Acid rain refers to a phenomenon in which “[precipitation] from the atmosphere [contains] higher than normal amounts of nitric and sulfuric acids”. The precipitation that results in acid rain comes from the pollution emitted by human activities, such as factories, electrical power plants and automobiles. Two main pollutants are sulfur dioxide (SO2) and nitrogen dioxide (NO2), which reacts with substances in the atmosphere, such as water and oxygen, to form acid rain. While rain water has a pH of 5.6, acid rain has a pH of 5 or less, which is acidic enough to harm plant life. Due to the reactivity of acid rain, the cell processes of plants are disrupted, and the cells die or become unable to function properly. Although this greatly damages ecosystems, this environmental issue brings concern to society. Today, with our growing population of more than 7 billion, humans have become hugely dependant on agriculture.
As such, acid rain has the potential to damage crops extensively, and thus, damage society as well through shortage of food or even famine. In addition, in countries that depend on the production of agricultural goods like Canada, the effects of acid rain can be tremendous. In this lab, we have chosen to examine the effects of acidic and basic environments on radish plants (Raphanus sativus), by implementing varying pH levels of buffer solution into the soil. We have allotted a total of four days (Tuesday, April 10, 2012- Friday April 13, 2012) to examine the effects of acid rain. Purpose: To investigate the effect of implementing buffer solutions of varying pH levels in soil on the growth in height of radish plants (Raphanus sativus). Independent Variable: The varying levels of pH of buffer solutions placed into the plants’ soil Dependent Variable: The height of the radish plants from the base to the tip of plant Controlled variables: The volume of water given to each plant, volume of buffer solutions given to each plant, room temperature, light exposure, mass of soil given to each plant, type of soil, type of water (tap water), size and type of plant container
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
- 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
Controlled Soil Plants (A and B): Both plants appear healthy; they have supple, herbaceous stems with soft, white trichome covering them. The plants are light green in colour and have multiple small, plump leaves with pinnate venation that are whorled. Acidic Soil Plants (A and B): The plants appear to be stunted in height. However, they still retain supple and springy stems covered in trichome and are light green. Basic Soil Plants (A and B): The plants seem to be stunted in height. They still retain supple and springy stems covered in trichome and are light green.
Controlled Soil Plants (A and B): The plants have grown significantly in height. They have bigger leaves attached to the stem by petioles, which appear to be thicker and stronger than previously observed in Day 1. The white, fuzzy trichome covering the stems are more prominent. The plants appear healthy and have a light green colour. Acidic Soil Plants (A and B): The plants appear to be slightly wilted. The stems are slightly limp and curves downwards; they do not provide support. The plants have not retained their light green colour, but have slightly yellowed. The leaves appear to be generally unaffected; however, some of the smaller leaves are limp to the touch. The plants have lost height significantly and appear to be extremely stunted. Basic Soil Plants (A and B): The plants appear to be slightly wilted. The stems are slightly limp and curve downwards and thus are unable to support the plants well. The plants have lost their initial colour and appear paler. The leaves have remained healthy and are not wilted. Plant A has grown slightly; however, Plant B has drastically reduced in height and appears stunted.
Controlled Soil Plants (A and B): The plants have not grown significantly in height. However, they appear to be healthy; the stems are longer and are covered in white trichome that are more prominent. In addition, they have retained their suppleness. In addition, the leaves have grown bigger and have thicker veins. Several lateral buds have grown on the stem. Acidic Soil Plants (A and B): The plants appear to be wilted, and more significantly than on Day 2. The stems are limp and have lost most of its fuzzy white trichome. The leaves are wilted and shriveled. Plant A has grown, but it is insignificant. In contrast, Plant B has grown significantly, although it appears to be limp. Basic Soil Plants (A and B): The plants appear to be pale and are slightly limp. The leaves are generally unaffected- only the smaller leaves have completely wilted. The stems are slightly wilted and have lost some of its trichome. There are no signs of leaf growth. However, Plant A and B have both grown significantly in height.
Controlled Soil Plants (A and B): The plants appear to be healthy. The stems have grown longer and are covered in trichome that thin along the top of the stem. The leaves have grown slightly, as well as the petioles, which are firmer and longer. As these plants were not exposed to harsh acidic or basic environments, they were able to grow without interference. These plants thus represent plants that are unaffected by acid rain (or basic conditions). Acidic Soil Plants (A and B): The plants are significantly stunted compared to its initial appearance in Day 1. The stems are completely wilted and are unable to support the plant at all. The leaves are wilted as well, and the plants have not retained its initial light green colour; it is a dark green/grey. As these plants were exposed to acidic soil conditions, they were unable to grow properly. Thus, these plants represent plants that are exposed to acid rain. Basic Soil Plants (A and B): The plants are wilted, although the stems are still able to somewhat support the plants. The leaves are slightly limp and yellowish in colour. However, Plant A still grew slightly, while Plant B was reduced in height. Although these plants were exposed to basic soil conditions, their growth was somewhat stunted. These plants represent plants that are exposed to liming, a natural phenomenon in which lime, a basic chemical compound, dissolves in water and makes soil basic.
In the time period of four days, the effect of varying pH levels (2.35, 4.0, 7.25, 10, and 7) on the growth of radish plants were examined. In basic and acidic conditions, the radish plants grew stunted in height and withered. All of the radish plants affected by the basic and acidic buffer solutions had limp stems and leaves that were unable to function properly. However, the radish plants kept at a pH of 7 appeared healthy and functioned efficiently, as they grew faster than the former. Thus, in conclusion, this lab proved that acidic and basic soil conditions reduced the plant growth of radishes. Modifications
In order to improve this lab, I would place each radish plant into separate containers. This would allow them to grow to their maximum potential, as they would not need to share or compete for resources. In addition, the buffer solutions would not mix together in the soil, which would improve the accuracy of our experiment.
E.P.A. (2007, June 08). Environmental protection agency. Retrieved from http://www.epa.gov/acidrain/what/index.html