Introduction: Biofuels are an important part of today's culture. Using biofuel as an alternative to petroleum-based fuel has numerous environmental, economic, and social benefits.
Objectives: Students will understand conversion of the sun's energy in plants through photosynthesis, the carbon cycle, and energy transformations; students will conduct their own experiments; students will calculate the leaf area index and crop growth rate for diverse plant species used in their experiments; students will participate in discussions on current and future energy needs and alternative energy sources.
Materials: Seeds: canola, radish, sunflower, soybean, etc., 8 - 1 gallon pots per group of 2-4 students, potting soil, microscope, lab balance, scissors, lab oven (or you can dry them at home the night before and bring into school) lab balance, graph paper, science journals to record their data.
Vocabulary to teach: Photosynthesis: The process by which green plants make carbohydrates such as sugar, using water, carbon dioxide, and sunlight.
Carbon cycle: The steps by which carbon (in the form of carbon dioxide) is extracted from the atmosphere by living organisms and ultimately returned to the atmosphere.
Leaf Area Index (LAI): An estimate of the size of the plant's photosynthetic system or in other words, the plant's light collector. This function is similar to that of a solar panel on a building. Net assimilation rate (NAR): The increase in carbon after losses due to growth and maintenance respiration are accounted for in the plant.
Background Information: Students should be familiar with the process of photosynthesis and respiration. Students should be familiar with the carbon cycle. Students should be familiar with using lab equipment such as a lab balance to determine weight.
Introduction: Students need an introductory lecture on photosynthesis and respiration prior to this lesson. Since the price of fuel is increasing due to the shortage of petroleum, countries worldwide are seeking alternative sources of fuels. One alternative source is biofuel, which is derived from the sun via green plants. Green plants capture solar energy and collect carbon dioxide
from the atmosphere and convert this energy into a stable chemical form. Instead of using solar panels to capture solar energy, plants use a canopy of leaves and stems to collect the sun's energy. The conversion of solar energy to chemical energy by plants is known as photosynthesis. During photosynthesis carbon from atmospheric carbon dioxide
is reduced to carbohydrates. Carbohydrates are transported from the leaf, most commonly in the form of sucrose (table sugar), to the developing seed. In the seed, the sucrose is converted to oil. Oil is stored in the seed to provide energy for the growing seedling during the seed germination process. But this seed-based oil may also be collected and used by humans as vegetable oil, or it can be converted to biofuel. Plants differ in how they capture solar energy and convert it to oil. To pick the plant that is most efficient, we need to compare photosynthesis in different plants. Remember, photosynthesis is affected by temperature, light, and water. Students will grow three different species of plants to test and compare.
Activities: Divide the class into groups of two to four students. Brainstorm questions related to photosynthesis and the carbon cycle. Go over the following questions as a class to help students generate their hypothesis. What factors are critical for determining which plants should be used for biofuel production? Does the architecture of a plant affect how efficient a plant is at converting solar energy to chemical energy? What are some different plant architectures? While growing different plants what data should be collected?
First you will decide what your question is, generate a hypothesis, and develop your procedures. Select 3 different plants to use in this experiment and examine the seeds under the microscope. Draw the seeds to scale, record size and any other observations you measure, Calculate and record the average weight of the seeds for each plant. For each plant species, plant 8-10 seeds per pot. Once seedlings have germinated you will thin seedlings to 5 per pot. Place pots in warm, well-lighted environment. Water and fertilize as needed to support plant growth. Observe and measure plant growth, including stem height and leaf length and width.
Once your plants have shown sufficient growth, clip the leaves. Weigh them. Trace them on graph paper to calculate the Leaf Area Index (length x width) Dry the leaves for 24 hours then reweigh and calculate the difference. Students should understand that the stem height, leaf area index and size of the seed help determine which plant is best suited to produce oil that can be converted to biofuel. Students can then record their observation and develop their conclusion/ results in their lab report. It is important to have the students create a chart for their data to show the growth over time. This will help them understand that crop growth rate is also important in the development of biofuel.
