Manipulation of Photosynthesis Using Various Methods

Abstract

These experiments in this study was to show how significant it is for plants to receive all its inputs, so it can produce all its outputs in photosynthesis. Our initial hypothesis was correct for all three experiments, because we predicted that the change in light and carbon dioxide would affect how much starch the plant produced. We also predicted that the baking soda would speed up the process of photosynthesis, which caused it to produce more oxygen. This helped us to conclude that sunlight, carbon dioxide and water are all necessary for photosynthesis to occur and to be successful.

Introduction

Plants are the foundation for many ecosystems and for humans as a whole. Agriculture in South Dakota alone leads the state in revenue and at the end of the day it all comes back to plants. Starch in plants positively affects agricultural yield of a number of crops (Stark). Plants produce starch (carbohydrates), oxygen and water through the process of photosynthesis. To start this process though, plants need sunlight, carbon dioxide and water (Mader). In this lab we manipulated the inputs of photosynthesis to see how it affected its outputs. We also tried to speed up photosynthesis using baking soda with a water plant. Even though marine plants rate of photosynthesis is very similar to that of terrestrial plants, we found a way to make it faster (Black). In both cases, we got to see what photosynthesis makes and how changing the inputs of it will change the outputs.

Materials and methods

We first started off by doing a little experiment to test for starch. We started off by placing a couple drops of starch, glucose, and distilled water in three different depressions of the spot plate. After this we placed a drop of iodine solution into each spot. We then recorded our observations.

Our next experiment started off by collecting three leaf samples from the greenhouse. Each leaf simulated different situations. One plant was in the dark room, another one was in a closed environment, and the third was left in the light but had a section of the leaf covered up. After the leaves were recovered, two beakers were filled. One was filled with water and one filled with alcohol. The amount of liquid put into either beaker does not matter, but we filled both half full. Both beakers were then brought to a boil. Once both were boiling, we placed one of the leaves into the boiling water for about a minute. Then we pulled it out with forceps and placed it into the boiling alcohol until the color pigments had been extracted. The leaf was then taken out of the boiling alcohol and dipped into the boiling water to soften it back up. Once the leaves were taken out of the boiling solutions, they were placed in a petri dish and then soaked in an iodine solution. After letting the leaf soak for a couple minutes, we then rinsed it off and floated it in water. We then observed the patter of staining. This was done with all three leaves.

Our second experiment was to test the effect of an external carbon source on photosynthesis. First, we filled up two separate beakers half full with water. We set one beaker aside and put two teaspoons of baking soda into the one beaker and labeled it. We then added equal amounts of Elodea into each beaker. After this, both beakers were covered with plastic wrap and set underneath a lamp for fifteen minutes. After the fifteen minutes we observed what we saw and wrote it down. Next, we covered both beakers completely with aluminum foil. Again, we let it sit for fifteen minutes and recorded your observations after. Results The first experiment results were that only one of the solutions turned a dark purple. Our results during the next experiment was what we expected. The leaves showed what we expected they would show. The leaf that was left in the light and had the part covered up showed the most purple color where the leaf was not covered up. The part where the leaf was covered showed little to no purple color which was expected. The leaf that was left in the dark showed almost no purple at all which was also expected. The leaf that was left in a closed environment had very little purple in it, only showing some towards the middle of the leaf.

Lastly, our results for the external carbon experiment was also expected. There appeared to be more gas produced in the beaker with the baking soda. This was what we hypothesized. In the second part of the experiment though, the one with baking soda had less bubbles.

Discussion

Based on the colors in the very first experiment, we could easily tell which liquid was starch because it turned purple right away. Iodine will turn starch purple, which helped us lead into the experiment dealing with the leaves. As we know, photosynthesis produces carbohydrates, which is a starch. Because it is a starch we could test for it in the leaves and again look for the purple color. The leaf that was left in the light was our control so we could see what a leaf should look like, but it had a part of it that was covered up and could not receive light. Once, we died the leaf the section that was exposed to light turned purple but the part that was not could not turn purple because it had no starch in it. It had no starch because it did not have light which is needed in photosynthesis. Sunlight, carbon dioxide and water are all needed in photosynthesis, so the part that was covered up could not properly do photosynthesis (Mader). This was also true for the plant that was left in the dark. Because it had no sunlight, it could not do photosynthesis so it appeared to have no purple color in it.

Lastly was the plant that was in a closed environment, which had another part to make photosynthesis was cut off. Instead of having no light this time, the plant had no carbon dioxide so it again could not complete the process of photosynthesis. We could see this because again there was no purple in the leaf when we stained it. In the experiment with the baking soda, we also got to observe the process of photosynthesis. When the beakers were just covered with plastic wrap, the plant with the baking soda produced more bubbles which means more gas. It had more bubbles that were collecting on the leaves because it is producing more oxygen. By adding NAHCO 3 the reagent is causing photosynthesis to speed up which is not present in the other solution. After we covered the beakers up though, the amount of bubbles in the baking soda slowed down and the one without baking soda caught up. This again proved that the baking soda helped speed it up. Overall, all three experiments helped to understand the process of photosynthesis. Without having all three inputs of photosynthesis, it is unable to produce its outputs. This was a good manipulation of it.