Photosynthesis is the process plants use to convert sunlight and water into the food they need to grow and thrive. Grade school students can explore this complex process with experiments to determine what kind of light is the best for growing plants. Other projects help them decide, “Does it matter how much light a plant gets?" or “How do plants affect temperature and humidity?" While exploring these concepts students will gain a basic understanding of photosynthesis. Each experiment will require time for the plant to grow. Prepare an area of the classroom or an area outside that will remain undisturbed during the length of the experiments.
Color and Type of Light – Easy Experiments
Students should review the basic cycle of photosynthesis to understand that plants use sunlight in combination with water to create food to grow. In this experiment students will test if the color of light effects how plants grow. Choose a quick growing plant such as beans or peas to use. Plant seeds in 3 containers such as styrofoam cups or small planters. The first experiment will test what color is best for plant growth, red, green or white. Place the first seed in a window where it will receive normal sunlight, this is the white light. Place the second seed in a window that has been covered with red acetate sheets or red Clingwrap. Place the third plant in a window that has been covered with green acetate or Clingwrap. Observe and record the daily growth of each plant over the course of three weeks. Each plant should receive the same amount of water at regular intervals. This experiment can be expanded to include other colors such as blue and yellow.
Change this experiment to test the types of light and how they affect plant growth. Compare natural sunlight, florescent light and grow lights to determine which are most effective. Follow the same process using the plant in natural sunlight as the control.
Duration of Light Activity
Students can study how much light is needed for plants to grow. This experiment requires the use of cardboard boxes to control how much light each plant receives. Plant seeds in three different planters. The first is the control and will be allowed to receive natural sunlight in an ordinary day. Record the time of sunrise and sunset for each day and if possible the amount of time the plant receives direct sunlight. The second plant will be allowed to receive 6 hours of sunlight each day. A cardboard box should be placed over the planter the rest of the time. The third plant will be allowed to receive only 3 hours of sunlight a day. Each plant should receive the same amount of water at regular intervals. Observe the growth of each plant and record daily measurements. Continue the experiment for three weeks and review the data upon completion.
Transpiration is the process where a plant loses water through its leaves. Students can learn about transpiration with this simple experiment. Three plants that have already been established and have at least three leaves on each are required. On the first day of the experiment place a bag over each of three separate leaves on one of the three plants being used. Tape the bags so they will stay in place for the entire week. On the third day of the experiment, place plastic bags on three leaves of the second plant and tape into place. On the fifth day, place plastic bags on three leaves of the final plant. Each plant should receive at least 3 hours of sunlight daily. Make daily observations of the plants, how much water is in the bags and any change in the health of the plant. Review the observations at the end of the experiment and discuss how plants can impact the temperature and humidity of their environments. Additional experiments can be done using plants with different sizes of leaves.
Students can test plants with different types of leaves to determine if the shape of a leaf affects transpiration. This project may need to be done at home if appropriate trees are not available on site at the school. Students can compare a pine tree, a decidous tree and a bush. Place a gallon clear plastic bag over one branch of each type of tree and secure in place with tape. The branch should have at least five leaves that can be inside the bag. Tie the bag in place and leave for two or three days. When the bags are removed, gently tap them to help the water collect at the bottom of the bag. Measure the water that accumulates and compare. This experiment can be expanded too include any type of tree of bush desired.
Advanced students may want to research what other life forms exist that use photosynthesis. These students can also be introduced to the chemistry of photosynthesis. A basic understanding of the process of photosynthesis will provide a foundation of knowledge for later environmental studies.