Lab Investigation: Photosynthesis

Lab Investigation: Photosynthesis

How do environmental factors such as intensity of light influence the rate of photosynthesis in plants?

Section 1:

Plants, are one of the most important pieces of our ecosystem. They are a source of food, provide habits for millions of species, and convert CO2 into oxygen gas, necessary for human life. The equation of the plants process of producing oxygen is 6CO2 + 6H2O -> C6H12O6 + 6O2, it requires light, and is called photosynthesis. Not only does this produce oxygen, but sugar (C6H12O6) which is used by the plant to create structures like stems and leaves. Since photosynthesis is such an important process in the biosphere it is important to understand the bet conditions in which it occurs. This leads to the question, how do environmental factors, such as intensity of light, influence the rate of photosynthesis in plants?

Section 2:

In order to determine if the distance a plant cell is from the light source affects the rate of photosynthesis the students designed an experiment using leaves, a light source, sodium bicarbonate, sodium chloride, tinfoil and a timer. A hole punch was used to create 5 sets of 10 leaf disc, each of which would be placed in a solution. Four solutions were sodium bicarbonate which replaces carbon dioxide in this reaction and provides a medium for the leaf disc to float as photosynthesis occurs and oxygen is produced. One solution was placed 10cm from a lamp used as the light source, one 25cm away, another was wrapped in tin foil and placed 10cm away from the light source, and the fourth was placed behind the lamp in only room light. The fifth set of ten leaf disc were placed into NaCl in order to prove that density was not the reason for floating. In order to reduce error each beaker contained 50mL of its respective solution and distance was measured by two separate students in a straight light from the light bulb in the lamp.

In order to remove any oxygen that had been previously created in the leaves, the disc were placed in a 10cc syringe with liquid soap. Inside the syringe a vacuum was created in order to pull the oxygen gas from the leaves. When all leaves sank in the soap water they were removed and placed in their solutions. In order to prevent false readings any leaves that immediately began floating from left over oxygen were removed from their solutions. All ten disc remained in the NaCL solution and the sodium bicarbonate at 10cm. Four had to be removed from the sodium bicarbonate at 25cm leaving 6 disc. Eight had to be removed from both the room light beaker and the tinfoil wrapped beaker leaving 2 leaf disc in each beaker. The timer was started when the leaves were placed in their separate solutions and were each beaker was agitated every 2min to encourage the disc to float when enough oxygen was present.

Section 3:

In this groups NaCl solution 1 of the 10 disc began to float after 18min in the sodium chloride. This was found to be an error as no other group reported a floating disc in their NaCl proving that density of the solution did not cause the disc to float. The error could have

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