What Factors Affect the Rate of Photosynthesis in Living Leaves?

Topics: Photosynthesis, Water, Carbon dioxide Pages: 6 (1761 words) Published: February 24, 2013
What Factors Affect the Rate of Photosynthesis in living leaves?

In this lab, four different types of leaves were tested to see the rate at which each leaf photosynthesized. This lab demonstrates how plants store light, capture light, and use light as energy for reproduction and growth, by photosynthesis. The control in this experiment was spinach, which was tested before any of the other plants were. The other plants that were tested were English Ivy, C4 Plant, and a multicolored plant. Each type of leaf was tested in a sodium bicarbonate solution and a solution of distilled water. It will be shown in the discussion whether the hypothesis made was correct or incorrect. It will be shown in the discussion what could have occurred during the experiment that could have affected the results. Introduction:

Photosynthesis can be defined as the process by which green plants, and other organisms make carbohydrates from carbon dioxide and water in the presence of chlorophyll, using energy captured from sunlight by chlorophyll, and releasing excess oxygen. Like all enzyme-driven reactions, the rate at which photosynthesis occurs can be measured by the disappearance of a certain substrate, or the accumulation of product. Photosynthesis consists of light reactions and dark reactions. This process can be simplified by the equation: 6CO2 + 6H2O + Energy --> C6H12O6 + 6O2

Shown in this equation 6 molecules of carbon dioxide (6CO2) and 12 molecules of water (12H2O) being consumed in the process, and glucose (C6H12O6), six molecules of oxygen (6O2), and six molecules of water (6H2O) being produced. The energy source is photons (light) from the sun. The rate of photosynthesis could be measured by the amount of moles of O2 produced for one mole of sugar. The rate of photosynthesis could also be measured by the amount of moles of CO2 that are consumed for every mole of sugar that is synthesized. Leaf disks float in water, most of the time. If air spaces are infused with CO2, however, the density of the disks will increase. When sodium bicarbonate is added to water, the bicarbonate will cause the disks to sink. As photosynthesis continues, oxygen is released into the leaf disks, changing the ability of the leaf disks to float in water, and causing them to rise. Since cellular respiration is taking place at the same time inside of the leaf disks, the oxygen generated by photosynthesis will be consumed. As a result, the rate at which the disks will rise is proportional to the net rate of photosynthesis. In this experiment, the rates of photosynthesis of various plant leaves were tested. The plant used as the control in this experiment was spinach. The spinach leaf was put under the influence of an intense light source and tested in distilled water, as well as sodium bicarbonate. The other leaves that were tested were: C4 plant, English Ivy, and a Multicolored Leaf. All three of these diverse plants were tested under the same conditions as the spinach leaf. The hypothesis given for this lab is that the leaf disk will all float to the top of both solutions within 15 minutes. *Hypothesis* the leaf disks will all have risen to the top of the solution within 10-15 minutes, except the disks in pure water.

* Timer
* 60 watt light bulb
* Hole puncher
* Baking soda (sodium bicarbonate)
* Liquid soap (approximately 5 mL of dishwashing soap in 250 mL of water) * 2 plastic syringes without needle (10 mL or larger)
* Plant leaves (spinach, ivy, C4 plant, and multicolored plant.) * 2 clear plastic cup

1. Prepare 300 mL of 0.2% bicarbonate solution for each experiment. (The bicarbonate will serve as a source of carbon dioxide for the leaf disks while they are in the solution.) 2. Label the first cup "CO2”

3. Pour the bicarbonate solution into a clear plastic cup to a depth of about 3 cm 4. Label the second cup “No CO2”
5. Fill a second cup...
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