Metabolic Pathways of Plants Nathan J. Smith Undergraduate in WFS Tennessee Technological University Cookeville, TN 38501

Project Summary  Photosynthesis is a highly integrated and regulated process which is highly sensitive to any change in environmental conditions. In order to achieve this, a plant must have carbon dioxide, water, light, and photosynthetic pigments. (Ensminger 2006)  Problem: If a plant (coleus) will not photosynthesize in the dark, what will it do to in order to survive?

Introduction  Leaves come in many different shapes, sizes, colors, and types.  Photosynthesis occurs in the mesophyll cells of leaves. Mesophyll cells are composed of tiny bodies called chloroplasts.  These pigments are used to catch the light energy needed for photosynthesis to occur.

Introduction Continued  Starch is a major storage component in plants which strongly affects how well the plant will mature. (Stark 1992)  Soluble sugars like sucrose and glucose play a very important role in plant structure and metabolism. (Ivan 2006)  Glucose can be converted into starch and stored. Also, both starch and sucrose can be turned back into glucose and used for cellular respiration.  As most plants will store starch, those that do not receive the proper amount of light will be forced to convert their starch back into glucose where it will be utilized in cellular respiration by the mitochondria.

Objective/Hypothesis Statement  Objective: The object of this experiment is to show how a plant (coleus) grown in the dark for two weeks will not photosynthesize and therefore convert its starch back to glucose in order to perform cellular respiration.  Hypothesis: I predict the plants grown in sunlight will photosynthesize and produce starch which will be stored. The plants grown in darkness will utilize their starch for cellular respiration. Once the plant uses all its starch, it should die.  Null Hypothesis: Both plants will photosynthesize, store their starch, and grow to maturity.

Methods and Materials  Materials needed for this experiment are: - Bunsen Burner -Two Beakers - Forceps - Watch glass or Petri dish - Light source and dark source - Boiling water - Denatured ethanol - Iodine solution - Coleus plants Data Form Data Form

Methods Continued  1) Set up the experiment.  2) Bring a beaker of water to a boil on the Bunsen burner and add the coleus leaf from set A (the leaf which has been exposed to light for two weeks).  3) Leave leaf in boiling water for a little over one minute in order to break down the waterproof layer.  4) Take the leaf out of the boiling water and place it into a smaller beaker filled with about 50 ml of ethanol.

Methods Continued  5) Place the test tube back into the beaker of hot water. The ethanol should begin to boil.  6) After the leaf has lost all pigments, take it out and place it back into the hot water to rinse the ethanol off.  7) Spread the leaf out flat on a Petri dish or watch glass. Add about five drops of iodine solution to the leaf and observe what happens. (If starch is present, the leaf will turn a black/purple color.  8) Repeat the same process using a leaf from set B (the leaf left in the dark for two weeks).

Expected Results  I expect group A to do much better than group B.  Group A should photosynthesize and store their glucose as starch.  Group B should convert its starch back to glucose for cellular respiration.  If Group B stays in the dark for a long time, the plants will use up all their starch and die.

Projected Timeline

Budget *Salary- $165 *Nonexpendable- $50 *Expendable- $65 *Indirect Costs - $25 *Travel- $25

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