Plant Growth and Acid Rain

The science background section provides teachers with more detailed information about the phenomena students explore in this unit. Below is an excerpt from the science background information on plant growth and acid rain. 

In the mid-1800s, people started noticing a connection between the locations of large industrial areas and damaged forests, observing that forests downwind of industrial plants weren’t growing as well. This was the first time acid rain had been observed. Acid rain is any form of precipitation that has high levels of nitric and sulfuric acids. It is caused primarily by the burning of fossil fuels, such as gas, oil, and coal, although a small percentage comes from natural causes, including volcanic emissions and forest fires. 

Despite being noticed in the 1800s, acid rain wasn’t considered a significant environmental threat until the 1970s, when scientists began noticing that some lakes and streams were becoming more acidic. Studying acid rain is important because too much acidity in the water harms many different living things. Acid rain is a form of pollution—any substance that has harmful effects on the environment.

Acid rain can also damage a plant’s leaves, causing them to look spotted or to drop earlier than normal. This causes the plant to become weak because leaves have most of the plant’s chloroplasts to collect sunlight and convert it into energy the plant can use to grow and develop through photosynthesis. When a plant’s leaves are damaged by acid rain, they can no longer photosynthesize as well.

Acid rain generally doesn’t kill plants directly. Instead, it damages their external structures, making it harder for them to grow and develop. For example, plants use their roots to anchor a plant in place and take nutrients and water from the soil. Scientists know that acidic water dissolves the nutrients and minerals in the soil and then washes them away before trees and other plants can use them to grow. Acid rain can also stunt root growth.

When the structures of a plant are damaged by acid rain, they are less able to complete their life cycle. A life cycle is the series of developmental stages an organism passes through on its way from birth to death. There is a pattern to the changes that all living things go through as they grow and develop. All life cycles include birth, growth, reproduction, and death.

The seed is the first step in a flowering plant’s life cycle. The seed protects the plant in a protective coat as it travels from its parent to a new location. With enough light and warmth from the sun, the seed will start to grow. During this step, the plant breaks out of its seed coat and begins to sprout, a process called germination. It grows roots, stems, and leaves. With leaves, it can capture energy from sunlight.

In the third step, the plant grows buds and flowers. Flowers are external structures where seeds form and pollination occurs. Flowers attract pollinators so the plant can make new seeds. Finally, the plant produces fruits that attract animals, or produce seed casings that allow the seed to travel by wind or water. The seeds grow and start the plant life cycle over again.

Acid rain can prevent a plant’s flowers from blooming or cause them to fall off the plant before they are pollinated. This affects a plant’s ability to reproduce. Reproduction is the ability of a mature organism to have offspring. Without reproduction, a group of organisms will die out. Because of this, reproduction is an essential step in the life cycles of all living things.