by Steven J. Wamback

Created on: April 11, 2007   Last Updated: September 19, 2008

An Experimental Demonstration of Photosynthesis

Several experiments were conducted in order to attain a better understanding of the process of photosynthesis. First, the process of plasmolysis was examined to look at the effects of salt concentrations on a cell. Next, a decolorized leaf was examined using iodine in order to determine the sites at which starch is stored and whether or not photosynthesis occurs at these sites. Then, paper chromatography was used to separate the pigments contained in a leaf in order to examine the wavelengths of light with which each pigment is associated. Finally, A demonstration was conducted to show that oxygen gas is produced through photosynthesis.

Introduction: Photosynthesis refers to the process by which most plants, algae, and some bacteria produce oxygen and sugar through reactions involving sunlight, water and carbon dioxide (Freeman, pgs 215-216). Organisms such as these are known as autotrophs due to their ability to produce their own food.
The process of photosynthesis occurs in two separate stages: the light-dependent phase and the light-independent phase or Calvin cycle. During the light-dependent phase, water is broken down to produce oxygen while the release of electrons leads to the formation of NADPH and the production of ATP. The NADPH is then used in the Calvin cycle to aid in the reduction of carbon dioxide while using ATP to produce sugars. The process of photosynthesis takes place in the chloroplasts of green plant cells (V.E. Wamback, VE, 2007).

Plants have several types of pigments. The main pigment type is known as chlorophyll. Chlorophyll is dominant in plants and is responsible for the green color of plants. The other pigments, known as accessory pigments, include carotenoids, which include carotenes and xanthophylls, and flavonoids. These accessory pigments are responsible mostly for protecting the chlorophyll from degradation (Freeman, 2005).
The following series of experiments set out to examine parts of plants in order to gain a better understanding of the processes by which photosynthesis occurs.

Likewise, the extent to which certain parts of a plant are affected by photosynthesis and the storage and transportation of sugar throughout the plant was also studied in order to determine if the process of photosynthesis occurs only in regions of the plant where specific pigments are present and does not occur where these pigments are not present.

Methods:

Plasmolysis - In this experiment, an elodea leaf

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