker and stronger petioles compared to Day 1. The stems of these plants also have a more prominent white, fuzzy trichome covering. Overall, these plants look healthy with a light green color.
In Acidic Soil (A and B), the plants seem to be slightly wilted. Their stems are somewhat limp and curve downwards, indicating a lack of support. These plants have also lost their initial light green color and turned slightly yellow. While most leaves are unaffected, some smaller ones appear limp to the touch. The plants in this soil have suffered a significant reduction in height and appear stunted.
Similar to the Acidic Soil, plants in Basic Soil (A and B) also show signs of slight wilting. Their stems are slightly limp and curve downwards, failing to provide proper support. Unlike before, these plants have lost their original color and appear paler. Nevertheless, their leaves remain healthy and not wilted. Plant A has experienced slight growth, while Plant B has drastically reduced in height and appears stunted.
Day 3
Controlled Soil Plants (A and B): The plants show no significant growth in height. However, they are healthy with longer stems covered in prominent white trichome. The stems remain supple and the leaves have grown bigger with thicker veins. Additionally, lateral buds have appeared on the stem.
Acidic Soil Plants (A and B): The plants seem to be more wilted compared to Day 2. The stems are limp and have lost most of their fuzzy white trichome. The leaves are wilted and shriveled. Plant A has grown insignificantly while Plant B has grown significantly, although it appears limp.
Basic Soil Plants (A and B): The plants appear pale and slightly limp. The leaves mostly remain unaffected, except for smaller leaves which have completely wilted. The stems are slightly wilted and have lost some of their trichome. There are no signs of leaf growth. However, both Plant A and B have significantly increased in height.
Day 4
Controlled Soil Plants (A and B): The plants are healthy with elongated stems covered in trichome, which become thinner towards the top. The leaves and petioles have also increased in size. These plants were not exposed to harsh acidic or basic environments, representing unaffected plants when it comes to acid rain or basic conditions.
Acidic Soil Plants (A and B): The plants have significantly stunted growth compared to their initial appearance on Day 1. The stems have wilted and cannot support the plants. The leaves are wilted and their color has changed from light green to dark green/grey due to exposure to acidic soil conditions. These plants depict the effects of acid rain on plant growth.
Basic Soil Plants (A and B): The plants are wilted but still somewhat supported by the stems. The leaves are slightly limp with a yellowish hue. Plant A showed some growth while Plant B’s height decreased. Despite being exposed to basic soil conditions, these plants experienced stunted growth, representing the impact of liming where lime dissolves in water and alkalizes the soil.
Conclusion
The objective of the experiment was to observe how different pH levels (2.35, 4.0, 7.25, 10, and 7) affected the growth of radish plants over a four-day period. Both acidic and basic conditions resulted in stunted growth and withering of the radish plants. The plants exposed to acidic and basic buffer solutions had limp stems and impaired leaf function. On the other hand, the radish plants kept at a pH of 7 remained healthy and grew faster than the others. Therefore, this experiment concluded that both acidic and basic soil conditions hindered the growth of radish plants. Adjustments were made accordingly.
To enhance this lab, I suggest individually placing each radish plant in separate containers. This would enable them to achieve their maximum growth potential by avoiding resource sharing and competition. Moreover, isolating the buffer solutions would prevent them from mixing in the soil and thereby enhance the experiment’s accuracy.
Citation
E.P.A. (2007, June 08). Environmental protection agency. [Online] Retrieved from http://www.epa.gov/acidrain/what/index.html
